Beddar A Sam, Suchowerska Natalka, Law Susan H
Department of Radiation Physics, Division of Radiation Oncology, University of Texas, M D Anderson Cancer Center, Houston, TX, USA.
Phys Med Biol. 2004 Mar 7;49(5):783-90. doi: 10.1088/0031-9155/49/5/009.
Over the last decade, there has been an increased interest in scintillation dosimetry using small water-equivalent plastic scintillators, because of their favourable characteristics when compared with other more commonly used detector systems. Although plastic scintillators have been shown to have many desirable dosimetric properties, as yet there is no successful commercial detector system of this type available for routine clinical use in radiation oncology. The main factor preventing this new technology from realizing its full potential in commercial applications is the maximization of signal coupling efficiency and the minimization of noise capture. A principal constituent of noise is Cerenkov radiation. This study reports the calculated capture of Cerenkov radiation by an optical fibre in the special case where the radiation is generated by a relativistic particle on the fibre axis and the fibre axis is parallel to the Cerenkov cone. The fraction of radiation captured is calculated as a function of the fibre core refractive index and the refractive index difference between the core and the cladding of the fibre for relativistic particles. This is then used to deduce the relative intensity captured for a range of fibre core refractive indices and fibre core-cladding refractive index differences. It is shown that the core refractive index has little effect on the amount of radiation captured compared to the refractive index difference. The implications of this result for the design of radiation therapy plastic scintillation dosimeters are considered.
在过去十年中，人们对使用小型水等效塑料闪烁体进行闪烁剂量测定的兴趣日益浓厚，因为与其他更常用的探测器系统相比，它们具有良好的特性。尽管塑料闪烁体已被证明具有许多理想的剂量学特性，但目前还没有这种类型的成功商业探测器系统可用于放射肿瘤学的常规临床应用。阻碍这项新技术在商业应用中充分发挥潜力的主要因素是信号耦合效率的最大化和噪声捕获的最小化。噪声的一个主要成分是切伦科夫辐射。本研究报告了在相对论粒子在光纤轴上产生辐射且光纤轴与切伦科夫锥平行的特殊情况下，光纤对切伦科夫辐射的捕获计算。计算了相对论粒子的辐射捕获分数作为光纤纤芯折射率以及光纤纤芯与包层之间折射率差的函数。然后利用这一结果推导出一系列光纤纤芯折射率和光纤纤芯 - 包层折射率差下的相对捕获强度。结果表明，与折射率差相比，纤芯折射率对捕获的辐射量影响很小。考虑了这一结果对放射治疗塑料闪烁剂量计设计的影响。
