A gamma spectrometer for boron neutron capture therapy irradiation beams

Abstract

The invention belongs to the technical field of binary targeted radiotherapy, in particular to a gamma spectrometer for boron neutron capture therapy irradiation beams, the spectrometer is used for measuring a BNCT irradiation beam, and comprises a gamma shielding cylinder (2) internally provided with a high-purity germanium semiconductor detector (1), a gamma shielding collimator (3) arranged inthe incident end of the gamma shielding cylinder (2), and a first neutron shielding layer (4) and a second neutron shielding layer (5) which are arranged outside the incident end of the gamma shielding cylinder (2), a BNCT irradiation beam sequentially passes through the first neutron shielding layer (4), the second neutron shielding layer (5) and the gamma shielding collimator (3) to irradiate the high-purity germanium semiconductor detector (1). The gamma energy spectrometer has the advantages of high energy resolution, small size, light weight and convenience in operation.

Description

technical field [0001] The invention belongs to the technical field of binary targeted radiotherapy, and in particular relates to a gamma energy spectrometer used for irradiation beams of boron neutron capture therapy. Background technique [0002] Boron neutron capture therapy (BNCT) is a dual-targeted radiotherapy, which injects boron-carrier drugs that are pro-tumor cells into the patient's blood. 10 B captures low-energy neutrons with a large reaction cross section (thermal or epithermal neutrons—thermal neutron beams for superficial tumors, and epithermal neutron beams for deep tumors) to irradiate the lesion to produce high linear energy transfer density (LET) alpha particles and 7 Li nuclei, the combined range of the two in the tissue is about 12-13 μm, which is equivalent to the size of a cell, so as to selectively kill tumor cells and achieve the effect of precise treatment. Determined by the way the radiation beam is generated and the needs of treatment, the BNCT...

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Problems solved by technology

The second method has the following disadvantages: 1) Since the BNCT irradiator usually uses a conical collimator, the outgoing beam is not a parallel beam, so there may be a non-unique correspondence between the measured secondary γ-ray energy and the primary γ-ray energy, thus The reconstruction of the spectrum brings a large error; 2) Since the energy spectrum of the secondary γ-ray is severely compressed relative to the energy spectrum of the primary γ-ray, the measurement uncertainty is relatively large (about 20%) in the important high-energy region; 3) is To improve energy resolution, it is necessary to make the opening angle of the germanium detector to the scatterer as small as possible, so similar to the direct measurement method, the germanium detector also needs to be shielded and collimated

The problems of this system are: 1) The neutron shielding body and the gamma shielding collimator are made of pure polyethylene and lead respectively, which cannot effectively shield neutrons and gamma rays. The supersaturation effect, the measurement needs to be carried out far away from the exit of the irradiation beam; 2) The whole shielding collimation system is relatively bulky (volume greater than 54000cm 3 ), the weight is greater than 320kg), and it is relatively scattered and inconvenient to operate; 3) The neutron shielding body is made of pure polyethylene, and the volume is large. 1 H(n,γ) 2 The H capture reaction produces more secondary γ-rays, which have a greater impact on the measured primary γ-ray energy spectrum

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