Modular gamma ray image formation device

Abstract

A system includes a gamma ray collimator including a plurality of collimator elements, each of the plurality of collimator elements associated with a respective set of image formation characteristics, wherein a first one of the plurality of collimator elements is removable from the collimator.

Description

MODULAR GAMMA RAY IMAGE FORMATION DEVICEBACKGROUND

[0001] According to single-photon-emission-computed-tomography (SPECT) imaging, a radioactive substance is administered to a subject and resulting ' / -radiation (i.e., consisting of high-energy photons) emitted from the subject is detected by a SPECT detector. The photons are detected at various locations of the detector and the detector generates a data set representing the detected photons and their two-dimensional distribution. This data set may be considered a planar projection image.

[0002] Tomographic reconstruction technology enables generation of three-dimensional images of a subject from a set of planar projection images of the subject. The planar projection images are acquired from several angular positions around the subject by placing the subject adjacent to a gantry' to which one or more detectors are attached and rotating the gantry' so as to move the detectors to each desired angular position. A tomographic reconstruction unit reconstructs a three-dimensional image based on the projection images.

[0003] A detector may detect photons received from many incoming angles and therefore from many possible points of origin. Accordingly, tomographic reconstruction cannot assume that the trajectory of a detected photon was perpendicular to the detector. To reduce the solution space and thereby facilitate tomographic reconstruction, a collimator is used to restrict the angle from which a detector may receive photons (i.e., the photon acceptance angle). The uncertainty' regarding the origin of the detected photons is modelled by a point spread function (PSF) which is determined by the physical construction of the collimator and is incorporated into the tomographic reconstruction using a convolution kernel.

[0004] The PSF associated with a collimator is typically independent of detector location. While focusing and multi-focusing collimators provide location-dependent acceptance angles, the PSF remains essentially the same (modulo a small cosine approximation) across the detector area. Collimator characterization tools may be used in reconstruction to account for small deviations from a designed PSF due to manufacturing tolerances. However, all current approaches assume acceptance of a specific range of spatial frequencies, singular emission, and location-independent PSF.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a block diagram of a gamma ray image formation system according to some embodiments;

[0006] FIG. 2 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0007] FIG. 2A is a perspective view of a collimator element receptacle including a contact for reading a collimator element identifier according to some embodiments;

[0008] FIG. 3 is a perspective view of a collimator with a removed collimator element according to some embodiments;

[0009] FIG. 4 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0010] FIG. 5 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0011] FIG. 6 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0012] FIG. 7 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0013] FIG. 8 is a perspective view of a collimator including a plurality of collimator elements according to some embodiments;

[0014] FIG. 9 is a perspective view of a collimator including a plurality of collimator elements and a detector according to some embodiments;

[0015] FIG. 10 is a perspective view of a collimator including a plurality of collimator elements and a detector according to some embodiments;

[0016] FIG. 11 A is a perspective view of a collimator including a plurality of individually - tiltable collimator elements according to some embodiments;

[0017] FIG. 1 IB is a perspective view of a collimator including a plurality of individually- tiltable collimator elements according to some embodiments; and

[0018] FIG. 12 illustrates components of a SPECT imaging system according to some embodiments;

[0019] FIG. 13 illustrates a radiotherapy system with an integrated SPECT imaging system according to some embodiments; and

[0020] FIG. 14 illustrates a portable small -footprint SPECT imaging system according to some embodiments.DETAILED DESCRIPTION

[0021] The following description is provided to enable any person in the art to make and use the described embodiments and sets forth the various modes contemplated for carry ing out the described embodiments. Various modifications, however, will remain apparent to those in the art. Independent of the grammatical term usage, individuals with male, female or other gender identities are included within the term.

[0022] Collimation systems are desired which efficiently provide different and operator- selectable PSFs across a detector area. Some embodiments provide a collimator including a plurality of independently-removable collimator elements. Each collimator element is associated with a detector area and the PSF of a collimator element may be taken into account during reconstruction based on photons detected within its associated detector area. Any of the collimator elements may provide a different PSF than any of the other collimator elements.

[0023] The different PSFs may be provided using any image formation techniques that are or become known. For example, one or more of the collimator elements may differ in one or more of aperture size, aperture shape, aperture length, aperture angle, septa thickness, etc. Any of the one or more collimator elements may comprise a Low Energy' All-Purpose (LEAP) collimator, a Low Energy High-Resolution (LEHR) collimator, a Medium Energy collimator or a High Energy collimator. Any of the one or more collimator elements may comprise a parallel hole collimator, a slanthole collimator, a converging collimator, a diverging collimator, a pinhole collimator, a fanbeam collimator, etc. In other examples, anyof the one or more collimator elements may provide, for example, multi-channel, multiplexed, coded aperture, multiplexed isolated, coded aperture isolated, or blocking (e.g.. with opaqueness from 0% to 100% of transmission) collimation.

[0024] FIG. 1 is a block diagram of a gamma ray image formation system according to some embodiments. Collimator 110 defines the lines-of-response of incoming gamma rays and filters out scattered or stray gamma radiation. Collimator 1 10 consists of two or more independently -removable and replaceable collimator elements. One or more of the collimator elements may exhibit a different physical construction than other ones of the collimator elements. As described above, one or more of the collimator elements may exhibit different image formation properties (e.g., PSF).

[0025] During operation, collimator 110 is positioned to detect gamma rays 125 emitted from volume 120. Certain ones of the gamma rays 125 are collimated by collimator 110, and the collimated gamma rays pass through cathode 132 due to its transparency to gamma rays. A gamma ray which passes through cathode 132 and penetrates into direct converter 130 interacts with direct conversion material 130 to generate electron-hole pairs. Cathode 132 is held at a negative bias potential while sensors 134 are held at a less-repelling potential. Consequently, the positively-charged holes drift towards cathode 132, while the negatively- charged electrons drift towards sensors 134. As the electrons approach a given sensor 134, a signal is induced at the given sensor and at its neighboring sensors. The system of converter 130, cathode 132 and sensors 134 may be referred to herein as a detector.

[0026] After collection of the electrons by the given sensor, readout electronics 140 may use the signals received from the neighboring sensors to determine a sub-pixel position of the given sensor at which the gamma ray will be assumed to have been received. The sub-pixel positions at which all gamma rays are received over a given time period may then be used to generate a projection image. A three-dimensional image of the subject may be reconstructed from a plurality of such projection images acquired at different projection angles as is known in the art.

[0027] Image reconstruction may be based on the different PSFs provided by the different elements of collimator 110. For example, a portion of the surface area of converter 130 may be associated with the element-specific PSF (or other image formation property) of a collimator element which is disposed directly adjacent to the portion. Reconstructiontherefore assumes that the incoming trajectories of photons detected at the portion of the surface area conform to the associated PSF of the adjacent collimator element.

[0028] Cathode 132 may comprise a continuous layer which is generally transparent to gamma rays within the energy bands to be detected. Converter 130 may comprise a singlecrystal semiconductor material such as Cadmium Zinc Telluride (CZT) or Cadmium Telluride (CdTe). Sensors 136 may comprise a grid of hexagonal or otherwise-shaped conductive anodes. Each sensor of sensors 136 is coupled to a dedicated signal line and is not in direct electrical contact with its adjacent neighboring sensors.

[0029] In the case of an indirect converter-based detector, the collimated gamma rays pass directly to an indirect converter material (e.g., aNal scintillator) and interact therewith to generate photons. The photons may pass through a light guide before being received by a matrix of PMTs. The PMTs generate electrical signals based on the received photons, which are used by readout electronics 140 as described above.

[0030] FIG. 2 is a perspective view of a portion of collimator 210 including a plurality of collimator elements according to some embodiments. Each of collimator elements 210a- 210g is hexagonal in cross-section but embodiments are not limited thereto. One or more of collimator elements 210a-210g may exhibit different-shaped or different-sized cross sections than others of elements 210a-210g.

[0031] Each of collimator elements 210a-210g may be fabricated independently, for example using traditional casting techniques or additive manufacturing techniques (e.g., 3D printing). In some embodiments, a collimator element 210a-210g is composed of tungsten and tungsten polymer. Each of collimator elements 210a-210g may be composed of different materials, the same materials in different ratios, and / or the same materials in different spatial distributions. The material composition and distribution of an element 210a-210g may be designed to exhibit a desired PSF.

[0032] Collimator elements 210a-210d are substantially identical parallel hole-type elements, collimator elements 210e and 210f are substantially identical parallel hole-type elements with larger holes than collimator elements 210a-210d, and collimator element 210g is a pinhole-type collimator element. Collimator elements 210a-210d may each be associated with a first PSF, collimator elements 21 Oe and 21 Of may each be associated with a second PSF, and collimator element 210g may be associated with a second PSF.

[0033] Tray 220 is configured to support collimator elements 210a-210g. Tray 220 may comprise any suitable materials, which may be substantially transparent to gamma radiation of the energies to be detected. Tray 220 may be constructed from carbon fiber using casting and / or additive manufacturing, for example.

[0034] Tray 220 defines seven receptacles for individually accepting each of collimator elements 210a-210g. According to the illustrated embodiment, a lower section of each of collimator elements 210a-210g is notched (e.g.., notch 212d) to facilitate reception into a receptacle of tray 220 while allowing the upper portions of collimator elements 210a-210g to remain closely packed. Tray 220 may comprise any more or fewer features to facilitate insertion, securing, and removal of collimator elements, including but not limited to a lower lip within each receptacle to support a bottom surface of the collimator element disposed therein.

[0035] As mentioned above, each of collimator elements 210a-210g delivers its photons to a particular portion of a detector surface according to a particular PSF. It would be beneficial to know the portion of the detector surface to which each of collimator elements 210a-210g delivers its photons so that the PSF of a collimator element 210a-210g may be associated with photons detected by its corresponding portion of the detector surface. According to some embodiments, contact 225 of each receptacle of tray 220 captures identifying information of the collimator element mounted therein, thereby facilitating the association of an appropriate PSF with the portion of the detector surface which is adjacent to the receptacle.

[0036] FIG. 2A is a magnified perspective view of a collimator element 230 with tag 235 affixed thereon according to some embodiments. Tag 235 is positioned to interface with contact 225 upon insertion of element 230 into receptacle 240 of tray 220. Tag 235 may include accessible data identifying a type, model number. PSF, and / or any other characteristic of element 230. Contact 225 may comprise any system suitable for reading the data of tag 235. An imaging system may be configured to read data acquired by each contact of tray 220 in order to identify the collimator element supported within each receptacle of tray 220. In some embodiments, an identifier of each collimator element is associated with an index indicating a receptacle of tray 220 and a detector coordinate (x, ) denoting the location of the center of the collimator element.

[0037] FIG. 3 is a perspective view of collimator portion 210 of FIG. 2 after removal of collimator element 210d from a receptacle of tray 220. In the present example, such removal causes contact 225 to detect the absence of a collimator element from tray 220. FIG. 4 depicts insertion of collimator element 410c within the open receptacle of collimator 210, resulting in collimator 410. A contact 225 within the open receptacle acquires data identifying collimator 41 Oh and associates collimator element 41 Oh with the detector surface area portion which was formerly associated with collimator element 210d. In this regard, collimator element 410h is substantially identical to collimator elements 210e and 210f, but embodiments are not limited thereto.

[0038] FIG. 5 is a perspective view of collimator portion 510 including collimator elements 510a through 510g supported by tray 220. The length of various ones of collimator elements 510a through 510g differ from one another. It is noted that the PSF of two collimator elements will differ if they are of different lengths, even if their cross-sections are identical. Moreover, the different lengths may result in shadowing effects which provide additional information as to photon origination.

[0039] Collimator portion 610 of FIG. 6 is identical to collimator portion 510 of FIG. 5 except for the replacement of collimator element 510g with collimator element 610g. Collimator element 610g is solid (i.e., with no photon-receiving holes) and may therefore provide more-effective energy-specific filtering than collimator elements 510a-510f. Any combination of collimator element ty pes, sizes and lengths may be employed according to some embodiments.

[0040] FIG. 7 illustrates collimator portion 710 including collimator elements 710a-710h individually mounted into tray 720. Collimator elements 710a-710h are of square crosssection and tray 720 may include receptacles with similarly-square openings to receive collimator elements 710a-710h. Collimator elements 710a-710h are of varying type and heights and may also be of varying composition.

[0041] Collimator portion 810 of FIG. 8 includes solid collimator elements of varying lengths. The collimator elements of collimator portion 810 may be composed of different materials. Again, the varying lengths may advantageously provide shadowing effects during photon detection.

[0042] FIG. 9 is a perspective view of collimator 910 including a grid of individuallyremovable collimator elements. The collimator elements are supported by tray 920 and exhibit respective PSFs. Each collimator element is further associated with a portion of the surface area of converter 930. According to some embodiments, tray 920 provides an outgoing signal associating each portion of the surface area of converter 930 with a collimator element and a corresponding PSF. The various PSFs may be used as inputs to a reconstruction algorithm as mentioned above.

[0043] FIG. 10 illustrates a configuration in which tray 920 may be controlled via an incoming signal to tilt with respect to converter 930. Any suitable mechanism for tilting tray 920 may be employed. Tilting of tray 920 causes tilting of holes of collimator 910, changing the acceptance angles thereof.

[0044] FIG. 11 A is a perspective view of collimator 1110 including a grid of individuallyremovable and tapered collimator elements. The collimator elements of collimator 1110 are supported by tray 1120 and are associated with respective PSFs and portions of the surface area of converter 1130. FIG. 1 IB illustrates tilting of a subset of the collimator elements of collimator 1110 according to some embodiments. Tray 1120 may therefore provide a suitable mechanism for independently tilting each receptacle thereof.

[0045] FIG. 12 illustrates SPECT system 1200 including at least one collimator as described above. Embodiments may utilize other SPECT system designs, including but not limited to cardiac cameras.

[0046] System 1200 includes gantry 1202 to which two or more detectors 1204a, 1204b are attached, although any number of detectors can be used. Each detector includes a collimator coupled to a converter as described above. The converter within each detector detects gamma photons 1203 (i.e.. emission data) emitted by a radioisotope within the body of a patient 1206 lying on a bed 1208. Bed 1208 is slidable along axis-of-motion A. At respective bed positions (i.e., imaging positions), a portion of the body of patient 1206 is positioned between detectors 1204a, 1204b in order to capture emission data from that body portion.

[0047] Control system 1220 may comprise any general-purpose or dedicated computing system. Accordingly, control system 1220 includes one or more processing units 1222 configured to execute program code to cause system 1220 to operate as described herein, andstorage device 1224 for storing the program code. Storage device 1224 may comprise one or more fixed disks, solid-state random access memory, and / or removable media (e.g., a thumb drive) mounted in a corresponding interface (e.g., a USB port).

[0048] Storage device 1224 stores program code of a control program, which one or more processing units 1222 may execute to, in conjunction with SPECT system interface 1226, control motors, servos, and encoders to cause detectors 1204a, 1204b to rotate along gantry 1202 and to acquire emission data at defined imaging positions during the rotation. The acquired emission data may be stored in memory71224. One or more processing units 1222 may also execute the system control program to reconstruct volumes from the emission data and based on a mapping of collimator elements to detector areas.

[0049] Terminal 1230 may comprise a display device and an input device coupled to system 1220. Terminal 1230 may display any of two-dimensional emission data, CT data, mu-maps, segmentation maps, etc., and may receive user input for controlling display of the data, operation of imaging system 1200, and / or the processing described herein. In some embodiments, terminal 1230 is a separate computing device such as, but not limited to, a desktop computer, a laptop computer, a tablet computer, and a smartphone.

[0050] Each component of system 1200 may include other elements which are necessary for the operation thereof, as well as additional elements for providing functions other than those described herein.

[0051] FIG. 13 is a view of system 1300 according to some embodiments. System 1300 includes radiotherapy system 1310 and SPECT imaging system 1320. Radiotherapy' system 1310 may deliver therapeutic radiation to a subject located within bore 1315 as is known in the art. Radiotherapy system 1310 may deliver any type of radiation-based therapy that is or becomes known, including but not limited to Intensity-Modulated Radiation Therapy and Volumetric Arc Therapy.

[0052] SPECT imaging system 1320 attaches to radiotherapy system 1310 via articulated arm 1325. SPECT imaging system 1320 includes ten detector units. Each detector unit may include a single monolithic converter on which is disposed a respective array of collimator elements as described herein. The collimator elements of one detector unit may be positioned and / or replaced independently of the collimator elements of another detector unit. Arm 1325may be manipulated to move the detector units of system 1320 to a desired position and orientation with respect to a subject positioned on table 1330.

[0053] FIG. 14 is a view of imaging system 1400 according to some embodiments. System 1400 includes mobile base 1410 which is configured to be easily movable by a single operator. SPECT imaging system 1420 includes ten detector units, each of which may include a single monolithic converter and a respective array of collimator elements as described herein. Mobile base 1410 is coupled to SPECT imaging system 1420 via an articulated arm. Mobile base 1410 and the articulated arm may be manipulated to move the detector units of imaging system 1420 to a desired position and orientation with respect to a subject positioned on bed 1430.

[0054] Those in the art will appreciate that various adaptations and modifications of the above-described embodiments can be configured without departing from the claims. Therefore, it is to be understood that the claims may be practiced other than as specifically described herein.NON-LIMITING ILLUSTRATIVE EMBODIMENTS

[0055] The following is a list of non-limiting illustrative embodiments disclosed herein:

[0056] Illustrative embodiment 1. A method comprising detecting removal of a first collimator element from a plurality of collimator elements of a collimator, where each of the plurality of collimator elements exhibit a respective set of image formation characteristics, and detecting replacement of the first collimator element with a second collimator element.

[0057] Illustrative embodiment 2. The method of illustrative embodiment 1, wherein the first collimator element and a second collimator element exhibit different sets of image formation characteristics.

[0058] Illustrative embodiment 3. The method of illustrative embodiments 1-2, wherein the first collimator element and the second collimator element have different lengths.

[0059] Illustrative embodiment 4. The method of any one of the preceding illustrative embodiments, further comprising disassociating the first collimator element from a first portion of a detector in response to the removal of the first collimator element, andassociating the second collimator element with the first portion of the detector in response to the replacement of the first collimator element with the second collimator element.

[0060] Illustrative embodiment 5. The method of any one of the preceding illustrative embodiments, wherein detecting replacement of the first collimator element with the second collimator element comprises reading an identifier of the second collimator element.

[0061] Illustrative embodiment 6. The method of any one of the preceding illustrative embodiments, further comprising changing a reconstruction algorithm in response to the replacement of the first collimator element with the second collimator element.

[0062] Illustrative embodiment 7. The method of any one of the preceding illustrative embodiments, wherein detecting replacement of the first collimator element with the second collimator element comprises reading an identifier of the second collimator element.

[0063] Illustrative embodiment 8. A system comprising a gamma ray collimator including a plurality of collimator elements, each of the plurality of collimator elements associated with a respective set of image formation characteristics, wherein a first one of the plurality of collimator elements is removable from the collimator.

[0064] Illustrative embodiment 9. The system of illustrative embodiment 8, wherein a first set of image formation characteristics associated with the first one of the plurality of collimator elements is different from a second set of image formation characteristics associated with a second one of the plurality of collimator elements.

[0065] Illustrative embodiment 10. The system of any one of illustrative embodiments 8-9, wherein a first length of the first one of the plurality of collimator elements is different from a second length of a second one of the plurality of collimator elements.

[0066] Illustrative embodiment 11. The system of any one of illustrative embodiments 8-10, further comprising a tray defining a plurality of receptacles, wherein each of the plurality of collimator elements is disposed in a respective one of the plurality of receptacles.

[0067] Illustrative embodiment 12. The system of any one of illustrative embodiments 8-11, further comprising a contact associated with each receptable, wherein the contact associated with a given receptacle touches an identifying tag disposed on a collimator element disposed in the given receptacle.

[0068] Illustrative embodiment 13. The system of any one of illustrative embodiments 8-12, further comprising a gamma ray converter, wherein each of a plurality of portions of the converter are associated with a respective one of the plurality of collimator elements.

[0069] Illustrative embodiment 14. The system of any one of illustrative embodiments 8-13, further comprising a gamma ray converter, wherein each of a plurality of portions of the converter are associated with a respective one of the plurality of collimator elements.

[0070] Illustrative embodiment 15. A system comprising a collimator including a plurality of collimator elements, each of the plurality of collimator elements associated with a respective set of image formation characteristics, and a tray defining a plurality of receptacles, wherein each of the plurality of collimator elements is disposed in a respective one of the plurality' of receptacles.

[0071] Illustrative embodiment 16. The system according to illustrative embodiment 15. wherein a first set of image formation characteristics associated with a first one of the plurality7of collimator elements is different from a second set of image formation characteristics associated with a second one of the plurality of collimator elements.

[0072] Illustrative embodiment 17. The system according to any one of illustrative embodiments 15 or 16, wherein a first length of the first one of the plurality7of collimator elements is different from a second length of a second one of the plurality' of collimator elements.

[0073] Illustrative embodiment 18. The system according to any one of illustrative embodiments 15-17, further comprising a contact associated with each receptable, wherein the contact associated with a given receptacle touches an identifying tag disposed on a collimator element disposed in the given receptacle.

[0074] Illustrative embodiment 19. The system according to any one of illustrative embodiments 15-18, further comprising a gamma ray converter, wherein each of a plurality of portions of the converter are associated with a respective one of the plurality7of collimator elements.

[0075] Illustrative embodiment 20. The system according to any one of illustrative embodiments 15-19. further comprising a gamma ray converter, wherein each of a pluralityof portions of the converter are associated with a respective one of the plurality of collimator elements.

Claims

WHAT IS CLAIMED IS:1 . A method comprising: detecting removal of a first collimator element from a plurality of collimator elements of a collimator, where each of the plurality of collimator elements exhibit a respective set of image formation characteristics; and detecting replacement of the first collimator element with a second collimator element.

2. The method according to Claim 1, wherein the first collimator element and a second collimator element exhibit different sets of image formation characteristics.

3. The method according to Claim 1, wherein the first collimator element and the second collimator element have different lengths.

4. The method according to Claim 1, further comprising: disassociating the first collimator element from a first portion of a detector in response to the removal of the first collimator element; and associating the second collimator element with the first portion of the detector in response to the replacement of the first collimator element with the second collimator element.

5. The method according to Claim 4, wherein detecting replacement of the first collimator element with the second collimator element comprises reading an identifier of the second collimator element.

6. The method according to Claim 4, further comprising: changing a reconstruction algorithm in response to the replacement of the first collimator element with the second collimator element.

7. The method according to Claim 1, wherein detecting replacement of the first collimator element with the second collimator element comprises reading an identifier of the second collimator element.

8. A system comprising: a gamma ray collimator including a plurality of collimator elements, each of the plurality of collimator elements associated with a respective set of image formation characteristics, wherein a first one of the plurality of collimator elements is removable from the collimator.

9. The system according to Claim 8, wherein a first set of image formation characteristics associated w ith the first one of the plurality of collimator elements is different from a second set of image formation characteristics associated with a second one of the plurality of collimator elements.

10. The system according to Claim 8, wherein a first length of the first one of the plurality of collimator elements is different from a second length of a second one of the plurality of collimator elements.

11. The system according to Claim 8 further comprising: a tray defining a plurality of receptacles, wherein each of the plurality of collimator elements is disposed in a respective one of the plurality of receptacles.

12. The system according to Claim 11, further comprising: a contact associated with each receptable, wherein the contact associated with a given receptacle touches an identifying tag disposed on a collimator element disposed in the given receptacle.

13. The system according to Claim 12, further comprising: a gamma ray converter, wherein each of a plurality of portions of the converter are associated with a respective one of the plurality of collimator elements.

14. The system according to Claim 8, further comprising: a gamma ray converter, wherein each of a plurality of portions of the converter are associated with a respective one of the plurality of collimator elements.

15. A system comprising: a collimator including a plurality of collimator elements, each of the plurality of collimator elements associated with a respective set of image formation characteristics; anda tray defining a plurality of receptacles, wherein each of the plurality of collimator elements is disposed in a respective one of the plurality of receptacles.

16. The system according to Claim 15, wherein a first set of image formation characteristics associated with a first one of the plurality of collimator elements is different from a second set of image formation characteristics associated with a second one of the plurality7of collimator elements.

17. The system according to Claim 16, wherein a first length of the first one of the plurality of collimator elements is different from a second length of a second one of the plurality of collimator elements.

18. The system according to Claim 15, further comprising: a contact associated with each receptable, wherein the contact associated with a given receptacle touches an identifying tag disposed on a collimator element disposed in the given receptacle.

19. The system according to Claim 18, further comprising: a gamma ray converter, wherein each of a plurality7of portions of the converter are associated with a respective one of the plurality of collimator elements.

20. The system according to Claim 15, further comprising: a gamma ray converter, wherein each of a plurality7of portions of the converter are associated with a respective one of the plurality of collimator elements.

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