 subvert the purse by substituting (Ri, MACi) in place of (Ri', MACi'). The problem is not remedied by changing KD, since then MACs must be recalculated on all the purse records. This could be costly for large files.
The same problem occurs if digital signatures are used instead of message authentication codes, since changing the public and private key pair each time a record in the file is changed will likewise require the signature for record in the file to be re-calculated. This no advantage is gained from a public key algorithm over a private or secret key algorithm. This application pertains to the art of radiant energy detection and more particularly, to apparatus for converting variations in incident, gamma or x-radiation into corresponding variations in an electrical property, such as changes in output voltage, current or resistance. The invention is particularly applicable to computerized axial tomographic scanners and will be described with particular reference thereto. It will be appreciated, however, that the invention has broader applications such as industrial flaw detectors and other apparatus which detect radiation with high resolution.
Generally, a computerized axial tomographic scanner comprises a source of radiation for irradiating a patient and a plurality of radiation detectors positioned opposite the patient from the radiation source. The detectors receive radiation beams which have passed through the patient along known paths. At least the radiation source is movably mounted for irradiating the patient from a plurality of directions. The detectors are positioned to detect the radiation beams along a plurality of intersecting paths through a planar slice of the patient. With well-known computer reconstruction techniques, the variation or attenuation of the radiation beams along the plurality of intersecting paths is reconstructed into an image of the planar region of the patient. The thickness of the beams along an axis generally transverse to the planar slice affects the thickness of the planar slice examined. The width of the beams affects the resolution of the reconstructed image. The width is an axis within the plane which is generally transverse to the thickness axis and transvierse to the path between the source and the detector. The radiation detectors generally consist of a scintillation crystal positioned to receive radiation and a photomultiplier tube optically coupled to the scintillation crystal. Alternately, the detectors may consist of a scintillation crystal optically coupled with a photodiode, a solid state radiation detector or an ionizable gas detector.
Generally, medical diagnosticians achieve the preferred results from tomographic scanners which have high resolution and low noise. A major factor in determining the resolution is the width of the
subvert the purse by substituting (Ri, MACi) in place of (Ri', MACi'). The trouble is not remedied by transfer KD, since then MACs must be recalculated on all the bag records. This could be dearly-won for large files. 
 The like problem occurs if digital signatures are use instead of message authentication codes, since change the public and private key pair each time a record in the file is changed will similarly require the signature for record in the file to be re - forecast. This no advantage is gained from a public key algorithm over a private or secret cardinal algorithm. This application pertain to the art of radiant energy signal detection and more particularly, to apparatus for converting variations in incident, gamma or x - radiation into comparable mutant in an electrical property, such as changes in output voltage, current or resistance. The invention is particularly applicable to computerized axial tomographic scanners and will be describe with particular reference thereto. It will be prize, however, that the invention hold broader applications such as industrial defect detectors and early apparatus which detect radiation with high resolution. 
 by and large, a computerized axial tomographic scanner comprises a source of radiation for irradiating a patient and a plurality of radiation detectors positioned opposite the patient from the radiation sickness source. The detector receive radiation beams which have passed through the patient along know paths. At least the radiation source is movably mount for irradiating the patient from a plurality of directions. The detector are positioned to detect the radiation radio beam along a plurality of intersect paths through a planar slice of the patient. With well - known calculator reconstruction techniques, the variation or attenuation of the radiation beam along the plurality of decussate paths is reconstructed into an image of the planar area of the patient. The thickness of the beams along an axis generally cross to the planar slice affects the thickness of the planar slice examined. The width of the radio beam affects the resolution of the reconstructed image. The width is an axis within the plane which is generally cross to the thickness axis and transvierse to the path between the source and the detector. The radiation detectors generally consist of a scintillation quartz glass positioned to receive radiation and a photomultiplier tube optically coupled to the scintillation crystal. Alternately, the detectors may dwell of a scintillation crystal optically coupled with a photodiode, a solid state radiation detector or an ionizable gas detector. 
 Generally, medical diagnosticians achieve the prefer results from tomographic scanners which have gamey resolution and low randomness. A major factor in determining the resolution is the width of the
 suhvert the purse by substltuting (Ri, MACi) nb placx of (Ri', MACi'). Thd problem is not remedied by cyangibg KD, since then MACs oust be rvcalculatwd oi all the purse cscords. Bkis ckmld bz rostly for largg files.
The sdme problem ocwufs if digital signatures are used inseead of mfssage authentycatpog cosvs, since changing the public ans privaue key pair each tome a record in the file id chwnged will likewisf require tye sytnature for fecord in uhz file to bg re-calculated. This no advantage is gcined from q pubphc key algocithm jver a privabv or sewret keu algorithm. Thls ap'licqtion pertains to the art of radiant engrgy detecdikn and more partixuoarly, to dppafqtur fkr cknvertlng variationa in incidebt, gamma or x-radiatoog into correspknding vwriations in an electrical property, sucv aa changes in output volrage, current or resisjance. The ynvention is particularly applicable to computerised aeixl uonograoyif scanners and will be described with particujzr rvference thereto. Lt will be apprecistfd, rowever, that jhe invzhtjon has broader apolicatijns sych as inqusttial flaw detectors and othwr apparatus qhich detect radiacion with hiyh resplutipn.
Generally, a computerived axjal tomograohic scanhdr comprises a suurbe ox radiation for irradiatind a patieit anb a plurxliti of raqiation dehectovv positioned opposlte tke padient from the radiation source. The detecvprs receive tadhatpon beams whicm have passed trrough the patnent aloug knodn paths. An least tie radiation source is moewbly mounted for irrwdiaring the pagkent from a plirality oy dirwctions. The detectprs zre positioned cu detect the radoatkon bvamx wnong a pluranity of onterrecting patms ghroigh a planar slice ox ths patient. With welk-kkown compoter recogstruction tevhniques, the variauion oc atteiuatiom os the radiation beams along ths pluralihy jf intersectyng iathf is reconxtructed into an image of the planar rejion of the patient. Thg thickness of the becmx along an exis gqnerally dransverse to the plqnar slice affectx the thickness of ths plandr sllce examined. The width of the beams affects the resolution of the reconsteucted image. The wjdth is at cxix withyn tie plane which is benerally transverse to the thirkness axiv cnd transvierse to the path brtdeen the sourze and the detector. The dadiatiom detectors generally consist og a scintillation crystak positiined fo recvjvx radiation and a phptomulcipliee tube iptigally coupled go yhc scintillwtioi cxystal. Alternately, the detectors nay cobslst of a scintilnation crysbau optpcally soupled with a pgotoslode, x solid state radiation detrctor or an ionizablv gws detector.
Gentrally, medical ciagnosnicians achiete the prefesred results from tomographic scanners which have hpgh resoluuion and lpw noise. A maklr factor in determinikg thq resolugion is the fidth of the
subvert the purse by substituting (Ri, MACi) of MACi'). The is not remedied MACs be recalculated on the purse records. could be costly for large files. same problem occurs if digital signatures are used instead of message authentication codes, changing the public and private key pair each time a record in the is will require signature for record in the file to be re-calculated. This no advantage is gained from a key algorithm over a private or secret key This application pertains to art of radiant energy detection more to apparatus converting in gamma or x-radiation corresponding variations in an electrical property, such as changes in output voltage, current or resistance. The invention particularly applicable axial tomographic and be with particular reference will be appreciated, however, that the applications such as industrial flaw detectors and other which detect with high resolution. Generally, a computerized tomographic scanner comprises a source of radiation for a patient and a plurality of radiation detectors positioned opposite the patient from the radiation detectors receive radiation beams have passed through patient known At the radiation is movably mounted for irradiating the patient from a plurality of The detectors are positioned to detect the radiation beams along of paths through a slice of the patient. well-known reconstruction techniques, the variation of radiation plurality intersecting is reconstructed into an of the planar region of patient. The thickness of generally transverse to the planar slice affects the of the planar slice examined. The width the beams affects the resolution of the reconstructed image. The width is axis within which is generally transverse to the thickness axis transvierse to the path the source and the detector. The radiation detectors generally of scintillation crystal to receive radiation a photomultiplier tube coupled to the Alternately, the may of optically coupled with a photodiode, a state detector or an ionizable gas Generally, achieve the preferred results from tomographic scanners which have high resolution and low noise. A in determining the resolution the of the
 subvert the purse by substituTing (Ri, MACi) In plaCe oF (Ri', mAci'). ThE proBlem is not remedIEd by Changing KD, since then MACS must Be REcalCUlAted oN all the PUrSE RecOrDs. thiS cOUlD be coStlY for larGe files.
The SamE pRoblem occurs IF dIgital signAtuRes are used inSteAd of meSsAge AUthenTicAtion Codes, sINce chaNging the pUbLIc and pRIvate keY PAiR eacH time a record in the FIlE Is changed will lIkewisE rEQuIRE thE siGnature for ReCord iN The file TO bE RE-CalCUlated. This no aDvantage is gAIneD from a PuBliC Key algOrithM oVEr a Private or seCret Key algoriThm. ThiS ApplicaTIon pertAins to The Art Of raDIaNt EneRgY DetECtIon ANd mOre partiCuLaRly, to AppaRATUS for ConVertIng vaRiations in incIdeNt, gaMMa oR x-radIatioN intO cOrresPondinG variAtIons in an electriCal pRoperty, suCh aS cHanGeS in ouTPut volTagE, cuRrent or ResistaNCe. THe INVEnTion is particularly ApPLIcAble to coMputerIZeD aXIal tomogRaPhiC scaNNErs anD wilL Be DescribeD with pARtIcUlar refErEnce thErEto. it wIll be APpreCiated, However, tHat thE Invention has brOAder applicatiONs SUCh AS indUstRial flaw detEctoRS and OtheR ApParATus whIch deTeCT rADiation with high resoLuTion.
GeNeralLy, a computerizEd axial tomOGRAphic scaNner COmPRises a source of RadiaTion for irrADiating a PatieNt and a plUrality of RADiation dEteCtoRs pOsiTIOnEd opposite the PATienT fRom the rAdiAtion soUrcE. ThE deTecToRs receive RadiatioN bEaMs WhIch Have pASsed throUgH thE pAtiEnt alONg knowN pathS. At lEaSt THe rAdiatioN SoURCe is MoVaBly mOunTeD for iRradIAtiNg the paTient from A plURaliTy Of DirectiOns. The detectoRs Are positioNeD to Detect THE radiatiOn beams along a plurality oF InterseCtiNg patHs thRough a plaNar Slice oF thE PatienT. With wEll-knOwN coMPUter rECOnStrUcTion techniQUEs, tHe varIaTion Or attenUation of the radiatiON beAms along the plUraLity OF InTerSEcTIng PaTHs iS REconstructed intO an image of ThE PlAnar region OF thE pAtient. THe thickNess oF The beamS along an aXis generaLlY traNSVerSe to the plaNar slice Affects thE ThickNEsS of thE plAnar slIcE exAmineD. The wiDTh oF the bEams afFeCts the ResolUtIon of the Reconstructed image. The wiDth is aN axis WitHin the plaNe wHIch Is generalLy trAnsverse to The ThiCknesS axIS and tRansVIeRse TO the pAth bETween the sOUrCe aND ThE detector. ThE RADiaTion dEteCTors geNeraLly consist of a scinTIllation crystaL posITIonEd tO ReceIvE radiation and a PhoToMULtiplier TuBe optically Coupled tO tHE scinTillatIon cryStal. AltERNaTEly, the DeteCtoRs may consIst Of A ScintilLaTiON crystAl opTiCally cOupled WIth a PHOtodiode, a solid stAte raDIAtion DEteCtor oR aN ionizaBLe gaS detector.
GEnerally, medIcal diAgnoSticiAns achiEvE the prEfeRrEd results fROm tomograPhic sCanners WhIch hAve High reSoluTIOn and Low nOiSe. A Major factOR In DEtErMIniNg thE resoLuTion Is the widtH Of the
 subvert the purse by subs tituting ( Ri, M ACi ) i nplac e of  (Ri', MACi'). Theproblem is not remedie d bych a ngin g  K D, si nce the n  M A C s m us tbere c al culat edon allthe purserec or ds. This cou l dbe costlyfor  large files .
T he sam epro b lem o ccu rs if  digit a l sign atures ar eu sed in s tead of m es sage  authentication c o de s , since changi ng the  p u bl i c  an d p rivate key  p air e a ch time ar e c ord in the file i s changed w i lllikewi se  re q uire t he si gn a tur e for recor d in  the file  to be re-calc u lated.This n o a dva ntag e  i sgai ne d  fr o ma p u bli c key al go ri thm o vera p r ivat e o r se cretkey algorithm . T hisa ppl icati on pe rtai ns  to t he art  of r ad iant energy det ecti on and mo repa rti cu larly ,  to ap par atu s for c onverti n g v ar i a t io ns in incident, ga mm a or  x-radia tion i n to  c o rrespond in g v aria t i ons i n an el ectrical  prope r ty ,such as  c hanges  i n o utp ut vo l tage , curr ent or r esist a nce. The inven t ion is partic u la r l ya ppli cab le to compu teri z ed a xial to mog r aphic  scan ne r sa nd will be describe dwith p artic ular referenc e thereto. I t  will be  app r ec i ated, however,  that  the inven t ion hasbroad er appli cations s u c h as ind ust ria l f law d et ectors and ot h e r ap pa ratus w hic h detec t r adi ati onwi th high r esolutio n. 
G en er all y, ac omputeri ze d a xi altomog r aphicscann er c om pr i ses  a sour c eo f  rad ia ti on f orir radia ting a p atientand a plu ral i ty o fra diation  detectors po si tioned opp os ite  the p a t ient fro m the radiation source. The det ect ors r ecei ve radiat ion  beams  wh i ch hav e pass ed th ro ugh t he pa t i en t a lo ng known p a t hs.  At l ea st t he radi ation source is mo v abl y mounted for  ir radi a t in g t h ep ati en t  fr o m  a plurality of  direction s. Th e detector s  ar epositio ned todetec t  the ra diation b eams alon ga pl u r ali ty of inte rsecting  paths th r ougha  p lanar  sl ice of  t hepatie nt. Wi t h w ell-k nown c om puterrecon st ructiontechniques, the variati on oratten uat ion of th e r a dia tion beam s al ong the pl ura lit y ofint e rsect ingp at hsi s rec onst r ucted int o  a n i m a ge  of the pla n a r  re gionoft he pat ient . The thickness o f  the beams alo ng a n axi s g e nera ll y transverse t o t he p lanar sl ic e affects t he thick ne s s ofthe pl anar s lice ex a m in e d. The  wid thof the be ams  a f fects t he  r e soluti on o fthe re constr u cted i mage. The widthis an a xis w i thi n the  p lane wh i ch i s generall y transvers e to t he t hickn ess axi sand tr ans vi erse to th e  path bet weenthe sou rc e an d t he det ecto r .  Theradi at ion  detector s ge n er al l y c onsi st of  a  sci ntillatio n  crystal  po s itioned  t o r e c eive r a di a t ion and apho tomul t i plier tube opti c al l y cou pled t o thescintil l ati on  crysta l.A l ternately , the det e cto rs  may  consist  o f asc int il lation crystalopticall y couple d with a  ph o todi o de, aso lid state ra diati on detecto r oran ioni z abl e g asdete cto r.
G e nerally, medical diagnos tici ans a c hie ve th e pre fe rred res u ltsfrom tom o graphic scann ers which haveh igh reso lut i on  a nd low no ise .  A ma jorfac torindete r m inin g  the re solu tion i s th ewi dth of th e
 subvert_the purse_by substituting (Ri, MACi)_in place_of_(Ri', MACi')._The_problem is not_remedied by changing_KD, since then MACs_must be recalculated_on_all the purse records. This could be costly for large files.
The same problem occurs_if_digital signatures_are_used_instead of message authentication codes,_since changing the public and_private key_pair each time a record in the file_is_changed will likewise_require the signature for record in the file to_be re-calculated. This no advantage is_gained from a_public_key_algorithm over a private_or secret key algorithm. This application_pertains to the art of radiant_energy detection and more particularly, to apparatus_for converting variations in incident, gamma_or x-radiation into corresponding variations_in an_electrical property, such as changes_in output voltage,_current or_resistance. The invention_is particularly applicable to computerized axial_tomographic scanners and_will be described with particular reference_thereto._It will be_appreciated,_however,_that the_invention has broader_applications_such as_industrial_flaw detectors and other apparatus which_detect_radiation with high resolution.
Generally, a computerized axial_tomographic scanner comprises a_source_of radiation for irradiating_a patient and a plurality_of radiation detectors positioned opposite the_patient from_the radiation_source. The detectors receive radiation beams which have passed through the_patient along known paths. At least_the radiation source is_movably mounted_for_irradiating the patient_from_a plurality_of directions. The detectors are positioned to_detect the_radiation beams along a plurality of_intersecting paths through a_planar_slice of the patient. With well-known_computer reconstruction techniques, the variation or_attenuation of the radiation beams_along_the_plurality of intersecting paths is_reconstructed into an image of the_planar region of_the patient. The thickness of the beams_along_an axis generally transverse to the_planar_slice affects the thickness of the_planar_slice_examined. The width of the_beams affects the resolution of the_reconstructed image. The width is an axis within the_plane which is_generally transverse to the thickness_axis_and_transvierse to the path between the source and the detector._The radiation_detectors generally consist_of a scintillation crystal positioned to receive radiation and a_photomultiplier tube optically coupled to the scintillation_crystal. Alternately, the detectors may consist of a scintillation crystal optically_coupled with a photodiode, a solid state radiation_detector or an ionizable gas detector.
Generally, medical_diagnosticians achieve the preferred_results_from tomographic scanners which have high resolution_and_low_noise._A major factor_in determining the_resolution is the_width of_the