CN108888286B

CN108888286B - PET detector, and PET detector setting method and PET detector detection method

Info

Publication number: CN108888286B
Application number: CN201810245033.0A
Authority: CN
Inventors: 安少辉; 张强
Original assignee: Shanghai United Imaging Healthcare Co Ltd
Current assignee: Shanghai United Imaging Healthcare Co Ltd
Priority date: 2014-05-28
Filing date: 2014-05-28
Publication date: 2022-05-27
Anticipated expiration: 2034-05-28
Also published as: CN114699099A; CN105425270B; CN108888286A; CN105425270A

Abstract

A PET detector, a method for setting the PET detector and a method for detecting the PET detector are provided. The PET detector includes: the crystal array comprises a plurality of crystal units arranged in an array manner and light splitting structures arranged on the surfaces of the crystal units, wherein the light splitting structures jointly define a light emitting surface of the crystal array; the semiconductor sensor array is arranged opposite to the light emitting surface of the crystal array and is suitable for receiving photons from the light emitting surface, and the semiconductor sensor array comprises a plurality of semiconductor sensors which are arranged in an array mode. Through set up the beam splitting structure on the crystal unit, for set up the light-guiding piece between crystal array and semiconductor sensor, can effectively shorten the transmission distance of photon, and then can avoid because the light-guiding piece arouses the optical transmission loss to can improve PET detector's resolution ratio.

Description

PET detector, and PET detector setting method and detection method

Technical Field

The invention relates to the technical field of optical detection, in particular to a PET (positron emission tomography) detector, a setting method of the PET detector and a detection method.

Background

Positron Emission Tomography (PET) detectors are commonly provided in various large medical devices that employ PET technology, such as: disposed in a Positron Emission Tomography-Computed Tomography (PET-CT) apparatus or a Positron Emission Tomography-Magnetic Resonance Imaging (PET-MRI) apparatus. The PET detector is used for receiving gamma rays generated in a patient body and feeding back position information of photons generated by the received gamma rays on the detector to other components of the large medical equipment, so that the other components of the large medical equipment can perform corresponding processing according to the position information.

Currently, as shown in fig. 1, a PET detector generally includes: a crystal array 102, an Avalanche Photo Diode (APD) array 104 coupled to the crystal array 102, and a light guiding sheet 106 disposed between the crystal array 102 and the APD array 104. The crystal array 102 is formed by arranging a plurality of crystal units according to a certain design, and the APD array 104 is formed by arranging a plurality of APDs according to a certain design. Each APD is in contact with at least one crystal cell

Gamma rays generated in the patient are received by one of the crystal units of the crystal array 102 and enter the crystal unit, the gamma rays excite photons in the crystal unit, the photons are transmitted between the crystal units of the crystal array 102, and finally enter the APD array 104 through the light guide sheet 106, and the photons are received by the APD array.

When the gamma ray excites a photon inside the crystal unit, only a part of the excited photon can enter the APD array 104 because the optical guiding sheet 106 causes a certain optical transmission loss, resulting in a low resolution of the PET detector.

Disclosure of Invention

The problem solved by the embodiments of the present invention is how to improve the resolution of the PET detector.

To solve the above problems, an embodiment of the present invention provides a PET detector, including:

the crystal array comprises a plurality of crystal units arranged in an array manner and light splitting structures arranged on the surfaces of the crystal units, wherein the light splitting structures jointly define a light emitting surface of the crystal array;

the semiconductor sensor array is arranged opposite to the light emitting surface of the crystal array and is suitable for receiving photons from the light emitting surface, and the semiconductor sensor array comprises a plurality of semiconductor sensors which are arranged in an array mode.

Optionally, a portion of the crystal units in the crystal array are coupled to corresponding semiconductor sensors in the semiconductor sensor array.

Optionally, at least one semiconductor sensor in the array of semiconductor sensors is coupled to a corresponding crystal unit in the array of crystals.

Optionally, the coupling comprises the semiconductor sensor being in contact with the crystal unit or by an adhesive material.

Optionally, a center of gravity of the semiconductor sensor array coincides with a center of gravity of the crystal array.

Optionally, the semiconductor sensor array covers the light exit surface or partially covers the light exit surface.

Optionally, the light splitting structure is a reflective film or a white reflective coating disposed on the surface of the crystal unit.

Optionally, the PET detector further comprises: the input end of the first amplifier is connected with the output ends of the semiconductor sensors in a preset row in the semiconductor sensor array.

Optionally, the PET detector further comprises: and the input end of the second amplifier is connected with the output end of a preset column of semiconductor sensors in the semiconductor sensor array.

Optionally, the arrangement of the spectroscopic structure on the surface of the crystal unit matches the light receiving area of the semiconductor sensor, the relative position between the semiconductor sensors, and the relative position between the semiconductor sensor and the crystal array.

Optionally, the number and location of the semiconductor sensors is related to the resolution of the crystal units on the image.

The embodiment of the invention also provides a method for setting the PET detector, which comprises the following steps:

adjusting the area of a light splitting structure arranged on each crystal unit in the crystal array;

and arranging the semiconductor sensor array opposite to the light emergent surface of the crystal array to obtain the PET detector.

Optionally, the adjusting the area of the light splitting structure disposed on each crystal unit in the crystal array includes:

adjusting the probability of photons occurring within each crystal unit;

and when the probability of the photons appearing in the crystal unit meets the resolution condition of the crystal unit on the image, setting the crystal unit according to the area of the light splitting structure corresponding to the probability.

Optionally, the adjusting the probability of the occurrence of the photon in each crystal unit includes:

adjusting the probability of photons occurring within the selected crystal unit using the following formula:

wherein N represents the total number of photons generated in any crystal unit of the crystal array except the selected crystal unit, m represents the number of photons appearing in the selected crystal unit when the total number of photons generated in the any crystal unit is N, P represents the probability that the photons appear in the selected crystal unit when 1 photon is generated in the any crystal unit, and P represents the probability that the number of photons appearing in the selected crystal unit when the total number of photons generated in the any crystal unit is N is m.

The embodiment of the invention also provides a detection method of the PET detector, which comprises the following steps:

the crystal unit of the PET detector receives gamma rays;

a semiconductor sensor of the PET detector receives photons generated by excitation of the gamma rays in the crystal unit;

and determining the position of the gamma ray generating photons inside the crystal unit according to the output of the semiconductor sensor.

Optionally, a center of gravity reading method is used to determine the position of the gamma ray generating photons inside the crystal unit.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

through set up the beam splitting structure on the crystal unit, for set up the light-guiding piece between crystal array and semiconductor sensor, can effectively shorten the transmission distance of photon, and then can avoid because the light transmission loss that the light-guiding piece arouses to can improve PET detector's resolution ratio.

By coupling a part of the crystal units in the crystal array with corresponding semiconductor sensors in the semiconductor sensor array, or coupling at least one semiconductor sensor with corresponding crystal units in the crystal array, without coupling each crystal unit in the crystal array with a corresponding semiconductor sensor, the number of semiconductor sensors can be set more flexibly, so that in the case of using the same number of crystal units, fewer semiconductor sensors can be used to meet the resolution requirement of the crystal units on the same image, and therefore the cost of the PET detector can be reduced.

The gravity center of the semiconductor sensor array and the gravity center of the crystal array are overlapped, so that the photon generation position can be more conveniently determined by a gravity center reading method in the follow-up process.

The semiconductor sensor array can completely cover the light-emitting surface of the crystal array and can also partially cover the light-emitting surface of the crystal array, so that the number and the positions of the sensors can be more flexibly set, and the requirements of the resolution ratios of the crystal units on the same image can be met by using fewer semiconductor sensors under the condition of the same number of crystal units, so that the cost of the PET detector can be reduced.

Through the arrangement of the first amplifier and the second amplifier, when the generation position of the photon is determined by adopting a gravity center reading method, the generation position of the photon can be directly determined according to the output of the first amplifier and the second amplifier without respectively reading the output of each semiconductor sensor, so that the data processing amount when the generation position of the photon is determined can be reduced, and the difficulty in determining the position of the photon is reduced.

By using formulas

The probability of photons appearing in each crystal unit is adjusted, the area of the light splitting structure on each crystal unit is further adjusted, and the requirement on the resolution ratio of the crystal units on the image can be met more quickly.

Drawings

FIG. 1 is a longitudinal cross-sectional structural schematic view of a prior art PET detector;

FIG. 2 is a schematic diagram of a longitudinal cross-sectional structure of a PET detector in an embodiment of the invention;

FIG. 3 is a schematic cross-sectional view of the PET detector of FIG. 2;

FIG. 4 is a schematic diagram of another PET detector cross-sectional configuration in an embodiment of the invention;

FIG. 5 is a schematic diagram of a cross-sectional configuration of yet another PET detector in an embodiment of the invention;

FIG. 6 is a schematic diagram of a cross-sectional configuration of yet another PET detector in an embodiment of the invention;

FIG. 7 is a schematic diagram of a cross-sectional configuration of yet another PET detector in an embodiment of the invention;

FIG. 8 is a schematic view of a light-splitting structure provided on a crystal unit in an embodiment of the present invention;

FIG. 9 is a schematic representation of the transmission of photons between two crystal units in an embodiment of the present invention;

FIG. 10 is another schematic illustration of the transmission of photons between two crystal units in an embodiment of the invention;

fig. 11 is a schematic diagram of the distribution of the probability of photons appearing inside each crystal unit in the 1 x 10 crystal array before adjustment;

fig. 12 is a schematic diagram of the distribution of the probability of photons appearing inside each crystal unit in the adjusted 1 x 10 crystal array;

FIG. 13 is a schematic cross-sectional view of another PET detector in an embodiment of the invention;

FIG. 14 is a schematic illustration of a probability distribution of photons occurring within each crystal unit of the PET detector of FIG. 13;

FIG. 15 is a two-dimensional image of the individual crystal unit locations obtained using the PET of FIG. 13 for detection simulation;

FIG. 16 is a flow chart of a method of setting up a PET detector in an embodiment of the invention;

FIG. 17 is a flow chart of a method of detecting a PET detector in an embodiment of the invention.

Detailed Description

Currently, in a PET detector structure as shown in fig. 1, after a gamma ray excites a photon within a crystal cell, the photon enters the APD array 104 through the light guiding sheet 106. The light guide plate 106 is disposed to increase the distance of photon transmission, thereby causing a certain light transmission loss, resulting in a decrease in the resolution of the PET detector.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Referring to fig. 2, an embodiment of the present invention provides a PET detector, which may include: crystal arrays and semiconductor sensor arrays.

The crystal array may include a plurality of crystal units 202 arranged in an array, and a light splitting structure 204 disposed on a surface of the crystal units 202. The light splitting structures 204 disposed on the crystal units 202 together define a light emitting surface 206 of the crystal array. The semiconductor sensor array is disposed opposite to the light emitting surface 206 of the crystal array, and includes a plurality of semiconductor sensors 208 arranged in an array. The semiconductor sensor array is integrated on a driving board 210, and the driving board 210 is connected with the semiconductor sensors 208 and is suitable for driving the corresponding semiconductor sensors 208 to work.

It should be noted that, in the embodiment of the present invention, the light emitting surface 206 is composed of the light emitting surface of each crystal unit 202, and the light emitting surface of each crystal unit 202 is: the photons enter the surface of the crystal unit that the corresponding semiconductor sensor 208 passes through last.

The crystal array includes at least three or more crystal units 202, the number and arrangement of the crystal units 202 are not limited, and those skilled in the art can set the number and arrangement according to the actual required PET detector size. Wherein the larger the number of crystal units 202, the larger the size of the PET detector. As shown in fig. 3-5, the crystal array may be an 8 x 8 arrangement, an 8 x 9 arrangement, or an 8 x 19 arrangement of crystal units 202, etc., with different numbers of crystal units corresponding to different sizes of PET detectors.

In particular implementations, the crystal unit 202 may be fabricated from a variety of materials. For example, the material of the crystal unit may be at least one of: bismuth germanate, lutetium silicate, lutetium yttrium silicate, lutetium gadolinium silicate, yttrium silicate, barium fluoride, sodium iodide, cesium iodide, lead tungstate, yttrium aluminate, lanthanum bromide, lanthanum chloride, lutetium aluminum calcium titanium, lutetium pyrosilicate, lutetium aluminate, and lutetium iodide.

The gamma rays excite photons in the crystal unit, and the photons are reflected when encountering the light splitting structure in the transmission process, so that the transmission path of the photons is changed, and therefore the photons excited in the crystal unit can enter the semiconductor sensor corresponding to the crystal unit from one surface of the crystal unit for limiting the light emitting surface, and can also enter the semiconductor sensor corresponding to other crystal units from one surfaces of the other crystal units for limiting the light emitting surface. The semiconductor sensor corresponding to the crystal unit and the semiconductor sensor corresponding to the other crystal unit may be the same semiconductor sensor or different semiconductor sensors. That is, one of the semiconductor sensors may receive photons from a face of one of the crystal units in the crystal array that defines the light exit surface, or may receive photons from a face of each of the plurality of crystal units that defines the light exit surface.

Therefore, when the semiconductor sensor array receives photons from the light emitting surface of the crystal unit array, various coupling modes can exist between the semiconductor sensor and the crystal unit. Wherein the semiconductor sensor is in contact with the crystal unit or may be in contact with an adhesive material, for example, to make the connection between the semiconductor sensor and the corresponding crystal unit more stable. In particular implementations, silicone grease may be employed as the bonding material.

In an embodiment of the present invention, a manner of coupling a part of the crystal units in the crystal array with corresponding semiconductor sensors in the semiconductor sensor array is adopted, so that the semiconductor sensors can receive photons from the light emitting surface of the crystal array. Wherein, some crystal units in the crystal array may correspond to one semiconductor sensor or correspond to a plurality of semiconductor sensors.

As shown in fig. 3, the cross-sectional structure of the PET detector is schematically illustrated, the crystal array of the PET detector is an 8 × 8 array, and the semiconductor sensor array thereof is a 2 × 2 array, wherein a part of the crystal units 202 of the crystal array respectively correspond to 4 semiconductor sensors 208 in the semiconductor sensor array. When gamma rays excite photons in the crystal units of the crystal array not covered by the semiconductor sensor 208, the photons can be transmitted to the crystal units covered by the semiconductor sensor 208 and then received by the semiconductor sensors corresponding to the crystal units covered by the semiconductor sensor 208 through the light splitting structures arranged on the surfaces of the crystal units not covered by the semiconductor sensor 208.

In another embodiment of the present invention, at least one semiconductor sensor in the semiconductor sensor array is coupled to a corresponding crystal unit in the crystal array, so that the semiconductor sensor can receive photons from the light emitting surface of the crystal array. The semiconductor sensor array may have only one semiconductor sensor with a corresponding crystal unit in the crystal array, or may have a plurality of semiconductor sensors with corresponding crystal units in the crystal array, as long as one semiconductor sensor in the semiconductor sensor array can receive photons from the light emitting surface of the crystal array.

As shown in fig. 6, the cross-sectional structure of the PET detector is schematically illustrated, the crystal array of the PET detector is an 8 × 8 array, and the semiconductor sensor array is a 2 × 2 array, wherein the semiconductor sensor 2081 and the semiconductor sensor 2082 are coupled to the corresponding crystal units 202 in the crystal array, and the semiconductor sensor 2083 and the semiconductor sensor 2084 do not have the corresponding crystal units 202 in the crystal array.

In another embodiment of the present invention, the semiconductor sensor array covers the light emitting surface of the crystal array or partially covers the light emitting surface, so that the semiconductor sensor can receive photons from the light emitting surface.

As shown in the schematic cross-sectional structure of the PET detector in fig. 7, when the semiconductor sensor array completely covers the light exit surface of the crystal array, each crystal unit in the crystal array is covered by a semiconductor sensor, and the crystal units 202 in the crystal array have corresponding semiconductor sensors in the semiconductor sensor array, where the corresponding semiconductor sensors may be part of or all of the semiconductor sensors in the semiconductor sensor array.

When the semiconductor sensor array partially covers the light-exiting surface of the crystal array, part of the crystal units in the crystal array are coupled with the corresponding semiconductor sensors 208. In an embodiment of the present invention, as shown in fig. 3, each semiconductor sensor 208 in the semiconductor sensor array is coupled to a crystal unit in the crystal array, and the semiconductor sensor array covers the light-emitting surface of a part of the crystal units in the crystal array. In another embodiment of the present invention, as shown in fig. 6, a part of the semiconductor sensors in the semiconductor sensor array is coupled to the crystal units in the crystal array, and the semiconductor sensor array covers only the light emitting surfaces of the part of the crystal units in the crystal array.

In order to more conveniently determine the position of the gamma ray exciting the photon in the crystal unit according to the output of the semiconductor sensor, the gravity center of the semiconductor sensor array and the gravity center of the crystal array can be arranged in a coincidence mode. When the center of gravity of the semiconductor sensor array is coincident with the center of gravity of the crystal array, the position of photon generation can be determined by using a center of gravity reading method. As shown in fig. 3 to 5, the semiconductor sensor array includes a semiconductor sensor 208 arranged in an array, the crystal array includes a plurality of crystal units 202 arranged in an array, the center of gravity of the semiconductor sensor array coincides with the center of gravity of the crystal array, and therefore, the center of gravity of the crystal array can be determined from the center of gravity of the semiconductor sensor array, and thus, the generation position of photons can be determined from the center of gravity of the crystal array.

In a specific implementation, the semiconductor sensor array includes at least three semiconductor sensors. The semiconductor sensor can be a photoresistor, a photodiode or a phototriode and other devices. Wherein the number and location of the semiconductor sensors is related to the resolution of the crystal units on the image. In the implementation, those skilled in the art can adjust the number and the positions of the semiconductor sensors in the above embodiments according to the requirement of the resolution of the crystal unit on the image. For example, the semiconductor sensor array may include 4, 5 or 8 semiconductor sensors according to different requirements of resolution of crystal units on an image, and the corresponding arrangement may be set, as shown in fig. 3 to 5.

It should be noted that the resolution of the crystal unit on the image is: the resolution of the position of the individual crystal units on the image obtained using the PET detector. The higher the resolution of the crystal units on the image, the clearer the positions of the image corresponding to the crystal units are, and the clearer the boundaries between the positions of different crystal units are.

As can be seen from the foregoing, in the embodiment of the invention, the limitation on the number and the positions of the semiconductor sensors is small, and each semiconductor sensor does not need to correspond to a crystal unit in the crystal array, so that, under the condition of ensuring the resolution of the crystal unit on an image, the number of the semiconductor sensors can be effectively reduced compared with the existing PET detector, and the cost of the PET detector can be reduced.

In the embodiment of the invention, the semiconductor sensor is adopted to convert the optical signal into the electric signal, and the semiconductor sensor is based on the internal photoelectric effect, and has the advantages of small volume, light weight, no influence of a magnetic field on working and the like compared with a device for converting the optical signal into the electric signal based on the external photoelectric effect.

For example, the size of the diameter of a photomultiplier tube that converts an optical signal into an electrical signal based on the external photoelectric effect is typically 3/4 inches, 1 inch, and 1.5 inches, while the size of the diameter of a semiconductor sensor is typically 3 × 3mm or 6 × 6 mm. A 1 inch photomultiplier tube may contact a crystal cell having an area of about 8 x 8cm when in contact with the crystal cell, while a 6 x 6mm semiconductor sensor may contact a crystal cell having an area of about 2 x 2 cm. The larger the area of the crystal unit contacted with the signal, the more the number of cases received in unit time, the longer the detection dead time of the PET detector, the more easily the signal is accumulated, and the poorer the detection sensitivity of PET is. It can be found by calculation that a 1 inch photomultiplier tube receives about 16 times as many instances per unit time as a 6 x 6mm semiconductor sensor. Under otherwise identical conditions, the detection dead time of the PET detector with the semiconductor sensor is about 2 to 3 times that of the PET detector with the semiconductor sensor, and therefore, the detection sensitivity of the PET detector with the semiconductor sensor is also higher. Moreover, the work of the PET detector with the semiconductor sensor is not influenced by a magnetic field, so that the use of a user can be more convenient.

When the light splitting structure is arranged on the surface of the crystal unit, the light splitting structure may be arranged on the surface of a part of the crystal units in the crystal array, or the light splitting structure may be arranged on the surface of each crystal unit. The positions and areas of the light splitting structures arranged on each crystal unit can be the same or different.

As shown in fig. 8, when a light splitting structure is provided on a surface of one of the crystal units 802, the light splitting structure may be provided on a part of the surface of the crystal unit 802, or the light splitting structure may be provided on each surface of the crystal unit 802. When a light splitting structure is disposed on a surface of the crystal unit 802 for defining a light emitting surface, the area of the light splitting structure should be smaller than that of the surface. The areas of the light splitting structures arranged on the surfaces of each crystal surface can be the same or different. For example, taking the surface 03 of the crystal unit 802 as a surface for defining the light exit surface as an example, the light splitting structure 01a may be provided on the surface 01 of the crystal unit 802, the light splitting structure 02a may be provided on the surface 02, and the area of the light splitting structure 01a may be the same as or different from the area of the light splitting structure 02 a. When the light-splitting structure is provided on the face 03, the area of the light-splitting structure should be smaller than that of the face 03.

When a gamma ray is received by the crystal unit 802, the gamma ray excites a plurality of photons inside the crystal unit 802. And part of photons enter the corresponding semiconductor sensor through the surface 03, the other part of photons enter other crystal units through the surface 01, the surface 02 or other surfaces, and the other part of photons finally enter the semiconductor sensors corresponding to the other crystal units after being transmitted among the other crystal units. The position of the photons excited by the gamma ray inside the crystal unit can be resolved from the output of the semiconductor sensor.

In specific implementation, the light splitting structure can be a reflective film or a white reflective coating arranged on the surface of the crystal unit. The area and the position of the light splitting structure on the surface are different, so that the quantity of photons transmitted to the surface of the light splitting structure to enter other crystal units through the surface is different, the number of photons received by each semiconductor sensor is different, and the result of analyzing the position of the photons according to the output of the semiconductor sensor is finally influenced. The following description will be made of the difference in the number of photons generated into other crystal units due to the difference in the arrangement of the light splitting structure, taking two crystal units as an example:

as shown in fig. 9 and 10, the crystal unit 902 and the crystal unit 904 are adjacent crystal units, and a white reflective coating (shown by a shaded portion) is disposed on a surface of the crystal unit 904 in contact with the crystal unit 902. The gamma ray excites 3 photons inside the crystal cell 902. When photons generated inside the crystal unit 902 are transmitted to the white reflective coating, the photons transmitted to the white reflective coating are reflected by the white reflective coating and cannot enter the crystal unit 904 through the white reflective coating. And when the photons are transmitted to the portion of the non-white light reflecting coating in the side of the contact, they may enter crystal unit 904 through the portion of the non-white light reflecting coating in the side of the contact.

As shown in fig. 9, since the area of the white light reflecting coating is equal to the area of the contacted side, no 2 photons transmitted to the contacted side enter the crystal unit 904 at this time. As shown in fig. 10, since the area of the white light reflecting coating is about half of the area of the side in contact, 1 photon of the 2 photons transmitted to the side in contact enters the crystal unit 904 at this time.

As can be seen from the above, the arrangement of the light splitting structures on the respective faces of the crystal units is different, resulting in different numbers of generated photons entering other crystal units. Therefore, in order to meet the requirement of resolution of the crystal units on the image, when the PET detector in the embodiment of the invention is arranged, the area of the light splitting structure arranged on each crystal unit can be adjusted by adjusting the probability of the photon appearing in each crystal unit.

A large number of practices prove that the probability of photons appearing in each crystal unit of the crystal array meets the following formula:

When the area of the spectroscopic structure provided on each crystal unit is adjusted by applying the formula (1), the N, m values and the p values can be obtained by corresponding detection equipment or a limited number of experiments. When the image analysis is performed on the photon generation position according to the output of the semiconductor sensor, the photon generation position can be accurately determined according to the image display result only when the resolution of the crystal unit on the image meets a certain requirement. In general, the greater the number of photons present in each crystal unit of the crystal array, the greater the resolution of each crystal unit on the image. And when the probability P of the photons appearing in the selected crystal unit meets the condition of the resolution of the crystal unit on the image, arranging the crystal unit according to the area of the light splitting structure corresponding to the probability P.

When the probability of photons appearing in the selected crystal unit is high, the area of the light splitting structure on the crystal unit can be reduced, the position of the light splitting structure on the crystal unit can be adjusted, or the position of the light splitting structure on the crystal unit can be adjusted while the area of the light splitting structure is reduced. On the contrary, the area of the light splitting structure on the crystal unit may be increased, the position of the light splitting structure on the crystal unit may be adjusted, or the position of the light splitting structure on the crystal unit may be adjusted while the area of the light splitting structure on the crystal unit is increased.

In an embodiment of the present invention, a 1 × 10 crystal array is selected, where the crystal array includes 10 crystal units, and each crystal unit is provided with a light splitting structure. Taking the PET detector composed of the 1 × 10 crystal array as an example, the following detailed description will be made on the adjustment of the spectroscopic structure disposed on the surface of each crystal unit by using formula (1):

as shown in fig. 11 and 12, fig. 11 shows a distribution diagram of the probability of occurrence of photons in each crystal unit in the crystal array before adjustment, and fig. 12 shows a distribution diagram of the probability of occurrence of photons in each crystal unit in the crystal array after adjustment. In fig. 11 and 12, the horizontal axis represents the position of each crystal unit, the waveform between two adjacent troughs represents the probability distribution of photons appearing at different positions in 1 crystal unit, and the vertical axis represents the probability value of photons appearing in each crystal unit. The larger the ratio of the peak to the trough of each waveform representing the probability of a photon occurring inside the crystal unit, the higher the resolution of the crystal unit on the obtained image.

As can be seen from comparing fig. 11 with fig. 12, in fig. 12, the ratios of the peaks to the troughs of the waveforms mostly representing the probability of photons appearing inside the crystal unit are all greater than the ratios of the peaks to the troughs of the waveforms representing the probability of photons appearing inside the corresponding crystal unit in fig. 11. That is, after the spectroscopic structure arranged on the surface of each crystal unit is adjusted by applying the formula (1), the PET detector with higher resolution can be obtained more quickly.

In a specific implementation, in order to better meet the requirement of the resolution of the crystal unit on the image, when the light splitting structure is arranged on the surface of the crystal unit, the light splitting structure on the crystal unit can be arranged according to the light receiving area of the semiconductor sensor, the relative position between the semiconductor sensors and the relative position between the semiconductor sensor and the crystal array. That is, the arrangement of the spectroscopic structure on the surface of the crystal unit is also required to match the light receiving area of the semiconductor sensor, the relative position between the semiconductor sensors, and the relative position between the semiconductor sensor and the crystal array.

Wherein the light receiving area of the semiconductor sensor is set at the time of shipment of the semiconductor sensor. For example, the light receiving area of a conventional semiconductor sensor is typically 3 × 3mm or 6 × 6 mm. In a specific implementation, in order to further reduce the size of the PET detector, a semiconductor sensor with a light receiving area of 3 × 3mm may be selected.

In general, among the factors such as the light receiving area of the semiconductor sensors, the relative position between the semiconductor sensors and the crystal array, and the probability of photons appearing in each crystal unit, after the parameters of one or more of the factors are determined, the parameters of the other factors can be adjusted to make the PET detector meet the requirements of the resolution of the crystal units on the image.

For example, in the case where the light receiving area of the semiconductor sensor is determined, the requirement for the resolution of the crystal units on the image can be satisfied by adjusting the relative position between the semiconductor sensors, the relative position between the semiconductor sensor and the crystal array, and the probability of occurrence of photons within each crystal unit. In the case where the light receiving area of the semiconductor sensor and the relative position between the semiconductor sensors are determined, the requirement for the resolution of the crystal units on the image can be satisfied by adjusting the relative position between the semiconductor sensor and the crystal array and the probability of occurrence of photons within each crystal unit. In the case where the light receiving area of the semiconductor sensor and the probability of occurrence of photons within each crystal unit are determined, the requirement for the resolution of the crystal unit on the image can be satisfied by adjusting the relative position between the semiconductor sensors and the relative position between the semiconductor sensor and the crystal array. In the case where the light receiving area of the semiconductor sensor, the relative position between the semiconductor sensors, and the relative position between the semiconductor sensor and the crystal array are determined, the requirement for the resolution of the crystal units on the image can be satisfied by adjusting the probability of the occurrence of photons in each crystal unit.

Therefore, when the PET detector in the embodiment of the present invention is disposed, the area of the spectroscopic structure disposed on each crystal unit in the crystal array may be adjusted first, and then the semiconductor sensor array is disposed with respect to the light emitting surface of the crystal array, or the semiconductor sensor array may be disposed with respect to the light emitting surface of the crystal array first, and then the area of the spectroscopic structure disposed on each crystal unit in the crystal array is adjusted. Regardless of the order of the two, it is sufficient if the resolution of the crystal unit on the image is satisfied.

In detecting the generation position of the photon by using the PET detector in the embodiment of the present invention, as described above, a certain crystal unit of the crystal array receives the gamma ray, and the gamma ray is excited inside the crystal unit to generate the photon. After the semiconductor sensor receives the photons from the light emitting surface of the crystal array, the position of the gamma ray generating the photons inside the crystal unit can be determined according to the output of the semiconductor sensor.

When determining the photon generation position by using the centroid reading method based on the output of the semiconductor sensors, it is necessary to calculate the total energy E of the generated photons and the energy X of the photons received by the semiconductor sensors in one row₁And the energy Y of the photons received by the semiconductor sensors of one of the columns₁Thus, the position X of the row of the photon generation position is X₁E, where the column position Y ═ Y₁and/E, determining the generation position of the photon according to the values of x and y. And wherein the total energy E of the generated photons has a value equal to the sum of the energies of the photons received by the individual semiconductor sensors of the PET detector, wherein the semiconductor sensors of a row receive photonsEnergy X₁Is equal to the sum of the energies of the photons received by the semiconductor sensors of one of the rows, and the energy Y of the photon received by the semiconductor sensor of one of the columns₁Equal to the sum of the energies of the photons received by the individual semiconductor sensors of said one of the columns.

At present, when determining the generation position of photons, the common practice is: the data of the output of each semiconductor sensor is read, and the position of the photon is determined based on the read data. That is, in the above manner, the number of data read is the same as the number of semiconductor sensors. Thus, when the PET detector includes a plurality of semiconductor sensors, the data processing amount for subsequently determining the photon generation position is increased, and the difficulty in determining the photon generation position is also increased. For example, when the PET detector shown in fig. 5 is used to determine the generation position of photons, since the PET detector includes 8 semiconductor sensors, the number of read data is 8 when the data of the semiconductor sensors is read. When the generation position of the photon is determined in the subsequent processing, 8 data are required to be processed to determine the generation position of the photon, so that the difficulty in determining the position of the photon is increased.

Therefore, in view of the above situation, in the embodiment of the present invention, when the PET detector is disposed, the PET detector may further include a first amplifier, and an input terminal of the first amplifier is connected to an output terminal of a predetermined row of semiconductor sensors in the semiconductor sensor array. The number of the first amplifiers can be set according to the number of rows of the semiconductor sensor array, and the number of the first amplifiers is less than or equal to the number of rows of the semiconductor sensor array. When the input end of the first amplifier is connected with the output end of a preset row of semiconductor sensors in the semiconductor sensor array, the input end of the first amplifier is respectively connected with the output ends of the preset row of semiconductor sensors, and the output data of each preset row of semiconductor sensors is input data of the first amplifier. Therefore, when the position of photon generation is determined by adopting a gravity center reading method, the output of the semiconductor sensor in one row can be directly determined according to the output of the first amplifier, the output of each semiconductor sensor does not need to be read respectively, the data processing amount in the subsequent process of determining the position of photon generation can be reduced, and the difficulty in determining the position of photon is reduced.

Similarly, when the PET detector in the embodiment of the invention is provided, a second amplifier may be further included, and an input terminal of the second amplifier is connected to an output terminal of a predetermined column of semiconductor sensors in the semiconductor sensor array. Specifically, the second amplifier may be set with reference to the description of the first amplifier, which is not described herein again.

In a specific implementation, the PET detector may include only the first amplifier, only the second amplifier, or both the first amplifier and the second amplifier. When the PET detector comprises the first amplifier and the second amplifier, the data processing amount in the process of determining the position where the photon is generated can be further reduced, and the difficulty in determining the position of the photon is reduced.

The arrangement and detection of the PET detector in an embodiment of the invention will now be described, taking the PET detector shown in fig. 13 as an example:

as shown in fig. 13, the PET detector includes: a crystal array in which the crystal units 202 are arranged in an 8 × 8 array, and a semiconductor sensor array in which the semiconductor sensors 2081 to 2084 are arranged in a 2 × 2 array.

When the PET detector is arranged, after specific semiconductor sensors are selected, the relative positions of the semiconductor sensors 2081-2084 and the relative positions of the semiconductor sensors and the crystals can be determined, and then the areas of the light splitting structures arranged on the surfaces of the crystal units are adjusted, so that the resolution of the crystal units on an image obtained by applying the PET detector meets certain requirements.

When the area of the light splitting structure arranged on the surface of each crystal unit is adjusted, the probability of photons appearing inside each crystal unit 202 can be adjusted, and when the value of the probability meets the condition of the resolution of the crystal unit on an image, the area of the light splitting structure corresponding to the value of the probability is set. For example, the probability distribution of photons occurring inside each crystal unit 202 can be adjusted to the probability distribution shown in fig. 14 by adjusting the probability of photons occurring inside each crystal unit 202. After the areas of the light splitting structures arranged on the crystal units are adjusted, the semiconductor sensor array is arranged opposite to the light emergent surface of the crystal array, and the PET detector can be obtained.

In order to facilitate the subsequent determination of the location of the photon generation from the output of the semiconductor sensor, a first amplifier as well as a second amplifier may also be provided in the obtained PET detector. When the first amplifier is provided, the first amplifier may be provided in a row where the

semiconductor sensors

2081 and 2083 are located, or in a row where the

semiconductor sensors

2082 and 2084 are located, or may be provided in both the row where the

semiconductor sensors

2081 and 2083 are located and the row where the

semiconductor sensors

2082 and 2084 are located. In the embodiment of the present invention, the first amplifier 1301 is provided in the row where the

semiconductor sensors

2081 and 2083 are located. Similarly, when the second amplifier is provided, the second amplifier may be provided in a column in which the

semiconductor sensors

2081 and 2082 are located, or in a column in which the

semiconductor sensors

2083 and 2084 are located, or may be provided in both a column in which the

semiconductor sensors

2081 and 2082 are located and a column in which the

semiconductor sensors

2083 and 2084 are located. In the embodiment of the present invention, the second amplifier 1302 is provided in the column where the

semiconductor sensors

2081 and 2082 are located, and the second amplifier 1303 is provided in the column where the

semiconductor sensors

2083 and 2084 are located.

The output of the first amplifier 1301 is out1, the output of the second amplifier 1302 is out2, and the output of the second amplifier 1303 is out 3. Thus, the total energy E of the photons, out2+ out3, is the energy X of the photons received by the semiconductor sensors of a row₁Out1, the energy Y of the photons received by the semiconductor sensors of one column₁Out2 or Y₁Out 3. It should be noted that after determining the one row and the one column, the one row and the one column are taken as an x-axis and a y-axis, and the coordinate system established by the x-axis and the y-axis is determinedThe location of the photon generation. Energy Y of photons received by the semiconductor sensors of one of the columns₁Out2, the position X of the row where the photon is generated is X according to the centroid reading method₁/E＝out1/(out2+out3)，y＝Y₁Out2/(out2+ out 3). In this way, the position where the photon is generated can be determined from the outputs of the first amplifier 1301, the second amplifier 1302, and the second amplifier 1303, and the data processing amount in determining the position where the photon is generated is effectively reduced compared to the case where the position where the photon is generated can be determined from the outputs of the

semiconductor sensors

2081, 2082, 2083, and 2084.

The two-dimensional image analysis results obtained by performing detection simulation using the PET detector are shown in fig. 15. Wherein the abscissa of fig. 15 represents the position of the column in which each crystal unit is located, and the ordinate represents the position of the row in which each crystal unit is located. As can be seen from fig. 15, the positions of the crystal units are arranged uniformly, and each crystal unit is clearly visible, and the resolution of the crystal unit on the corresponding image is higher. When the PET detector is applied to actually detecting the generation position of the photon, the position of the photon can be accurately obtained.

In order to enable those skilled in the art to better understand and implement the embodiments of the present invention, the method corresponding to the above-mentioned PET detector is described in detail below.

As shown in fig. 16, an embodiment of the present invention also provides a method for setting a PET detector, which may include:

step 1602: and adjusting the area of the light splitting structure arranged on each crystal unit in the crystal array.

When the area of the light splitting structure arranged on each crystal unit in the crystal array is adjusted, the probability of photons appearing in each crystal unit can be adjusted first, and when the probability of photons appearing in the crystal unit meets the condition of the resolution of the crystal unit on an image, the crystal unit is arranged according to the area of the light splitting structure corresponding to the probability.

When adjusting the probability of photons occurring in each crystal unit, the above formula (1) may be used to adjust the probability of photons occurring in the selected crystal unit.

Step 1604: and arranging the semiconductor sensor array opposite to the light emergent surface of the crystal array to obtain the PET detector.

In the specific implementation, the order of implementing the

steps

1602 and 1604 is not limited. That is to say, the area of the light splitting structure disposed on each crystal unit in the crystal array may be adjusted first, and then the semiconductor sensor array is disposed opposite to the light emitting surface of the crystal array, or the area of the light splitting structure disposed on each crystal unit in the crystal array may be adjusted first, and then the semiconductor sensor array is disposed opposite to the light emitting surface of the crystal array, and then the area of the light splitting structure disposed on each crystal unit in the crystal array is adjusted, which is not limited herein.

When the PET detector is set by applying the setting method in the embodiment of the present invention, the setting method may be implemented by referring to the description of the embodiment of the PET detector, and details are not repeated here.

As shown in fig. 17, an embodiment of the present invention also provides a detection method of a PET detector, which may include:

step 1702: the crystal unit of the PET detector receives gamma rays.

Step 1704: the semiconductor sensor of the PET detector receives photons generated by the gamma ray excited in the crystal unit.

Wherein

steps

1702 and 1702 may be implemented as described above for the embodiment of the PET detector.

Step 1706: and determining the position of the gamma ray generating photons inside the crystal unit according to the output of the semiconductor sensor.

In a specific implementation, a centroid reading method may be used to determine the position of the gamma ray generating the photon inside the crystal unit, which may be implemented with reference to the above description of the embodiment of the PET detector.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A PET detector, comprising:

a crystal array including a plurality of crystal units arranged in a single layer and a light-reflecting film disposed on a surface of the crystal units; and

a semiconductor sensor array comprising a plurality of semiconductor sensors, at least some of the crystal units in the crystal array coupled to the semiconductor sensors, the number of crystal units in the crystal array being greater than the number of semiconductor sensors in the semiconductor sensor array;

the area of the reflective film on the surface of each crystal unit is adjusted by adjusting the probability of photons appearing in each crystal unit.

2. The PET detector of claim 1, wherein at least one crystal unit in the crystal array is coupled to one semiconductor sensor in the semiconductor sensor array.

3. The PET detector of claim 1, wherein at least one semiconductor sensor of the array of semiconductor sensors is coupled to one crystal unit of the array of crystals.

4. The PET detector of claim 1, wherein the coupling comprises the semiconductor sensor being in direct contact with the crystal unit or being in contact through an adhesive material.

5. The PET detector of claim 1, wherein the reflective films collectively define a light exit surface of the crystal array, the semiconductor sensor array either completely covering the light exit surface or partially covering the light exit surface.

6. The PET detector of claim 1, wherein a distance between two adjacent semiconductor sensors in the array of semiconductor sensors is greater than a distance between two adjacent crystal units in the array of crystals.

7. The PET detector of claim 1, wherein two adjacent semiconductor sensors in the array of semiconductor sensors span at least one crystal unit in the array of crystals.

8. The PET detector of claim 1, wherein the surface of at least one of the plurality of crystal units includes a top surface, a bottom surface, and a side surface between the top and bottom surfaces, at least a portion of the side surface being provided with the light-reflective film.

9. The PET detector of claim 1, wherein the probability of a photon occurring within each crystal cell in the crystal array satisfies the following equation:

10. The PET detector of claim 1, wherein a center of gravity of the semiconductor sensor array coincides with a center of gravity of the crystal array.