GEL FOR 3D DOSIMETRY BY OPTICAL TOMOGRAPHIC DENSITOMETRY

本项目旨在开发一种新型的、组织等效的电离辐射凝胶剂量计，该剂量计能够使用光学层析密度测量法产生关于三维剂量分布的高分辨率和准确的数据。 剂量-响应机制依赖于在辐射吸收位点的凝胶中产生瑞利散射微粒，其中分散在凝胶中的丙烯酸共聚单体聚合。穿过光学混浊介质的准直光的吸收和散射产生光强度的净衰减，其可以被测量并且与剂量直接相关。 光密度在不同方向上的投影的测量可用于重建凝胶内辐射剂量的分布。 10戈伊量级的剂量可以用<1毫米的空间分辨率测量。 在之前的工作中，已经研究了凝胶的MRI特性，并非常成功地用于创建3D剂量图，但使用更简单的光学方法来阅读凝胶存储的剂量分布具有显着优势。 该凝胶将广泛用于放射治疗实践，用于均匀和拟人幻影中的3D测量，确认计算机化治疗计划和质量保证程序。 第一阶段的目标是设计和评估一个协议，方便和廉价的原型聚合物-凝胶剂量计的制备优化光学密度，以证明其稳定性和再现性以及空间均匀性的剂量响应，并评估构建一个低成本的台式光学扫描仪的可行性重建的三维剂量分布。 这些研究将为开发更有效的聚合物凝胶和第二阶段的光学阅读器奠定基础。 拟定商业应用： 估计每年可分发5000个聚合物凝胶。 这一估计是基于（a）每年30个新加速器，40个X射线和电子束场;（B）超过3000台现有治疗机每年将使用10个凝胶进行剂量测定;（c）研究中心每年可能使用5个凝胶进行非常规剂量分布。 仅凝胶的年销售额就可以产生100万美元的销售额。 此外，如果光学装置的价格为50 000美元，那么每年可以出售20个这样的装置，相当于目前使用的“水箱”系统的数量。

This project aims to develop a novel, tissue-equivalent gel-dosimeter of ionizing radiation, which is capable of producing highly-resolved and accurate data on three dimensional dose distributions using optical tomographic densitometry. The dose-response mechanism relies on the production of Rayleigh scattering micro-particles in the gel at the site of radiation absorption, where acrylic comonomers dispersed in the gel are polymerized. Absorption and scattering of collimated light passing through the optically turbid medium produces a net attenuation of light intensity that can be measured and is directly related to the dose. Measurements of the projections of the optical density into different directions can be used to reconstruct the distribution of radiation doses within the gel. Doses of the order of 10 Gy can be measured with a spatial resolution <1mm. In previous work, the MRI properties of the gel have been investigated and used very successfully to create 3D dose maps, but there are significant advantages to the use of a simpler optical method of reading the dose distribution stored by the gel. The gel will find widespread use in radiation therapy practice, for 3D measurements in homogeneous and anthropomorphic phantoms, confirmation of computerized treatment planning and in quality assurance procedures. The goals of Phase I are to devise and evaluate a protocol for convenient and inexpensive preparation of a prototype polymer-gel dosimeter optimized for optical densitometry, to demonstrated its stability and reproducibility as well as spatial uniformity of the dose-response, and to evaluate the feasibility of constructing a low-cost bench top optical scanner for the reconstruction of 3D dose distributions. These studies will prepare the ground for the development of more efficient polymer-gels and an optical reader in Phase II. PROPOSED COMMERCIAL APPLICATION: Estimated 5000 polymer-gels could be distributed annually. This estimate is based upon (a) 30 new accelerators per year, and 40 X-ray and electron beam field; (b) over 3000 existing treatment machines will use 10 gels per year for dosimetry; (c ) research centers might use 5 gels annually for non-routine dose distributions. The annual sales of the gels alone could produce $1,000,000 sales. In addition, if the optical device is available for a cost of $50,000, then 20 such devices per year could be sold, comparable to the number of "water-tank" systems that are in current use.