CN106291656A - Prompt fission gammas's imaging system - Google Patents

Abstract

The invention discloses prompt fission gammas's imaging system, by measuring prompt fission gammas's photon, measure particle range and beam position in patient body in real time, make the line inciding in patient body visible.The present invention includes following sections: longitudinal gamma detector (1), laterally gamma detector (2), detector is formed detector array by multiple gamma-ray probes (3), and each gamma-ray probe is made up of scintillation crystal (4), photoelectric sensor (5) and grating (6).Cylindrical PMMA material (7) simulated human tissue, tumor (8) is on its interior, particle beam (9) passes human body simulation tissue bombardment to tumor, inspire gammaphoton on its path passed, by measuring the distribution of gammaphoton, gamma detector determines that the range of particle and beam position are distributed.This system can be widely used for proton heavy particle therapy terminal.

Description

Prompt fission gammas's imaging system

Technical field

Belong to beam diagnostics and fields of measurement, be applied particularly to proton heavy ion medical terminal, measure line in real time in diseaseRange in human body, generates beam pattern picture.Can also be used on other types accelerator installation, and section's grinding device.

Background technology

Proton heavy particle therapy is a kind of precisely pencil beam scanning that cancer treatment method, especially last decade grow upMethod, intensity modulated therapy method, the premise that these methods are achieved is particle being accurately positioned in patient body.A kind of basic sideCase is to optimize Beam Transport Systems, treatment plan, is accurately positioned treatment chair or therapeutic bed, comes by optimizing equipment and software precisionRealize precisely treatment.But a lot of uncertain factors still can affect the range of particle and the breathing of the distribution of dosage, such as patient,The inhomogeneities of tissue, focus self mobile etc..

Summary of the invention

It is an object of the invention to design a kind of prompt fission gammas's imaging system, by measuring prompt fission gammas's photon, measure in real timeParticle range and beam position in patient body, make the line inciding in patient body visible.This system can be widely used for protonHeavy particle therapy terminal.

As it is shown in figure 1, prompt fission gammas's imaging system includes following sections: longitudinal gamma detector (1), horizontal gamma is visitedSurveying device (2), detector is formed detector array by multiple gamma-ray probes (3), and each gamma-ray probe is by scintillation crystal (4), photoelectricitySensor (5) and grating (6) composition.Cylindrical PMMA material (7) simulated human tissue, tumor (8) is on its interior, particle beamStream (9), through human body simulation tissue bombardment in tumor, inspires gammaphoton on its path passed, and gamma detector leads toCross the distribution measuring gammaphoton to determine range and the beam position distribution of particle.

Longitudinal gamma detector (1) is positioned at cylindrical PMMA material (7) top, and spacing is 60mm；Laterally gamma detector(2) being positioned at cylindrical PMMA material (7) rear portion, spacing is 110mm.

It is logical with substance in vivo interaction radiation gammaphoton, such as proton that particle (proton and heavy ion) injects tissueCross reaction¹⁶O(p, p*)¹⁶O* launches 6.129 MeV, 6.916 MeV, the gammaphoton of 7.115 MeV energy.Gammaphoton producesVolume is followed at the bragg peak trailing edge of proton end-of-range and is drastically declined, and determines proton range by measuring gammaphoton,As in figure 2 it is shown, the cylindrical PMMA material of a diameter of 200mm of the Proton-Induced Reactions of 160MeV, long 400mm.Gammaphoton yieldIt is scattered in corresponding relation with particle, the distribution of gammaphoton can be measured to measure the distribution of line.

The critical piece of gamma-ray probe (3) is scintillation crystal (4) and photoelectric sensor (5), and scintillation crystal is by incident galHorse photon excitation, produces photoelectron, photoelectric sensor output signals, and backend electronics learns position and the energy letter of record gammaphotonBreath.

Scintillation crystal selection principle is that photoyield is high, and decay constant is little, and refractive index is low, is difficult to deliquescence, easily cuts into littleBlock.Fig. 3 lists several optional crystal parameter, reasonable such as LYSO crystal, LaBr₃: Ce crystal.

Photoelectric sensor selection principle is that the rise time is short, biases low, and volume is little, is easily integrated as multichannel array.Fig. 4List several optional sensor parameters, reasonable selection such as avalanche photodide (APD), silicon photomultiplier(SiPM)。

As it is shown in figure 5, the gammaphoton (61) incident in order to only receive vertical direction, around scintillator, there is provision of lightGrid (6).Grating is in close contact with scintillator.In order to stop lateral incident high energy gammaphoton (63), grating not only to wrap entirelyWrap up in crystal, also long than crystal.Crystal section 9mm × 9mm in the present embodiment, long 20mm, grating wall thickness 1mm, long 70mm.

Owing to offspring (62) and grating material effect also can produce gammaphoton (621 ~ 622), this part gamma lightSon has part (621) to be directly incident in probe, but the energy of this part gammaphoton is relatively low, generally less than 5 MeV, such as figureShown in 6.Therefore the window energy of gamma detector elects 5 MeV as.I.e. only has the energy gammaphoton just meeting more than window energyBy detector record.

Longitudinal gamma detector (1) measures the range of particle, as it is shown in fig. 7, longitudinal gamma detector (1) is by multipleThe array that gamma-ray probe (3) forms, each probe mark is P (X, Y, Z), and X, Y, Z correspond in this probe crystal geometryThe heart space coordinates, matrix initial point is positioned at the particle incidence point in tissue.Each probe sectional dimension pixel is the least, surveysThe precision of amount is the highest.The present embodiment longitudinal direction gamma detector is 9 × 40 probes.

Owing to the transmitting of gammaphoton is isotropic, the path that therefore particle can be passed is considered as line source,In the case of being not added with grating, each probe will receive the gammaphoton from each point, and probe 1 and 2 all receives A and B point and sends outThe gammaphoton gone out, the genesis analysis of gamma detector gained will be unable to determine the range of particle, as shown in Figure 8.

In order to only measure the gammaphoton of vertical incidence, need to be arranged around grating at probe, the higher atomic number of gratingThe metal of number is made, and can effectively stop gammaphoton, uses tantalum in the present embodiment.The gamma distribution such as figure measured after grating is setShown in 9, pop one's head in 1 and receive the gammaphoton that A point sends, pop one's head in 2 and receive the gammaphoton that B point sends, therefore, it is possible to measureThe range of particle.

One group of parallel gamma light of any incident direction can be selected in principle.To select to be perpendicular to the parallel of beam directionLight is optimal, can reduce processing cost and installation difficulty；If selecting the directional light being more than 90 ° with line angle, then can reduce heatNeutronic noise, in the case of this, probe installation direction is parallel to gammaphoton.

Laterally gamma detector (2) measures the cross direction profiles of end-of-range particle, is made up of 9 × 9 probes, thus measuresThe cross section of particle range end line.As shown in Figure 10.

Longitudinal gamma detector (1) can be used for measuring the lateral cross section of line, as shown in figure 11, given longitudinal coordinateValue Zi, takes probe P (-4,15, Zi) and can provide grain at longitudinal degree of depth Zi to the data that P (4,15, Zi) nine pops one's head inHorizontal (X) distribution cross section of son.To the cross section of Y-direction at detection Zi, also needing to increase by one group of detector, its position is perpendicular to indulgeTo gamma detector (1).

Comprehensive longitudinal gamma detector (1), the data of horizontal gamma detector (2) can obtain line reality in human bodyTime image information, including the range of particle, beam cross section.As shown in Figure 12 and Figure 13.By image combining method, show in real timeLine 3-D view in patient body, as shown in figure 14.

It will be apparent to those skilled in the art that can technical scheme as described above and design, make other variousCorresponding change and deformation, and all these changes and deformation all should belong to the claims in the present invention protection domain itIn.

Accompanying drawing explanation

Fig. 1-prompt fission gammas's imaging system schematic diagram；

Fig. 2-bragg peak and gammaphoton profiles versus；

Fig. 3-scintillation crystal parameter list；

Fig. 4-photoelectric sensor parameter list；

Fig. 5-gamma-ray probe；

Fig. 6-100MeV neutron is beaten tantalum and is produced photons spectrum；

Fig. 7-longitudinal direction gamma detector array；

Fig. 8-no-raster measures gammaphoton distribution；

Fig. 9-have grating measuring gammaphoton to be distributed；

Figure 10-horizontal gamma detector；

Figure 11-horizontal (X) distribution cross section；

Figure 12-beam pattern is as XZ cross section；

Figure 13-particle range end beam pattern is as XY cross section；

Figure 14-line 3-D view.

Claims (10)

1. prompt fission gammas's imaging system, it is characterised in that including:

Longitudinal gamma detector, is made up of multiple gamma-ray probes, is arranged on directly over target or patient, for measuring penetrating of particleJourney and the lateral cross section of line；

Laterally gamma detector, is made up of multiple gamma-ray probes, is arranged on target or patient rear portion, be used for measuring end-of-range bundleThe lateral cross section of stream；

Each gamma-ray probe is made up of scintillation crystal, photoelectric sensor and grating.

Particle the most according to claim 1, it is characterised in that include proton and the heavy ion for the treatment of of cancer.

Prompt fission gammas's imaging system the most according to claim 1, it is characterised in that particle beam injects target or patient,On the path that particle passes, inspiring gammaphoton, gammaphoton yield is at the bragg peak trailing edge of particle range endFollow and drastically decline, determine particle range by measuring gammaphoton；Gammaphoton yield is scattered in corresponding with particle simultaneouslyRelation, the distribution of particle is measured in the distribution of detector measurement gammaphoton.

Gamma-ray probe the most according to claim 1, it is characterised in that scintillation crystal, by incident gamma photon excitation, producesThird contact of a total solar or lunar eclipse electronics, photoelectric sensor output signals, backend electronics learns position and the energy information of record gammaphoton；Scintillation crystal is wantedAsking photoyield high, decay constant is little, and refractive index is low, is difficult to deliquescence, easily cuts into fritter, such as LYSO crystal, LaBr₃: Ce is brilliantBody；Photoelectric sensor requires that the rise time is short, biases low, and volume is little, is easily integrated as multichannel array, such as avalanche optoelectronic two polePipe (APD), silicon photomultiplier (SiPM).

Gamma-ray probe the most according to claim 1, it is characterised in that scintillator is arranged around grating, makes gamma-ray probe onlyReceiving the gammaphoton that assigned direction is incident, grating is in close contact with scintillator, and grating wraps up crystal entirely, and longer than crystal, withStop lateral incident high energy gammaphoton；Grating material selects the metal of higher atomic number to make, and can effectively stop gammaPhoton, such as tantalum.

Gamma detector the most according to claim 1, it is characterised in that the window energy threshold value of gamma detector is 5MeV, the most only energy just can be by detector records more than the gammaphoton of window energy threshold value；Each gamma-ray probe is labeled as P(X, Y, Z), X, Y, Z correspond to this probe crystal geometric center space coordinates, initial point is positioned at particle in tissueIncidence point, each probe sectional dimension is the least, and the precision of measurement is the highest.

Longitudinal gamma detector the most according to claim 1, it is characterised in that each gamma-ray probe is parallel to each other, measuresOne group of parallel gammaphoton that assigned direction is incident, to measure the range of particle；Selection is perpendicular to the directional light of beam directionMost preferably, processing cost and installation difficulty can be reduced；If selecting the directional light being more than 90 ° with line angle, then can reduce thermal neutronNoise.

Longitudinal gamma detector the most according to claim 1, it is characterised in that can be used for measuring the transverse cutting of lineFace, given longitudinal coordinate value Z, take the data of probe in X-direction and can provide the horizontal X distribution cross section of particle at longitudinal degree of depth Z；To the cross section of Y-direction at detection Z, then increasing by one group of identical gamma detector, its position is transversely to the machine direction gamma detector.

Horizontal gamma detector the most according to claim 1, it is characterised in that be made up of M × N number of gamma-ray probe, measuresThe line lateral cross section of particle range end.

Prompt fission gammas's imaging system the most according to claim 1, it is characterised in that comprehensive longitudinal gamma detector, laterallyThe data of gamma detector obtain line real-time imaging information in human body or target, including the range of particle, beam cross section；By image combining method, display line 3-D view in patient body in real time.