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EP-3876244-B1 - DEVICE FOR THE DETECTION OF GAMMA RAYS WITH ACTIVE PARTITIONS

EP3876244B1EP 3876244 B1EP3876244 B1EP 3876244B1EP-3876244-B1

Inventors

  • ILISIE, Víctor
  • BENLLOCH BAVIERA, José María
  • SÁNCHEZ MARTÍNEZ, Filomeno

Dates

Publication Date
20260506
Application Date
20191030

Claims (9)

  1. A device for the detection of gamma rays (1) coming from a source (2), comprising at least two contiguous detection cells (3), wherein each of said detection cells (3) comprises: - a collimation element (4) comprising an opening (5) through which the gamma rays (1) coming from the source (2) can penetrate, defining a cone (6) of incidence; - a detection space (7) adapted to receive the gamma rays (1) that penetrate through the opening (5), wherein: - said detection space (7) comprises one or more gamma ray detection assemblies (8, 8') equipped with at least a scintillating material (9) and a photodetector (10); - the theoretical projections of the cones (6) of incidence of the gamma rays (1) in the two detection cells (3) have an overlap volume (11) within the detection space (7); - at least one of the detection assemblies (8') is arranged such that it stands in the way of the gamma rays (1) coming into the overlap volume (11); and - the detection assemblies (8, 8') comprise at least one gamma ray blocking surface (12) arranged as a separating partition between the detection cells (3); characterized in that - said partition is in contact on both sides with the detection assemblies (8, 8') of said detection cells (3); and - the blocking surface (12) comprises one or more reflective elements (13).
  2. The device according to the preceding claim, wherein the separating partition and/or the detection assemblies (8, 8') are arranged in a perpendicular manner with respect to a plane defined by the collimation element (4).
  3. The device according to any of the preceding claims, wherein at least one of the reflective elements (13) comprises a rough or polished, retro-reflective or diffuse specular reflector or a combination thereof.
  4. The device according to any of the preceding claims, wherein one or more detection assemblies (8, 8') comprise an optically painted surface.
  5. The device according to any of the preceding claims, wherein the scintillating material comprises a pixelated solid, a monolithic solid, a liquid, gas or a combination thereof.
  6. The device according to the preceding claim, wherein each detection cell (3) comprises different scintillating materials.
  7. The device according to any of the preceding claims, wherein the photodetector (10) of at least one of the detection assemblies (8, 8') comprises photomultipliers, avalanche diodes, photodiodes, phototransistors, photo-ICs or a combination thereof.
  8. A system for generating images by means of the detection of gamma rays (1), such as in SPECT, characterized in that it comprises: - one or more gamma-ray detection devices according to any of the preceding claims, - electronic signal readout and processing means connected to the gamma-ray detection devices, and - an image-reconstruction device adapted for reconstructing images from the signals processed by the electronic signal readout and processing means.
  9. The system according to the preceding claim, wherein said system is arranged on a mobile platform adapted to be oriented towards different regions of the source of gamma radiation.

Description

FIELD OF THE INVENTION The present invention is comprised in the field relating to imaging by means of gamma rays. More specifically, the invention relates to the design of devices for the detection of gamma radiation to obtain information about same, for example nuclear imaging medical devices, such as gamma cameras or single photon emission computed tomography (SPECT) equipment, among others. BACKGROUND OF THE INVENTION High-sensitivity and high-resolution gamma cameras are of particular interest today, given that they present a high potential in the field of the nuclear medicine. Said cameras allow, for example, small-sized tumors to be diagnosed early, and are also useful in a wide range of pre-clinical studies, which allows, for example, more effective treatments against cancer to be designed. The basic operation of a gamma camera device consists of injecting into a patient a radioactive contrast agent, such as 99mTc, which will break down, emitting a photon (gamma ray) of 140 keV of energy, according to the following process: T99mc→T99c+γ. This high-energy photon passes through a collimator, preferably made of a dense material that is highly impenetrable for gamma rays in this energy range, typically formed by lead (Pb) or tungsten (W), before reaching a radiation sensitive detector. This process is shown schematically in Figure 1 herein, for two typical types of collimators (with parallel holes on the left side of the image, and pinholes on the right side of the image). Radiation-sensitive detectors of cameras of this type are usually made from a dense, gamma ray-sensitive material, typically a block of Nal scintillating crystal or the like. In said block, the gamma ray is absorbed by a nucleus or electron of the material, the energy of which is emitted again in the form of a quantity in the order of thousands of optical photons, which are detected by a photodetector. This process is shown schematically in Figure 2 herein. A common problem for gamma cameras is their low sensitivity. This is because only gamma rays which are emitted in parallel to the collimators (for the case of a parallel collimator, Figure 1, left) or within a certain angular region (for the pinhole collimator, Figure 1, right) effectively reach the detector. In this context, in the case of gamma cameras, with collimation openings, to increase sensitivity, which means increasing the number of gamma rays detected, the number of pinholes and/or the angular aperture of each pinhole must be increased. Nonetheless, by increasing the number of said openings, the unwanted effect known as image overlap (or the problem of multiplexing) is generated, as schematically shown in Figures 3a-3b, showing different perspectives of this effect. As is seen in said figures, within the overlap region of the detector it is impossible to unequivocally identify the opening through which the incident gamma ray has previously passed before it is detected. In the absence of this information, usually what is done is all the possible combinations are considered in the calculations performed in the image reconstruction method. As an example, in the case of positron emission tomography (PET), said reconstruction method consists of calculating lines of response (LOR) through the field of view (FOV). In the case of gamma cameras, LORs are constructed by merging the point of impact of the gamma ray in the detector with the corresponding opening (through which it previously passed). At this point, when the correct opening in the overlapping region cannot be identified and all the combinations of possible gamma ray paths have to be made, this translates into considering incorrect LORs for image reconstruction. This, therefore, introduces noise into the final reconstructed image, as well as possible spurious images, commonly referred to as artifacts (see, for example, in references [1], [2], [3] mentioned at the end of this section). In addition to being associated with images with noise, artifacts are highly dangerous given that they may have serious consequences in a possible incorrect diagnosis of patients (for clinical cases), or may lead to mistaken conclusions in pre-clinical studies. The aforementioned problems also occur in known detectors based on collimators which do not produce overlapping, such as for example those described in patent applications US 2006/0065840 A1 and US 2006/0000978 A1. Nevertheless, in said detectors, the elimination of overlap causes, in contrast, the truncation of images and a smaller FOV (which may contain blind regions). In recent years, a number of studies have been performed to improve gamma cameras and SPECT systems (see mentioned references [1], [2], [3], [4]) to eliminate overlap effects. However, to date, no generic solution has been found which can be used in any detection system, given that the problem largely depends on the complexity of the object of study (small animals, organs, etc.), on the FOV or on the desired resolu