DOSIMETRY OF BRACHYTHERAPY SOURCES IN MILLIMETER RANGE

描述：（改编自申请人的摘要）：缓刑是 冠状动脉成形术的主要局限性。 最近，近距离放射治疗已经 作为一种潜在的再狭窄治疗方法出现， 如192 Ir、125 I、103 Pd和β发射体如32 P、90 Sr和90 Y。 两 正在研究的血管内近距离放射治疗的方法是：（i）使用 （ii）在导管末端的放射源， 在闭塞部位植入放射性支架。 第一个是 放射源暂时性腔内近距离放射治疗的例子 放置在靶病变附近的体腔中;另一个是示例 永久性近距离放射治疗，其中放射源被植入 靶病变。 众所周知，剂量梯度在即刻 放射源附近的辐射非常高，因为几何 和组织衰减效应。 传统上，目标的剂量是 在距源1 cm处指定。 在这个参考距离 近距离放射治疗源的剂量测定是相当完善的。 然而，血管内近距离放射治疗的预期照射靶点 在1 - 3 mm的范围内。在这些短距离处， 剂量测定法是高度不确定的，需要改进。 的一个主要 短距离剂量不确定性的原因可能是 低能量的二次辐射，例如荧光X射线，β粒子， 二次电子等，它们主要被吸收在 包封或源周围最初几毫米的组织。 他们的 在传统的近距离放射治疗剂量测定中， 只有一小部分目标体积受到它们的影响。 这是， 然而，对于血管内近距离放射治疗并不正确， 可能在辐射源的毫米范围内。 目前，许多调查 正在进行中，主要是在商业支持下，以确定 血管内近距离放射治疗，不仅需要 标准化剂量处方，但重要的是还要确定 在短距离内输送的剂量。 这种剂量测定法很可能是 根据具体的放射性核素和设计， 的来源和应用程序。 在这个项目中， 将研究用于治疗再狭窄的近距离放射治疗剂量学 使用热释光剂量计芯片和薄片，辐射变色胶片， 聚合物凝胶剂量计，用于微剂量测定的Rossi型正比室， 蒙特卡洛模拟。 最后，组织异质性和 导管和支架对光子和β射线的自屏蔽效应 粒子也将被研究。

DESCRIPTION: (Adapted from the applicant's abstract): Restenosis is the major limitation of coronary angioplasty. Recently brachytherapy has emerged as a potential treatment for restenosis using photon emitters such as 192Ir, 125I, 103Pd and beta emitters such as 32P, 90Sr, and 90Y. Two approaches under investigation for intravascular brachytherapy are: (i) use of a radioactive source at the end of a catheter, (ii) permanent implantation of a radioactive stent at the occlusion site. The first is an example of temporary intracavitary brachytherapy where radioactive sources are placed in a body cavity near the target lesion; the other is an example of permanent brachytherapy where radioactive sources are implanted in the target lesion. It is well known that dose gradients in the immediate vicinity of the radioactive sources are very high because of the geometric and tissue attenuation effects. Traditionally, the dose to the target is specified at a distance of 1 cm from the source. At this reference distance the dosimetry of brachytherapy sources is reasonably well established. However, the intended target for irradiation in intravascular brachytherapy is much smaller, in the range of 1 - 3 mm. At these short distances, the dosimetry is highly uncertain and needs improvement. One of the major reasons for dose uncertainty at short distances may be the contribution from low energy secondary radiations, such as fluorescent x rays, beta particles, secondary electrons etc., which are primarily absorbed in the source encapsulation or the first few mm of tissue around the source. Their effects are largely ignored in traditional brachytherapy dosimetry because only a small fraction of the target volume is affected by them. This is, however, not true for intravascular brachytherapy where the entire target may be within millimeters of the source. With many investigations currently underway, mostly with commercial support, to determine the efficacy of intravascular brachytherapy, there is a tremendous need to not only standardize the prescription of dose, but importantly to also determine the dose delivered over short distances. This dosimetry may well be significantly different depending on specific radionuclide as well as design of source and applicators. In this project, the physics of intravascular brachytherapy dosimetry for treatment of restenosis will be investigated using thermoluminescent dosimeter chips and sheets, radiochromic film, polymer gel dosimeters, Rossi-type proportional chamber for microdosimetry, and Monte Carlo simulations. Finally, effects of tissue heterogeneity and self-shielding effects of catheters and stents for photons and beta particles will also be investigated.