评价离子重组和极性对光子深度剂量测量的影响,使用迷你和微型离子室
Antonella Fogliata1, Andrea Bresolin1, Pasqualina Gallo1
1Radiotherapy and Radiosurgery Dept, Humanitas IRCCS Research Hospital and Cancer Center, Milan-Rozzano, Italy.
Journal of applied clinical medical physics
|November 2, 2024
概括
离子再组合和极性校正对于准确的百分比剂量深度 (PDD) 测量至关重要,特别是在没有平面过器 (FFF) 的光束中. 了解这些因素可以确保精确的放射治疗剂量测量.
科学领域:
- 医学物理 医学物理
- 辐射瘤学 辐射瘤学
- 剂量测量方法 剂量测量方法
背景情况:
- 精确的剂量确定是放射治疗的基础.
- 离子重组和极性效应可以在剂量计测量中带来不确定性.
- 越来越多地使用平面化无波器 (FFF) 梁,需要对其剂量测量特性进行彻底了解.
研究的目的:
- 研究离子重组和极性校正因子对百分比剂量深度 (PDD) 曲线的影响.
- 为了在不同的离子室,光束类型 (平面和FFF) 和场大小中评估这些效应.
- 提出一种评估和纠正这些测量变化的方法.
主要方法:
- 根据国际原子能机构TRS-398协议,评估了离子重组 () 和极性 () 校正因子.
- 使用PTW Semiflex-3D,PinPoint-3D和Semiflex-31010离子室获得的PDD测量结果.
- 测量了PDD从dmax到32厘米深度的各种场大小和电压,计算了校正后的值.
主要成果:
- 对于Semiflex-3D来说,深度和字段大小是独立的,但对于PinPoint-3D来说,深度随着深度的增加而增加.
- 随着剂量速率的增加 (随着深度的减少) 增加,平面光束的变化为~0.1%,FFF光束的变化高达0.8%.
- 发现了一种二次多项式合适,适用于对原始扫描数据进行校正,无论是还是效应.
结论:
- 离子重组效应可以显著影响FFF光束中的PDD测量,可能导致更深处的误差高达1%.
- 这些校正对于保持放射疗法剂量测量的准确性至关重要,特别是使用先进的光束技术.
- 拟议的方法允许直接纠正扫描数据,提高PDD测量的可靠性.
关键词:
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF离子重组因子的离子重组因子这些光子束是光子束.极性效应是极性的效应.相关概念视频
Mass Spectrometers
9.6K
This lesson details the instrumentation of a mass spectrometer—a physical instrument to perform mass spectrometry on analyte molecules and record the characteristic mass spectra. This is achieved via three chief functions:
9.6K
Mass Analyzers: Overview
2.0K
The mass analyzer is a crucial component of the mass spectrometer. In the ionization chamber, the vaporized sample is bombarded with a high-energy electron beam to generate a radical cation and further fragment into neutral molecules, radicals, and cations. A series of negatively charged accelerator plates accelerate the cations into the mass analyzer. The mass analyzer separates ions according to their mass-to-charge (m/z) ratios and then directs them to the detector. The common types of mass...
2.0K
Mass Analyzers: Common Types
2.0K
The quadrupole mass analyzer consists of four cylindrical metal rods arranged in a diamond carrying a DC voltage and a radio-frequency AC voltage. The motion of ions through the quadrupole depends on the field strength, causing only ions of a certain m/z to resonate successfully and strike the detector at a given field strength. Though the transmission rate for these analyzers is high, the exact elemental composition of the sample is not determined because of low resolution; however, they are...
2.0K


