随累积剂量变化的光激励发光剂量计（OSLD）剂量学特性变化。

Changes in optically stimulated luminescent dosimeter (OSLD) dosimetric characteristics with accumulated dose.

机构信息

West Michigan Cancer Center, 200 North Park St., Kalamazoo, Michigan 49007, USA.

出版信息

Med Phys. 2010 Jan;37(1):132-40. doi: 10.1118/1.3267489.

DOI:10.1118/1.3267489

PMID:20175474

Abstract

PURPOSE

A new type of in vivo dosimeter, an optically stimulated luminescent dosimeter (OSLD), has now become commercially available for clinical use. The OSLD is a plastic disk infused with aluminum oxide doped with carbon (Al2O3:C). Crystals of Al2O3:C, when exposed to ionizing radiation, store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. The effects of accumulated dose on OSLD response were investigated.

METHODS

The OSLDs used in this work were nanodot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x rays and gamma rays from Co-60 and Ir-192. The signal on the OSLDs after irradiation is removed by optical annealing with a 150 W tungsten-halogen lamp or a 14 W compact fluorescent lamp was investigated.

RESULTS

It was found that OSLD response to dose was supralinear and this response was altered with the amount of accumulated dose to the OSLD. The OSLD response can be modeled by a quadratic and an exponential equation. For accumulated doses up to 60 Gy, the OSLD sensitivity (counts/dose) decreases and the extent of supralinear increases. Above 60 Gy of accumulated dose the sensitivity increases and the extent of supralinearity decreases or reaches a plateau, depending on how the OSLDs were optically annealed. With preirradiation of OSLDs with greater than 1 kGy, it is found that the sensitivity reaches a plateau 2.5 folds greater than that of an OSLD with no accumulated dose and the supralinearity disappears. A regeneration of the luminescence signal in the dark after full optical annealing occurs with a half time of about two days. The extent of this regeneration signal depends on the amount of accumulated dose.

CONCLUSIONS

For in vivo dosimetric measurements, a precision of +/- 0.5% can be achieved if the sensitivity and extent of supralinearity is established for each OSLD and use. Methods are presented for accomplishing this task.

摘要

目的

现在，一种新型的体内剂量计，光激励发光剂量计（OSLD），已经可以商业购买并应用于临床。OSLD 是一种注入了掺碳氧化铝（Al2O3:C）的塑料圆盘。当 Al2O3:C 晶体暴露于电离辐射时，会储存能量，当 OSLD 用激发光（540nm）照射时，这些能量会以发光（420nm）的形式释放出来。发光的强度取决于 OSLD 吸收的剂量和激发光的强度。本研究调查了累积剂量对 OSLD 响应的影响。

方法

本研究中使用的 OSLD 是纳米点剂量计，使用 MicroStar 读取器（Landauer，Inc.，Glenwood，IL）进行读取。OSLD 的剂量由 6MV X 射线和 Co-60 和 Ir-192 的伽马射线提供。照射后，用 150W 钨卤素灯或 14W 紧凑型荧光灯进行光退火以去除 OSLD 上的信号。

结果

发现 OSLD 对剂量的响应呈超线性，并且这种响应会随着 OSLD 累积剂量的增加而改变。OSLD 响应可以用二次方程和指数方程来建模。对于累积剂量高达 60Gy 的情况，OSLD 的灵敏度（计数/剂量）降低，超线性程度增加。累积剂量超过 60Gy 后，灵敏度增加，超线性程度降低或达到平台，这取决于 OSLD 如何进行光退火。对 OSLD 进行大于 1kGy 的预照射，发现灵敏度达到无累积剂量 OSLD 的 2.5 倍的平台，超线性消失。完全光退火后，在黑暗中会发生发光信号的再生，半衰期约为两天。这种再生信号的程度取决于累积剂量的大小。