GAMMA RAY DETECTOR WITH PLANAR SYMMETRY, MULTI-PINHOLE COLLIMATOR AND VARIABLE SAMPLING REGION

Abstract

A planar-symmetry device for high-sensitivity gamma ray detection, which allows real-time tomography image reconstruction with very good spatial resolution. Advantageously, the multi-pinhole collimators of the device move during data collection and/or one or more of the pinholes thereof moves independently, thereby allowing possible artifacts resulting from overlap areas of the detector to be completely eliminated.

Claims

1. An imaging device for imaging radiation-emitting objects from the gamma ray detection coming from said source of radiation, comprising: a detector equipped with one or more gamma radiation-sensitive materials; electronic processor configured for the reading and processing of one or more gamma radiation detection signals by the detector; a gamma ray collimator equipped with a plurality of pinholes which the gamma rays can penetrate, and arranged, relative to the detector, such that they provide at least one sampling region on the field of view of the detector; wherein the detector, the electronic processor and the gamma ray collimator are arranged in substantially parallel respective planes, adopting a camera configuration with planar symmetry; wherein the position of the pinholes of said collimator is variable relative to the position of the detector, such that the sampling region on the field of view of the detector, provided by one or more cones of incidence of gamma radiation upon passing through the pinholes, is modified with the variation of the positions of said pinholes with respect to the detector; and wherein the collimator and the detector are arranged such that the variation of the position of the pinholes of the collimator with respect to the detector takes place continuously, and such that the pinholes travel a relative distance with respect to the detector, but without occlusion of said pinholes along said distance during sampling.

2. The device according to claim 1, wherein the positions of the pinholes are independently movable with respect to one another in the collimator.

3. The device according to claim 1, wherein the position of the collimator and/or the pinholes exhibits relative rotational and/or translational movement with respect to the position of the detector.

4. The device according to claim 3, wherein the position of the collimator and/or the pinholes exhibits relative rotational movement with respect to the position of the detector, about an axis substantially perpendicular to the plane formed by the collimator, where said axis does not go through any of the pinholes of the collimator.

5. The device according to claim 4, wherein the collimator is mobile with respect to the detector, such that each of its pinholes describes a circular path around its corresponding center of rotation, being different for each of the pinholes.

6. The device according to claim 5, wherein said fixed point is such that the angles of visibility of the field of view areas of the detector, under the movement of the collimator, are not repeated until a complete or partial rotation of said collimator has been achieved.

7. The device according to claim 1, wherein the axes of all the pinholes of the collimator are substantially parallel, such that the sampling region on the field of view of the detector provided by a plurality of cones of incidence of gamma radiation upon passing through the pinholes does not exhibit any overlap for at least two of said pinholes.

8. The device according to claim 1, wherein one or more of the pinholes of the collimator are covered by corresponding plugs, the plugs being arranged on the collimator, or on a support arranged thereon, wherein said support is equipped with pinholes adapted for housing the plugs.

9. The device according to claim 1, having zero, one, or more overlapping areas between the cones of incidence on at least one detection surface of the detector, and wherein said areas are modified with the variation of the positions of the pinholes with respect to the detector.

10. The device according to claim 1, comprising a plurality of detectors arranged around the source of radiation, forming a closed or open ring structure, wherein the collimator forms a structure coaxial to that of the detector.

11. The device according to claim 10, wherein the structure formed by the collimator is a rotating structure, or rotates and moves by translation describing a helical movement, relative to the structure formed by the detectors.

12. The device according to claim 1, wherein the collimator has: circular groove-shaped pinholes, and wherein said pinholes are partially covered by a plug with a variable position in said groove; and cylindrical-, wedge-, or double cone-shaped pinholes.

13. The device according to claim 1, wherein the pinholes of the collimator are distributed such that each of said pinholes, except those arranged in the perimetral region of the collimator, has six neighboring pinholes, located at the same distance, forming a regular hexagon; and wherein said pinholes optionally have the same angular aperture.

14. An imaging system, comprising one or more devices according to claim 1, wherein the electronic processor for the reading and processing of the signals of the detector are connected to an image reconstruction device, from the processing of said signals.

15. The system according to claim 14, comprising a mobile platform adapted for orienting the device towards different regions of a source of gamma radiation.

Description

DESCRIPTION OF THE DRAWINGS

[0033] The above and other features and advantages will be more fully understood from the detailed description of the invention and of the preferred embodiments relating to the attached figures, which are described in the following paragraphs.

[0034] FIG. 1 shows a schematic depiction of a preferred embodiment of the object of the present invention relating to a gamma detection device made up of a mobile multi-pinhole collimator with planar symmetry.

[0035] FIG. 2 shows a schematic depiction of an array of plugs for the gamma radiation configured to be housed in the pinholes of the plane collimator of FIG. 1.

[0036] FIG. 3 shows a schematic depiction of a preferred embodiment of the object of the present invention relating to a gamma detection device made up of a mobile multi-pinhole collimator with planar symmetry, where the continuous relative rotational movement between said collimator and a detector is depicted, where the axis of said rotation does not coincide with any of the axes of the pinholes of the collimator.

[0037] FIGS. 4A-4C show a schematic depiction of a possible multi-pinhole collimator translational movement sequence with respect to the detector of the device, in a preferred embodiment of the invention.

[0038] FIGS. 5A-5B show a depiction of a possible center of rotation for a circular movement of the collimator around a fixed point, which is positioned, for example, at ¼ of the distance between two consecutive pinholes (the circumferences depict the areas of incidence on the surface of the detector, corresponding to each pinhole). Said point of rotation allows a non-cyclic sampling (until a rotation of 360° has been achieved) of the field of view. The circumferences of FIG. 5B depict the bases of the cones of incidence of the gamma rays on the detection surface, which in this case do not exhibit overlap.

[0039] FIG. 6 shows a schematic depiction of a collimator with circular groove-shaped, partially covered, pinholes the covered areas of which vary while collecting data.

[0040] FIG. 7 shows a schematic depiction of a distribution of pinholes which is periodically repeated, where each pinhole, except the one located on the edge of the collimator, has six neighboring pinholes located at the same distance, forming a regular hexagon.

[0041] FIG. 8A shows a two-dimensional schematic depiction of a gamma camera with a multi-pinhole collimator and a gamma ray detector. The area of incidence of the gamma rays, allowed by the collimator (which would correspond to cones of incidence in three dimensions) is also shown schematically. The angular aperture allows there to be overlap of the cones of incidence on the surface of the detector, which increases the sensitivity of the camera.

[0042] FIG. 8B shows a schematic depiction of a possible way to cover the pinholes of a multi-pinhole collimator according to the invention, in order to temporarily prevent access of the gamma rays to the overlapping area on the detection surface.

REFERENCE NUMBERS USED IN THE DRAWINGS

[0043]

TABLE-US-00001 (1) Gamma ray detection device (2) Detector equipped with gamma radiation-sensitive means (3) Optical photosensors, gamma radiation detection electronics (4) Multi-pinhole collimator (4′) Axis of rotation of the collimator with respect to the detector (5, 5′) Pinholes (6) Plug for the pinholes (7) Support of the plugs for the pinholes (8) Gamma rays (9) Source of radiation (10) Cone of incidence of the gamma rays (11) Overlapping areas of the cones of gamma radiation

DETAILED DESCRIPTION OF THE INVENTION

[0044] A detailed description of the invention relating to different preferred embodiments thereof based on FIGS. 1-8 herein is provided below. Said description is provided for purposes for illustrating but not limiting the claimed invention.

[0045] As described in the preceding sections, the imaging device (1) for imaging radiation-emitting objects from the gamma ray detection of the invention comprises at least the following essential elements (FIG. 1): [0046] a detector (2) equipped with gamma radiation-sensitive means and a corresponding detection electronics (3), configured to calculate the energy from the interaction of the incident gamma rays on the device (1), as well as to determine the position where said interaction occurs; and [0047] a mobile gamma ray collimator (for example, of lead, tungsten or the like) (4), equipped with a plurality of pinholes (5) (through which the gamma rays penetrate), adapted for performing a sampling of multiple regions of the field of view (FOV) of the detector (2), which guarantees, by means of a suitable processing of the data acquired by the detector (2) (for example, through a computer connected to the detection electronics (3)), the absence of artifacts and obtaining a complete final image, without truncation.

[0048] Preferably in the device, and as shown in FIG. 1, the detector (2), the electronic reading and processing means (3) and the gamma ray collimator (4) of the device of the invention are arranged in substantially parallel respective planes, thus adopting a camera configuration with planar symmetry.

[0049] In a complementary or alternative manner, the pinholes (5) are adapted in the device (1) so that they can be covered and/or uncovered, therefore equipping the collimator (4) with different configurable aperture patterns. An example of this embodiment is shown in FIG. 2, where a collimator (4) is depicted with pinholes (5) which are covered by a plurality of plugs (6), formed, for example, from tungsten and/or lead. In different embodiments of the invention, said plugs (6) can be arranged directly on the collimator (4) or on a support (7) arranged thereon, where said support (7) is equipped with pinholes (5′) adapted for housing the plugs (6). In any of the preceding configurations, the variation of the position of the pinholes (5) of the collimator (4) with respect to the detector (2) takes place continuously, i.e., the pinholes (5) travel a relative distance with respect to the detector (2), but without occlusion of said pinholes along said distance, except possibly by plugs placed prior to acquisition.

[0050] In another preferred embodiment of the invention, the positions of the pinholes (5) can move independently with respect to other in the collimator (4). Optionally, the detector (2) can furthermore be configured to rotate and/or move around the region of interest of the object/animal/patient in respect of which images are to be obtained. Therefore, the overlapping areas, if they exist on the detection surface of the detector (2), vary during image acquisition.

[0051] In another preferred embodiment of the invention, the position of the collimator (4) and/or of its pinholes (5) exhibits continuous relative rotational movement with respect to the position of the detector, about an axis (4′) substantially perpendicular to the plane formed by the collimator (4), and where said axis (4′), even more preferably, does not go through any of the pinholes (5) of the collimator (4). Said situation is illustrated in FIG. 3.

[0052] In another preferred embodiment of the invention, the axes corresponding to the pinholes (5) of the collimator (4) are substantially parallel, such that the sampling region on the FOV of the detector (2) provided by the cones of incidence of gamma radiation upon passing through the pinholes (5) does not exhibit any overlap for at least two of said pinholes (5).

[0053] As mentioned for different embodiments of the invention, the relative movement between the collimator (4) and the detector (2) is, preferably, a translational and/or rotational movement, as shown in FIGS. 4 and 5, respectively. The example of the translational movement (FIG. 4A) consists of moving the collimator (4) with respect to the detector (2) (FIGS. 4B-4C), so that the pinholes (5) adopt different configurations for one and the same region of the field of view (FOV).

[0054] For the case of rotation (FIGS. 5A-5B), in a preferred embodiment of the invention, the collimator (4) moves in a relative manner with respect to the detector (2), such that each of its pinholes (5) describes a circular path around its corresponding center of rotation (different for each of the pinholes, FIG. 5A), the final position coinciding with the initial position. In another embodiment of the circular movement (FIG. 5B), the collimator (4) can rotate around a fixed point (F) in space, and with relative movement with respect to the detector (2). Said point is preferably the center of the detector (such that the axis of rotation passes through the center of the detector).

[0055] In a third preferred embodiment in the case of rotation (FIG. 6), the collimator (4) has circular groove-shaped pinholes (5). Preferably, said pinholes (5) are partially covered by a plug (6) (for example, plotting a circular portion), where the covered area varies while collecting data with the device (1), such that the pinholes (5) plot a circular path in space.

[0056] In another preferred embodiment of the invention (FIG. 7), the pinholes (5) of the collimator (4) are distributed such that each of said pinholes (5) (except those arranged on the edge of the collimator (4)) has six neighboring pinholes (5), located at the same distance, forming a regular hexagon. Preferably, said pinholes (5) have the same angular aperture, which ensures that each pinhole (5) allows uniform sampling to be performed during imaging.

[0057] By way of operating example, FIGS. 8A-8B show two situations where, in one of them, the device (1) of the invention has all the pinholes (5) of the collimator (4) uncovered, and where in another, one of said pinholes (5) is covered with a plug (6). Preferably, the device (1) of the invention allows gamma rays (8) coming from a source (9) of radiation to be detected. Likewise, the aperture of each pinhole (5) defines a cone (10) of incidence. Additionally, as can be seen in FIG. 8A, the cones (10) of incidence can have overlapping areas (11) with the cones (10) defined by the neighboring pinholes (5). In any of the preceding configurations, the variation of the position of the pinholes (5) of the collimator (4) with respect to the detector (2) takes place continuously, i.e., the pinholes (5) travel a relative distance with respect to the detector (2), but without occlusion of said pinholes along said distance, except possibly by plugs placed prior to acquisition.

[0058] In turn, as can be seen in FIG. 8B, the pinholes (5) of the collimator (4) can be covered and/or moved independently, for the purpose of obtaining a general statistical sampling on the field of view (FOV) or to temporarily prevent the penetration of the gamma rays (8) in the overlapping area (11). With it and by means of a suitable processing of the detection data read by the electronics (3), it is possible to completely or partially eliminate the unwanted artifacts which produce the overlapping areas (11), as well as to obtain a complete image without truncation in the device.

[0059] The sensitive material of the detector (2) can be any radiation-sensitive material that produces a measurable physical quantity when radiation interacts with said material. Examples of detectors (2) usable in the scope of the invention are monolithic or pixelated scintillating crystals, organic or inorganic crystal scintillators, liquid scintillators and/or gaseous scintillators. The scintillators can produce a detection signal that is due to both scintillation and Cherenkov radiation processes. Organic crystal scintillators can be, for example, anthracene, stilbene, naphthalene, liquid scintillators (for example, organic liquids such as p-terphenyl (C 18H14), 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole PBD (C20H14N2O), butyl PBD (C24H22N2O), gas scintillators (such as nitrogen, helium, argon, krypton, xenon), inorganic crystal scintillators, or combinations of any of same. Commonly known inorganic scintillator crystals may be, for example, cesium iodide (CsI), thallium doped cesium iodide (CsI (TI)), bismuth germanate (BGO), thallium doped sodium iodide (NaI (TI)), barium fluoride (BaF2), europium doped calcium fluoride (CaF2(Eu)), cadmium tungstate (CdWO4), cerium doped lanthanum chloride (LaCb(Ce)), cerium doped yttrium lutetium silicates (LuYSiOs(Ce)(YAG(Ce)), silver doped zinc sulfide (ZnS(Ag)) or cerium doped yttrium aluminum garnet (III) Y3 Al5O 12 (Ce) or LYSO. Additional examples are CsF, KI(TI), CaF2(Eu), Gd2SiO5[Ce] (GSO), LSO, GAGG(Ce).

[0060] As mentioned, the scintillators can be monolithic crystals or pixelated crystals, or any combination thereof.

[0061] Scintillating photon detection devices may be formed by, for example, but not limited to, photosensors. The photosensors may be silicon photomultiplier arrays (SiPMs), single photon avalanche diodes (SPADs), digital SiPMs, avalanche photodiodes, position-sensitive photomultipliers, phototransistors, photo-ICs, or combinations thereof. This means that one detector (2) may be coupled, for example, to an SiPM array and another detector (2) in the same device (1) may be coupled to a phototransistor array, according to the above definitions.

[0062] Likewise, solid-state detectors (2) based on semiconductors such as Si, Ge, CdTe, GaAs, PbI2, HgI2, CZT, HgCdTe (also known as CTM), etc., and/or scintillation detectors (2) based on xenon and/or Cherenkov radiation detectors (2) based on PbF2, NaBi (WO4)2, PbWO4, MgF2, C6F14, C4F10 or silica aerogel, can be used.

[0063] Furthermore, the sensitive materials of the detector (2) can be encapsulated or exposed, coupled to an optical reflective surface and/or use any known technique to improve the quality of the collected data. The optical reflective surface can be polished or rough, specular, diffuse, retroreflective or composite. Likewise, one or more detectors (2) may comprise one or more optically painted surfaces.

[0064] Another object of the present invention relates to an imaging system by means of gamma ray detection, comprising one or more devices (1) according to any of the embodiments described herein. In said system, the electronic means (3) for the reading and processing of the detection signals of the gamma rays are preferably connected to an image reconstruction device from the processing of said signals.

[0065] In a preferred embodiment of the system of the invention, said system can be arranged in a mobile platform adapted for being oriented towards different regions of the source of gamma radiation.