Search

CN-121995426-A - Single-layer Compton camera system and imaging method

CN121995426ACN 121995426 ACN121995426 ACN 121995426ACN-121995426-A

Abstract

The invention discloses a single-layer Compton camera system and an imaging method, and relates to the technical field of nuclear radiation imaging. The system comprises a single-plane pixel type gamma ray detector, a shielding structure, a judging and imaging module and a detecting and imaging module, wherein the single-plane pixel type gamma ray detector is used for collecting gamma ray interaction event data, the gamma ray interaction event data comprises time information, energy information and two-dimensional position information in a detector plane of each interaction, pixel counting distribution is formed, the shielding structure is arranged on one side of the detector plane and is positioned in a local area of the detector, the shielding structure is used for enabling the pixel counting distribution to generate local counting missing characteristics when gamma rays are incident from one side of the shielding structure, and the judging and imaging module is used for judging a gamma ray incidence side based on the local counting missing characteristics and executing Compton imaging reconstruction in a corresponding hemispherical field of view range according to the judged incidence side. The invention can carry out partitioned omnidirectional imaging on the radioactive source without the action depth information of the detector, and simultaneously avoid the generation of mirror image artifacts.

Inventors

  • WEI QINGYANG
  • QIU YUHANG

Assignees

  • 北京科技大学

Dates

Publication Date
20260508
Application Date
20260116

Claims (10)

  1. 1. A single-layer compton camera system comprising: The single-plane pixel type gamma ray detector is used for collecting gamma ray interaction event data, comprises time information, energy information and two-dimensional position information in a detector plane of each interaction, and forms pixel count distribution; The shielding structure is arranged on one side of the plane of the detector, is positioned in a local area of the detector and is used for enabling pixel counting distribution to generate local counting missing characteristics when gamma rays are incident from one side of the shielding structure; And the judging and imaging module is used for judging the incidence side of the gamma ray based on the local counting missing feature, and executing Compton imaging reconstruction in the corresponding hemispherical field of view according to the judged incidence side to obtain a reconstructed image in the hemispherical field of view.
  2. 2. The single-layer compton camera system of claim 1 wherein said single-plane pixel gamma ray detector is a two-dimensional array of a plurality of detector units forming a detection plane; the single plane pixel type gamma ray detector is any one of a pixelated scintillator detector array or a pixelated semiconductor detector array.
  3. 3. The single-layer compton camera system of claim 1 wherein said shielding structure is made of a material having an attenuation effect on the gamma energy region of interest, capable of producing partial absorption and/or scattering of gamma rays incident from the side thereof and passing through the shielding structure, such that the detector area corresponding to the projection of the shielding structure forms a localized count missing feature in the pixel count distribution, representing a low count window area.
  4. 4. The single layer compton camera system of claim 1, wherein said shielding structure is disposed adjacent to or in contact with the detector plane, said shielding structure being in the shape of any one of a block, a plate, a strip, or a combination thereof.
  5. 5. The single-layer compton camera system of claim 1, wherein said discriminating and imaging module specifically comprises: a counting matrix construction unit for forming a pixel counting matrix according to the pixel counting distribution of the detector; the local low count detection unit is used for scanning by adopting a sliding window on the pixel count matrix, comparing the count in the sliding window with the peripheral annular neighborhood of the sliding window, and detecting whether a local low count area caused by a shielding structure exists or not; An incident side hemisphere selecting unit which adopts a threshold method to determine a local low count area and judges the incident side; A sequence determination unit for determining Compton scattering sites and absorption sites of interaction for events comprising at least two interactions; and the Compton image reconstruction unit is used for performing Compton imaging reconstruction only in the hemispherical view field range corresponding to the incidence side, so as to obtain a reconstructed image in the hemispherical view field range.
  6. 6. The single-layer compton camera system of claim 5, wherein said incident side hemisphere selection unit is determined by: The following discriminants are defined: Count miss ratio: Normalized residual: Wherein, the For the total count within the sliding window, For the number of pixels of the window, Mean value of pixel count in annular neighborhood And/or When it is determined that there is a local low count region, And Is a preset or adaptive threshold.
  7. 7. The single-layer compton camera system of claim 5, wherein said sequence determination unit employs any one or more of an energy comparison method, a time-sequential method, or a probability determination method based on physical constraints.
  8. 8. The single-layer compton camera system of claim 5, wherein said compton image reconstruction unit employs any one or more of back projection, filtered back projection, statistical iterative reconstruction, algebraic reconstruction, maximum likelihood-type reconstruction, or maximum a posteriori-type reconstruction; wherein, compton scattering angle θ is calculated according to Compton scattering formula: Wherein, the For incident gamma ray energy or estimated energy, Energy is deposited for the scattering sites and, Is the electron stationary energy constant.
  9. 9. The single-layer compton camera system of claim 1, wherein said system further comprises: and the output display module is used for outputting and displaying the reconstructed image.
  10. 10. A method of imaging based on the single-layer compton camera system of any one of claims 1-9, the method comprising: s1, collecting gamma ray interaction event data and screening out events meeting Compton imaging conditions, wherein the event data comprises time information, energy information and two-dimensional position information in a detector plane of each interaction; S2, judging an incidence side, namely constructing a pixel counting matrix, carrying out local contrast analysis on the pixel counting matrix to detect local counting missing features caused by a shielding structure, and judging a gamma ray incidence side according to a detection result; s3, determining the sequence of Compton scattering sites and absorption sites for the event comprising at least two interactions; And S4, compton reconstruction in the hemispherical view field, namely, according to the incidence side judging result, compton imaging reconstruction is only carried out on the event data in the hemispherical view field range corresponding to the incidence side, and a reconstructed image in the hemispherical view field range is obtained.

Description

Single-layer Compton camera system and imaging method Technical Field The invention relates to the technical field of nuclear radiation imaging, in particular to a single-layer Compton camera system and an imaging method. Background Compton camera is a passive gamma ray imaging device and is widely applied to fields such as astronomical physical observation, nuclear medicine imaging, nuclear industry flaw detection, nuclear safety monitoring and the like. Compton cameras utilize the Compton scattering principle to invert the direction distribution of the radiation source by recording the position and energy of the two interactions of Compton scattering and subsequent photoelectric absorption of a primary photon in the detector that fit a time window. Conventional Compton cameras mostly employ a "two-layer" or "multi-layer" detector structure, with the front layer acting as a Compton diffuser and the back layer acting as a photoelectric absorber. This structure can easily distinguish from which direction a photon is incident, but requires two or more detection planes, and the system is bulky. To improve system compactness, a "single layer" Compton camera has recently emerged that uses a single detector volume to record two interactions. Single-layer compton cameras are typically composed of an integrated three-dimensional position-sensitive detector capable of acquiring three-dimensional coordinates of each interaction, thereby enabling omnidirectional imaging. However, for a planar pixelated detector with only photon two-dimensional position readout capability, lacking depth of action information acquisition capability, the two interaction points of the Compton event are located only on the detector plane, with unknown depth coordinates. This can cause "mirror image" blurring problems in that when the source is located on one side of the detector plane, the resulting coincidence events are indistinguishable in the ideal geometry from coincidence events from the source at opposite mirror positions, resulting in simultaneous true and mirror image false sources at both symmetric positions of the detector in the reconstructed image. Such image artifacts can seriously affect the accuracy of the imaging results. In the prior art, to avoid the solution of mirror ambiguity, it is common practice to fix the imaging field of view to a certain side of the detector in advance, for example, it is assumed that the radiation source is only in the half space above the detector, but if the actual source is present at the opposite side or both sides, the reconstructed result will be distorted or even the true source position cannot be known. Another approach is to place a large area of shielding material on one side of the detector, blocking the incident photons on the other side to prevent image interference. However, the shielding layer adds significant weight to the device and high energy photons may still penetrate the shielding causing residual interference. It can be seen that the existing flat panel detector compton imaging system still lacks an effective and simple solution to solve the uncertainty of the incident direction when implementing full-space imaging. Disclosure of Invention In view of the foregoing, it is an object of the present invention to provide a single-layer compton camera system and an imaging method, so as to implement partition-type omni-directional imaging of a radiation source without needing depth of action information of a detector, and avoid generation of mirror image artifacts. In order to solve the technical problems, the invention provides the following technical scheme: In one aspect, there is provided a single layer compton camera system comprising: The single-plane pixel type gamma ray detector is used for collecting gamma ray interaction event data, comprises time information, energy information and two-dimensional position information in a detector plane of each interaction, and forms pixel count distribution; The shielding structure is arranged on one side of the plane of the detector, is positioned in a local area of the detector and is used for enabling pixel counting distribution to generate local counting missing characteristics when gamma rays are incident from one side of the shielding structure; And the judging and imaging module is used for judging the incidence side of the gamma ray based on the local counting missing feature, and executing Compton imaging reconstruction in the corresponding hemispherical field of view according to the judged incidence side to obtain a reconstructed image in the hemispherical field of view. Optionally, the single-plane pixel gamma ray detector comprises a plurality of detection units to form a two-dimensional array to form a detection plane; the single plane pixel type gamma ray detector is any one of a pixelated scintillator detector array or a pixelated semiconductor detector array. Optionally, the shielding structure is made of a materia