GEL FOR 3D DOSIMETRY BY OPTICAL TOMOGRAPHIC DENSITOMETRY

该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，它能够利用光学层析成像密度计产生高分辨率和准确的三维剂量分布数据。剂量-效应机制依赖于辐射吸收处凝胶中瑞利散射微粒的产生，分散在凝胶中的丙烯酸酯共聚单体在凝胶中聚合。准直光通过光学混浊介质的吸收和散射产生可测量的光强度的净衰减，并且与剂量直接相关。光密度向不同方向投射的测量可用于重建凝胶内的辐射剂量分布。10Gy量级的剂量可以用1 mm的空间分辨率测量。在以前的工作中，凝胶的MRI特性已经被非常成功地研究并用于创建3D剂量图，但使用更简单的光学方法来读取凝胶存储的剂量分布具有显著的优势。这种凝胶将在放射治疗实践中得到广泛应用，用于同质和拟人模型的3D测量，确认计算机化的治疗计划，以及质量保证程序。第一阶段的目标是设计和评估一种简便和廉价的方案，以制备最适合光学密度测量的原型聚合物凝胶剂量计，展示其稳定性、重复性以及剂量-响应的空间一致性，并评估构建用于重建3D剂量分布的低成本台式光学扫描仪的可行性。这些研究将为第二阶段开发更高效的聚合物凝胶和光学阅读器奠定基础。 建议的商业应用： 据估计，每年可以分发5000个聚合物凝胶。这一估计是基于(A)每年30个新的加速器和40个X射线和电子束场；(B)3000多台现有的治疗机每年将使用10个凝胶进行剂量测定；(C)研究中心可能每年使用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，如果光学设备的价格为50,000美元，那么每年可以售出20个这样的设备，与目前使用的“水箱”系统的数量相当。

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.