Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient.
Detecting prompt gamma emission during proton therapy: the effects of detector size and distance from the patient.
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DOI：
10.1088/0031-9155/59/9/2325
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发表时间：
2014-05-07
影响因子：
3.5
通讯作者：
Beddar S
中科院分区：
文献类型：
--
作者：
Polf JC;Mackin D;Lee E;Avery S;Beddar S
最近的研究表明，质子治疗过程中激发核发射的瞬发伽马(PG)特性有利于确定治疗过程中的束流射程。由于PGs仅在束流开启时发射，因此使用PGs进行在线治疗验证的可行性在很大程度上取决于高效探测器的设计。这项工作的目的是表征PG检测如何随着距离患者的距离而变化，作为指导临床即时伽马成像检测器的设计和使用的一种手段。用蒙特卡罗模型(GEANT4.9.4)研究了高纯锗探测器在质子辐照过程中的总PG发射和6.13 MeV PG特征发射的探测效率(每入射质子数)。(1)用质子铅笔束照射水模体；(2)用扫描束质子治疗野(侧野大小：~6 cm×6 cm，射束范围：23.5 cm)照射前列腺癌患者。然后建立了PG探测率与等中心距离、探测器尺寸和质子束能量的函数关系的解析表达式。在40 MeV铅笔束照射水模时，探测器距等中心11 cm时，对氧气的检测率为1.3×10−6，对总PG排放的检测率为3.9×10−4。当束流能量大于150 MeV时，总PG探测率提高~85±3%。在前列腺癌的扫描束治疗过程中，单束铅笔束的氧气和总PG排放的检出率分别约为2.1×10−6和1.7×10−3。在通常用于质子治疗的束流能量范围内，点光源照射已知直径的圆柱形探测器的模型很好地描述了在单质子铅笔束照射水模时PG检测率随离等中心的距离的函数关系。对于患者研究，有必要将点源方程除以指数因子，以便正确地预测PG检测率作为距等中心距离的函数的衰减。
Recent studies have suggested that the characteristics of prompt gammas (PG) emitted from excited nuclei during proton therapy are advantageous for determining beam range during treatment delivery. Since PGs are only emitted while the beam is on, the feasibility of using PGs for online treatment verification depends greatly on the design of highly efficient detectors. The purpose of this work is to characterize how PG detection changes as a function of distance from the patient as a means of guiding the design and usage of clinical prompt gamma imaging detectors. Using a Monte Carlo model (GEANT4.9.4) we studied the detection rate (PGs per incident proton) of a high purity Germanium detector for both the total PG emission and the characteristic 6.13 MeV PG emission from 16O emitted during proton irradiation. The PG detection rate was calculated as a function of distance from the isocenter of the proton treatment nozzle for: (1) a water phantom irradiated with a proton pencil beam and (2) a prostate patient irradiated with a scanning beam proton therapy treatment field (lateral field size: ~6 cm × 6 cm, beam range: 23.5 cm). An analytical expression of the PG detection rate as a function of distance from isocenter, detector size, and proton beam energy was then developed. The detection rates were found to be 1.3 × 10−6 for oxygen and 3.9 × 10−4 for the total PG emission, respectively, with the detector placed 11 cm from isocenter for a 40 MeV pencil beam irradiating a water phantom. The total PG detection rate increased by ~85±3% for beam energies greater than 150 MeV. The detection rate was found to be approximately 2.1 × 10−6 and 1.7 × 10−3 for oxygen and total PG emission, respectively, during delivery of a single pencil beam during a scanning beam treatment for prostate cancer. The PG detection rate as a function of distance from isocenter during irradiation of a water phantom with a single proton pencil beam was described well by the model of a point source irradiating a cylindrical detector of a known diameter over the range of beam energies commonly used for proton therapy. For the patient studies, it was necessary to divide the point source equation by an exponential factor in order to correctly predict the falloff of the PG detection rate as a function of distance from isocenter.
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影响因子：
3.5
作者：
Peterson SW;Robertson D;Polf J
通讯作者：
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DOI：
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