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A fault-tolerant air data and inertial navigation reference system utilizes skewed axis inertial sensors and fault-tolerant redundant electronics to provide higher redundancy with fewer parts. Parallelly operating processor circuits each receive the individual outputs of six skewed-axis gyros and six skewed-axis accelerometers. Each processor independently processes parity equations using the outputs to identify malfunctioning sensors. Further, the output of each processor is transmitted to three parallelly operating voter circuits. The voters are operable to discard a processor if its output does not agree with the majority. The voter outputs are similarly fed back to the processor circuits, which compare these outputs, and discard any voter whose output disagrees with the majority, thus providing a completely integrated system.
1. An inertial navigation reference system, comprising:
a plurality of greater than three redundant gyroscopes, any one of said gyroscopes being skewed with respect to all of the others, each gyroscope being operable to provide an output signal;
a plurality of greater than three redundant accelerometers, any one of said accelerometers being skewed with respect to all of the other accelerometers, each accelerometer also being operable to provide an output signal;
a plurality of redundant processor circuits, each being operable to receive the output signal from each one of said gyroscopes and accelerometers, and to calculate navigational reference signals therefrom, and said plurality of processor circuits operating in parallel so that all of said processor circuits receive said output signals and produce said navigational signals substantially simultaneously; and
a plurality of redundant voter circuits, each voter circuit being operable to receive the navigational reference signals produced by each one of said processor circuits, and to output said navigational reference signals from at least one of said processor circuits to an avionics bus, said plurality of voter circuits operating in parallel so that all of said voter circuits receive said navigational signals from all said processor circuits substantially simultaneously, and further, each voter circuit being further operable to discard the navigational reference signals of a malfunctioning processor circuit; and
wherein each processor circuit is further operable to discard the output signal of a malfunctioning gyroscope or accelerometer, and each processor circuit is still further operable to monitor the output of all of said voter circuits, and to discard the output of a malfunctioning voter circuit.
2. The inertial navigation reference system of claim 1, wherein said plurality of redundant gyroscopes includes six gyroscopes, each of which is skewed with respect to the others.
3. The inertial navigation reference system of claim 1, wherein said plurality of redundant accelerometers includes six accelerometers, each of which is skewed with respect to the others.
4. The inertial navigation reference system of claim 1, wherein said plurality of redundant processor circuits includes at least four processor circuits.
5. The inertial navigation reference system of claim 1, Wherein said plurality of voter circuits includes at least three voter circuits.
6. The inertial navigation reference system of claim 1, wherein said processor circuits are operable to discard a malfunctioning gyroscope by comparing signals from preselected sets of three gyroscopes.
7. The inertial navigation reference system of claim 6, wherein said processor circuits are operable to discard a malfunctioning accelerometer by comparing signals from preselected sets of three accelerometers.
8. A fault-tolerant navigation reference system, comprising:
a plurality of six independent accelerometers, each of which is in skewed orientation with respect to the others;
a plurality of six independent gyroscopes, each of which is in skewed orientation with respect to the other gyroscopes; and
at least four independent but parallelly operating processor circuits, each individual processor circuit being connected to each gyroscope and each accelerometer to receive an output signal from each gyroscope and each accelerometer, and each processor circuit being operable to discard the output signal of any malfunctioning accelerometer or gyroscope, and to calculate navigational reference signals from the output signals of the remaining accelerometers or gyroscopes, so long as at least four accelerometers and at least four gyroscopes remain functional, said processor circuits calculating said navigational reference signals substantially simultaneously.
9. The fault-tolerant navigation reference system of claim 8, further including at least three independent but parallelly operating voter circuits, each voter circuit being connected to each processor circuit to receive the navigational reference signals produced by each processor circuit, and each voter circuit being operable to output said navigational reference signals from at least one of said processor circuits onto an avionics bus.
10. A fault-tolerant navigation reference system, comprising:
a plurality of six independent accelerometers, each of which is in skewed orientation with respect to the others;
a plurality of six independent gyroscopes, each of which is in skewed orientation with respect to the other gyroscopes; and
processor means operable to calculate navigational reference signals from the outputs of said accelerometers and gyroscopes, and further operable to discard the output of any malfunctioning accelerometer or gyroscope, and to calculate navigational reference signals from the remaining accelerometers or gyroscopes, so long as at least four accelerometers and at least four gyroscopes remain functional;
wherein said processor means includes at least four independent but parallelly operating processor circuits, each individual processor circuit being connected to each gyroscope and accelerometer, and operable to receive the output signal from each gyroscope and accelerometer, and to calculate navigational reference signals therefrom, said processor circuits calculating said navigational reference signals substantially simultaneously;
wherein said processor means further includes at least three independent but parallelly operating voter circuits, each voter circuit being connected to each processor circuit, and operable to receive the navigational reference signals produced by each processor circuit, and further, each voter circuit being operable to output said navigational reference signals from at least one of said processor circuits onto an avionics bus; and
wherein each processor circuit is further operable to monitor the output of each voter circuit onto said avionics bus, and to discard the output of a malfunctioning voter circuit.
The present application is a continuation-in-part of an earlier application filed on Oct. 16, 1989, which is identified in the U.S. Patent Office by Ser. No. 422,145, now abandoned.
1. Technical Field
The invention disclosed here relates to inertial reference systems and air data systems that are used for controlling aircraft flight. More particularly, the invention relates to inertial reference and air data systems that have built-in redundancies for avoiding system failure in the event of a fault in one or more components making up the system.
2. Background Art
In the decade between the introduction of the Boeing Company's 747 and 767 models, advances in technology resulted in a two-to-one reduction in cost of inertial reference and air data systems, and a five-to-one increase in the reliability of these systems. These cost/reliability benefits resulted primarily from the development and implementation of "strap-down" inertial reference systems, and digital air data computers used in conjunction with ARINC 429 interfaces.
Boeing's commercial air transports of the current generation (Boeing 757 and 767) use three, independent ARINC 704 strap-down inertial reference units (IRUs) to provide the inertial reference information required for primary flight deck displays, and automatic flight control and navigation. These are respectively indicated at 1, 3 and 5 in FIG. 4, which is labeled "prior art". As would be familiar to a person skilled in the art, each IRU 1, 3, 5 is an independent modular unit having a set of three orthogonally-oriented gyroscopes (gyros), and three orthogonally-oriented accelerometers. Each IRU 1, 3, 5 contains its own processor. Standby attitude is provided by a panel-mounted, self-contained gyro/horizon instrument 9.
Air data parameters for current generation transports are provided by two ARINC 706 air data computers (ADCs). These are connected to conventional pitot tubes and static ports by pneumatic tubing that runs throughout the aircraft. Certain standby air data instruments and other systems, including primary flight control modules located in aircraft tail areas, are also connected to the pitot/static port tubing.
The conventional air data system is not shown in FIG. 4, nor is it illustrated elsewhere in the drawings as it would be well familiar to a person skilled in the art. The skilled person would know, for example, how an air data computer takes static air pressure and ram air pressure data from the static ports and pitot tubes, and uses such data to determine aircraft altitude, airspeed and rate of climb or descent.
In order to achieve significant improvements in the operational efficiency of the next generation of commercial aircraft, it will be necessary to redesign many onboard systems, including the inertial reference and air data systems. The kinds of specific improvements that will be sought lie in the areas of reducing equipment price, maintenance costs, weight, volume and power requirements. Although the current generation inertial reference and air data sensor systems have demonstrated excellent performance, and indeed, have proven to be more reliable than what was initially predicted, the cost of producing these systems, and associated maintenance costs, currently represent significant components of an aircraft's overall operating costs. The thrust of the present invention, therefore, is to provide a functionally better inertial reference and air data system that also provides cost improvements.
To facilitate a better understanding of the development of the invention, reference is first drawn to FIG. 5. The top half of this FIG. shows the major components making up a typical inertial reference and air data system used on modern aircraft, like the current generation Boeing 767, for example. This system is basically divided into two parts: a redundant primary system 11 and a standby system 13. The primary system 11 is redundant in the sense that it includes the redundant IRUs 1, 3, 5 shown in FIG. 4, which make up the inertial reference system 15 shown there, and redundant air data computers 17, 19, which make up an air data system 21. The standby system 13 typically includes a single, panel-mounted gyro/horizon display 23, an altimeter 25 and an air speed instrument 27.
The cockpit display of attitude, airspeed and altitude is regarded as "flight critical". Current regulations require the maximum probability of functional loss for flight critical functions to be less than one in one billion flight hours. This requires extremely high system integrity, the responsibility for which is shared between the primary and standby systems 11, 13.
The IRUs 1, 3, 5 described above are essentially modular units. Each has three orthogonal gyros and three orthogonal accelerometers. A problem with this type of design is that if one gyro or one accelerometer in an individual IRU 1, 3, 5 fails, the entire unit is taken out of service. In other words, one failed sensor can essentially cause the unit's remaining five nonfailed sensors to be wasted.
In order to meet flight safety requirements in the event of an IRU failure, airlines are forced into maintaining large inventories of spare IRUs. For example, a spare IRU, as schematically indicated at 29, may be kept in inventory for each aircraft in service. The primary system 11, including a spare IRU 29, therefore represents a total of twelve gyros (three per IRU), twelve accelerometers (three per IRU) and seven processors.
Seven processors are required because each IRU (four, including the spare) utilizes a processor, and the two air data computers each utilize a processor. Furthermore, although two, redundant air data computers are shown as being included in the primary system 11, the airlines typically must keep a spare 31 in the event of an in-service failure. This makes a total of seven processors required.
As will become apparent, utilization of the present invention reduces the numbers of gyros and accelerometers required, and significantly reduces the number of processors required. Further, as will also become apparent, overall system reliability is increased substantially over current generation systems.
The design philosophy leading to the development of an air data inertial reference system (ADIRS) in accordance with the present invention is schematically illustrated at 10 and 35 in FIG. 5. The significant attribute of the invention is that it retains the classic primary and standby architecture 11, 13 of present-day systems, but proposes a more integrated architecture that features skewed axis inertial sensors, fault-tolerant electronics, and remote air data modules (ADMs). Its fault-tolerant electronic design allows it to be configured at lower cost, and with additional redundancy beyond that required to meet regulatory aircraft dispatch minimums, thus providing the airlines with the option of deferring maintenance until a convenient time.
An important part of an ADIRS system in accordance with the invention is the inertial navigation reference system. This portion includes a plurality of greater than three gyroscopes (gyros), and preferably, at least six gyros in order to meet desired redundancy levels. The gyros are skewed with respect to each other, meaning none are parallel or perpendicular. However, they are preferably skewed in symmetric fashion, in order to facilitate mathematical processing of their outputs.
An inertial navigation reference system in accordance with the invention also includes a plurality of greater than three accelerometers and, like the gyroscopes, the system preferably has six accelerometers. Like the gyros, the accelerometers are in symmetrically skewed relationship With respect to each other.
Implementing the gyros and accelerometers in the above manner provides a way of attaining a much higher degree of functional redundancy while, at the same time, utilizing far fewer parts. The sensor outputs of all gyros and accelerometers are received substantially at the same time by a plurality of four processor circuits operating in parallel. These circuits individually calculate navigational reference signals from the sensor outputs, by processing and comparing the outputs of sets of three gyros and accelerometers. The processor circuits also parallelly output navigational signals to three voter circuits.
The three voter circuits, which also operate in parallel, individually receive the outputs of all processor circuits. Each voter circuit compares the navigational reference signal output from one processor with those of the others, and discards the output from any malfunctioning processor.
The voters further output processor navigational signals onto an avionics bus. However, the output of each voter circuit is fed back to each processor circuit and, prior to output on the bus, each processor checks for malfunctioning in the voter circuits. Voter output is compared in substantially the same way as processor output, and a voter circuit is discarded if it malfunctions.
The avionics bus has three bus terminals, and the outputs of each are likewise fed back to each processor circuit. Each processor circuit checks for malfunction of the bus terminal circuits. If a majority of processors determine that a bus terminal is transmitting data on the bus which is different from what was received from the processors, they cease to supply data to the bus terminal, and shut it down.
Preferably, the processor circuits would also process air data from remotely located air data modules (ADMs), a process formerly performed by discrete air data computers. This would result in complete integration of the redundant components making up the primary system 11 of the current generation ADIRS (see FIG. 5).
A fully integrated ADIRS in accordance with the invention would, like the current generation ADIRS of FIG. 5, have a standby system. The architecture of the current generation standby system 13 has certain attractive features associated with it which should be retained, if possible. First, the standby system is totally dissimilar in design to the primary system 11. Second, it is physically separated from the primary system and can be supplied with independent power and sensor inputs. These two factors minimize the potential of common mode faults.
An ADIRS in accordance with the invention would include a low cost standby attitude and air data reference unit (SAARU), and thus adapts the primary/standby approach of the current generation ADIRS. The SAARU would carry on the desirable features of the current generation standby system in that it would be physically separated from the primary system. Also, to the extent possible, it would preferably have design dissimilarities in order to avoid common mode faults. Regardless, the SAARU would incorporate the above-described fault-tolerant integration of gyros, accelerometers and processors, although at a lower degree of redundancy, meaning fewer of these parts would be used.
The invention provides many potential benefits over and above current air data and inertial reference systems. Its integration of redundant primary reference systems, and multiple standby systems, into a single primary and single standby system, including the use of skewed axis inertial sensors, results in a total system architecture that exceeds the functional integrity of current systems. As mentioned above, this is accomplished by using about half as many parts.
Reduction in numbers of parts is beneficial because it results in a proportional reduction in weight and power consumption. Further, the total number of failures that occur over a given period of time is directly proportional to the number of parts in the system. Reducing part numbers, therefore, inherently results in fewer failures.
The invention provides an integrated fault-tolerant system that can be designed to have any desired level of redundancy, and thus functional integrity. A minimum redundancy configuration is required so that an aircraft can be dispatched following a single component failure in the system. As mentioned above, this permits deferring maintenance until it can be scheduled conveniently at some future time, thus eliminating the current need for airlines to maintain large inventories of spares or other maintenance capability. Increasing redundancy in accordance with the invention may in fact allow dispatch after many failures, and may possibly eliminate all maintenance capability for the system at the airline level.
The invention also reduces the complexity and/or eliminates the need for conventional built-in test equipment (BITE). Most modern digital avionics contain electronic circuits and software algorithms specifically designed to detect and isolate system failures. These BITE systems are typically designed after the basic system is designed, with BITE integration being the last stage in overall system development. It has been found that BITE design, development, integration and certification costs represent a very significant portion of the total nonrecurring costs associated with developing the overall system. Further, problems associated with BITE performance following certification represents significant recurring costs to both the manufacturer and the airlines. The invention disclosed here eliminates the need for conventional BITE systems.
The invention will become more completely understood after consideration of the following description when taken in conjunction with the drawings.
In the drawings, like reference numbers and numerals indicate like parts throughout the various views, except where indicated otherwise, and wherein:
FIG. 1 is a view of a fault-tolerant inertial reference system with deferred maintenance provision in accordance with a preferred embodiment of the invention;
FIG. 2 is a simplified block diagram of the air data inertial reference unit shown in FIG. 1 and illustrates the use of accumulator and memory circuits to process the sensor outputs of a group of six gyros and six accelerometers;
FIG. 3 is a schematic of an overall ADIRS architecture which utilizes the system shown in FIGS. 1 and 2;
FIG. 4 is a schematic illustrating the current generation inertial reference system, and is labeled "prior art";
FIG. 5 is a schematic illustrating the evolution of air data inertial reference systems (ADIRS) from the current generation to that which is provided by the invention disclosed herein showing the current generation in the upper portion of the FIG. and the design of the invention in the lower portion;
FIG. 6 is a pictorial view of a skewed axis sensor assembly in accordance with the invention;
FIG. 7 is a schematic exploded view of the sensor assembly shown in FIG. 6;
FIG. 8 is a schematic view of a three-dimensional space or graph, illustrating how the failure direction of a sensor used in accordance with the invention can be determined from parity equations;
FIG. 9 is a schematic view of a three-dimensional space similar to FIG. 8, but shows an envelope of maximum allowable sensor errors, and normal errors; and
FIG. 10 is a schematic showing the skewed axis alignment of a sensor system in accordance with the invention.
Referring now to FIG. 1, therein is shown at 10 a fault-tolerant inertial reference unit in accordance with a preferred embodiment of the invention. The unit 10 preferably has six gyros, indicated generally at 12, and six accelerometers, indicated generally at 14. The signals from each gyro and accelerometer are substantially simultaneously received by four processor circuits 16, 18, 20, 22.
Referring briefly to FIG. 2, gyro and accelerometer outputs 12a-f, 14a-f may be received and organized in conventional accumulator and memory circuits 36, 38, 40, 42 prior to further processing. Preferably, each gyro 12a-f is a single degree of freedom gyro. The accelerometers 14 are conventional seismic-mass accelerometers having rebalance coils. Although the gyros 12 and accelerometers 14 are skewed, they are preferably skewed in symmetric fashion, as shown at 37 in FIG. 3.
Preferably, each gyro 12a-12f is oriented with its input axis along one of the perpendiculars to six out of a possible twelve faces of a regular dodecahedron. Referring briefly to FIGS. 6 and 7, for example, FIG. 6 shows a sensor assembly 60 in accordance with the invention having six sensor modules 62, 64, 66, 68, 70, 72 in a dodecahedral arrangement. As the skilled person would know, a dodecahedron is a polyhedron having twelve faces. The assembly 60 shown in FIG. 6, therefore, makes up half of an actual dodecahedron. The outer faces 62a, 64a, 66a, 68a, 70a, 72a of each respective sensor module 62, 64, 66, 68, 70, 72 correspond to six out of twelve possible faces of a dodecahedron.
FIG. 7 shows the sensor modules 62, 64, 66, 68, 70, 72 of the FIG. 6 assembly exploded and, in accordance with the preceding description, the input axis of each gyro is positioned along axes 62b, 64b, 66b, 68b, 70b, 72b. Similarly, each accelerometer 14 is aligned along each of the same six axes.
The type of gyro used in the above-described arrangement is preferably a hemispherical resonating gyro, which is well known, and has long been used in the field. Other types of gyros such as, for example, ring laser gyros, could also be used. As mentioned above, conventional seismic mass accelerometers are preferably used to measure accelerations along each of the six axes, 62b, 64b, 66b, 68b, 70b, 72b.
Each processor 16, 18, 20, 22 reads all six gyros and accelerometers, and translates their signals into a mathematically equivalent three-axis orthogonal system that can be related to the pitch, roll and yaw axes of the aircraft. These resultant orthogonal signals are then used to compute aircraft navigational information.
Sensor errors are determined by using parity equations. For example, the sensor output of any one gyro sensor 12a-f or acceleration sensor 14a-f can be mathematically determined using linear algebra from any other group or set of three gyros or accelerometers. Equation 1 below illustrates this relationship where S6 may, by way of illustrative example, identify the output of one gyro sensor in a group of six skewed-axis gyros (as shown in FIG. 10); S1, S2 and S3 indicate the outputs of three other gyros in such system; and a1 -a3 represent linear algebraic co-efficient whose values are easily determined by the physical orientation of sensors S1 -S3 relative to sensor S6.
S6 --(a1 S1 +a2 S2 +a3 S3)=O+P Eq. (1)
If the rate generated in the above equation from (a1 S1 +a2 S2 +a3 S3) is subtracted from the output of S6, it creates a parity equation that is equal to zero plus whatever sensor errors (P) appear on sensors S1, S2, S3 and S6. Ideally, if there are no errors, P should be equal, or nearly equal, to zero.
It is therefore possible to generate a combination of parity equations that make sensor errors observable without having to identify actual rates or accelerations. As mentioned previously, it is desirable that the six gyro or accelerometer sensors used in the present invention be arranged dodecahedrally. The reason for this is that it positions the sensors optimally with respect to each other for facilitating fault detection. Three independent parity equations (set forth in equations 2-4 below) would be sufficient for such a system in order to detect sensor errors.
P1 =a1 S1 +a2 S2 +a3 S3 +a4 S4 +a5 S5 +a6 S6 Eq. (2)
P2 =b1 S1 +b2 S2 +b3 S3 +b4 S4 +b5 S5 +b6 S6 Eq. (3)
P3 =c1 S1 +c2 S3 +c3 S3 +c4 S4 +c5 S5 +c6 S6 Eq. (4)
Once again, the co-efficients a1 -a6, b1 -b6, c1 -c6 in Eqs. 2-4 above represent linear algebraic co-efficients whose values are easily determined from the physical dodecahedral orientation of the sensors. In actuality, and as the skilled person would know, some of the co-efficients may have a negative value, or a value of zero.
The parity equations of equations 2-4 can be graphed in accordance with FIG. 8 to determine sensor failures. Preferably, the value of each linear equation (equations 2-4) is calculated in real time, and plotted in a parity space, also in real time for defining a vector PT.
In FIG. 8, for example, PT is essentially a three-dimensional plot of P1, P2, P3 from an origin. Failure directions for any given sensor are determined by examining the co-efficients of the above parity equations (Eqs. 2-4). A dot product is taken between each of the known sensor failure directions, as determined from the co-efficients of Eqs. 2-4, and the calculated real-time vector. The largest dot product value indicates the closest alignment to the actual measured vector PT. This also indicates the most likely failed sensor.
A threshold of maximum allowable errors is selected (see FIG. 9), and if the dot product exceeds such threshold, then a fault is detected. The actual sensor can be isolated by running dot products relative to sensor failure directions as determined from the parity equations.
Because there are certain normal sensor errors that continually occur, the threshold value for maximum allowable errors must be sufficiently distanced from normal errors. Otherwise, failures cannot be detected reliably without false alarms. This difference is also shown in FIG. 9, where reference numeral 76 indicates the threshold of maximum allowable errors, and numeral 78 indicates normal errors.
Applying the above equations to detect sensor errors, and to discard malfunctioning sensors, is the function of processor circuits 16, 18, 20, 22. Each of such circuits independently processes parity equations 2-4 and determines sensor errors therefrom.
As previously described, each gyro is oriented with its input axis along one of six perpendiculars to the faces of a regular dodecahedron. Similarly, each accelerometer is aligned along one each of the same six axes. Each processor 16, 18, 20, 22 reads all six gyros and accelerometers, and translates their signals into a mathematically equivalent three-axis orthogonal system that can be related to the pitch, roll and yaw axes of the aircraft. These resultant orthogonal signals are used to compute navigation information. Signals from the six accelerometers 14 are processed in the same manner as the gyros 12.
Referring again to FIG. 1, the signals from the gyros and accelerometers 12, 14 are received substantially simultaneously by the processors 16, 18, 20, 22. As mentioned above, conventional accumulator and memory circuits 36, 38, 40, 42 may be used in conjunction With each processor to receive the signals from each sensor 12a-f, 14a-f. Each processor 16, 18, 20, 22 calculates navigational information from the sensors 12, 14 in the above-described manner, and after discarding any malfunctioning gyro or accelerometer 12, 14, outputs navigational signals to each one of three voter circuits 24, 26, 28.
Each voter circuit 24, 26, 28 individually compares the output of each processor circuit 16, 18, 20, 22. To better understand the drawings, the output of processor 16 to voters 24, 26, 28 is identified by lines 16a, 16b, and 16c. Similar outputs from processors 18, 20 and 22 are identified by lines 18a-c, 20a-c and 22a-c, respectively. If the output of one does not correspond to the outputs of the other three (a comparison of 16a, for example, to 18a, 20a and 22a), then the voter circuit logic knows that that processor has malfunctioned (processor 16 in this example), and discards its output.
Further, the voter outputs 24a, 26a, 28a are fed back to each one of the processor circuits 16, 18, 20, 22. Each processor circuit then similarly compares the voter outputs, and if one does not agree with the others, it is discarded. Unless there is a malfunction, the outputs of the voter circuits 24, 26, 28 are transmitted onto DATAC buses 30, 32, 34 via conventional DATAC buffers 44, 46, 48. For a good explanation of the operation and protocol features of a DATAC bus, reference is drawn to U.S. Pat. No. 4,471,481, and the patents cited therein.
FIG. 3 illustrates how the IRU system 10 of FIG. 1 is employed in the architecture of an overall ADIRS system onboard an aircraft 49. Preferably, the system 10 would be a primary system similar to the primary system 11 (see FIG. 5) of the current ADIRS. As indicated previously, the architecture of FIG. 3 would also have a standby system (SAARU), indicated generally at 35. The two systems 10, 35 are physically separated, and preferably can be supplied with independent power and sensor inputs. These two factors would minimize the potential of common mode faults between the two systems.
FIG. 3 illustrates conventional pitot probes 50a, 50b, 50c, a TAT probe 52, angle of attack (AOA) vanes 54a, 54b, 54c, and static ports 56a-f. Air data modules (ADMs) 58 output data from the pitot probes 50 and static ports 56 onto DATAC buses 30, 32, 34. As mentioned previously, the processors included in system 10 are provided with the functional capability of replacing the previous air data computers. The processors in the SAARU 35 may have a similar function. The SAARU 35 has fewer skewed-axis gyros and accelerometers (preferably four), and fewer redundant processors and voters because it is a standby unit.
To summarize, and as was stated previously, an ADIRS in accordance with the invention includes six gyros and six accelerometers. This represents an excess of redundancy over that which is required to meet minimum aircraft dispatch requirements, and provides a "spares in the box" approach, thus allowing an aircraft to remain dispatchable, and fully functional, even after several component failures have taken place. The result is that the time is increased between required maintenance actions because multiple failures of "like" component types must occur before maintenance becomes mandatory. Further, it eliminates the need for "on condition" line maintenance at the airline level; eliminates the need for airline spares; and allows maintenance to be scheduled at the convenience of the airline, all of which reduces costs significantly.
An ADIRS in accordance with the invention is therefore many times more reliable than the conventional IRU system shown in FIG. 4. The reason for such reliability is that any three gyros can be used with any three accelerometers to provide navigational functions. When a gyro or accelerometer fails, it may be taken out of service without significantly degrading the navigation function of the ADIRS. By way of comparison, in the system of FIG. 4, for each IRU 1, 3, 5 shown there, each must have six fully-operational sensors (three gyros and three matching accelerometers) to have a functional system. Loss of one sensor out of the six, whether it is a gyro or an accelerometer, takes the entire IRU out of service, thus wasting the remaining five sensors.
As is evident from the sensor assembly 60 shown in FIG. 6, each sensor module 62, 64, 66, 68, 70, 72 is physically partitioned to facilitate the separation and mechanical replacement of a failed component part. The processor 16, 18, 20, 22 and voter 24, 26, 28 portions of the ADIRS are preferably physically configured in similar fashion.
An ADIRS in accordance with the invention assumes full responsibility for determination of its own health. Thus, the ADIRS' redundant resources are used to detect and isolate failed modules, and to reconfigure themselves to use only healthy modules. Fault detection and isolation using comparisons of redundant modules and/or majority voting provides high coverage, approaching 100% for random faults, so long as a minimum number of healthy redundant modules remain. This high integrity fault coverage and diagnostic capability eliminates the need for complex shop test equipment or test programs. Also, no voting in user subsystems such as autopilot, FMC, auto-throttle, etc. is required.
The description set forth above is the currently-known best way to carry out the invention. It is to be understood and appreciated that the preceding description is not to be taken in the limiting sense. Further developments in the technology relating to the advanced ADIRS disclosed herein may reveal that there are alternative ways of implementing the invention which provide better performance or otherwise have certain attributes which are more desirable. For these reasons, the invention is not limited by the preceding description, but is to be limited only by the subjoined patent claim or claims, wherein such claims are to be interpreted in accordance with the conventional, well-established doctrines of patent claim interpretation.
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A fiber optic based probe has been designed to sample the fluorescence or phosphorescence signal from animal or human tissues, such that the light intensity is not multiply scattered. This type of measurement allows a linear detection of the concentration of the luminescent compound non-invasively from the tissue. The basic principle of the fiber probe is to use fiber optics which are smaller in diameter that the average scattering length of the tissue. In order to increase the detected signal to a stronger level, multiple fibers are used by spacing them out on the surface of the tissue so that each fiber samples an isolated section of tissue. Each fiber delivers the excitation light to the tissue, and receives the emission light from the tissue. All fibers are coupled into the same detector to integrate the overall signal. Sampling of the scattered excitation signal intensity is also done to correct for changes in the scattering coefficient between tissues. This fiber bundle can be used to quantify the concentration of fluorescence or phosphorescent chemicals in vivo non-invasively. One application of this device is as a dosimetry tool, to monitor photosensitizer drug concentration within tissue for photodynamic therapy.
1. A method for detecting fluorescence or phosphorescence signals from a tissue sample containing a fluorophore or phosphor concentration therein, the method comprising the steps of:
providing an optic probe for detecting luminescence from a tissue sample containing a fluorophore or phosphor concentration therein, the optic probe having a plurality of optic fibers maintained in a bundle, each of the plurality of optic fibers having,
a first end where the fibers are arranged in a substantially contiguous array and collectively form a first bundle end, and
a tissue contact end where the fibers are arranged in a spaced apart arrangement at a substantially constant minimal spacing between near neighbor fibers, the spaced apart arrangement forming a tissue contact bundle end for placement against the tissue sample;
aligning the first bundle end with an optical detection device;
placing the tissue contact bundle end with a site on the tissue sample;
passing an excitation light through the optic fibers; and,
monitoring fluorescence or phosphorescence transmitted through the optic fibers from the tissue sample with the optical detection device.
2. A method for detecting fluorescence or phosphorescence signals from a tissue sample containing a fluorophore or phosphor concentration therein, the method comprising the steps of:
providing a plurality of optic probes, each optic probe having a plurality of optic fibers maintained in a bundle, each of the plurality of optic fibers having,
a first end where the fibers are arranged in a substantially contiguous array and collectively form a first bundle end, and
a tissue contact end where the fibers are arranged in a spaced apart arrangement at a substantially constant minimal spacing between near neighbor fibers, the spaced apart arrangement forming a tissue contact bundle end for placement against the tissue sample;
aligning the first bundle end of each of the plurality of optic probes to an optical detection device;
placing the tissue contact bundle end of each of the plurality of optic probes with the tissue sample;
passing an excitation light through the optic fibers;
monitoring fluorescence or phosphorescence signals transmitted through the fibers of each of the optic probes from the tissue sample with the optical detection device; and,
integrating said fluorescence or phosphorescence signals.
3. An optic probe for detecting luminescence from a tissue sample containing a fluorophore or phosphor concentration therein, the optic probe comprising:
a plurality of optical fibers maintained in a bundle, each of said plurality of optic fibers having,
a first end where said fibers are arranged in a substantially contiguous array and collectively form a first bundle end, and
a tissue contact end where said fibers are arranged in a spaced apart arrangement at a substantially constant minimal spacing between near neighbor fibers, said spaced apart arrangement forming a tissue contact bundle end for placement against the tissue sample.
4. The optic probe of
5. The optic probe of
6. The optic probe of
7. The optic probe of
8. The optic probe of
9. The optic probe of
10. The optic probe of
11. The optic probe of
12. The optic probe of
13. The optic probe of
This application claims benefit to provisional application No. 60/101,407 filed Sep. 22, 1998.
This invention consists of an improved method for the use of fiber optics as a means to evaluate human and animal bodily tissues.
Fluorescence detection from tissue is increasingly being used as a diagnostic probe to either detect early cancer, to monitor treatment dose in photodynamic therapy, to monitor fluorescent drug pharmacokinetics, or to assay for fluorescent reporters of metabolic processes. It is well recognized that the pigments of a tissue may reduce the intensity of a light signal, so that fluorescence measurements from one sample cannot be directly compared to another without some type of empirical calibration. Also variation in blood flow and tissue heterogeneity can confound a series of fluorescence measurements, due to the fact that the excitation and fluorescent light are multiply scattered. At present there is no standard method for quantitative tissue fluorescence measurement in vivo, and many investigators rely upon the use of radioactive labeling or tissue extraction methods to yield quantitative drug uptake measurements. A new type of fiber optic probe has been developed and tested here in tissue-simulating phantoms, which is insensitive to the local background absorbing molecules, and detects fluorescence signals which are linearly proportional to the fluorophore concentration. This design allows quantitative measurement of fluorophore concentration for certain applications, and minimizes the need for expensive and time consuming tissue extraction or radio-labeling methods. This fiber optic method may allow non-invasive quantification of fluorescence for any applications where the inter-sample variations of tissue optical properties affect the measurements.
The prior art teaches that most tissue fluorescence measurements use large core fiber bundles, or separate source-detector fibers which allow the excitation and emission light to be multiply scattered in the tissue, and hence the fluorescence intensity is affected by the long pathlength of travel in the tissue. One practical approach to quantitative tissue fluorescence measurements has been to use relative fluorescence as a ratio at two different wavelengths, or from comparing the fluorescence intensity of two different species present in the tissue. These approaches suffer from problems in calibration and wavelength variations in the tissue optical properties; hence, the measurements must be carefully interpreted. Alternatively, several researchers have developed models of fluorescence propagation in tissue to predict fluorescence signals from multiple scattering samples such as tissue for a given fluorophore concentration. By applying time-resolved or frequency-domain instrumentation, the lifetimes and concentrations of a fluorophore can be calculated, assuming that the light propagation in the tissue can be accurately modeled by diffusion theory, or with Monte Carlo scattering models. The diffusion theory approach has the constraint that the region of tissue sampled needs to be sufficiently large and homogenous. The Monte Carlo approach is generally used to exactly model the tissue geometry with boundaries and changes in optical properties at the microscopic level. This latter approach can be very successful, but is limited to applications where the tissue properties and layers are well understood. Both of these methods require some apriori knowledge about the tissue in order to quantitatively estimate the fluorophore concentration from the detected signal.
Alternatively fluorescence measurements can be obtained from tissue using very small sample volumes, and by confining the region of tissue probed to a diameter smaller than the average scattering length, where the effects of tissue scatter and absorption can be minimized. This latter approach has the benefit of significantly minimizing the tissue effects upon the detected fluorescence signal so that intensity variations due to the tissue intrinsic chromophores are not detected. Practical implementation of this approach requires limiting the detected volume of tissue to a region smaller than the typical mean free path for scattering in tissue, which is approximately 100 microns (a micron is equal to one millionth of a meter). While limiting the volume of tissue sampled can significantly lower the detected fluorescence signal, current light detectors can be used to quantify fluorescence from sub-micromolar levels of some photosensitizers. This concept was demonstrated using confocal detection both in tissue phantoms and excised tissues. This study extends that work to examine the use of small fiber optics to measure minimally scattered fluorescence from tissue-simulating media in this manner. To realize this experimentally, a new fiber optic bundle is demonstrated which allows detection of fluorescence from confined regions of tissue, while sampling from multiple locations simultaneously to maximize the detected signal. Applications of this system will likely be in non-invasively measuring luminescent drugs taken up in vivo, and monitoring pharmacokinetics of fluorescently labeled metabolites non-invasively.
A new design for a fiber optic bundle was demonstrated to measure fluorescence signals from tissue, where the intensity of the signal is not significantly affected by the medium's absorption and scattering coefficients, and hence only depends upon the fluorophore's properties. Monte Carlo simulations of light scattering were used to design and verify the results obtained. The fiber optic bundle was tested on tissue-simulating phantoms and compared to the use of a standard non-imaging fiber optic bundle. The new bundle was composed of 30 individual 100 μm ("μm" is used as the abbreviation for diameter in microns) fibers, where each fiber was separated by approximately 1 mm ("mm" is used as the abbreviation for millimeters) from each other fiber on the end of the bundle which contacts the tissue surface and are without separation on the opposite end. This design allows integration of the signal over several locations, while maintaining localized sampling from regions smaller than the average mean free scattering path of the tissue. The bundle was tested by measuring fluorescence signals from tissue-simulating solutions containing a fluorescent compound. These studies demonstrate that the new bundle reduces the effect of the intrinsic absorption in the medium, allowing detection of fluorescence that is linearly proportional to the fluorophore concentration.
FIG. 1. Schematic diagram of the geometry for both Monte Carlo simulations and experimental measurements of fluorescence from an individual fiber 1 in contact with tissue-simulating media 2. Both excitation (dark arrows, 3) and fluorescence (light arrows, 5) can be captured by the fiber optic 6 when in contact with the medium. Fluorescent events (stars, 4) occur when the photon is absorbed by the fluorophore.
FIGS. 2a-2 f. Monte Carlo simulations of excitation fluence in the medium (FIGS. 2a-2 c) and fluorescence fluence that is captured by the fiber optic (FIGS. 2d-2 f). The left pair of images (FIGS. 2a and 2 d) show the excitation and captured fluorescence fluence for a broad beam illumination from the surface. The middle pair of images (FIGS. 2b and 2 c) show the same calculations for a 2 mm diameter fiber optic, and the right pair of images ( FIGS. 2c and 2 f) are for a 100 μm fiber optic. Scattering media properties were fixed at μs /=10.0, μa=0.01 mm−1, and g=0.90. (Note "μs /" is used as the abbreviation for reduced scattering coefficient; "mm−1" is used as the abbreviation for units of inverse millimeters; and, "μa" is used as the abbreviation for absorption coefficient or absorption concentration.)
FIG. 3. Theoretical calculations (Monte Carlo) of the average number of scattering events in the detected excitation signal and the detected fluorescence signal versus fiber optic radius. Medium optical properties were as in FIG. 2.
FIG. 4. Schematic diagram of the apparatus, including an enlarged view of the end of the fiber optic probe 7 designed for these measurements. The fiber optic bundle 8 consisted of 30 individual fibers, each 100 μm core diameter, with the interfiber separation increased to 1 mm average on the tissue contact end, and without any separation on the opposite end. Excitation light 9 from an Argon laser 10 was delivered to the fiber bundle by reflection from a dichroic mirror 11. The captured fluorescent light was transmitted through the dichroic, and collected by a lens system 12, through a rejection filter 13, and into a fiber coupled 14 photomultiplier tube 15. The current from the photomultiplier tubes was measured with an oscilloscope terminated in 50 Ohms, and the intensity in mV ("mV" being the abbreviation for "milli-volts") for each measurement is plotted in FIGS. 5(b) and 6. A single fiber 16 was used from the bundle to sample the excitation light intensity reflected from the tissue surface, by filtering out the emission light 18 and detecting the intensity with a second photomultiplier tube 17. The system was tested on tissue-simulating solutions with a fluorophore added to it.
FIG. 5(a). Monte Carlo calculations of fluorescence detected from a fiber optic at the surface of a scattering medium, μs=10.0 mm−1, g=0.90, using both a 1 mm simulated fiber and a 100 μm simulated fiber. A range of fluorophore absorption coefficients were used with two different endogenous absorption values of (μa=0.003 mm−1 and 0.03 mm−1.
FIG. 5(b). Fluorescence measurements from two similar sets of tissue-simulating solutions containing serial dilutions of fluorophore, with one set containing no absorber (μa=0.0026 mm−1), and the other containing 1.5% ink (μa=0.073 mm−1). Measurements were taken both with a standard 1 mm fiber bundle and with the new fiber bundle depicted in FIG. 4 using separated 100 μm fibers.
FIG. 6. Fluorescence (at 650 nm) ("nm" is the abbreviation for "nanometer" which is equal to one billionth of a meter) and scattered excitation light (at 488 and 514 nm) were detected from several solutions, all containing a constant 62 μM of fluorophore, but with increasing concentration of Intralipid, and hence increasing scattering coefficient. Here the ratio is plotted of fluorescence/scattered light. The background absorption coefficient was also constant at 0.01 mm−1.
The invention includes a fiber probe that is used with fiber optics smaller in diameter that the average scattering length of the tissue. The detected signal is increased through the placement of multiple fibers on the surface of the tissue so that each fiber samples an isolated section of tissue. Each fiber delivers the excitation light to the tissue, and receives the emission light from the tissue. All fibers are coupled into the same detector to integrate the overall signal. Adjustments to excitation signal intensity are performed to correct for changes in the scattering coefficient between tissues.
The goal of the experimental work was to develop a small fiber optic system which could be used to deliver excitation light to a tissue sample and to detect the emission from the same fiber using fiber optics of 100 μm or less. Preliminary attempts to develop such a system were limited by the minimal light which was captured by the fiber resulting in a very noisy signal. As a more practical approach, a novel multi-strand fiber bundle was developed to increase the light detected signal while maintaining isolated sampling of fluorescence from the tissue (schematic shown in FIG. 4). Monte Carlo simulations shown in the Results section, indicated that if each fiber was separated by more than a 500 μm radius center-to-center from the other fibers, there would be less than 10% interaction (or crosstalk through the tissue) between the signals from the fibers. The exact level of crosstalk would depend on the optical properties of the tissue, in that more highly scattering or highly pigmented tissues would attenuate the light more and decrease the inter-fiber crosstalk through the tissue, and vice versa.
The prototype multi-strand fiber was constructed with 100 μm fiber optics, using an inter-fiber spacing between 0.5 mm to 1 mm on the tissue contact surface (see FIG. 4). A total of 30 fibers were included in this bundle, and light was coupled into and out of the fiber with a standard fluorescence microscope arrangement of a dichroic mirror and rejection filter. The excitation beam was directed onto the end of the multi-strand fiber bundle, with approximately 1 mm diameter. The emission light was captured from the end of the fiber bundle after passing through the dichroic mirror and onto a focusing lens. A rejection filter removed the scattered excitation light, before the beam was then focused into another fiber which lead to the photomultiplier tube detector. A multi-line argon laser, running at approximately 20 mW, was used as the excitation source, and the fluorescent compound used was sulphorhodamine B (Exciton Inc., N.J.) dissolved in a stock solution of 5 mM in ethylene glycol. This fluorescent dye was chosen simply to illustrate the potential of the system with a standard small Argon laser for excitation, while more physiologically relevant dyes can be used with another laser source for excitation. The dye has a high extinction at 488 and 514 nm, the excitation maximum of the laser, and has a peak fluorescence emission at 635 nm with fluorescent quantum yield of φfl=0.7. The tissue simulating samples were mixed with 1% Intralipid by volume, which is a well known tissue-simulating medium, with scattering coefficients of 7.9 mm−1 and 4.7 mm−1, at 514 nm and 635 nm respectively. In order to simulate the absorbing pigment present in tissue, such as melanin or hemoglobin, an inert absorber was needed, and India ink was used for this case since it has a relatively constant absorbance across the visible spectrum. Preliminary measurements were taken to assess the absorption coefficient of the ink, and it was found to be 5.0 mm−1 for a 1% stock solution by volume, at 633 nm. The wavelength variation over the region 514 to 635 nm is less than 5%. Two series of solutions were prepared with serial dilutions of the fluorophore, one with no ink present (μa=0.0026 mm−1) and one with 0.1 ml of the ink stock solution added to each 7 ml sample (μ1=0.073 mm−1). While the absorption coefficient of different tissues varies considerably, this range of coefficients agrees well with skin, brain, and fat over most wavelength ranges and muscle and liver, in the red region of the spectrum. A more detailed study is needed for application in darker tissues such as liver and muscle in the blue-green region of the spectrum.
Each tissue-simulating sample was measured for fluorescence with the new fiber bundle, and with a standard 1 mm fiber bundle (Edmond Scientific, Barrington N.J.) for comparison. The standard fiber bundle was a multi-strand quartz fiber bundle of 50 micron fibers with no coherence preservation, with a total outer diameter of 1 mm.
Monte Carlo simulations of the fluence in the medium are shown for three different fiber diameters, in FIG. 2. In the upper three panels, the excitation fluence is reported for an infinite incident diameter (left), a 2 mm incident diameter (middle), and a 100 micron incident diameter fiber (right). The lower three panels depict the fluorescent fluence which is eventually captured by the fiber for the same three fiber diameters, respectively. This latter fluence was calculated by selecting only those photon paths which end up passing into the fiber after scattering in the medium. These simulations required 107 photon packets, which took 30 minutes of computation time for each image on a 233 MHz Pentium processor.
Simulations were completed for a series of fiber diameters between 100 mm and 20 μm where the average number of elastic scattering events in both the excitation signal and the fluorescence signal were calculated. The results are plotted in FIG. 3. Optical properties of the medium were the same as in FIG. 2. Photon packets which re-entered the fiber were counted in the simulation, and binned as either excitation or fluorescent photons. The number of elastic scatter events that each photon packet underwent before detection was recorded, and multiple packets were averaged to obtain statistics on the number of elastic scattering events in the signal. This was repeated for each particular fiber radius simulated.
Simulations were used to calculate the intensity signal detected from a fiber optic using the same medium optical properties as above for a series of fluorophore concentrations using both a 1 mm fiber optic and a 100 μm fiber optic. These calculations are plotted in FIG. 5(a), as a theoretical comparison to the experimental measurements. Two different endogenous absorption values were used for each fiber size, first with μa=0.003 mm−1 and with μa=0.030 mm−1 (corresponding to low and high absorption in the FIG. 5(a)).
Measurements using the fiber optic system shown in FIG. 4 were taken with solutions of 1% Intralipid, with increasing amounts of sulphorhodamine dye. The fluorescence versus dye concentration was measured for two different concentrations of India ink in solution (to simulate endogenous absorber). The fluorescence measurements were repeated for a standard 1 mm diameter fiber bundle for comparison. All of these measurements are plotted in FIG. 5(b). The data of fluorescence versus fluorophore concentration is linear when the slope on the log-log graph equals 1.0, and the slopes for the standard fiber optic bundle used here are 0.82 and 0.89, corresponding to high and low absorption coefficient respectively (FIG. 5). The slopes of log fluorescence versus log fluorophore concentration are 0.98 and 1.00 when the new fiber optic bundle is used, for low and high absorption respectively (FIG. 5).
Reflected excitation intensity was also recorded in order to monitor variations in the scattering coefficient of the medium. There was no variation in the ratio of fluorescence/scatter when the background absorption coefficient was changed over the range of μa=0.0026 to 0.073; however, changes in the scattering coefficient of the medium can alter this ratio. In FIG. 6, the ratio of fluorescence to scattered excitation detected intensities are plotted for a series of solutions, containing the same amount of fluorophore in each (62 μM of the sulphorhodamine B) but with increasing amounts of Intralipid, to change the scattering coefficient. There is a correlation between the two signals, suggesting that the simultaneous measurement of scattered excitation light in parallel with the fluorescence measurement can be used to normalize the detected fluorescence from the tissue. While the ratio of these two signals is not constant, especially at low scatter coefficients, it may be used to calibrate for differences in fluorescence due to changes in the scattering coefficient of tissue. In this case, the scattering signal is smaller than the excitation simply because only one fiber was used for the scattering detection, while 30 fibers were used for the fluorescence collection (see FIG. 4).
The goal of this study has been to examine the theoretical foundations of micro-sampling of tissue fluorescence for quantitative measurement, and the practical development of a fiber bundle which can accomplish this.
Monte Carlo simulations of the fluorescent light detected from fiber optics give an illustrative prediction, while allowing variation of parameters such as fiber radius, tissue optical properties and fluorophore properties. The simulations used in this study are somewhat idealized, however the results indicate promising results for sampling fluorescence from tissue with small fiber optics. In general, as the size of the fiber decreases to smaller than the mean free path in the tissue (1/ μs), then the signal is weakly attenuated by the tissue itself. FIG. 3 shows that when a 100 μm fiber is used that the average number of elastic scattering events in the fluorescent signal is less than 1. This calculation indicates that the average path of the fluorescent signal in tissue is perhaps a distance of 1=100 μm, which according to Beer's law (I=Io exp(−μa1) ) would have an overall attenuation of 5%, assuming μa=0.05 mm−1 which is a high value for most tissues. Interestingly, if tissues with higher attenuation are to be used, the fiber diameter could be reduced further to minimize effects of absorption in the tissue. Since fiber optics as small as 10 microns are commercially available, measurement of weakly-scattered fluorescence signals from most tissues should be possible. It should be noted that using small fiber optics to sample the fluorescence in this manner limits the depth sampled in the tissue, so that the applications of this method may be limited ultimately to the surface layers of tissues.
The multi-strand fiber optic probe was developed to increase the intensity of the detected fluorescent light from the tissue. Ideally single fibers could be used, but the detected fluorescence is too low when typical metabolic concentrations of fluorescent dyes are used. The Monte Carlo simulations indicated that for the tissue optical properties used in FIG. 2, that a fiber separation of 0.5 mm would be sufficient to lower the inter-fiber exchange of fluorescent light in the tissue to less than 10%. This estimate is based upon Monte Carlo calculations of the exiting intensity at a distance 500 microns away from the excitation fiber, for μa=0.01 and μs=1.0. Changes in the tissue optical properties will definitely alter this amount of crosstalk, however it should be noted that these coefficient values are relatively low, and any increase in absorption or scattering will simply decrease the inter-fiber cross talk. In the fiber design here, this distance was taken as a minimum, and the actual distance between fibers was between 0.5 and 1 mm.
The measurements of fluorescence plotted in FIG. 5(b) demonstrate that for solutions with a higher background absorption concentration (μa=0.074 mm−1) that the detected signal is lower than for solutions with less background absorption (μa=0.0026 mm−1). In this case, the measurements from the two sets of solutions with the standard fiber bundle (FIG. 5(b) also) differ by 40% on average, whereas the measurements with the specially designed fiber bundle differ by 10% on average. The use of even smaller fiber optics are expected to lower this difference even further. The simulation results plotted in FIG. 5(a) are in good qualitative agreement with the experimental results in (b), as the change in intensity with absorption coefficient of the sample is similar. There are quantitative differences in the experimental and simulated values, but in general the larger fiber demonstrates a sensitivity of the detected intensity to the medium's absorption coefficient, while the small 100 micron fibers minimize this effect.
It should be noted that the scattered excitation signal is sampled from a single 100 micron fiber which is adjacent to one of the excitation fibers, so that the signal has traveled through a thickness of tissue which is larger than the sampled path of the fluorescence signal. This design was used because there is no good method of sampling the scattered light from the same fiber which delivers it, without having significant reflections from both ends of the fiber which will confound the signal.
In summary, it should be noted that the concept of reducing the volume of tissue sampled can lead to quantitatively consistent measurements of fluorescence, independent of the background (or endogenous) absorption present. The system outlined here will be useful to monitor the concentration of photosensitizers taken up in tissues, monitor pharmacokinetics and photobleaching rates in vivo without the need for tissue extraction, or possibly to monitor DNA or protein stains in situ for animal models. The excitation laser to allow excitation of photosensitizers at 440 nm wavelength, improving the optical alignment to allow more light to be captured, and using a series of bifurcated optical fibers to allow easier separation of the scattered excitation light and remitted fluorescence. Previous calculations suggested that this method could be used to detect quantities of fluorophore near 10−7 Molar, assuming that an optimized optical system is developed for light collection, and can likely be lower when multiple fibers are used to integrate the signal over larger tissue regions.
The measurement of fluorescence signals from tissue is complicated by photochemical changes in the fluorescence quantum yield, and attenuation of the light by the tissue. While this fiber optic bundle cannot help deduce changes due to the physiochemical environment of the fluorophore, it can help reduce the effect of the light attenuation in the tissue. Thus as applications for fluorescence detection from tissue become more sophisticated, the ability to separate tissue attenuation changes from physio-chemical changes will be more important. This study suggests that detecting fluorescence from regions of tissue which are smaller than the average scattering length of the tissue may be a useful method for quantitative fluorophore measurement, which does not require model interpretation of the light signal.
Light propagation in tissue can be simulated accurately with a Monte Carlo technique where individual packets of photons are followed as they travel through different scattering and absorption events. One of the main advantages of this type of simulation is the simplicity and versatility of adding specific boundary conditions, source locations and detector positions, especially when these are located in small regions of space. In order to better understand the photophysical interaction of excitation and fluorescent light with tissue using small fiber optics as source-detector probes, a Monte Carlo simulation was developed. This approach was initially used for confocal detection studies, where the light was delivered and detected from the same objective lens. Using fiber optics, the physical simulation is essentially identical, with a small correction to inject and collect photons into the tissue with the numerical aperture of the fiber.
The salient features of our simulation will be outlined. The simulation assumed the photons scattered with an average mean free path governed by the inverse of the scattering coefficient, μs, which meant that the average pathlength was given by:
During the simulation the random length of travel before each scattering event is:
where εi is a random number between 0 and 1, and si is the distance the photon moves for step i. Equation (2) gives a random pathlength which has an average equal to equation (1), i.e. <s>=1. The absorption was added in by attenuating the photon packet according to Beer's law after each scattering event, with an absorption coefficient, μa, so that the weight, w, of the photon packet at any time scattering event i, is given by:
where the script s denotes that it is a scattered excitation wavelength rather than a fluorescent photon wavelength. At the end of the photons packets travel, when the path has crossed a boundary, the weight is added to the total of all the photon packet weights exiting the tissue, to contribute to the calculated light signal, so that the scattered signal, SΦ, exiting the tissue is:
where N is the number of photon packets launched in the simulation. The angle of each scattering event is governed by the phase function, and here the Henyey-Greenstein formula was used since it has been demonstrated to simulate tissue scattering reasonably well. It should be noted that there are other scattering phase functions which are thought to better simulate tissue scatter angles, but the Henyey-Greenstein function is accurate enough for this study, and only requires the input of the average cosine of the scattering angle, g. The absorption event due to the fluorophore was simulated using the probability of Beer's law attenuation, where a comparison was made at each scattering event between a random number ε, and the probability of absorption given by:
If the random number was less than this probability, than the photon was absorbed by the dye, and generated a fluorescent photon, with a new weight:
where the script F refers to fluorescent photon packets, and φfl is the fluorescent quantum yield which was kept at 1.0 here for simplicity. A lower fluorescent quantum yield would mean less fluorescent photons were generated and a lower intensity. The fluorescent photons packets were initiated at the site of the absorption event, with an initial isotropic scatter direction. Once a fluorescent photon packet was generated, it was followed in the simulation using the same scattering coefficient, anisotropy parameter, and absorption coefficient, but without any possibility for re-absorption of the fluorescent photons by the dye. The detected fluorescence signal is calculated by summing the weights of all fluorescent photon packets that exit the tissue surface:
This simulation is an idealized representation of light scattering, since the scattering and absorption coefficients of the excitation and fluorescence are likely to be different if they are at different wavelengths, however scattering changes in tissue are known to be a modest function of wavelength, and the absorption due to the Ink used in our simulations is not strongly wavelength dependent. The assumption that there was no re-absorption of the fluorescence by the fluorophore is accurate if the Stoke's shift of the molecule is larger than the Q-band absorption peak width and is generally true for the dye used experimentally here.
In these simulations a fixed numerical aperture of 0.22 was used with tissue optical properties μa=0.01 mm−1, μs=10.0 mm−1 and g=0.90. The geometry of the simulation is shown in FIG. 1, where the fiber is in orthogonal contact with the tissue surface and excitation photons and fluorescence photons are illustrated as scattering in the medium. Simulations were completed for various fiber diameters and fluorophore concentrations in order to examine the average number of scattering events in the detected signal, as well as to visualize the fluence or photon density, which is defined as the number of photons passing through a unit spherical area within the medium.
The essence of the invention in its preferred embodiment is that a fiber optic bundle is designed to contain 30 individual fibers that have a diameter of 100 microns wherein each fiber contained in the bundle is separated from the other fibers by approximately 500 microns at the end of the bundle that comes in contact with the surface of the tissue; there is no separation of the bundle on the opposite end. Preferably, the fibers are arranged such that the tissue contact end of the bundle is generally circular in cross-section. Although the preferred embodiment employs the separation by said 500 microns, the essence of the invention is to separate the fibers whether performing the evaluation of tissue or other type of application in order to obtain improved readings of light from tissue. For example, the separation of the fibers could be as little as 300 microns or as much as 2,000 microns or 2 millimeters, but is preferably no more than 1,000 microns or 1 millimeter (1,000 microns equals one millimeter; a millimeter is equal to one thousandth of a meter) from each other on the tissue contact surface. In addition, the number of fibers in a fiber optic bundle does not have to be exactly 30 individual fibers; the number of fibers in a fiber optic bundle can vary, for example from 2 to 500 fibers, but more preferably between 10 and 100 fibers. Moreover, the diameter of each individual fiber is preferably at least 10 microns, and can be up to 500 microns, but preferably no more than 200 microns; the purpose of limiting the diameter of each fiber is that the fiber should be thin enough to minimize the multiple scattering in the captured luminescent signal. The improvement is that a bundle of fiber optics are separated by a designed distance at the tissue surface in order to enable improved readings for the evaluation and diagnosis of the tissue.
In the preferred embodiment, a fluorescent or phosphorescent chemical or drug is introduced into a patient and said bundle of optic fibers are placed in contact with the tissue to be examined. Thereafter, light which is capable of being absorbed by said fluorescent or phosphorescent chemical or drug is injected into said fiber bundle and then the fluorescent or phosphorescent light generated by the chemical or drug is captured back into the fiber bundle. Said light that is captured back into the fiber bundle is separated by a dichroic mirror and then delivered into a detector capable of transmitting the optical intensity into an electrical signal. Said electrical signal will provide a basis for determining the concentration of said chemical or drug present in the tissue. In addition, some of the light that is captured back into the fiber bundle is analyzed by a second detector and a correction for different tissues scattering is completed by application of a calibration of the captured luminescent light to the captured scattered excitation light. The second detector could be combined and or eliminated depending on the capabilities of the first detector.
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Through several hands-on tutorials, instructor Todd Perkins shows how to best build dynamic, streamlined sites using Flash CS3 Professional. Learn how to create custom keyboard shortcuts, apply advanced text techniques such as animating scrolling text with custom easing controls, and using advanced animation techniques. Flash CS3 Professional Beyond the Basics covers many challenging features, including adding complex interactivity to a Flash CS3 project and getting Flash content on a phone. Exercise files accompany the tutorials.
Before start writing a bunch of code to create our MP3 player, let's take a look at our project plan. If you're following along in the Exercise Files folder, find the Chapter 09 folder and then find the 02 folder, and open up 02_Flow.swf. I'm going to expand this file to take up the full screen. Now let's talk a little bit about the structure of our classes. So we have our Main FLA at the top and that's going to be used to create an instance of a class called the Mp3 player class.
And all the classes we'll use will be custom classes that we create. The Mp3 player class will act as the master class for our Mp3 player. Through the MP3 player class, we'll create an instance of a class called the SoundLoader class. The SoundLoader class will control loading and playing of all of our songs. The Mp3 player class will also hold properties that are instances of the PlayPauseButton class, the SkipButtons class, VolumeControl class, and the ProgressSlider class.
These instances will be created through the SoundLoader class. The classes on the right will control the interactivity elements. So first we have the PlayPauseButton class. This class will control the playing and pausing of the sounds. It will do that by communicating through the Mp3Player class to the SoundLoader class to control the sound. The SkipButtons class will control the next and the previous buttons for the Mp3 player. Like to PlayPauseButton class, the SkipButtons class will communicate to the SoundLoader through the Mp3Player class to control skipping tracks in the sound.
The VolumeControl class will work in the same way. It will communicate through the Mp3Player class to the SoundLoader class to control the volume of the songs. The ProgressSlider class will also work in the same way. It will communicate through the Mp3Player class to the SoundLoader class to display and set the progress of the songs that are playing. So we're going to be creating a lot of classes and they're all going to be working with each other.
We're going to be writing a lot of code throughout this chapter, and if any of the code sounds unfamiliar or classes even sound unfamiliar, I definitely recommend viewing the ActionScript 3.0 in Flash CS3 Essential Training title. That will give you a lot of practice in working with sound and practice working with classes. Throughout this chapter if you ever get confused about the structure of our project or how objects are communicating to each other, you can always come back to this file and take a look in a how the structure our classes is setup.
So now that we have a good idea of how our application's going to be set up, let's start making it.
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I have a lilac which is about two years old. Two of the three main branches have grown very long, disproportionately to the third. Should I cut them back, if so when and how?
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I've cut some Dahlia for the house which are now dropping seeds. I've built up a fair amount over the summer, so should I try to grow them? If so, how?
At this year's RHS Show at Chelsea there was a company selling lilly trees - with a quite magnificent display of their wears! Does anyone know their trading name or web site please? They were also present at the Cardiff show.
Watered most days if it hasn't rained and certainly been well fed. My gut reaction is that they are having too much water? Cheers.
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YIELD: Makes about 3 cups
In a dry small heavy skillet toast seeds over moderate heat, shaking skillet, until fragrant, about 1 minute, and cool. With a mortar and pestle or with bottom of a heavy skillet coarsely crush seeds. Drain olives and thinly slice lemon. With flat side of a large knife lightly bruise thyme and in a bowl stir together all ingredients. Marinate olives, covered and chilled, at least 3 days and up to 1 week. Bring olives to room temperature, about 15 minutes, before serving.


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The secret to holiday party success? Sending guests home healthy and happy. Protect beverages and condiments with ZACK's Limbo bottle stopper, so there's no pressure to finish everything in sight. The stainless steel top keeps contents optimally fresh and sits on a nice wood display when not in use. You'll be the toast of the town.
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You Can Opt to Deduct Sales Taxes
Q: Will the Internal Revenue Service be allowing taxpayers a sales-tax credit for purchasing a new vehicle in 2011 like they did last year?
P.C.A., Roseville, Calif.
A: The specific law you're asking about isn't available for 2011.
But that isn't the end of the story. You may be able to benefit from another law that's very much alive. Since this is a tricky issue, even by tax-law standards, here is some background.
Our reader—and two other readers—are asking about a now-defunct federal income-tax provision originally designed to encourage people to buy new cars and other vehicles. It was enacted by law, not handed down by the Internal Revenue Service, and it wasn't a "credit."
Although that specific break now is dead, there is another law that can help many people—as long as they itemize their deductions, says Mark Nash, partner, personal financial services, at PricewaterhouseCoopers in Dallas.
Under that law, taxpayers have an unusual choice. They are allowed to deduct general state and local sales taxes paid, instead of deducting state and local income taxes paid, he says.
"This can be a great tax benefit" for many taxpayers who live in Florida, Texas and other states that don't have a state income tax, Mr. Nash says.
Picking the sales-tax deduction can be a smart move for many people in other states, too, such as taxpayers who make large purchases during the year (including a new vehicle) and who owe very little in state and local income taxes.
"But this is only for taxpayers who itemize," Mr. Nash says. It doesn't help those who claim the standard deduction.
Calculating how much to deduct can be complex.
Taxpayers have a choice in how to figure the amount. They are "allowed to claim the actual sales tax they paid, or they can choose to deduct an amount from a table provided by the IRS that varies based on [a person's] state of residence, income level and number of dependents claimed," says Mr. Nash.
"If you use the tables," he adds, "you are allowed to add to the table amount any general sales taxes paid on a vehicle purchase" or on certain other items, such as a home improvement.
For tips and guidance on calculating the sales-tax deduction, go to the IRS website . For example, check out this page: "Sales Tax Deduction Calculator—Frequently Asked Questions."
DEATH AND TAXES: The federal estate-tax exclusion is scheduled to increase next year, thanks to an inflation adjustment. For an estate of someone dying in 2012, the basic estate-tax exclusion amount will be $5,120,000, says the IRS. That's up from $5 million for 2011.
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Governor's school students host 15th annual Model UN
Nearly 400 central Virginia high school and middle school students assembled at Maggie L. Walker Governor's School recently to participate in the 15th annual Governor's School Model United Nations Conference (GSMUN XV), around 150 being students from Henrico County.
The conference is completely student-run, consisting of a staff of around 70 Governor's School students. With more committees available to debate in than ever before, GSMUN XV prides itself in being one of the largest high school Model UN conferences in the Virginia. Six members of the secretariat staff are Henrico county residents.
Model United Nations allows students to simulate official United Nations proceedings by conducting research on global topics, representing their assigned countries, debating with other nations, and practicing the art of diplomacy to ultimately create resolutions to real international issues. Student delegates at GSMUN XV participated in committees that focused on problems such as the European Union financial crisis, infrastructure and regime development of Sudan, human trafficking, and antibiotic resistance.
This year, GSMUN XV staff and participants also raised funds to support Pencils of Promise, an international organization whose mission is to build schools in the developing world and to train young leaders to take action at home and abroad. The charity supported by last year's conference received $4,000 from the event.
'Proof of Heaven' coming to Glen Allen
Dr. Even Alexander, a New York Times best-selling author who has been featured on Oprah and Dr. Oz, was in town last week to promote his June 27 talk, "Proof of Heaven," at Glen Allen High School.
Alexander (pictured, at right, while Unity of Bon Air church member Harry Simmons interviews him) has written about what he considers to be his journey through the afterlife.
Tickets to this month's event are $25 and will support the new Bon Secours Hospice House being built later this year. > Read more.
Innsbrook Rotary celebrates 25 years
The Innsbrook Rotary Club, which is celebrating its 25th year in 2015, has completed a number of volunteer projects this year and raised thousands of dollars for various organizations through three events.
The club's annual rose sale, benefit for youth live auction and Virginia Fire Games competition, combined with individual and corporate donations, have raised nearly $70,000 – money that the club contributes back to the community.
FeedMore is the beneficiary of the club's 25th anniversary project, which provides refrigerated trailers to be used for the distribution of food throughout Central Virginia. > Read more.
Voltaggio to host three-course dinners at Family Meal July 21-22
Chef Bryan Voltaggio will host a special three-course dinner event July 21-22 at his Willow Lawn Family Meal restaurant. The menu will consist of his favorite dishes and offer diners the chance to purchase a signed copy of his newly released book, HOME.
Voltaggio will attend and cook at each dinner, as well as share stories that inspired recipes for the book. > Read more.
Va. Guard soldiers, airmen eligible for Va. Veterans ID card
Land Lovers, Clean Businesses honored
Henrico Schools holding job fair to recruit bus drivers
Fairfield MS band wins 5 awards
'NuckolsPlace' shopping center planned in Far West End
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Jun. 18, 2015Click here to read the print edition.
Voltaggio to host three-course dinners at Family Meal July 21-22
Fan favorite shines in new West End home
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The Cultural Arts Center at Glen Allen announces 2015-16 season
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Obituaries – Bernard Howard
Obituaries – Milton N. Parma
Obituary – William Talbott Neal
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'Proof of Heaven' coming to Glen Allen
Innsbrook Rotary celebrates 25 years
Holman student named Miss Va. Coed Junior Teen
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My daughters' other dads
All hail to mothers and the hardest job of all
Cabin fever cures - and blessings
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Athlete of the Week – June 19: Sydney Whitaker
Steward School's Enright drafted by NY Mets
Athlete of the Week – June 12: Claire Frank
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ClassifiedsGET FREE OF CREDIT CARD DEBT NOW! Cut payments by up to half. Stop creditors from calling. 877-467-4560
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CalendarThe Henricopolis Soil and Water Conservation District will offer a DIY Rain Barrel Workshop from 6 p.m. to 8 p.m. at the Henrico County Human Services building, 8600 Dixon Powers… Full text


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Rich, full-bodied Starbucks® espresso combined with hot water for the European alternative to American-style brewed coffee. Nutritional Facts Table - Size Tall Serving Size 12 fl. oz. Amt Per … see full wiki
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Learn more about Speed X Cyclone RC Remote Control - White:
Manufacturer: NQD
Mfg Part#: B-XCyclone-W
Sku: 221292945
Package Weight: 3 lbs
Batteries: Not Applicable
See more in Remote Control Vehicles
|The Speed Cyclone is....how do you put it? It's a cyclone of speed. Pretty self-explanatory right? This RC boat is ready to go right out of the box. Its sleek lines and flashy decals make for an appearance not easily duplicated. Powered by an explosive 380 Type Racing Motor and equipped with professionally designed PC Twin Propellers, the Speed Cyclone is capable of producing a tremendous amount of power. Its vector-push design allows for easy control and handling. Coupled with its 100% metal actuating mechanism, which ensures proper start up, your Coastal Brother will always be ready to go. Included also are a set of high-capacity rechargeable batteries and a beautiful display stand for when your not in the water.


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Standing on the edge of the Burfell volcano, you realize what a fragile construct modern civilization is.
McKean looks so fragile and world-weary as he speaks in his Chicago accent, he seems to require rescue.
As of Wednesday morning the latest bout—like ones before it—had ended in a fragile ceasefire, reportedly brokered by Egypt.
1510s, "liable to sin, morally weak;" c.1600, "liable to break;" a back-formation from fragility, or else from Middle French fragile (14c.), from Latin fragilis (see fragility). Transferred sense of "frail" (of persons) is from 1858.