• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Method and device for the detection of gamma rays with the capacity to determine multiple interactions and their corresponding time sequence. The present invention refers to a method for the detection of gamma rays capable of determining multiple interactions and their corresponding time sequence, which comprises the use of a device comprising: one or more means of detecting the energy charge qi deposited on the coordinates (x, y, z) of a detector element and the time instant ti corresponding to the detection of said deposition; electronic means for reading and acquiring data connected to the detection means of the device, said electronic means being configured to capture, digitize and transmit the detection signals of the device; and at least one processing unit connected to the electronic means, configured with software and/or hardware means for recording and/or processing the data generated by the electronic data reading and acquisition means. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2783173A1
    申请号:ES201930239
    申请日:2019-03-14
    公开日:2020-09-16
    发明作者:Baviera José María Benlloch；Victor Ilisie；Alventosa Vicent Gimenez；Martinez Filomeno Sanchez；Martinez Antonio Javier Gonzalez
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；Universidad Politecnica de Valencia；
    IPC主号:
    专利说明:

    [0002] METHOD AND DEVICE FOR THE DETECTION OF GAMMA RAYS WITH THE DETERMINATION CAPACITY OF MULTIPLE INTERACTIONS AND THEIR CORRESPONDING TIME SEQUENCE
    [0004] FIELD OF THE INVENTION
    [0006] The present invention falls within the field of gamma ray imaging. More specifically, the invention relates to the design of devices capable of detecting gamma radiation and obtaining information from it, such as medical devices used in nuclear imaging, such as positron emission tomography (PET) equipment, both for purposes diagnostic physicians such as for dose control during irradiation processes, as well as astrophysical gamma ray telescopes (for example, Compton telescopes) or other technical applications, such as control processes in the dismantling of nuclear power plants and / or of National security.
    [0008] BACKGROUND OF THE INVENTION
    [0010] Compton cameras are widely used today, for example in the field of astronomy, astrophysics or nuclear medicine. However, although these cameras can have a very high energy resolution, they have a significant limitation in terms of the temporal resolution of the detected events. This means that, in these systems, it is not possible to accurately determine the time sequence of different scattering events of the gamma rays entering the aforementioned cameras. Another important aspect to take into account is the fact that the known detection devices are based on multilayer configurations or on detectors of pixelated blocks, but none of them contemplate the possibility of using detectors formed by compact monolithic blocks, with the capacity of recognizing various Compton interactions, reconstructing their impact coordinates, energies, and time sequences.
    [0012] A proposal to improve the known systems in this regard is described in patent application WO 2016/185123 A1. However, the reconstruction method disclosed in said document is, in practice, difficult to implement experimentally. This is because the aforementioned method is essentially based on apply a series of geometric approximations that are difficult to generalize to an arbitrary detector. Therefore, the described method only works on very specific types of detectors, and with a limited resolution.
    [0014] On the other hand, there are also other methods of temporal reconstruction of events in gamma detectors based on the calculation of their flight time, such as the method described in patent application WO 2017/077164 A1. To do this, the detectors that implement said method are configured to measure three-dimensional interaction positions in the detector, and the energy deposited in said positions. However, these methods have the limitation that, in order to calculate the flight time of gamma rays, the detectors used must necessarily have a layered structure, which implies added complexity to the detector, which implies greater time and costs. manufacturing, as well as an increased risk of loss of precision.
    [0016] In light of the previous limitations of the state of the art, it is necessary in the present technical field to develop new gamma ray detection methods that allow the interaction events associated with them to be temporarily resolved and that, at the same time, are usable in any detector structure, thus not being restricted to detectors with layered structures. The present invention proposes a solution to this need, by means of a novel method for the detection of gamma rays with the capacity to determine multiple interactions and their corresponding time sequence, and of a gamma ray detection device that implements said method.
    [0018] BRIEF DESCRIPTION OF THE INVENTION
    [0020] As described in the preceding paragraphs, a first object of the invention refers to a method for the detection of gamma rays with the capacity to determine multiple interactions and their corresponding time sequence, which comprises the use of a device that, at in turn, includes:
    [0021] - one or more means for detecting the energy charge qi deposited on the coordinates (x, y, z) of a detector element and the time point ti corresponding to the detection of said deposition;
    [0022] - electronic means for reading and acquiring data connected to the detection means of the device, said electronic means being configured to capture, digitize and transmit the detection signals of the device; Y
    [0023] - at least one processing unit connected to the electronic means, configured with software and / or hardware means for the recording and / or processing of the data generated by the electronic means of reading and acquiring data.
    [0025] Advantageously, the detection method of the invention preferably comprises the following steps:
    [0026] - the center of mass of the values of the deposited charges q, and / or of the charges divided by their time stamp, q / t, is calculated with respect to the coordinates (x, y, z) of the detector element;
    [0027] - The inertial tensor f Map is calculated with respect to the center of mass of the load; - the matrix corresponding to the inertia tensor is diagonalized, to extract its eigenvectors, determining the symmetry axes of said matrix;
    [0028] - the load values q, (or q / t,) detected are projected on the axes defined by the eigenvectors;
    [0029] - alternatively distributions q, M / 1, N can be used, where M and N are two natural numbers that represent the power to which the value of the load rises and the value of the timestamp, to make the peak of the distribution is more appreciable;
    [0030] - the number of interactions suffered by each gamma ray in the detection device, and its coordinates (x, y, z) and corresponding times t, are determined from the projection of the charges q, (or q / t, ) calculated in the previous step, identifying an interaction with a maximum in the function of said projection represented on each axis corresponding to each eigenvector.
    [0032] In a preferred embodiment of the invention, the projection of the charges q is adjusted numerically to a mathematical function, estimating the coordinates (x, y, z) and / or the corresponding deposited energy from the properties of said function. Most preferably, the mathematical function is a Gaussian type distribution.
    [0034] In another preferred embodiment of the invention, the detection method additionally comprises the determination of the depth of interaction (DOI) of the gamma rays, from the dispersion of the energy charge distribution q, in the projections obtained in the axes of eigenvectors.
    [0036] In another preferred embodiment of the invention, once the number of interactions suffered by each gamma ray has been determined, its temporal sequence is established from the coordinates (x, y, z) of said interactions, from the detection times t, and of the determination of the speed of the gamma rays and / or of the optical photons propagated in the detector element, obtained from the speed of light in vacuum c and the refractive index n of said detector element.
    [0038] A second object of the present invention refers to a gamma ray detection device that preferably comprises:
    [0039] - one or more means for detecting the energy charge qi deposited on the coordinates (x, y, z) of a detector element and the time point ti corresponding to the detection of said deposition;
    [0040] - electronic means for reading and acquiring data connected to the detection means of the device, said electronic means being configured to capture, digitize and transmit the detection signals of the device; Y
    [0041] - at least one processing unit connected to electronic means.
    [0043] Advantageously, the device's processing unit comprises software and / or hardware means for recording and / or processing the data generated by the electronic data reading and acquisition means, configured to carry out a method according to any of the described embodiments. in the present document.
    [0045] In a preferred embodiment of the invention, the gamma ray detector element comprises one or more monolithic or pixelated scintillators, one or more solid-state detectors or one or more Cherenkov radiation detectors, isolated or in combination.
    [0047] More preferably, the solid state detector element comprises Si, Ge, CdTe, GaAs, Pbh, Hgh, CZT or HgCdTe semiconductors, and / or the Cherenkov detectors comprise PbF 2 , NaBi (WO 4 ) 2 , PbWO4, MgF 2 , C 6 F 14 , C 4 F 10 or silica airgel.
    [0049] More preferably, the scintillators comprise organic or inorganic crystal scintillators, liquid scintillators and / or gaseous scintillators. And, even more preferably:
    [0050] - organic crystal scintillators comprise anthracene, stilbene and / or naphthalene;
    [0051] - Inorganic crystal scintillators comprise cesium iodide (CsI), thallium doped cesium iodide (CsI (Tl)), bismuth germanate (BGO), thallium doped sodium iodide (NaI (Tl)), barium fluoride (BaF 2 ), europium doped calcium fluoride (CaF 2 (Eu)), cadmium tungstate (CdWO 4 ), cerium doped lanthanum bromide (LaBr3 (Ce)), cerium doped yttria lutetium silicates (LuYSiOs ( Ce) (YAG (Ce)), sulfide silver-doped zinc (ZnS (Ag)) or cerium (III) doped yttrium aluminum granite Y 3 AI 5 O 12 (Ce), LYSO, CsF, KI (Tl), CaF 2 (Eu), Gd 2 SiÜ 5 [Ce] (GSO), and / or LSO;
    [0052] - liquid scintillators comprise p-terphenyl (C 18 H 14 ), 2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole PBD (C 20 H 14 N 2 O), butyl PBD (C 24 H 22 N 2 O), PPO (C 15 H 11 NO), dissolved in solvents such as toluene, xylene, benzene, phenylcyclohexane, triethylbenzene or decalin; Y
    [0053] - the gaseous scintillators comprise nitrogen, helium, argon, krypton and / or xenon.
    [0055] In another preferred embodiment of the invention, the detector element comprises one or more photodetectors. More preferably, said photosensors comprise arrays of silicon photomultipliers (SiPM), single photon avalanche diodes (SPAD), digital SiPM, avalanche photodiodes, position sensitive photomultipliers, photomultipliers, phototransistors, photodiodes, photo-ICs, or combinations thereof.
    [0057] In another preferred embodiment of the invention, the gamma ray detector element is coupled to one or more optically reflective surfaces, said surfaces being polished or rough, specular, diffuse, retro-reflective or mixed.
    [0059] A third object of the invention relates to the use of a method or a device according to any of the embodiments described herein, in a medical nuclear imaging equipment and / or in a gamma ray telescope.
    [0061] Additionally, a list of definitions of some of the terms used in this description is provided below:
    [0063] - Interaction cloud: refers to an accumulation of all kinds of particle interactions (photoelectric, Compton, Bremsstrahlung, Cherenkov, ...) that presents a measurable magnitude, such as the deposited energy, instantaneous time, electrical charge, etc. . This "interaction cloud" is made up of one or more interactions that are close enough, spatially and / or temporally, to be experimentally indistinguishable.
    [0065] - Spatial information: refers to any type of data that is a function of the spatial dimension N (N <3), whether these dimensions are discrete or continuous, and their coordinates (x, y, z).
    [0066] - Sensitive material: refers to any physical material that interacts with radiation producing a measurable physical quantity.
    [0068] - Detector: refers to any device with the ability to record a certain physical quantity (such as spatial and / or temporal information and / or any other physical quantity) that corresponds to one or more interaction clouds. The spatial information can be obtained, for example, by processing the energy deposition distribution and / or the time stamp distribution and / or the electric charge distribution, etc. These detectors can be made up of one or more sensitive materials, one or more acquisition devices, and reading electronics that extract the signals from the detector. The terms "particle detector", "detector", "detector module" and "detection module" will be used synonymously in the present description.
    [0070] - Event: it is defined as the total number of interactions that a single incident gamma ray and its secondary particles produce, until its initial energy is totally or partially lost (depositing, being absorbed, etc.).
    [0072] - The terms "light reflective surface" and "optical reflective surface" are considered synonymous in the present description.
    [0074] - Temporal order, temporal sequence: these are expressions used interchangeably and refer to the knowledge of the information t ' > t, for example, where t and t' are two instants of time (or time stamps), their values being known or not.
    [0076] - Acquisition device: refers to a device used to extract one or more signals generated in a detector, or in one or more sensitive materials.
    [0078] - Charge (energy): refers to the energy deposited in some acquisition device. In the present description, the symbol q is used to denote the energy deposited in some region of the acquisition device, as for example in a determined pixel of a photodetector.
    [0080] - Time stamp: refers to the time information registered by the acquisition device, corresponding to an interaction. The symbol ti will be used to denote said time stamp.
    [0081] - Detection device: refers to a set of detectors, which may or may not be independent, with the same structure or not, which work together.
    [0083] - Data matrix: refers to the information extracted from the reading of one or more acquisition devices of one or more detectors. This information can be relative to any type of measurable physical quantity, such as energy, electrical charge, time stamp, etc. The readings can be processed to combine the acquired data into a single matrix, or more than one. A data matrix can be a matrix of dimension 1 or greater, in any coordinate system.
    [0085] DESCRIPTION OF THE DRAWINGS
    [0087] The foregoing and other characteristics and advantages will be more fully understood from the detailed description of the invention, as well as from the preferred embodiment examples referred to the attached drawings, in which:
    [0089] Figure 1 shows the center of mass of a discrete distribution of charges (energies) with respect to an arbitrary orthogonal reference frame (x, y) and the eigenvectors (u 1 , u 2 ) of the inertial tensor f Map (with respect to the center of mass of the load).
    [0091] Figures 2a-2b show the summed and grouped projections of the discrete load distribution on the eigenvectors (u 1 , u 2 ) of the inertia tensor f Map, respectively.
    [0093] Figures 3a-3b show the summed and grouped projections of the discrete load distribution on the eigenvectors (u 1 , u 2 ) of the inertia tensor f Map, respectively, for a simulated case (long dashed line curves). The dotted curves correspond to Gaussian-type fit curves.
    [0095] Figures 4a-4c show the summed and grouped projections of the q / ti distribution on the eigenvectors of the inertial tensor FMq / tafi (with respect to the center of mass of the q / t distribution) (Figure 4a), the summed projections and grouped of the qt distribution on one of the eigenvectors of the inertia tensor FMq / tafi (Figure 4b) and the summed and grouped projections of the qi / ti distribution on one of the eigenvectors of the load inertia tensor FMap (Figure 4c) , for a simulated case (long dashed line). The dotted lines correspond to the Gaussian-type fit curves.
    [0096] Figure 5 shows the simulated charge (energy) distribution for a Philips-type digital SiPM photodetector (with 8 ^ 8 energy reading and 4x4 timestamp reading) for an incident gamma ray undergoing a Compton interaction. and a photoelectric interaction (referred to as C and P, respectively). The black arrows are the eigenvectors of the inertia tensor f Map with respect to the center of mass of charge, the crossed circle is the center of mass of charge, and the black circle is the center of mass of the q / ti distribution . The "X" marks correspond to the coordinates of the two interactions reconstructed with the method of the present invention.
    [0098] Figure 6 shows the simulated charge (energy) distribution for a possible SiPM digital photodetector (with 18x18 reading both in energy and timestamp) for an incident gamma ray that undergoes a Compton interaction and a photoelectric interaction (referred to as C and P). The black arrows are the eigenvectors of the inertia tensor f Map with respect to the center of load masses, the crossed circle is the center of load masses, and the black circle (which in this case overlaps with the crossed circle) is the center of mass of the q / ti distribution . The "X" marks correspond to the coordinates of the two interactions reconstructed with the method of the present invention.
    [0100] Figure 7 shows a representation of the fastest scintillation optical photons (1, 2) traveling at speed c / n, where c is the speed of light in vacuum and n is the index of refraction of the detector material. Depending on the angle ^, the photon (1) or, conversely, the photon (2) will first reach the photodetector, as explained in the detailed description of the invention.
    [0102] Figure 8 shows the most probable configuration (forward scattering) for the incident gamma ray multiple scattering case. Using the formula for the Compton angle, the energy deposited in the first Compton interaction is small compared to the incident energy. Since the fastest beam of optical photons (those that reach the photodetector first) are below the final interaction (which is due to the photoelectric effect in the example in the figure), the center of mass of the qi / ti distribution will be more near the last interaction.
    [0104] Figure 9 shows the most unlikely configuration (backscatter) for the multiple scattering of incident gamma rays. Using the formula for the Compton angle, the energy deposited in the first Compton interaction represents a high fraction of the incident energy. As the fastest beam of optical photons is found below the first interaction (which is a Compton scatter in the example in the figure), the center of mass of the q / ti distribution will be closer to the first interaction.
    [0106] Figure 10 shows a probable configuration for the case of multiple scattering of an incident gamma ray where the interaction depths are similar. Since the deposited energies are also similar, the center of mass of the q / ti distribution will be closer to the first interaction, as in the case of Figure 9.
    [0108] DETAILED DESCRIPTION OF THE INVENTION
    [0110] A detailed description of the invention is set forth below, referring to different preferred embodiments thereof, based on Figures 1-10 herein. Said description is provided for illustrative, but not limiting, purposes of the claimed invention.
    [0112] As described in the preceding paragraphs, the present invention relates to a gamma ray detection device (suitable for use, for example, in PET or Compton cameras) comprising one or more pixel, monolithic or layered detectors. In such detectors, the incident gamma rays can be scattered inside (Compton scattering) and / or be absorbed by the photoelectric effect. Both Compton scattering and the photoelectric effect, in the case of scintillators, produce scintillation photons (optical photons), typically of the order of thousands per MeV, which are uniformly and isotropically distributed over a solid angle of 4n steradians (distribution spherical). In this context, the pixelated photodetectors of the device of the invention are configured to provide electronic reading of the information related to the scintillated optical photons, including in said information, essentially, at least the energy deposited in each pixel (referred to as said energy as " load ”) and the time point (or" timestamp ") when the scintillation events occur. By combining the aforementioned information about the deposited energy (charge) and the time stamp information in each pixel, the detectors of the device of the invention can accurately determine the coordinates of multiple Compton interactions and / or photoelectric effect. Furthermore, using charge distribution, detectors can also calculate the depth of interaction (or DOI ) of each gamma ray, as well as estimate its energy deposited at each impact. This information combined It can be used to obtain improved PET and Compton cameras with respect to the systems known from the state of the art.
    [0114] As described in the previous sections, and thanks to the pixelated photodetectors described (capable of obtaining information about the charge and the time stamp of each interaction event for each gamma ray), a first object of the present invention refers to a method for the detection of gamma rays with the ability to determine multiple interaction clouds and their corresponding time sequence. In said method, for an incident gamma ray, the output of the electronic reading of the pixelated detector is presented, preferably, as two data matrices, where one of said matrices contains the information on the energy (charge) deposited in each pixel, and the other contains information about the timestamp for each interaction and pixel.
    [0116] As mentioned, each element of the charge matrix corresponds to the energy deposited by the optical photons in its corresponding pixel. As optical photons can be considered as monoenergetic, the total energy corresponding to a pixel will be given by the number of photons detected by each pixel. On the other hand, the matrix containing the time stamps will contain information about the instant of detection of the first optical photon detected in a pixel, or a group of pixels. Therefore, the information generated by each pixelated detector can be considered as a discrete charge distribution, together with a time stamp distribution, both two-dimensional (on the pixel map). Therefore, the vector coordinates of the center of mass of charge vcm of a distribution of charges q, (with i = 1 .... N) are given by the following expression:
    [0118]
    [0120] center of mass, it is possible to calculate the components of the inertial tensor PMap (which is a matrix of dimension 2 * 2) of discrete distribution with respect to said center of mass:
    [0122]
    [0124] However, depending on the events to be detected, in a real case it is possible to obtain lower quality projections, requiring an adjustment of the reading results obtained. An example of such a type of adjustment is shown in Figs. 3a-3b for a numerical simulation, where the longer dashed lines correspond to the distribution of collected load, projected on the axes designated by the eigenvectors, the vertical lines are the real coordinates of the interactions and the dotted lines (trace finer) correspond to numerical fits to Gaussian-type distributions:
    [0126]
    [0128] where A is a convergence constant of the fit, y is the mean value of the fit, and a is the standard deviation of the distribution. From the mean value y, the 2D coordinates of the interactions can be estimated, and the constant A can be used to extract the energy deposited for each interaction (impact).
    [0130] The above settings can be further improved, using the time stamp information. In a possible embodiment of the method of the invention, instead of using only the timestamps of the fastest photons, it is possible to use, instead, the complete distribution thereof, for example by means of a parameter corresponding to the quotient of the charge divided by time, q / u, where is the charge deposited on a pixel i, and t , is the timestamp corresponding to that pixel. This makes it possible to expressly contemplate the charge distribution in the regions where the optical photons reach detector first. Thus, in this embodiment, the previous steps are carried out (using Equations 1-3), making the substitution:
    [0132]
    [0134] The timestamp (corresponding to the lowest timestamp) cannot be set to zero in this case, although it is possible to set an infinitesimal value constant s to be added to all timestamps t ,. Having calculated the center of mass vector rq / tcM of the distribution q, / t, and also the inertia tensor f M'q / tap and its eigenvectors, it is possible to calculate the distribution of charge divided by the timestamp on the axes defined by these eigenvectors. This allows obtaining an improved profile of the interaction clouds, as shown by way of example in Figure 4a. The distribution of charge can also be projected onto the eigenvectors of q / t, or vice versa (Figs. 4b-4c, respectively). With a statistical verification test, for example using a x2 test, it is possible to choose the best fits and use them to estimate the 2D coordinates (x, y) of the incident gamma ray interactions. An example of such a result is shown in Figure 5, for a Philips-type digital silicon photomultiplier detector (32 * 32 mm2 size), with 8 * 8 energy reading and 4 * 4 independent time stamps. In the above figure, C and P represent the real Compton and photoelectric interactions, the cross in a circle represents the center of mass, and the two orthogonal arrows are the eigenvectors of f Map. The black circle represents the center of mass q / t. The "X" marks represent the reconstructed coordinates of the interaction points, using the method described above.
    [0136] The use of smaller pixels improves both the energy estimation and the 2D coordinate reconfiguration structure. In this sense, in the example shown in Figure 6, where the electronic reading has been simulated for a detector of the same size (32 * 32 mm2), but with an energy reading of 18 * 18 and 18 * 18 independent time stamps . The figure shows the real and reconstructed gamma-ray interactions, as well as the center of mass and the eigenvectors of f Map, as in Figure 5 above.
    [0138] The charge (energy) deposited for each Compton / photoelectric interaction can be estimated from the numerical adjustments (i.e., as in Equation 3) or from the energy distribution in the vicinity of the reconstructed coordinates, corresponding to the points of interaction of gamma rays. Depth of Interaction (DOI) can also be estimated in a similar way, using the information of the width (dispersion) of the energy distribution. Another method may be to use the reading of an additional lateral and / or upper photodetector, or both. This option improves both the DOI estimation and the load estimation, and can also further improve the reconstruction of the (x, y) coordinates.
    [0140] Having estimated the DOI, the remaining task is the recognition of the time sequence of the interactions. Here again we must make the distinction between the first interaction of gamma rays and the interaction whose scintillated optical photons reach the photodetector first. Ideally, a limiting angle y, (which only depends on the refractive index n as shown below) helps to accurately distinguish between the different possible cases. As an example (Figure 7), we consider the interaction of an incident gamma ray that undergoes a Compton scattering and a photoelectric interaction. The fastest optical photons (those that arrive first at the pixelated photodetector, indicated as (1, 2) in the figure) generated by these interactions are those that travel in a straight line towards the photodetector, orthogonal to it, as shown in shown in Figure 7 (left), with speed c / n (where c is the speed of light in vacuum and n is the index of refraction). Since the incident gamma ray is a high-energy photon, it travels at speed c, and the scattered Compton gamma ray will also travel at the same speed c. Hence, of the optical photons (1, 2), the photon that will be detected first will depend on which one, between the scattered gamma ray traveling at speed c, and the optical photon (1) traveling at c / n, arrives before to the dotted line shown in Figure 7. Said line is the line parallel to the photodetector that crosses the point where the photoelectric effect occurs, which is the source of the optical photon (2). From this line, both the photon (1) and the photon (2) travel the same distance at the same speed. As represented in the triangle in Figure 7 (right), we obtain:
    [0143] ' n ¿2 (Eq. 7) The conclusion is therefore that
    [0145] , one
    [0146] 1 1 <Í2 s¡ and only if <z>> arceae -
    [0147] n (Eq. 8)
    [0149] Thus, it is possible to define a limiting angle y¡ = arccos (l / n) and, therefore, if y <y¡ the optical photon (2) reaches the photodetector first, and if y> y¡ the optical photon (1 ) is the one that reaches the photodetector first. As an example, for a LYSO scintillation crystal, where n - 1.8, the limiting angle is y - 57 °. It is important to keep in mind that the fastest optical photon can be scattered, absorbed or even reach the photodetector without being detected. Therefore, instead of relying on the timestamp of a single optical photon (or just a few), it is possible to also consider the entire q / t distribution , as presented below.
    [0151] By way of example, three possible cases of interest will be illustrated, as shown in Figs. 8, 9 and 10. Since Compton scattering at 511 keV occurs mostly forward, the first case (Figure 8) represents the most likely case of interaction. From Compton's equation:
    [0153]
    [0155] (where Ey and E 'y are the energy of the incident and scattered gamma ray, respectively, and me is the mass of the electron), it follows that, in the case of forward scattering, the deposited energy ( Edep = Ey - E' y) in the first Compton interaction is small ( Edep «) compared to the total energy. Thus, the amount of energy deposited will be greater for the final photoelectric absorption. Since the angle $ is small, the fastest group of optical photons from the second interaction will reach the photodetector before the photons from the first interaction. To eliminate possible statistical fluctuations, the center of mass of the q / ti distribution will be used as an estimator . In the case shown by Figure 8, the center of mass q / t shifts closer to the last interaction.
    [0157] For the second configuration (Figure 9), the opposite case is analyzed in which the gamma ray deposits a large amount of energy in the first Compton interaction ( Edep ») and is scattered backwards. The result of the detector reconstruction of the two interactions is indistinguishable from the first. The detector output would be two interactions, one with high energy deposition and one with low energy deposition and different DOIs. Furthermore, in this case the center of mass q / t shifts closer to the first interaction.
    [0159] For the third case (Figure 10) where the energy deposited in the first Compton interaction has an intermediate value (denoted as E -) and the heights are similar, the center of mass q / t is closer to the first interaction. They are due, in general terms, to the fact that the angle $ ~ 90 ° »y.
    [0160] Although in the cases described above only two interactions occur, the method of the invention can be extended to an arbitrary number of interactions.
    [0162] In summary, the present invention is essentially characterized by the fact that the gamma ray detection device is configured to spatially distinguish between different interaction clouds, deduce their time sequence and also their corresponding fraction of deposited energy (with respect to the total energy deposited from an event), making use of any type of registered spatial information and / or temporal information and / or energy information. For example, for a scintillating crystal, the detector will preferably use the deposited energy distribution, or information about the energy distributions and time stamp and / or the qMi / tNi distribution , to obtain the necessary spatial information, the energy deposited by each interaction cloud and its time sequence. In the present description, qi has been used as the charge and t as the information of the time stamp of a pixel i (of a pixelated photodetector) and M , N as two real numbers, which represent arbitrary powers to which said values can be raised. to make the corresponding distributions have a more defined peak.
    [0164] The spatial information can be, for example, the distribution of the number of optical photons produced by a scintillation crystal, the distribution of the electrical charge produced in a semiconductor detector, detection of Cherenkov radiation, etc. It is important to note that, without the time stamp information, the detector can still spatially distinguish between different interaction clouds, but cannot establish their time sequence. In view of this fact, the most important characteristic of the detector of the present invention is the fact that it is capable of carrying out such measurement with monolithic block detectors coupled to pixelated photosensors.
    [0166] In a second object of the invention, the gamma ray detection device described in the present document preferably comprises one or more detectors, independent or not, where said detectors can be grouped in any type of structure, such as a multilayer format. , independent, forming a detector ring etc. Likewise, the detectors are preferably equipped with data reading and acquisition electronics, configured to capture, digitize and send the detection signals to a processing unit for subsequent analysis. Said unit will be configured with software and / or hardware means to carry out the detection method of the invention, in any of its preferred embodiments, as described in the previous sections.
    [0167] The acquisition devices of the detectors can be coupled to the sensitive materials, using any type of technology or material known and used in the state of the art, such as, for example, optical grease. It can also be attached without any intermediate material.
    [0169] The sensitive material of the detection device can be any material that produces a measurable physical quantity when radiation interacts with such material. Some examples are scintillating, monolithic or pixelated crystals, semiconductors such as Si, Ge, CdTe, GaAs, Pbl2, Hgl2, CZT, etc. for solid state detectors, xenon for Cherenkov scintillation and radiation detectors, etc. Additionally, sensitive materials 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. Optical reflective surfaces can be polished or rough, specular, diffuse, retro-reflective or mixed. Also, one or more sensing assemblies may comprise an optically painted surface.
    [0171] In a detection system according to the invention, each detector device can be adjacent to another that forms a certain set, said set being able to be organized with respect to another, for example forming a closed or open structure. The components of a detector system can be identical or different, depending on their specific design conditions.
    [0173] Each detector in the device can have an arbitrary shape, and can measure any physical quantity that provides spatial and / or temporal information of at least one interaction cloud of one or more sensitive materials. Examples of such detection elements are solid state detectors, scintillation detectors, etc.
    [0175] Examples of solid state detectors are semiconductors such as Si, Ge, CdTe, GaAs, PbI 2 , HgI 2 , CZT or HgCdTe (also known as CTM). Cherenkov radiators such as PbF 2 , NaBi (WO 4 ) 2 , PbWO4, MgF 2 , C 6 F 14 , C 4 F 10 or silica airgel. Scintillation elements can also be used, such as organic or inorganic crystal scintillators, liquid scintillators or gaseous scintillators. Scintillators can produce a detection signal that is due to both scintillation and Cherenkov radiation processes.
    [0176] Organic crystal scintillators can be, for example, anthracene, stilbene, naphthalene, liquid scintillators (for example, organic liquids such as p-terphenyl (C 18 H 14 ), 2- (4-biphenylyl) -5-phenyl-1, 3,4-oxadiazole PBD (C 20 H 14 N 2 O), butyl PBD (C 24 H 22 N 2 O), PPO (C 15 H 11 NO), dissolved in solvents such as toluene, xylene, benzene, phenylcyclohexane, triethylbenzene or decalin), gas scintillators (such as nitrogen, helium, argon, krypton, xenon), inorganic crystal scintillators, or combinations of any of these.
    [0178] Commonly known inorganic scintillation crystals can also be used, for example cesium iodide (CsI), thallium doped cesium iodide (CsI (Tl)), bismuth germanate (BGO), thallium doped sodium iodide (NaI (Tl)), Barium fluoride (BaF 2 ), europium doped calcium fluoride (CaF 2 (Eu)), cadmium tungstate (CdWO 4 ), cerium doped lanthanum bromide (LaBr3 (Ce)), silicates of lutetium yttria doped with cerium (LuYSiOs (Ce) (YAG (Ce)), zinc sulfide doped with silver (ZnS (Ag)) or granite of yttrium aluminum doped with cerium (III) Y 3 Al 5 O 12 (Ce) or LYSO Additional examples are CsF, KI (Tl), CaF 2 (Eu), Gd 2 SiO 5 [Ce] (GSO), LSO.
    [0180] As previously mentioned, the scintillators according to the present invention can be monolithic crystals or pixelated crystals, or any combination thereof. Preferably the scintillator, however, will be a single crystal (monolithic block), as pixelized crystals introduce more areas of dead space into the gamma ray detector, thus providing less sensitivity to the detector device compared to single crystals.
    [0182] The detection device (of the scintillating photons) can be formed by photosensors. The photosensors can be silicon photomultiplier arrays (SiPM), single photon avalanche diodes (SPAD), digital SiPM, avalanche photodiodes, position sensitive photomultipliers, photomultipliers, phototransistors, photodiodes, photo-ICs, or combinations thereof. . This means that one detector device can be coupled, for example, to a SiPM matrix and another detector device can be coupled to a phototransistor matrix in a detector system according to the above definitions.
    [0184] The information extracted from the detector can be a 2D spatial and / or temporal data matrix. However, the method can be trivially generalized to any dimension, depending on the reading format.
    [0185] A single listener can produce one or more arrays of data. For example, if an acquisition device is used for different regions of the detector, a number of data matrices can be obtained equal to or greater than the number of said regions. In addition, the readings from the acquisition device can also be combined to create a single data matrix. Another example might be a large detector using two acquisition devices in a single region. The combination of the two read arrays can form a unified data array, if desired.
    [0187] Alternatively or complementary, a plurality of detectors can provide a single data matrix. For example, if a detector is not large enough to cover a desired surface area, two or more detectors can be arranged in an array, and their readings combined to obtain a larger array of data. The data matrix can be expressed using any desired coordinate system (Cartesian, cylindrical, spherical, etc.).
    [0189] Regardless of the dimension number or the coordinate system of the data matrix, the procedure used by the invention to obtain the coordinates of the impact position is the same. For example, in a D-dimensional data matrix with discrete or continuous values (and D> 1, where D is integer) as functions of D spatial dimensions (D> 1). In general, the method to be carried out comprises the following steps:
    [0191] to)
    [0193] b) Calculate the inertia tensor with respect to the center of mass of charge and / or the center of mass of the distribution qM / tNi.
    [0195] c) The matrix corresponding to the inertia tensor is diagonalized to extract its eigenvectors. These vectors provide the axes of symmetry for the N-dimensional data matrix.
    [0197] Any other method that extracts the lines of symmetry from the data matrix is also valid and would be within the scope of the invention. An alternative example could be the use of machine learning techniques, as in neural network techniques.
    [0198] There are several ways to obtain the coordinates if there are multiple interaction clouds. As an example, you can project data from the data matrix along the axes defined by the eigenvectors of the inertia tensor, and fit these projections to a known function or a combination (linear or not) of functions. In the case of a 2D matrix, for a scintillation detector, these projections can be fitted to a linear combination of Gaussian-type functions.
    权利要求:
    Claims (14)
    [1]
    1 Method for the detection of gamma rays capable of determining multiple interactions and their corresponding time sequence, comprising the use of a device that, in turn, comprises:
    - one or more means for detecting the energy charge q deposited on the coordinates (x, y, z) of a detector element and the time instant t corresponding to the detection of said deposition;
    - electronic means for reading and acquiring data connected to the detection means of the device, said electronic means being configured to capture, digitize and transmit the detection signals of the device;
    - at least one processing unit connected to the electronic means, configured with software and / or hardware means for recording and / or processing the data generated by the electronic data reading and acquisition means;
    and said method being characterized in that it comprises performing the following steps:
    - the center of mass of the deposited charges q is calculated with respect to the coordinates (x, y, z) of the detector element;
    - The inertial tensor f Map is calculated with respect to the center of mass of charge q; - the matrix corresponding to the inertia tensor is diagonalized, to extract its eigenvectors, determining the symmetry axes of said matrix;
    - the detected load values qt are projected on the axes defined by the eigenvectors;
    - the number of interactions suffered by each gamma ray in the detection device, and its coordinates (x, y, z) and corresponding times ti, are determined from the projection of the charges qi calculated in the previous step, identifying a interaction with a maximum in the function of said projection;
    - the temporal sequence of the interactions suffered by each gamma ray is established from the coordinates (x, y, z) of said interactions, the detection times ti and the determination of the speed of the gamma rays and / or of the optical photons propagated in the detector element, from the speed of light in vacuum c and from the refractive index n, and / or statistically as a function of the coordinates of the different interactions.
    [2]
    2.- Method according to the preceding claim where, in the steps corresponding to the calculation of the center of mass and the projection of the load values q, said values they are divided by their corresponding time t, in the form qMi / tNi, where M and N are two real numbers.
    [3]
    3.
    [4]
    Four.
    [5]
    5.
    [6]
    6. - Detection device comprising:
    - one or more means for detecting the energy charge qi deposited on the coordinates (x, y, z) of a detector element and the time point ti corresponding to the detection of said deposition;
    - electronic means for reading and acquiring data connected to the detection means of the device, said electronic means being configured to capture, digitize and transmit the detection signals of the device;
    - at least one processing unit connected to the electronic means; said device being characterized in that the processing unit comprises software and / or hardware means for recording and / or processing the data generated by the electronic data reading and acquisition means, configured to perform a method according to any of the following previous claims.
    [7]
    7.
    [8]
    8.
    [9]
    9.
    [10]
    10. - Device according to the preceding claim, where:
    - organic crystal scintillators comprise anthracene, stilbene and / or naphthalene;
    - Inorganic crystal scintillators include cesium iodide (CsI), thallium doped cesium iodide (CsI (Tl)), bismuth germanate (BGO), thallium doped sodium iodide (NaI (Tl)), barium fluoride (BaF 2 ), europium doped calcium fluoride (CaF 2 (Eu)), cadmium tungstate (CdWO 4 ), cerium doped lanthanum bromide (LaBr3 (Ce)), cerium doped yttria lutetium silicates (LuYSiOs ( Ce) (YAG (Ce)), silver doped zinc sulfide (ZnS (Ag)) or cerium (III) doped yttrium aluminum granite Y 3 Al 5 O 12 (Ce), LYSO, CsF, KI (Tl) , CaF 2 (Eu), Gd 2 SiO 5 [Ce] (GSO), and / or LSO;
    - liquid scintillators comprise p-terphenyl (C 18 H 14 ), 2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole PBD (C 20 H 14 N 2 O), butyl PBD (C 24 H 22 N 2 O), PPO (C 15 H 11 NO), dissolved in solvents such as toluene, xylene, benzene, phenylcyclohexane, triethylbenzene or decalin;
    - the gaseous scintillators comprise nitrogen, helium, argon, krypton and / or xenon.
    [11]
    eleven.
    [12]
    12. - Device according to the preceding claim, where the photosensors comprise arrays of silicon photomultipliers (SiPM), single photon avalanche diodes (SPAD), digital SiPM, avalanche photodiodes, position sensitive photomultipliers, photomultipliers, phototransistors, photodiodes , photo-ICs, or combinations thereof.
    [13]
    13.
    [14]
    14. Use of a device according to any of claims 6-13 or of a method according to any of claims 1-5, in a medical nuclear imaging device and / or in a gamma ray telescope.
    类似技术:
    公开号 | 公开日 | 专利标题
    US10281594B2|2019-05-07|Gamma-ray Compton TOF camera system
    US7635848B2|2009-12-22|Edge-on SAR scintillator devices and systems for enhanced SPECT, PET, and compton gamma cameras
    US7238946B2|2007-07-03|Nuclear imaging system using scintillation bar detectors and method for event position calculation using the same
    JP2005533245A|2005-11-04|Gamma-ray detectors for positron emission tomography | and single photon emission computed tomography |
    Kishimoto et al.2014|Performance and field tests of a handheld Compton camera using 3-D position-sensitive scintillators coupled to multi-pixel photon counter arrays
    JP2014122898A|2014-07-03|Gamma ray scintillation detector preserving original scintillation light distribution
    CN107110981A|2017-08-29|For X-ray or the detector assembly of gamma-ray detector
    Kishimoto et al.2017|Development of a compact scintillator-based high-resolution Compton camera for molecular imaging
    US9304211B2|2016-04-05|Scintillation detector with active light guide
    Jeong et al.2020|Development of hand-held coded-aperture gamma ray imaging system based on GAGG | scintillator coupled with SiPM array
    ES2783173B2|2021-01-20|METHOD AND DEVICE FOR THE DETECTION OF GAMMA RAYS WITH THE CAPACITY OF DETERMINING MULTIPLE INTERACTIONS AND THEIR CORRESPONDING TIME SEQUENCE
    Aguiar et al.2012|A feasibility study on the use of arrays of discrete SiPMs for MR compatible LYSO readout using Monte Carlo simulation
    Bettiol et al.2016|A Depth-of-Interaction encoding method for SPECT monolithic scintillation detectors
    US20050029461A1|2005-02-10|Gamma camera using rotating scintillation bar detector and method for tomographic imaging using the same
    Després et al.2006|Investigation of a continuous crystal PSAPD-based gamma camera
    Randall et al.2014|A method of providing directionality for ionising radiation detectors—RadICAL
    Lee et al.2020|Development of a Position-Sensitive 4π Compton Camera Based on a Single Segmented Scintillator
    ES2757984B2|2021-02-16|DEVICE FOR THE DETECTION OF GAMMA RAYS WITH ACTIVE SEALS
    Patel2016|An Experimental Investigation to Assess the Feasibility of Imaging Medical Radioisotopes with the ProSPECTus Compton Camera
    KR102316574B1|2021-10-21|A Compton Imager and a Single Photon Emission and Positron Emission Tomography System including the same
    Kato et al.2012|High position resolution gamma-ray imagers consisting of a monolithic MPPC array with submillimeter pixelized scintillator crystals
    Yang et al.2018|Development and Application of Gamma Camera in the Field of Nuclear Medicine
    US20210239862A1|2021-08-05|Imaging detector system for gamma radiation using unidirectional and bidirectional compton scattering processes
    Kim et al.2018|Optimization of DPC dSiPM-Based DOI Compton Camera by Monte Carlo Simulation
    Sharif et al.2015|Study of Radiation Detection Properties of a Pixellated CsI Gamma Imaging Module
    同族专利:
    公开号 | 公开日
    WO2020183052A1|2020-09-17|
    EP3940430A1|2022-01-19|
    ES2783173B2|2021-01-20|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20180289349A1|2015-05-04|2018-10-11|Siemens Medical Solutions Usa, Inc.|Data-driven surrogate respiratory signal generation for medical imaging|
    FR3036500B1|2015-05-18|2017-06-23|Alain Iltis|SYSTEM AND METHOD FOR DETECTING GAMMA RADIATION OF COMPON CAMERA TYPE.|
    ES2629092B1|2015-11-04|2018-07-04|Consejo Superior De Investigaciones Científicas |GAMMA RAY COMPTON CAMERA SYSTEM WITH FLIGHT TIME MEASUREMENT|
    法律状态:
    2020-09-16| BA2A| Patent application published|Ref document number: 2783173 Country of ref document: ES Kind code of ref document: A1 Effective date: 20200916 |
    2021-01-20| FG2A| Definitive protection|Ref document number: 2783173 Country of ref document: ES Kind code of ref document: B2 Effective date: 20210120 |
    优先权:
    申请号 | 申请日 | 专利标题
    ES201930239A|ES2783173B2|2019-03-14|2019-03-14|METHOD AND DEVICE FOR THE DETECTION OF GAMMA RAYS WITH THE CAPACITY OF DETERMINING MULTIPLE INTERACTIONS AND THEIR CORRESPONDING TIME SEQUENCE|ES201930239A| ES2783173B2|2019-03-14|2019-03-14|METHOD AND DEVICE FOR THE DETECTION OF GAMMA RAYS WITH THE CAPACITY OF DETERMINING MULTIPLE INTERACTIONS AND THEIR CORRESPONDING TIME SEQUENCE|
    PCT/ES2020/070181| WO2020183052A1|2019-03-14|2020-03-13|Method and device for detecting gamma rays with ability to determine multiple interactions and their corresponding time sequence|
    EP20771020.3A| EP3940430A1|2019-03-14|2020-03-13|Method and device for detecting gamma rays with ability to determine multiple interactions and their corresponding time sequence|
    [返回顶部]