text:
In a device (10) for in-vivo measurements of quantities in living organisms that comprises a catheter-like tube (11) receiving in a removable manner a setting needle (14) provided for inserting the tube in the organism, with at least one aperture (12) being provided in the wall of the tube (11); and a sensor (18) for detecting the quantity to be measured in the interior of the tube; the sensor (18) is mounted on a separate oblong carrier (17) whose cross sectional dimensions are smaller than those of the interior of the tube. After the setting needle (14) has been pulled out of the tube (11), the sensor can be inserted in said tube (11).
1. The system according to the tubular carrier has at least one opening in its wall located adjacent to an open, distal end thereof.
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8. A system for in-vivo measurements of quantities in a living organism, comprising
a catheter-like tube having a tubular wall with only one single lumen therein and at least one aperture in its tubular wall;
a removable setting needle for inserting the catheter-like tube in the organism;
a separate, oblong tubular carrier for applying a medicament, on which a sensor for detecting the quantity to be measured is mounted for insertion in the single lumen of the catheter-like tube, the carrier being sealed against the tubular wall of the catheter-like tube;
a base for supporting the carrier when inserted in the single lumen, the base being arranged for insertion into an end of the catheter-like tube;
a line extending through the base for supplying a liquid for rinsing or calibrating the sensor on the carrier;
the cross sectional dimensions of the carrier and of the setting needle being smaller than the cross sectional dimension of the single lumen, and the single lumen having a cross section adapted for only alternately receiving either the setting needle or the carrier with the sensor, whereby the carrier is in place of the setting needle after replacement of the setting needle with the carrier; and
the carrier, when inserted in the single lumen being supported by the base inserted at the end of the catheter-like tube, and defining a channel for the liquid substantially having an annular section between the carrier and the wall of the catheter-like tube, the line extending through the base being in flow connection with said annular channel.
Applicants claim priority under 35 U.S.C. Ï119 OF Austrian Application No. 1594/99 filed Sep. 17, 1999. Applicants also claim priority under 35 U.S.C. 365 of PCT/AT00/00247 filed Sep. 18, 2000. The international application under PCT article 21(2) was not published in English.
The invention relates to a device for carrying out in-vivo measurements of quantities in living organisms, comprising a catheter-like tube that accommodates, in a removable manner, a needle that is provided for inserting the tube in the organism; at least one opening in the wall of the tube; and a sensor for detecting the quantity to be measured in the interior of the tube.
It is frequently necessary in many areas in the field of medicine and in comparable fields to measure in a repeated or continuous manner concentrations or compositions of body fluids primarily for the purpose of being able to detect disorders of the homeostasis and to be able to treat such disorders, if necessary. For example, diabetes mellitus is a disorder of the metabolism that is reflected by various symptoms, whereby it is possible to control the concentration of the blood glucose by a therapy with insulin. Although this therapy with insulin substantially promotes the well-being of the patient, it is not possible to prevent late complications such as, for example premature blindness, heart and kidney failure, or neuropathies in most cases, but only to delay such complications. One of the most important causes for the late consequences of this disease is the not optimal coordination of the insulin injections with the blood glucose. Therefore, so as to be able to adapt the insulin injections to the needs of the body as required, the glucose concentration has to be measured repeatedly (or continuously) in a precise manner.
All kinds of different methods have been proposed for measuring the glucose in the organism, including blood sugar-measuring devices; non-invasive measuring methods; indirect determination of the glucose via other body parameters; or measurement of the glucose in body fluids other than the blood, for example in the sputum, in the perspiration, or in the urine. Because of the problems encountered when measurements are taken in such fluids, quantification of the glucose in the fluid of the tissue, which is closely connected with the plasma glucose, has been increasingly given more attention in the last few years. Problems arising in the blood such as, for example coagulation, the risk of infection, or protein loading, are highly reduced in this connection if they cannot be avoided, to begin with.
Various possibilities for measuring the glucose in the fluid of the tissue in a continuously manner have been proposed as well:
(1) Minimally invasive sampling methods such as the open micro-perfusion technique, the micro-dialysis, or the ultra-filtration technique.
(2) Sensors that are directly inserted in the tissue; or
(3) Techniques by which the tissue fluid is collected through the skin (the so-called suction technique, inverse iontophoresis).
In addition to the open micro-perfusion method and micro-dialysis, sensors that are directly inserted in the tissue have been found to be particularly well-suited for a continuous measuring system.
In connection with the open micro-perfusion technique and micro-dialysis, perfusion of a catheter inserted in the tissue is carried out with a rinsing liquid that, in connection with the open micro-perfusion method, mixes with the fluid of the tissue, whereas in connection with micro-dialysis, an exchange takes place via a membrane. This membrane, on the one hand, permits that the exchange of molecules between the tissue fluid and the rinsing liquid can be controlled in a selective manner; on the other hand, this property is altered by the deposits of endogenous substances (predominantly of proteins, but also of cells). Such deposits go hand in hand with a change in the transport properties of the molecules via the membrane, which is reflected by a diminished concentration of the molecules in the rinsing liquid. This drawback can be circumvented by macroscopic perforations in connection with the open micro-perfusion technique.
The equilibration between the fluid of the tissue and the rinsing liquid is a function of the exchange area and the flow rate of the rinsing liquid. If the flow rate is infinite, complete equilibration between the two liquids takes place. Because of the low flow rate, two decisive drawbacks ensue for the measurement of the substances in the rinsing liquid: firstly, the amount of fluid collected per unit of time is very small, and secondly, the delay caused by the length of the hose (system delay) will increase accordingly.
A higher flow rate is frequently selected for that reason in order to make more liquid available more rapidly. The drawback of this mode of operation consists in the not-complete mixing of the two liquids, which, if possible, has to be compensated by measuring other parameters. This causes additional requirements that the measuring technique needs to satisfy, which is found to be difficult particularly in connection with on-line measurements.
In addition to the sampling methods, which permit an ex-vivo measurement (sensor is located outside of the body), proposals already exist for in-vivo measurements, whereby the sensor is directly inserted in the tissue. In addition to the higher requirements the sensor needs to meet with respect to bio-compatibility, mechanical stability and size, it is necessary to pay attention to the problem posed by the calibration of the sensor. Although the sensors exhibit very good in-vivo characteristics, characteristics are observed that are changed in vivo. In order to take such changes into account, different starting points exist: a frequently employed starting point is the calibration of the sensor value against one or more blood values, whereby it is implicated that, in the case of a glucose measurement, the concentration of the glucose in the fluid of the tissue is equal to the concentration in the blood. So as to be able to render this a correct statement, the concentration of the glucose has to be in a state of equilibrium between the blood and the fluid of the tissue because a shift in terms of time exists between these two compartments. In addition to the painful stress affecting the person involved, calibrating changes "away" (for example infections in the tissue, encapsulation of the sensor) constitutes a substantial shortcoming of this measurement.
So as to avoid the drawbacks of the sampling methods (time delay), incomplete equilibration, a membrane disposed in between) and the implanted sensor (no calibration possibility, mechanical stability), a sensor (e.g. a glucose, lactate or glutamate sensor) can be inserted in a specially shaped catheter or general a tube or hose, and inserted in the tissue with the help of such a catheter or tube or hose); compare, for example U.S. Pat. No. 5,299,571 A, or U.S. Pat. No. 5,568,806 A. The catheter has a macroscopic opening, so that an exchange can take place between the fluid of the tissue and the sensor. After the sensor has been inserted in the respective tissue with the help of a setting needle present in a lumen, said setting needle is removed from the catheter. The setting needle or the associated lumen take up a mayor portion of the cross section of the catheter, and the sensor is arranged in a fixed manner in the lumen located adjacent to the lumen receiving the setting needle. The aforementioned opening in the catheter tube is located adjacent to the sensor. Suitable conduits lead from said sensor to the outside in order to permit a connection to an electronic measuring system. The manufacture of the catheter tube requires relatively much expenditure because of the two special lumens, whereby, furthermore, a relatively large cross section, notably the one receiving the setting needle, cannot be used for carrying out the measurement and has to be viewed as a lost volume.
Other types of catheter systems have already been proposed—compare, for example U.S. Pat. No. 5,779,665 A; U.S. Pat. No. 5,586,553 A; or U.S. Pat. No. 5,390,671 A, whereby the setting needle is present there outside of the catheter tube, approximately parallel with said catheter tube (U.S. Pat. No. 5,779,665 A), or with inclusion of the catheter tube. This entails drawbacks when the catheter is set such as, for example the impermissible fact that the catheter tube is being taken along via a thread (U.S. Pat. No. 5,779,665 A1), or causes pain when the relatively thick unit comprising the setting needle and the catheter tube is inserted. In connection with such known arrangements, the sensor is present in the remaining catheter tube, whereby it has been proposed also (compare U.S. Pat. No. 5,390,671 A) to mount the sensor in a displaceable manner in a rigid, strip-shaped carrier in the catheter tube, said carrier being bent at a right angle.
In connection with the last-mentioned embodiments, a set of setting utensils is provided or required for setting the catheter with the sensor in place. This entails additional expenditure.
Now, the problem of the invention is to provide a measuring system of the type specified above that permits working with the smallest of cross sections when the catether-like protective tube is set in place, so that the catheter or the catheter-like tube can be set in a simple manner and largely without causing pain, whereby, furthermore, no set of setting utensils and no trained personnel are needed, but self-application is made possible instead.
The device as defined by the invention of the type specified above is characterized in that the sensor mounted on a separate, oblong carrier as it is known per se, the cross sectional dimensions of which are smaller than the ones of the interior of the tube, and can be inserted in said tube after the setting needle has been pulled out of the tube.
In connection with the present device, therefore, the lumen of the catheter-like protective tube is used in two ways, so that no second lumen is required (for the sensor). In the preferably only one lumen of the tube, the setting needle is accommodated first by inserting it in the tissue with the help of the tube. The setting needle is subsequently pulled back, which releases the lumen of the tube, in order to then insert the sensor with the help of a carrier. The carrier, of course, has to possess a certain rigidity in order to permit such insertion in the catheter-like tube, even though a certain flexibility of the carrier is entirely possible and advantageous as well. This technique permits a minimal cross section of the tube with the sensor finally accommodated therein, and it is possible also to directly measure the respective quantity such as, for example glucose etc. After the tube has been set in place, it is possible also in this connection to replace the sensor without requiring another piercing, i.e. setting of the catheter.
Furthermore, owing to the fact that the sensor carrier has smaller cross sectional dimensions than the lumen of the tube, a space is created between the catheter tube and the carrier or sensor, through which liquids can be introduced from the outside. Preferably, provision is made in this connection that a channel having a generally ring-shaped cross section for a rinsing or calibration liquid or the like is formed between the sensor carrier in the installed condition, and the inner wall of the tube.
The admitted liquids per se may assume different functions as follows:
(1) The liquid contains the substance to be measured and may therefore serve as the calibration medium (e.g. Ringer solution with 5 mmols/liter addition of glucose for calibrating glucose sensors;
(2) due to an increased high speed of the liquid, it is possible to remove deposits on the sensor, i.e. to flush such deposits away;
(3) it is possible to add substances to the liquid in order to cause different effects such as, for example buffers for a constant pH, high-oxygen agents against an oxygen deficit in the tissue, infection-inhibiting agents, increase of the permeability, or substances lowering the blood sugar (e.g. insulin).
Of primary importance in this connection is the—periodic—calibration of the measuring device with the help of a channel formed in the passage between the sensor carrier and the wall of the tube, and likewise the periodic rinsing, which is useful for obtaining an exact measurement.
However, it is particularly advantageous if the separate sensor carrier has the shape of the tube because if the carrier of the sensor is realized in the form of a tube (and the sensor is positioned on the outer side of the tube), it is possible—due to the inner lumen of the carrier tube—to additionally introduce in an advantageous manner a medication, for example insulin, if such a substance may not come into any direct contact with the sensor.
For an increased feed of said substance or substances, it is advantageous also in the present case if the tubular sensor carrier has at least one opening in its wall that is positioned adjacent to its open distal end.
In order to prevent the substance from flowing back into the space between the sensor carrier and the catheter tube and to thereby safely avoid any direct contact of the substance with the sensor, it is favorable, furthermore, if a ring seal providing sealing against the inner wall of the catheter-like tube is arranged on the tubular carrier in a site located between the open distal end or, if need be, the opening in the wall of the tubular sensor carrier, on the one hand, and the sensor on the other. Therefore, if a seal is thus mounted between the tip of the carrier and the sensor, the substance can exit only into the tissue.
Therefore, it is overall possible with the embodiment of the device as defined by the invention to measure directly on site, and the sensor can be calibrated and "maintained". Furthermore, active substances can be introduced for the measurement, and it is possible also to feed substances into the tissue in response to the measuring result by penetrating the tissue only once.
When the sensor is directly inserted in the tissue, the ambient temperature is preset by the body temperature, which is relatively constant. Therefore, a measurement of the temperature as it is required in connection with ex-vivo measurements, can be omitted. By omitting the pumping devices, which are required in connection with sampling methods for ex-vivo measurements, the structure of the device is substantially simplified, which reduces the costs. Hose pumps are employed, as a rule, in connection with sampling methods because different directions of flow can be synchronized with such pumps, whereby most of the energy is consumed with such type of pumps for deforming the pump hoses, so that the consequence is a very poor degree of efficiency (which is critical in particular in conjunction with portable devices). Since it is possible in connection with the device as defined by the invention to employ injector pumps for feeding calibrating or rinsing liquid, or active and therapeutic substances, the operation of the system, furthermore, requires less energy.
Moreover, by omitting suction pumps, no dilution of the tissue fluid by a rinsing or calibrating solution liquid will occur with the device as defined by the invention in normal measuring operations, which means that a completely equilibrated solution is available on the sensor. This also means, furthermore, that it is no longer necessary to determine the re-finding rate. Since no tissue fluid is extracted from the body permanently, the tissue fluid cannot become poor around the catheter. The only consumption of tissue fluid takes place directly on the sensor; however, such consumption is negligible.
For the intensive, safe contact of the sensor with the tissue fluid, it is also advantageous in this connection if the wall of the catheter-like tube has several openings successively located one after the other in the axial direction within the area of the sensor. In this way, tissue fluid can flow to the sensor through a number of openings, i.e. macroscopic perforations in the wall of the catheter tube, which, furthermore, means that the given position of the sensor is relatively uncritical, so that when the carrier with the sensor is pushed into the catheter-like tube, no exact positioning of the sensor has to be achieved after the setting needle has been pulled back.
In order to safely avoid any damage to the sensor by rubbing on the inner wall of the catheter-like tube when the carrier with the sensor is pushed into the catheter-like tube, the aim should be that the sensor has the smallest possible dimensions in the radial direction, i.e. the sensor should project from the carrier as little as possible. Accordingly, it is advantageous if the sensor is produced by application of the thin-film technology or silicon technology, as it is known per se. Furthermore, it is favorable for this purpose as well if the sensor is at least partially embedded in the carrier. In this connection, the sensor may have an expanse in the longitudinal direction of the carrier that is greater than it is usually the case, which is particularly advantageous if the catheter-like tube has a plurality of apertures.
The measuring principle of the sensor is known per se and may consist of physical and chemical methods as well as also combinations of the two methods. For example, an electrochemical measurement is suitable for the determination of the substance. According to current practice, an amperometric method with constant polarization voltage for the quantification is particularly well-suited in this connection (see U.S. Pat. No. 5,462,645 A). In this process, an enzyme (e.g. glucose oxidase, glutamate oxidase, lactate oxidase, etc.) is converted according to a chemical reaction into hydrogen peroxide, which is oxidized on an electrode by the constant polarizing voltage. The quantity of the sensor current generated in this process is dependent upon the concentration of the substance to be determined. The following applies by way of example to glucose measurements:
Various technologies are available for the manufacture of the sensors (see, for example FRASER, D.: Biosensors In The Body. Wiley 1997, page 199f). A technique commonly employed at the present time would be also the thick-film technology, by which is it possible to realize structures of 0.1 mm. However, with the thin-film technology, it is possible to obtain structures in the μm-range, and with the silicon-technology it is possible to build sensors even in the sub-μm range. Since the invasiveness of the system increases with the increase in the diameter, it is important that the sensor has small dimensions in the radial direction. Especially the thin-film technology or the silicon technology are well-suited for that reason for realizing the sensor. So that the volume required for the sensor can nonetheless be made available, the sensor can be expanded in the axial direction, as mentioned before. A sensor comprising a size and technology that could be considered for realizing the present measuring system is represented by the sensor described by JOBST G ET AL in: Thin-Film Microbiosensors For Glucose-Lactate Monitoring, Anal. Chem. (68) 18, pp 3173-3179, 1996.
An embodiment of the catheter that is feasible within the framework of the invention, comprises perforating (by means of a laser beam or using a mechanical drill) a commercially available vein-dwelling cannula. Various sizes of the catheter are possible, whereby the outside diameter may be in the range of from 0.6 mm to 2.0 mm. The diameter of the carrier for the sensor can be adapted to the inner tube, so that the sensor mounted on the surface of the carrier can be inserted in the catheter without any problems. With the smallest embodiment of the arrangement (outside diameter of the catheter=0.6 mm; diameter of the carrier=0.3 mm), which conforms to the size of the needle of an insulin pump, the radial expanse of the sensor may amount to 0.15 mm at the most. These dimensions can be realized without any problem with the aforementioned technologies, primarily with the thin-film and the silicon technologies.
Finally, for safety reasons, i.e. in order to safely exclude any damage to the connection cables and to the sensor as well, it is advantageous, furthermore, if the sensor is connected to electrical cables that are embedded in the carrier.
The invention is explained in the following in greater detail with the help of preferred exemplified embodiments shown in the drawings. However, the invention is not limited to such exemplified embodiments. In detail, the drawings show the following:
FIG. 1 is a schematic representation of a measuring device as defined by the invention.
FIGS. 2A, 2B and 2C show the successive phases involved when the catheter-like tube of the present measuring device is placed in position with the help of a setting needle (see FIG. 2A), whereby the setting needle is then pulled back (see FIG. 2B), and a carrier supporting a sensor is then finally pushed into the catheter-like tube (see FIG. 2c).
FIG. 3 shows an axial section through the catheter-like tube with the sensor mounted on the carrier installed in said tube, on a scale enlarged versus FIG. 1.
FIGS. 4 and 5 show cross sections according to the section lines IV—IV and V—V in FIG. 3.
FIGS. 6, 7 and 8 show a modified device conforming to the respective representations in FIGS. 3 to 5, with a longitudinal section (in FIG. 6) and cross sections (in FIGS. 7 and 8), whereby the sensor is arranged in the present case in a recess of the carrier, and whereby the connection cables leading to the sensor are embedded in the carrier.
FIG. 9 shows by a diagram the calibration and the measurement processes, using the present measuring device.
FIG. 1 shows by a schematic representation a device for carrying out in-vivo measurements of quantities in living organisms. Said measuring device as a whole is denoted by 10 and comprises a catheter-like tube, or protective tube, simply referred to in the following as the catheter 11. The selection of the material of said catheter 11 can be based on the experience gained with currently employed vein-dwelling catheters or vein-dwelling cannulas with respect to bio-compatibility, strength, sliding ability, size etc. In its front area, the catheter 11 is provided with the macroscopic apertures 12, which may have a diameter, for example in the order of magnitude of 0.2 to 0.5 mm. At its front, distal end 13, the catheter 11 is pointed in order to conform in this way to an originally inserted setting needle 14 (see FIG. 2A). At its rear, i.e. proximal end, the catheter 11 is provided with a widening 15 in order to receive in said widening a stopper-like base 16 for a tubular, oblong sensor carrier 17. On its outer side near its front, distal end, said carrier 17 supports a sensor 18 drawn only schematically. In the condition in which the catheter 11 is in place in a tissue (not shown) as shown in FIGS. 1 and 3, said sensor is located in the area of the apertures 12. Via the connection cables 19, the sensor 18 is connected to the measuring electronics, concretely to an evaluation and control unit 20, which per se is structured in the conventional manner and needs not to be explained here in greater detail. A display unit 21 is connected to said evaluation and control unit 20. Furthermore, from said evaluation and control unit 20, control lines may lead to pumps, for example to the injector pumps 22, 23. With the help of such pumps, liquids can be pumped through the interior 32 (see FIG. 3) of the tubular carrier 17 and the ring-shaped channel 35 located between the carrier 17 and the catheter 11—see also the lines 24 and 25. This is explained in greater detail farther below.
As shown in FIG. 2A, the catheter 11 is inserted in the tissue with the help of the setting needle 14—see the arrow 26 in FIG. 2A, whereby the distal end 13 of the catheter 11—as mentioned before—ends with a conical shape for the purpose of simplifying the insertion process. After the catheter 11 has been placed in position in the tissue, the setting needle 14 is pulled back—see the arrow in FIG. 2B—and subsequently replaced by the tubular carrier 17 for supporting the sensor 18, for the connections 19 of the sensor 18, and for a seal 28 that may be realized in the form of a sealing ring. This insertion movement of the carrier 17 is indicated in FIG. 2C by an arrow 29. The distal end 30 of the carrier 17, which is simply referred to in the following as the inner tube, and which is open, is formed by the catheter 11—compare also FIGS. 1 and 3 in addition to FIG. 2C. The proximal part of the original lumen of the catheter 11 is separated from the distal part by the seal 28. The distal part, which is referred to here as the lumen 31, is thus forming a new lumen, namely the ring-shaped channel 35.
In order to increase the outlet area of the lumen 32, which is formed by the inner tube 17, the additional perforations 33 are provided in the inner tube 17 near the distal end of the latter. The purpose of enlarging the outlet area is to make clogging of the inner tube 17 more difficult because it is possible that tissue particles may have penetrated the catheter lumen 31 through the distal face side 34 of the catheter 11, or through the front-most perforations provided on the catheter 11. If the device is correctly applied, a substance, and in particular a medication, for example insulin, can be admitted into the lumen 31 formed by the catheter 11 through the inner tube 17, and can be passed on from said lumen into the tissue by way of the distal face side 34 and possibly through the front-most perforations 12′. Such a medication can be (but does not have to be) supplied in response to the measurement taken by means of the sensor 18.
According to FIGS. 1 to 4, the sensor 18 is mounted on the surface (outer side) of the inner tube 17. The connection lines 19 of the sensor 18 may be simply installed on the surface of the inner tube 17, or may be embedded in the latter (compare FIGS. 5 and 6). Said connecting lines 19 are installed extending through the base 16 for the inner tube 17, and lead to the evaluation and control unit 20. The base 16 can be either screwed to or plugged (clamped, for example by means of a Luer adapter) into the catheter 11, i.e. the widening 15 of the latter.
Via the perforations 12, the sensor 18 is communicatively connected with the tissue fluid. Preferably, the sensor 18 is directly located under one of the apertures 12 in order to keep the distance of migration of the tissue fluid as short as possible. Another tube for rinsing and calibrating liquids serving as the conduit 25 is extending through the base 16 for the inner tube 17. Via the ring-shaped channel 35, which is formed by the inner wall of the catheter 11 and the outer side of the inner tube 17, said liquids are received by the sensor 18 and can be directly transferred into the tissue via the apertures 12.
In order to avoid any direct contact of the respective liquid that is admitted via the lumen 32 of the inner tube 17 with the help of the pump 22, with the sensor 18, the seal 28 is mounted between said two spaces for liquid. At the same time, said seal 28 serves as a spacer and guide element when the inner tube 17 is inserted (see FIG. 2C), in order to keep the sensor 18—which is mounted behind it—away from the inner wall of the catheter 11, and to safely avoid in this manner any damage to the sensor 18 while the inner tube 17 is being inserted.
So as to achieve an even higher degree of safety in this regard, provision may be made also—as mentioned before and apart from the embedded connection lines 19 for the sensor 18—to mount the sensor 18 in a recess of the inner tube 17, as it is shown in FIGS. 6 and 7. In all other respects, the embodiment according to FIGS. 6 to 8 corresponds with the one according to FIGS. 1 to 5, so that the description needs not to be repeated.
For the sake of completeness, the procedure followed for calibrating the measuring device is explained in greater detail in the following with the help of FIG. 8.
The sensor 18 is calibrated with the help of a calibrating liquid, which is transported to the sensor 18 by way of the channel 35 between the catheter 11 and the carrier (the inner tube) 17. The calibrating liquid contains in this connection a defined, known concentration of the substance to be measured (in connection with a measurement of the glucose, for example a concentration of 5 mmols/liter glucose). The electrical current of an amperometric glucose sensor 18 set in this process can be associated with said glucose concentration. If the sensitivity "E" of the sensor 18 (current change per change in the concentration in nA/mmol/liter) is known, the concentration of the substance of interest here can be calculated backwards based on the measured current. If the sensitivity of the sensor 18 is not known, the sensor 18 has to be calibrated with two calibration liquids having different concentrations. The sensitivity "E" and the zero current I0 of the system can be calculated based on the known difference in concentration and the resulting difference between the two currents of the sensor 18 at said concentrations.
FIG. 9 illustrates an example of the calibration of a glucose sensor 18 and the subsequent measurement of the glucose. The arrows in FIG. 9 indicate the direction of the information flow; the numerals 1 to 8 conform to the sequence during the calibration and measurement.
The interrelation between a glucose concentration Gx and the associated, measured current Ix can be generally stated in the linear range as follows:
where E is the sensitivity E and I0 is the zero current. By calibrating with two different calibration solutions with the —known—concentrations G1 and G2, and the correspondingly determined currents I1 and I2, it is therefore possible to determine the sensitivity E and the zero current I0 as follows:
With knowledge of the sensitivity E and the current zero current I0, it is, in turn, possible to calculate the glucose concentration Gx acting on the sensor 8 by measuring the current Ix:
From this follows the following procedure for calibrating the system:
(1) Admission to the sensor 18 of the one calibrating medium G1.
(2) Measurement of the associated current I1.
(3) Admission to the sensor 18 of the other calibrating medium G2.
(4) Measurement of the associated current I2.
(5) Calculation of the system parameters E, I0.
(6) Testing of the system parameters for their quantity and change.
(7) Measurement of the current Ix.
(8) Calculation of the corresponding glucose concentration Gx.
If the calibration is carried out at regular time intervals, the operational behavior of the sensor 18 can be determined by changing the sensitivity E and the zero current I0. Changes in the sensitivity E and the zero current I0 may have different causes and consequences: a reduced action of the enzyme; deposits or encapsulation with the body's own substances (protection against foreign bodies). By determining the two quantities (E, I0), it is possible to draw conclusions with respect to the cause, and appropriate steps can be implemented accordingly. If a deposit or encapsulation is found to be present, it is possible to flush it away with the calibration liquid and to restore the original sensitivity. If that is unsuccessful, the useful life of the sensor 18 can be estimated based on the reduction in the sensitivity E or the increase in the zero current I0, and it is thus possible to determine the point in time for replacing the sensor 18 in due time.
The in-vivo calibration represents another advantage of the device described above. In such a calibration, the concentrations determined with the device are compared with blood values. The determination, for example of the glucose from the blood is a standard method and is carried out several times each day by the patient himself. If the relation between the two determined values (glucose determined in the blood in relation to the glucose in the tissue fluid) changes, it is possible to infer from such a change a change in the body. The change may be physiological (time delay between the two signals), but also patho-physiological (inflammation around the catheter 11, reaction of rejection, etc.). Furthermore, such changes may be followed by appropriate steps as well (e.g. replacement of the sensor 18; new insertion of the catheter 11; testing of the system).
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As summer cools down, the Village of Hatch heats up. Labor Day weekend heralds the annual Hatch Chile Festival, a two-day celebration of their world-famous crop. The festival attracts over 30,000 visitors from all over the United States, including such notables as the Food Network and the BBC. Festival goers can sample famed chile recipes, watch the crowning of the chile festival queen, or toss a horseshoe in celebration of our most famous crop. The event also features chile ristra contests, artisan and food booths, and a carnival. For more info visit: http://www.hatchchilefest.com/
This sounds like my idea of heaven, sadly we don't have anywhere in the UK that does anything this, or do we?
If you live in or are visiting the USA and feel like taking a trip to New Mexico to attend this event and need a hotel with a family room/suite to accommodate your big family, check out www.roomfor5.co.uk the biggest, most comprehensive list of hotels/guest houses that have family rooms to sleep 5 or more on the web! And with over 5000 hotels listed in the US alone, you're sure to find something suitable!

subset: commoncrawl


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New JAX® Mice strains
As a worldwide distributor of and repository for thousands of mouse models, our collection of JAX® Mice is increasing by about 700 new strains annually, many of which are listed at the links below or at the right.
Register your interest for awaiting transfer and in progress strains
Complete the web form at the register interest link at the top of the strain datasheet.
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Awaiting transfer from the donor to our facility
We import strains from researchers and facilities worldwide. Once we start the process of acquiring a strain, prospective customers are encouraged to register interest in it.
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The strain development process (i.e., importation, rederivation, and colony expansion) usually takes 6 months or longer. Placing orders for strains under development allows us to better size the colony to meet demand and offers earliest access to new models. Learn more about the strain development timeline. Once a strain arrives at our facility, its "Estimated available for distribution" date is posted on the strain data sheet and will be updated if necessary.
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Notre Dame falls to Watkins Glen
Watkins Glen pulled away in the fourth quarter to beat Notre Dame 57-44 in IAC boys' basketball action Friday.
With the win the Senecas are now tied with the Crusaders atop the IAC Small School Large South standings at 9-1.
Watkins jumped out to a 19-14 first quarter lead but Notre Dame hung in there in the second, out scoring them 14-13. After both teams scored nine points each in the third quarter Watkins used a 16-7 run in the fourth quarter to secure the win.
Darius Garvin had 16 points, nine boards, four assists and two steals to lead the Crusaders while Devon Jackson and Derek Marshall had eight points each. Marshall added three assists.
Brian Hale added four points while Jonas McCaig and Devonte Gaskins had three points each. Sean Brown rounded out the Crusaders scoring with two.
Jesse Teeter led Watkins Glen with 24 while Josh Teeter and Brady Myers had 12 points each.
Watkins Glen won the JV game.
Notre Dame has Newfield and Waverly left on the schedule, hosting Newfield on Tuesday.
Liberty 39, Northeast Bradford 28
LERAYSVILLE - The Mountaineers picked up an NTL crossover boys' basketball win Friday during Northeast Bradford's pink game.
Jacob Spring led Liberty with nine points while J.J. Walker and Cody Fritz added eight points each. Cody Schmouder scored six, Dalton Litzelman added four while Kenny Kreiger and Tyler Upham netted two a piece.
Shawn Hakes led Northeast Bradford with 12 points and three steals on his birthday.
Todd Bonin added seven points while Jordan Goodwin had six points, 10 boards and three blocks.
Elijia Arias added two while Nikolaus Geiser scored one.
Liberty won the JV game 36-14 behind 13 from Dilan Ford. Aaron Pifer led the Panthers with six.
Northeast travels to Sayre Monday.
Williamson 47, Mansfield 42
The Warriors moved one game closer to qualifying for districts as they held off the Tigers in NTL West boys' basketball action Friday.
The win moves Williamson to 9-8 on the year with 11 needed to qualify for districts.
Mansfield led 11-9 after the first quarter but a 14-4 run by Williamson in the second put them up 23-15 at the half. The Tigers out scored them 27-24 in the second half but couldn't get over the hump.
It was a team effort for Williamson as they had five players score between seven and 10 points. Hunter Huyett and Troy Adriance had 10 points each while Canyon Black and Shea Daly added eight. Nick Cevette chipped in with seven.
Kyle Haight and Josh Bradbury rounded out the scorers with two a piece.
Taylor Hillson had 23 points, 11 boards and five steals to lead Mansfield while Reece Correll added seven points, five boards and two blocks.
Bo Burleigh chipped in with six points and seven boards while Dallas Dziuba and Sam Rotella netted three points each.
Mansfield won the JV game 55-40 behind 23 from Ryan Campbell.
The Tigers host Sayre on Wednesday.
Wyalusing 53, Sayre 48
The Rams held on to pick up the NTL East boys' basketball win Friday.
Sayre led 22-15 after the opening quarter while Wyalusing rallied for a 31-29 halftime lead. They would go on to out score the Redskins 22-19 in the second half to hold on for the win.
Jeremy Allyn had a double-double of 22 points and 12 rebounds to lead the Rams while Jonah Shotwell added nine points. Keyshon Gardner added eight while Shane Salsman scored six.
Dylan Bulick chipped in with four while Cody Pickett and Matt Woodruff had two points each. Terron Millard added three steals.
Seth Murrelle led Sayre with 14 points and eight steals while Nick Skerpon had 12 points and six steals. Marshall Higley added seven points while Jeremy Kyc scored four.
Adam Wampole, Joey Galizia and Cuyler Kochin had three points each while Nick Sweet netted two.
Sayre won the JV game 41-37 behind 17 from Sweet.
Wellsboro 69, Cowanesque Valley 25
The Hornets moved one game closer to securing the NTL West title Friday.
Mike Pietropola led Wellsboro with 19 points while Joey Doganiero (16 points) and Dylan Prough (10) were also in double figures. Jordan Jackson added eight points, Matt Reese and Dawson Prough had five each, Nick Marple added four while Kieron Smethers chipped in with two.
Brandon Whitesell and Tyler Melko had six points each to lead the Indians while Bryant Painter added five. Josh Nudd netted three, Nate Bonham and Dakota Corwin scored two points a piece while Luke Plummer rounded out the scoring with one.
Wellsboro JV won.
Athens 55, Troy 43
The Wildcats had three players in double figures as they held off Troy in NTL East boys' basketball action Friday.
Garrett Clark led Athens with 17 points, eight boards, five assists and three steals while Luke Wright added 11 points, six boards and four assists and Dan Moyer scored 10 with eight boards.
Brandon Fauver added nine points with two assists, Robert Fauver scored six with seven boards and two assist with Curt Moore chipping in with two.
Evan Polly led Troy with 16 points while Brandon Mattocks added nine. Jed Wright and Ryan Reeves had seven points each while Chad Cole and Thomas Swain had two points a piece.
Athens won the JV game.
Troy will host Wyalusing on Monday as a make-up.
Waverly 65, Newark Valley 56
The Wolverines held off the Cardinals in IAC boys' basketball action Friday.
Waverly built a 38-24 first half lead but Newark Valley cut it to 46-36 after the third quarter. The Cardinals went on to score 20 points in the fourth quarter but Waverly kept up, adding 19 of their own, to secure the win.
Patric Bronson had 21 points and eight boards to lead the Wolverines while Dylan Perry had 16 points, a career high nine boards and three steals.
Tim Sutton and Zach Cooney had six points each while Cody Marchese added five with nine assists and three steals. Chris Raupers and Ryan McFarland had four points a piece, Matt Lee added two while Alex Uhl netted one.
Waverly won the JV game 73-34 behind 22 from Hunter Bodine while Payton Miller added 16.
The Wolverines travel to Edison Tuesday.
Odessa-Montour 82, Tioga 35
The Tigers fell in IAC boys' basketball action Friday.
Dan Graves led Tioga with 11 points while Dalton Wojcuich added six. John Dougherty scored five, Sam Burns and Dakota Skinner had three each, Zach Worthington netted two while Dylan Babcock added one.
Morgan Shutter had 21 for OM while Ryan Gardner added 20.
Odessa won the JV game 50-44 as Noah Schumacher had 10 points to lead the Tigers.
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text:
A method for fabricating graded refractive index (rugate, optical filters as well as complex rugate filters having prespecified refractive index verses thickness profiles is disclosed. A plurality of at least two different compatable thin film deposition source components of different refractive index, which are stoichiometrically combinable in variable proportion, such as silicon nitride and silicon oxide, or zinc sulfide and zinc selenide, are used to form a thin film material with a refractive index which varies as a function of the proportions of the components. Each source component is separately laser flash evaporated and codeposited on a substrate to form a coating while monitoring the physical and optical thicknesses of the coating, to allow adjustment of the respective laser flash evaporation rates of the source components.
1. A method for fabricating a rugate filter comprising the steps of
providing a predetermined refractive index-thickness profile for a rugate filter,
providing a plurality of at least two different compatible thin film deposition source components of different refractive index which are stoichiometrically combinable in variable proportions to form a thin film material having a refractive index which varies as a function of the proportion of said thin film components therein,
separately laser flash evaporating each of said plurality of source components and co-depositing said thin film source components on a substrate to form a coating on said substrate of varying composition and refractive index while simultaneously monitoring the physical thickness and optical thickness of the coating to provide measured physical thickness and optical thickness values of the coating,
comparing the measured physical thickness and optical thickness values with said predetermined refractive index-thickness profile during deposition, and
adjusting the respective laser flash evaporation rates of said thin film deposition components with reference to the measured physical thickness and optical thickness values and said predetermined profile to conform the physical and optical thickness profile of the deposited coating with the predetermined profile.
2. A method in accordance with claim 1, wherein said simultaneous monitoring of the physical thickness and optical thickness values of the coating is carried out by heterodyning interferometric monitoring.
3. A method in accordance with claim 2 wherein one of said source components is silicon nitride and wherein a different one of said source components is a silicon oxide and wherein said deposited coating comprises a stoichiometric mixture of varying layer composition.
4. A method in accordance with claim 2 wherein one of said source components is zinc sulfide and wherein a different one of said source components is zinc selenide, and wherein said deposited coating comprises a stoichiometric mixture of varying layer composition.
5. A method in accordance with claim 2 wherein one of said source components is aluminum oxide and wherein a different one of said source components is aluminum nitride, and wherein said deposited coating comprises a stoichiometric mixture of varying layer composition.
This invention was made with Government support under Air Force Contract No. DLA900-80-C-2853. The Government has certain rights in this invention.
The present invention is directed to methods and apparatus for the design and fabrication of graded refractive index (rugate) optical filters as well as to complex rugate filters having prespecified refractive index versus thickness profiles.
The term "filter" is used herein in a comprehensive sense to include active and passive absorption devices, transmission devices and/or reflection devices. Typically, such optical filter devices function in a wavelength range which is at least in part within the visible, near UV and/or near IR electromagnetic spectrum range.
Optical filters are conventionally provided by depositing alternating layers of dielectric materials of different refractive index, having the respective layers being of a thickness determined in the desired constructive or destructive interference desired at the wavelength(s) of interest. In order to provide various optical filter functions, a plurality of dielectric stacks each of different optical filtering properties are conventionally provided in adjacent array. However, such composite optical filter devices have disadvantages of undesirably low efficiency and discrimination capability. Improved optical filters of increased efficiency, filter function complexity and/or discrimination capacity would be desirable.
Optical filters are conventionally manufactured by depositing dielectric layers on a suitable substrate, such as a reflective or transparent substrate. The monitoring and controlling of the deposition process is a limiting factor in the manufacture and performance of optical filters.
Monitoring of deposit thickness and refractive index during deposition have utilized reflectance monitoring combined with a crystal thickness monitoring, elipsometric monitoring, interferometric monitoring or a combination of these techniques. Conventionally, reflectance monitoring measures only the optical thickness (nt) rather than the physical thickness (t). In order to obtain individual values for both the index of refraction (n) and physical thickness, a crystal thickness monitor which varies in oscillation frequency with increasing deposit thickness may be used to measure the physical thickness (t) of the deposited films, permitting calculation of the index of refraction from the reflectance monitor. However, crystal monitors tend to have limited accuracy, and can accommodate only a limited deposit thickness. Removing the deposit or replacing the crystal monitor may require breaking of the deposition chamber vacuum, thereby increasing the potential for impurities in the deposited film.
Elipsometric measurement techniques utilize iterative solution of transcendental functions to obtain values for n and t, which prolongs measurement response time and expense, and presents difficulties in respect to deposition-time error correction. In addition, elipsometric measurement accuracy decreases with increasing film thickness, which conventionally may require the use of witness coupons that must be replaced after a short number of fabrication cycles.
Interferometric monitors are also conventionally utilized to control or monitor layer deposition in the fabrication of optical filters. However, while interferometry potentially has several advantages over reflectance and elipsometric monitoring techniques, conventional interferometric monitoring systems have disadvantages with respect to the efficient, rapid and accurate determinationof both refractive index and thickness of the deposited layer(s) of an optical filter during fabrication.
Accordingly, it is an object of the present invention to provide new optical filters, particularly such filters which provide complex optical filtering functions, and methods for designing and fabricating such filters. It is a further object to provide methods and apparatus for rapidly and accurately measuring the thickness and the refractive index of optical filters. It is another object to provide methods and apparatus for fabricating optical filters in which the layer thickness and refractive index are continuously monitored and in which the deposition is controlled in response to the measured thickness and refractive index values. These and other objects wil be apparent from the following description and the accompanying drawings.
FIG. 1 is a schematic illustration of an embodiment of deposition apparatus which continuously monitors the thickness and refractive index of a deposited optical filter, and which controls the deposition parameters in a process controlled feedback loop based on the measured thickness and refractive index, to provide complex graded refractive index filters having a predetermined refractive index/thickness profile.
FIG. 2 is a schematic illustration of the laser flash optical system of the apparatus of FIG. 1 for rapidly and controllably evaporating optical layer materials for deposit during fabrication by means of the apparatus of FIG. 1; and
FIG. 3 is a schematic flow diagram of a system for determining the complex thickness/refractive index profile for a graded refractive index optical filter to be fabricated by means of the apparatus of FIG. 1;
FIG. 4 is a schematic flow diagram of the graded refractive index fabrication system in accordance with the present invention;
FIG. 5 is an enlarged cross sectional view, partially broken away, of an embodiment of graded refractive index complex optical schematic filter together with a graphic representation of refractive index of the substrate and optical filter layer in registration with the thickness dimension of the layer;
FIG. 6 is a graphical representation of the visible and near infrared spectra of an embodiment of a fabricated complex rugate filter, illustrating transmittance of the filter by solid line and reflectance of the filter by dotted line;
FIG. 7 is a schematic view of the thickness monitor of the apparatus of FIG. 1 for continuously and simultaneously measuring both thickness and refractive index during fabrication of an optical filter; and
FIGS. 8A and 8B are, respectively, schematic illustrations of a Twyman-Ggeene heterodyne interferometer and the operation of the spinning halfwave plate and quarterwave plate components of the thickness monitor of FIG. 7.
Various aspects of the present invention are directed to graded refractive index (rugate) optical filters and methods and apparatus for designing and fabricating such filters. Graded refractive index optical filter devices generally comprise film material with a refractive index continuously varying as a function of thickness to provide a desired optical filter functional response. The refractive index variation with film thickness can be designed to cause a reflection or transmission band at a desired wavelength, as will be described in more detail hereinafter.
The attainment of rugate filter bands occurs due to the addition of inphase reflections from multiple layers of varying refractive index. At particular wavelengths, the reflected radiation adds in-phase to provide high transmission or reflection. The design condition for high reflectance is that the period of the rugate structure equals half the wavelength of the radiation to be reflected. For low reflectance, the period should be equal to the wavelength of the radiation to be transmitted. The width of the spectral range over which high transmission or reflection is to occur increases with the amplitude of the rugate index profile. The magnitude of transmission or reflectance increases with the index amplitude and the number of rugate cycles in the coating. This is similar in some respects to conventional stack coatings in which similar relations hold as the difference in index of alternating layers and the number of layers increases. However, there are major differences in the way conventional stack and rugate coatings are physically realized. In rugate coatings, the discontinuous material interfaces are replaced by a controlled homogeneous refractive index profile in the coating. This is achieved by changing the stoichiometry of the material as the film is grown.
Rugate filters provide several significant advantages over quarterwave dielectric stacks. Below is a comparison of properties between the two filters:
______________________________________ Quarter-Wave Stack Rugate______________________________________Structure Many layers of stressed Nearly homogeneous dissimilar materialsOptical Limited to existing film Graded throughIndex materials alloy mixingSelectionBandwidth Limited by practical Very narrow materials indices to >2.5% λrejOptical Limited by number of With increasedDensity (OD) layers to ≦ 3 thickness, higher ODs are achievableField of Comparable to rugates Comparable toview stacksSideband Reduced through complex Substantiallyeffect stack designs Eliminated through gaussian damping of index profileMultiple not practical Multiple bandsrejection (except by sandwiching) permittedbandsPhysical Limited by adhesion, Approaches that ofintegrity residual stress, and monolithic optical thermal mismatch crystalsLaser Limited by dissimilar Potentially veryDamage material interfaces highThreshold______________________________________
Suitable optical filter devices include narrow band reflection filters (high OD), narrow band transmission filters, multi-line (pass/stop) filters, anti-reflection (AR) coatings, high-reflection (HR) coatings, tuned filters, beam splitters, aperture sharing elements, broad stop band filters, and side band suppression filters.
The present invention is also directed to methods and apparatus for fabricating rugate filters having a predetermined refractive index and thickness profile. Important components of the synthesis process include the synthesis system, a real-time monitoring system for measuring both thickness and refractive index during deposition, and a control system for controlling the deposition process based on the measured values. The filter design system is also provided for design of the thickness and composition parameters of rugate filters having preselected optical properties. As synthesis proceeds, the real-time optical monitoring system independently determines the refractive index (n) and the thickness (t). The measured values of n and t are then compared with the desired values (previously stored) and an error signal is generated to drive the process parameters of the synthesis system. The process is continued until the complete filter is fabricated.
The manufacture of optical filters and the like requires the ability to accurately monitor both the thickness and refractive index during deposition of optical film materials. The accuracy and speed with which this monitoring must be accomplished depends on the center wavelength of the filter, the complexity of the index profile, the rate of deposition, and the refractive index of the materials being deposited. In the simple example of a single line filter, the total optical path of one cycle is smaller for shorter wavelengths implying a more rapid variation of the refractive index. Similarly, if high index materials are being deposited, the physical thickness of one cycle is smaller than for low index materials. For more complex index profiles, e.g., a multiline filter, the refractive index is also likely to vary rapidly.
The interferometer reads physical and optical thickness directly and n is determined from a closed form equation involving only one division operation. This means that deposition-time error correction is quite simple. Interferometers are provided in accordance with the present invention which directly monitor the optical filter and its substrate, eliminating possible errors in calibration between the substrate and a witness. The provision of such interferometers permits monitoring of the optical filter throughout the entire deposition process without breaking vacuum. If a heterodyning interferometer is used, as will be more fully described hereinafter, the accuracy is of the order of Angstroms. The speed of operation of such heterodyning interferometers is dependent on the heterodyne frequency, and accordingly, millisecond sampling times may be provided, which are beneficial to rapid and efficient process feedback control.
The determination of the thickness and refractive index profile for a desired rugate device may be carried out, for example, by Fourier synthesis or sinusoidal design techniques. In this regard, computer algorithms may be utilized which take a desired input spectrum, and calculate the refractive index profile that will provide the closest approximation to the desired optical filter function for the intended spectrum by transforming the index requirement from the frequency to the spatial domain. The design of the rugate coating may be defined in terms of four independent parameters: the number of cycles (M), the average index (Nα), the index difference (ΔN) and the period (P).
In the manufacture of a rugate device for a particular spectral filtering purpose, a refractive index versus film thickness profile is calculated which will meet the desired spectral requirements. By such suitable Fourier synthesis or sinusoidal design techniques, the performance of an optical filter for particular parameters of the change in peak-to-peak refractive index, number of modulation cycles, peak reflectivity and fractional bandwidth may be maximized for a selected material system.
The range of the achieveable refractive index for a selected material system is an important factor in the rugate design and performance. In accordance with various aspects of the present invention, multi-maxima graded refractive index optical filter devices are provided in which the refractive index of the device varies along the optical path in a manner which provides a desired optical processing function. Such optical devices will generally have at least about 5, and typically from about 10 to about 100 or more local refractive index maxima in the refractive index profile along the optical path of the optical filter device. By designing suitable refractive index profiles, efficient, as well as complex optical processing functions may be provided. Such refractive index gradations may be produced by depositing materials of varying composition in which the refreactive index is a function of the composition deposited. For example, the system ZnSx Se1-x (mixed zinc, sulfide-selenide) provides compositions to be deposited which vary smoothly in composition and refractive index from that of pure zinc sulfide (ZnS), to that of pure zinc selenide (ZnSe), with appropriately varying refractive index. Similarly, the silicon dioxide-silicon nitride system permits deposition of homogeneous compositions which range from that of substantially pure silicon dioxide (SiO2) to that of substantially pure silicon nitride (Si3 N4). Another useful material system is the aluminum oxide-aluminum nitride system with compositions and refractive indices which range from substantially pure alumina to substantially pure aluminum nitride. A wide variety of other material systems similarly exhibit an index of refraction variation by stoichiometric variation and may be deposited on a suitable substrate in accordance with the present invention to provide rugate optical devices. As will be discussed hereinafter, a wide range of substrate materials may also be utilized for the rugate coating.
Having generally described the various aspects of the present invention, the invention will now be more particularly described with respect to the various specific embodiments of the drawings.
FIG. 1 is a schematic illustration of an embodiment of rugate deposition apparatus 10 which continuously monitors the thickness and refractive index of a deposited optical filter, and which controls the deposition parameters in a process controlled feedback loop based on the measured thickness and refractive index to provide complex graded refractive index filters having a predetermined refractive index/thickness profile. Rugate coatings may be provided which have very high reflectance and increased resistance to environmental and laser damage.
The apparatus 10 may be utilized to produce high reflectance graded refractive index (rugate) coatings on large optical surfaces. As shown in FIG. 1, the apparatus comprises a vacuum deposition chamber system 100 which includes multiple target boats or supports 102, 104 adapted to receive components which are to be evaporated for deposition in the manufacture of rugate optical filters by means of apparatus 100. The substrate 106 on which layers of continuously varying composition, blended from the target materials positioned within the holders 102, 104, is held by substrate holder 108. The target materials in the target holders 102, 104 (such as pure silicon dioxide, and pure silicon nitride, respectively) are evaporated by laser beam introduced into the vacuum chamber 100 through respective optical ports 110, 112. The laser evaporation beam is directed through the ports 110, 112 by a motorized mirror system. The laser beams are provided by laser evaporation apparatus comprising a carbon dioxide laser 114, attenuators 115, 116 and detectors 117, 119, 121, which system will be described in more detail hereinafter with respect to FIG. 2. The apparatus 10 further includes internal shields 118, 120 and a quartz crystal monitor 122.
An important feature of the apparatus 10 is heterodyning interferometer 124 which provides real time measurements for simultaneously determining the thickness and refractive index of the deposited film upon the substrate 106, as will be described in more detail hereinafter. The apparatus 10 further includes control systems for the various components including a shield control system 140 for the shields 118, 120, and a motor control 142 for directing the laser beam mirrors. In addition, a vacuum control 144 is provided to control the vacuum pump system of the vacuumized deposition chamber 100, an interferometer control system 146 is provided for the interferometer 124, a detector control system 148 is provided for the laser evaporation system detectors 117, 119, 121 and an attenuator control system 150 is similarly provided for the laser evaporation system attenuators 115, 116. In a similar manner, as shown in FIG. 1, the carbon dioxide laser 114 is provided with a laser power supply 152 for controlling the output of the laser 114. A stepping motor control 160 is utilized to position the target holders 102, 104 during evaporation of the target materials retained therein, and the output from the quartz crystal monitor is analyzed by a monitor control apparatus 162.
The shield control system 140, the motor control system 142, the vacuum control system 144, the interferometer control system 146, the detector control system 148 and the attenuator control system 150 all indirectly provide data to and receive instructions from a microprocessor control apparatus 170 through a microprocessor interface 172. The stepping motor control, the quartz crystal monitor data input and the laser power supply are all directly under the control of the microprocessor 170 as shown in FIG. 1.
While the illustrated embodiment 10 utilizes a laser flash evaporation system, rugate filters may also be fabricated using other deposition techniques such as chemical vapor deposition (CVD), and physical vapor deposition (PVD) techniques. However, using laser flash evaporation, nearly any metal, semiconductor or dielectric material system can be deposited. Also, virtually any material (at temperatures from ambient to 500° C.) can be used as a substrate, including plastics which must be kept at cool temperatures.
Substrates of large, flat and curved dimensions may be coated using systems such as the apparatus of FIG. 1. Substrates in excess of 20 inches in diameter with curvatures as low as f15 may be coated with uniform rugate films if the substrates are spun at moderate rates. Only the size of the deposition chamber limits the maximum substrate size. Rugate coatings are useful as hardened high reflectance films.
The laser flash evaporation system of the apparatus 10 of FIG. 1 is shown in more detail in FIG. 2. As shown in FIG. 2, the high intensity carbon dioxide laser beam from the carbon dioxide laser 114 is directed to a first mirror M1 through a lens L1 to a second mirror M2 and lenses L2, L3 to provide a highly collimated beam which is split by beam splitter BS into two beams for respective evaporation of multiple components. The first beam is passed through attenuator 115, while the second beam is passed through attenuator 116 which are independently controlled by attenutator control 150 so that the evaporation rate produced by each respective beam is independent of the other. Beam splitters BS1, BS2 provide monitoring beams directed through a chopper apparatus through respective pyroelectric detectors 117, 119 for monitoring the intensity of the respective beams. The evaporation beams are respectively transmitted through ports 110 and 112, and reflected by mirrors M4, M5 to a 4-mirror beam stirring system 240, through respective lenses L4, L5 to mirrors M6, M7 and through the ports 110, 112 of the vacuum chamber system 100.
The computer-controlled Apollo 575W tunable CO2 laser 114 (CW/pulsed/chopped/Q-switched) mounted to the bottom of a 4 foot by 6 foot NRC optical table (with vertical and horizontal isolation legs) is used as the laser source for deposition. All transmitting optics are ZnSe. Mirrors are 99% reflective, coated Pyrex. The CW/pulsed CO2 laser 114 provides high deposition rates and fine control of the deposition process.
The laser beam is steered up and onto the top of the table where it is deflected into the optical path. The resulting 8 mm diameter laser beam is then directed by mirrors M1 and M2 through the beam attenuation optical path. Before attenuation, 5% of the beam is diverted to a calorimeter detector that measures the power of the laser output. This power reading is fed into the control computer 170, and feedback to the laser maintains a constant laser output. The resulting 95% of the light is focused and recollimated.
As shown in FIG. 2, the laser beam is split into two equal components and guided through shutters. Both beams pass through CdTe modulator attenuators 115, 116 to control the power levels of each leg independently. The CdTe modulators rotate the polarization of incoming light as voltage is applied across the crystal. Computer-controlled 0-10,000 V power supplies are used to drive the modulators. The emerging light then passes through a polarizer which causes attenuation of the beam as its polarization changes.
To control the laser power to the deposition materials (power will be different for the two beams), the pyroelectric detectors 117 and 119 (2 J max. energy, S/N=106) sample 5% of each component beam and input their readings to a computer for control of the attenuation levels of the two beams using the input readings and index and thickness information.
The beam steering system (two mirrors for each beam with x, y, z mounts) guides the laser beams to positions above the chamber 100. The beams are then reflected through the top laser ports by mirrors M6 and M7. In the illustrated embodiment, lenses of 30 in. focal length focus the laser beams onto the deposition materials. These materials are evaporated onto the substrate 106 placed 14 in. above the targets.
The two rotating shields 118, 120 protect the laser ports 110, 112 from deposition. The shield window rotates past a small window area. When that area is coated, a clean window section is rotated to the opening, allowing the laser intensity to be reduced by only a miniscule amount.
Two mechanisms work together to expose fresh source material to the laser beam: the sources are rotated and the laser beam is rastered across the source. The source is stepped slowly around at an empirically determined speed to give a maximum deposition rate. After each revolution, a mirror outside the vacuum system diverts the laser beam to a new position resulting in illumination of a new concentric circle on the source. This sequence is repeated until the deposition is complete.
Different refractive indices in the evaporated material deposited on the substrate 106 are obtained by varying the stoichiometry of a deposited material system. The composition of the deposited mixture is controlled by varying the evaporation rates from the two material sources. The evaporation rate can be controlled by controlling laser output power, pulsed beam pulse width and/or pulse repetition frequency.
The choice of a particular control parameter or combination of parameters can affect the overall deposition rate and the composition of the species nucleating on the substrate. Controlling the deposition rate by adjusting the power incident on the source is analogous to direct thermal evaporation where the source is conventionally heated by resistive or e-beam heating, except that only a small portion of the source is heated and a fresh area of unperturbed composition can be continuously chosen for irradiation by scanning the beam across the source surface. The use of this technique to control evaporation rate can in some cases lead to decomposition of the source material. Whether the desired stoichiometry in the film can be obtained will depend on the mixing of atomic constituents in the vapor phase and the mobility of atomic species on the substrate prior to nucleation.
In accordance with conventional practice, compounds having the same composition as the source material have been deposited by control of the pulse rate. To obtain films congruent with the starting material the pulses should be fast enough to prevent decomposition of target material during heating. Therefore, to evaporate molecular species, the peak power pulses should be high enough to flash the molecular species from the target surface in one or a few pulses.
While the refractive index can be controlled by varying the mixing ratio of molecular species on the substrate, considerations other than the refractive index may influence the desired form of the deposited material. Laser output power, pulse width, and pulse repetition frequency all have strong influences on the physical state of a deposited material. For example, long-term compositional stability, mechanical properties and physical integrity of the film can be enhanced by selecting the form of deposition rate control.
In operation of the illustrated embodiment, the Apollo 575 CO2 laser 114 output beam is diffraction-limited and vertically polarized. The minimum spot size of the 8 mm beam when passed through a 30 inch focal length lens, and from the focal length and diameter (from rs =2Fλ/πw) is 0.64 mm. For operation at 20 W (average) power reaching each target, the peak laser power density at the target is 6.2 kW/cm2, 31 kW/cm2 or 180 kW/cm2, depending on whether the laser is operating CW, pulsed or Q-switched, respectively. The laser power at the target is controlled by computer system 170, 150, 152 by applying appropriate voltages to the power supply driving the CdTe modulators.
Minimum pressure of the illustrated system is 5 ×10-9 torr. Typical base pressure for the chamber is 2×10-7 torr, and deposition pressure is typically varied from 7×10-7 torr to 2×10-6 torr.
For a source-to-substrate separation of 14 inches and a laser power of 400 W, the maximum deposition rate is usually between 1000 Angstroms/min and 2000 Angstroms/min. Typical rates during deposition have averaged between 400-600 Angstroms/min.
Both deposition rate and film quality can be affected dramatically by the particle size of the source material. The use of pressed discs as sources resulted in no deposition due to the high thermal conduction away from the irradiated spot, while fine powder proved problematic because of powder eruption. The most satisfactory source configuration that deposited good quality films was 1-2 mm size lumps of powder.
In deposition operation, the substrate can be maintained at temperatures between 23° C. and 500° C. (depending on the temperature limits of the substrate material and/or desired deposition temperature) allowing in situ annealing of the film.
As previously discussed, the desired refractive index profile for a given material system may be calculated from the desired spectral profile of the optical filter by means of an appropriate computer algorithm. The method of calculation is schematically illustrated in FIG. 3. In this regard, the desired spectral profile date 302 (such as the desired filter performance data for a particular input spectrum) and the material constraint data 304 (such as the transmission and refractive index properties of the component materials and intermediate compositions prepared therefrom) may be processed by an appropriate computer algorithm to provide a calculated refractive index profile for fabrication of an optical filter device having the desired spectral profile within a predetermined degree of accuracy. As shown schematically in FIG. 4, the calculated refractive index profile data 308 may be utilized to control the operation of rugate fabrication apparatus to produce the desired optical filter. In this regard, the index profile data 308 may be introduced into a control computer 170 which controls the laser flash evaporation synthesis equipment by means of a process control feedback loop system utilizing data from the real time interferometric measurement of deposit thickness and refractive index to control the deposition process to provide an optical filter having the desired refractive index profile and optical performance. In this regard, illustrated in cross-section in FIG. 5, in greatly enlarged form, is a rugate filter 500 of arbitrary refractive index variation with thickness. The rugate coating 502 of varying composition, such as may be deposited under control of apparatus 10 to prescribed parameters as previously described, is deposited on a suitable substrate 504 of constant dielectric constant. As shown in FIG. 5, the index of refraction (r) of the deposited rugate coating 502 may be varied smoothly and arbitrarily within the limits of the material system components being deposited.
Rugate filters having desirable optical properties may be readily provided in accordance with the present invention. In this regard, illustrated in FIG. 6 are the visible-near infrared spectra of a fabricated rugate filter which has been deposited on a polycarbonate plastic substrate.
As previously discussed, the heterodyning, real-time interferometer for simultaneously determining physical thickness and optical thickness (and therefore, index of refraction) is an important part of the apparatus of FIG. 1. Such interferometers may also find significant use in other deposition and film measurement systems and applications.
As shown in FIGS. 8A, and 8B respectively (G.E. Sommargren, JOSA, 65, 960, 1975), incoming linearly polarized light of optical frequency ν selected to be within the functional spectral range of the optical filter device which is to be fabricated, impinges on a half-wave plate 704 spinning at frequency ω. This causes the polarization vector to spin at 2ω. The incoming linearly polarized light responds as the linear combination of right and left circularly polarized light whose polarization vectors are rotating at ν, such that the spinning half-wave plate 704 upshifts the rotation rate of the left circularly polarizing vector by 2ω and downshifts the rotation rate of the right circularly polarized light by the same amount. When this light is passed through a quarter-wave plate 706 with axis oriented at 45°, The result is orthogonal linear polarization, one upshifted and the other downshifted by 2.
In the interferometer 124, as shown in FIGS. 8A, and 8B respectively the polarized laser light is passed through a frequency shifter as described above, and directed into a Twyman-Greene type interferometer with a polarization neutral beam splitter. In the illustrated embodiment, vertical polarization is selected in the reference leg, and horizontal polarization is selected in the sample leg. After recombining at the beam splitter, a parallel component of each beam is transmitted to the detector through a linear polarizer at 45°. Since these two beams are separated in frequency by virtue of the frequency shifter, a beat or heterodyne signal is seen by the detector. The phase of this signal with respect to that of a signal picked off the incoming beam depends on the relative optical paths of the sample and reference legs. Thus, a change in optical thickness of the sample of 1/2 wavelength will cause a 360° phase shift in the heterodyne signal since the interferometer is double pass.
The thickness monitor 124 utilizing these principles is shown in FIG. 7. The thickness and refractive index data provided by the optical monitor is used in the laser flash evaporation system to control the deposition in real time. The laser beam passes through the frequency shifter and a small portion is diverted by a beam splitter to establish the reference signal. The beam is then directed into the deposition chamber through a high quality fused silica window and steered to the beam splitter. The sample and reference beams are steered to the sample and reference substrates by four mirrors and the appropriate polarizers. The retro-reflected beams recombine at the beam splitter and are detected at the physical thickness detector. The transmitted beams also recombine at the beam splitter and are detected at the optical thickness detector.
As the film grows on the sample substrate, the path length in the retro-reflected sample beam decreases by 2t and the path length of the transmitted sample beam increased by (n-1)t. The resultant phase shift is read by phase meters with an accuracy of ±0.1 degrees. The values of n and t are calculated from these phase shifts throughout the entire deposition.
The illustrated heterodyne interferometer 124 (FIGS. 1, 7) measures both physical thickness and optical thickness in situ, and in real time. The measurements are carried out for each incremental layer, thereby minimizing cumulative errors. The measurement accuracy is estimated to be in the 20-30 Angstrom range.
The optical monitor can be used with almost a wide variety of materials which have at least limited transmission. The physical thickness leg of the interferometer can be used with metallic materials also.
In accordance with the present invention, the composition, deposited thickness and refractory index may be rapidly and accurately monitored and controlled to deposit films which have a predetermined compositional variation along the thickness of the film. This compositional variation in turn provides a graded refractive index profile resulting in desired spectral properties.
To deposit rugate structures, the individual components of a material system are evaporated and subsequently deposited at varying rates, under control of the feedback control system and the measured physical and optical thickness values, which are provided to the real time monitor system. The system has demonstrated a precision of ∓0.2 degrees of phase or ±3 Angstroms and an accuracy of better than ±1% on deposited films.
The use of laser flash evaporation processes for the deposition of thin films may be carried out in a pulsed, or continuous (CW) manner, with the evaporation and corresponding deposition controlled by the laser pulse rate, pulse width and/or intensity. The flash evaporation is easily precisely controlled, with the deposition process stopping substantially immediately with cessation of the laser energy input. Very high rates of deposition may be provided, depending on the material to be evaporated. Contamination free films may be deposited, and the substrate may be maintained at room temperature. Most refractory materials, including substantially all materials that can be deposited by conventional PVD methods may be deposited by Laser Flash Evaporation techniques. Laser flash evaporation processes also produce a minimization of pressure rise in the vacuum chamber, which permit the deposition of thin films in ultra high vacuum. Depending on the particular deposition conditions, reactive sputtering may be conducted in laser flash evaporatin systems. On the other hand, laser flash evaporation may be carried out with elimination of deleterious static charges at high active gas pressures. Laser flash evaporation may also be carried out under conditions which are favorable for the growth of epitaxial layers, and provide for reduction of impurity deposition to a minimum due to inherent cleanliness of the process.
In operation, the interferometer, quartz crystal monitor, and the laser detectors provide information to the computer. These measured values of index, thickness and laser power are compared to theoretical values. Error and change algorithms then drive the CO2 laser and attenuators to give the proper deposition rates of the two source materials which produce the predetermined, desired index of refraction and thickness. The sources, laser port shields, and beam raster mirrors are moved and adjusted to give maximum deposition rate. Vacuum pumpdown and control is also automatic. The system utilizes the starting parameters and a starting prompt to fabricate the desired rugate filter.
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Garmin GPSMAP 3006C Network Bundle DISCONTINUED
This product has been discontinued. It is replaced by the Garmin GPSMAP 3206C Network Bundle.
Receive a $150 MAIL-IN REBATE from Garmin when you purchase this item at Tiger GPS through March 24, 2006! Click for details.
Garmin now offers the GPSMAP 3006C Network Bundle at Tiger GPS. It includes the 3006C display unit, GMS 10 Network Port Expander, GSD 20 Remote Black-Box Sounder Module, and GDL-30A XM Satellite Receiver. Just add a transducer and radar to complete the network. This bundle package saves you over $500 and makes ordering your network easy!
The GPSMAP 3010C and the GPSMAP 3006C launch Garmin into the world of Marine networking, with plug-and-play systems that put GPS, weather, sonar, radar, and other important data at boaters' fingertips.
Both units are waterproof and feature a sunlight readable, 256-color, 640 x 480-pixel VGA display. The screen size for the GPSMAP 3006C is 6.4" diagonal. These multifunction displays (MFDs) are powered by a high-speed processor and graphics controller for fast redraw of charts and weather graphics. They communicate with the Garmin Marine Network through a 100-megabit Garmin-proprietary ethernet-based network. The entire system is waterproof and completely plug-and-play—the MFDs automatically detect any and all peripherals once they're connected. Boaters can connect a GPS antenna and one remote sensor directly to the MFD. Or, with the addition of the GMS™ 10 Network Port Expander, users can connect multiple MFDs and sensors to the same network. Each networked MFD can be configured independently.
A unique feature to the Garmin Marine Network is the addition of the GDL 30 weather data receiver. Through a partnership with XM WX Satellite Weather, mariners can—for the first time—access real-time graphical weather data for the United States directly on the GPSMAP 3010C or 3006C—without the need for a separate PC interface. For those wanting more than 120 channels of XM Satellite Radio along with weather data, Garmin also offers the GDL 30A—which provides a unique audio-channel interface on the 3010C and 3006C that allows for connection to an on-board stereo.
GPSMAP 3000 series products receive sonar data through the GSD 20, a proprietary "black box" sounder which offers 4,000 watts of peak-to-peak power (500 watts RMS) in a dual-frequency transducer. The Garmin Marine Network will be compatible with Garmin's new marine radar that is expected for the 2005 marine season. More information on the radar should be available in late 2004.
The Garmin Marine Network also offers a unique network upgrade system. The user simply prompts the MFD to read the current software version of all components within the network, and writes them onto a Garmin data card. Then the user uploads this data via a PC to the Garmin website, where the newest software versions are downloaded to the data card. The entire system is automatically updated once the card is re-inserted into the MFD.
GPSMAP 3006C Features:
Box Contains:
Image shows multiple MFDs and sensors connected to the Garmin Marine Network
- Designed to support the connection of multiple sensors & GPSMAP 3000 series chartplotters to the new Garmin Marine Network.
- Connections are completely waterproof.
- The switch has LED indicators for individual line status.
- Completely plug-&-play (automatically detects unit at connection).
- 100 Mbit Garmin proprietary network.
- Same network cable for direct unit-to-unit or unit-to-port expander.
- Meets rigid IEC 60529 IPX7 submersible standard.
Seamless Integration: By networking various sensors with the 3000 series plotters, boaters can have complete awareness of what's happening around them.
Easy-to-use: MFDs automatically detect any and all sensors once connected and the data displays on all plotter screens.
Expandable: boaters can connect a GPS antenna and one network sensor directly to the MFD, or, with the addition of the GMS 10, users can connect multiple MFDs and sensors to the same network.
- Wrist / Fitness GPS
- Automotive GPS Units
- Handheld GPS Units
- Chartplotters / GPS
- Fishfinders / GPS
- Motorcycle / ATV GPS
- Two-Way Radio / GPS
- Safety & Tracking
- Camping & Outdoors


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Gear Review
not bad, not great
i liked the helmet for style and fit, however the adjuster wheel for the back strap has very fine teeth and stipped within the first few days of use. found the chin strap easy to use and comfy, rides a little high on the head. The red mammoth logo was serious hit with the little ones...
View More Details on Mammut Skywalker 2 Climbing Helmet


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Below is the poem entitled Lyrics of Light which was written by poet
Fassbender. Please feel free to comment on this poem. However, please remember, PoetrySoup is a place of encouragement and growth.
Read Poems by
Shani Fassbender
Trust, hope, love, and belief is what we all want in the end
Yet unseen scars are bleeding and burning within
Walls of mistrust and misery are closing in
"Time can never mend the careless whispers of a good friend"
Open hearts and minds aren't to blame
Harmony is shattered at a cost
Among ignorance, tolerance is lost
"We're one but we're not the same"
When dust settles and you can again find the path
May your soul gather peace with its journey
May you meet others whose hearts are free
"Just remember you are not alone in the aftermath"
The stars, they may not always align
Though the ones that can, will glow forever
Join them, endure, just be…however
"You just gotta ignite the light and let it shine"
George Michael, U2, Adam Lambert, Katy Perry


text:
An Ode to Springtime
The spring, with lively, lovely paint of every vibrant hue –
Goldenrod, purple thistle, honeysuckle too.
This poet praises not the spring, its sights nor sounds nor smells,
But remedies for allergies which every drugstore sells.
Sudafed, Allegra, Nasonex and Singulair
Without thee, I would stay inside and never smell Spring air.
And praises too for Kleenex, for its soothing soft relief,
Allowing pleasure in each bloom and every greening leaf.
So come thou, Spring! show thy blossoms; flaunt thy plumage true!
Redbud, Dogwood, burst out color! I shan't reply "AAAHCHOO!"


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Tomato Success Kit, Loden
Customers Also Bought
Exclusive | Success Kits Grow Bigger, Healthier Tomatoes – Garden-Tested and Guaranteed!
- The most convenient, foolproof way to grow your own delicious tomatoes
- Self-watering to provide a steady supply of moisture for optimal tomato production
- Container growing reduces weeding and chances of soil-borne disease
- Includes planter, cage support, soil mix and fertilizer
- For easy mobility, add a set of optional casters, sold separately
Our exclusive Tomato Success Kits have helped thousands of gardeners grow big crops of healthier, tastier tomatoes. The self-watering planter has a generous, 4-gallon reservoir that provides a steady flow of moisture to plants. This eliminates the "drought and drown" cycle that stresses plants, helping your tomatoes outperform garden-grown plants by 30% or more. The kit includes a two-part stacking tomato cage and 40 quarts of our exclusive Self-Watering Container Mix. It also includes 1-1/2 lbs. of Gardener's Best Organic Tomato Fertilizer, an 8-5-5 slow-release fertilizer that is fortified with 4-1/2% calcium to help prevent blossom end rot.
- Self-Watering Planter is 26" L x 19-3/4" W x 10-1/2" H
- Tomato Cage is 14-1/2" W x 21-1/2" D x 30" H with 8" legs (38" overall)
- Two 20-quart bags of Self-Watering Container Mix
- 1-1/2 lbs. of 8-5-5 Gardener's Best Organic Tomato Fertilizer (contains meat, bone and blood meals; hydrolyzed feather meal, sulfate of potash and calcium)
- For best results, plant two determinate or one indeterminate tomato
- Tomato plants not included
- Patented
- Gardener's Supply Exclusive
Reviewed by 1 customer
- Clean Look
- Compact
- Excellent results
- Space Saving
- Water-saving
- Shallow Root Zone
Best Uses
- Moveable
- Patio Gardening
- Prevents Shading Crops
- Put It Where The Sun Is
- Saves Room In Raised Beds
I purchased these to make the best use of space in my narrow side yard which is not usable as a vegetable bed but receives tons of sun during the day. Because the tomato kits are movable, you can position your plants next to a wall where they will get lots of heat and the most sun possible. They also prevent the shading of other crops that happens when you plant tomatoes in a raised bed. I can't wait to use them for other crops in the fall/winter. Excellent value. I planted 6" tomatoes 6 weeks ago and they are already taller than the cage and have fruit.
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How It Works
Product InstructionsDownload instructions for Tomato Success Kit as a PDF
There are no special shipping restrictions or charges associated with this item. For detailed information about our delivery methods and charges, click here.
We're proud of the fact that this item is shipped to you directly from our warehouse in Vermont, by one of our 250 employee-owners. In-stock items are packed with care and shipped within the next business day to ensure prompt delivery to your home and garden!


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By John J. KruzelAmerican Forces Press Service
WASHINGTON, Sept. 12, 2008 As a man afflicted with prostate cancer, the top Defense Department military health official has a unique perspective on the importance of promoting awareness about the disease.
Now in his eighth year living with an aggressive form of cancer, Ward Casscells, M.D., the assistant secretary of defense for Health Affairs, understands the importance of early detection. But he realizes the stigma that members of the military culture often attach to certain screening methods.
"It's hard enough to get them to wear a motorcycle helmet," he said in an interview today, which falls almost on the ides of September -- National Prostate Health Month.
The doctor sought treatment in his forties when he began feeling vague discomfort in his pelvic region. After undergoing a colonoscopy, his doctor told him his Prostate-Specific Antigen (PSA) readout -- which measures the protein produced by the cells of the prostate gland, and can indicate the presence of cancer -- was at a normal level.
But by age 49, further testing showed that Casscells in fact had prostate cancer with a PSA level around 94 – well above the healthy average readout of four. In addition, he learned that the cancer had spread to other parts of his body.
Casscells believes that his early tests – a blood test and CAT scan – had been misdiagnosed. He says problems of misinterpretation can be mitigated by patients being prepared to inquire about their health.
"I always have a list of questions, and I don't leave until I get an answer," he said of his regular doctor's visits.
Casscells also urged current and retired military members age 40 to 50 to get a screening, and to consult multiple medical sources. For patients who are deemed "at risk," or who are on "watchful waiting," the doctor recommends changing their diets, becoming more active, increasing their intake of vitamin D. He also emphasized the importance of upping one's exposure to sunlight. "I bought myself a convertible and threw away the sunscreen," he said.
Cancer targeting the prostate is the most common form of cancer developed in men. Accordingly, he said, the onus is on servicemembers to encourage their buddies to seek treatment as their forties approach.
Casscells' story is one of unique intrepidity. After being diagnosed with his potentially terminal cancer, he experienced a common reaction: physical and emotional hardships, some depression, even grief. His response afterwards, however, was anything but ordinary.
The doctor, who had served as the Distinguished Professor of Medicine (Cardiology) and Public Health at the University of Texas Health Science Center in Houston, never missed a day of work. Later, after deploying to Iraq as a doctor in the Army Reserve, he underwent chemotherapy in Baghdad.
After learning that his improved health required a radical change in behavior, Casscells, who described himself as not very athletic earlier in life, adopted a regimen of running and a diet absent meats, despite his appetite for char-grilled burgers. He advocates similar modifications for afflicted, or at-risk, men.
"If I can do it," he said humbly, "anybody can."


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Our webinars give you the chance to learn more about anaphylaxis and have your questions answered by experts. Sign up to participate in the next live webcast, and make sure to watch and share our past webinars.
November 2013 - Ask the Allergist for Registered Dietitians
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August 2013 - Back to School - How to Manage Allergies this School Season
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September 2012 - New Food Allergen Labelling Regulations
May 2012 - Food Allergy Prevalence in Canada