DOSIMETRY OF BRACHYTHERAPY SOURCES IN MILLIMETER RANGE

毫米范围内近距离治疗源的剂量测定

• 批准号: 2685523
• 负责人: RAVINDER NATH
• 金额: $ 24.59万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-04-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2685523
• 关键词: biomedical equipment development; clinical biomedical equipment; iodine; iridium; linear energy transfer; method development; palladium; phosphorus; radiation therapy dosage; radionuclide implant; radionuclide therapy; radionuclides; restenosis; single photon emission computed tomography; statistics /biometry; strontium; yttrium

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.

描述：（改编自申请人的摘要）：再狭窄是 冠状动脉成形术的主要局限性。 最近近距离放射治疗 使用光子发射器作为对再狭窄的潜在治疗方法 如192IR，125i，103pd和Beta发射器，例如32p，90SR和90y。 二 血管内近距离放射治疗正在研究的方法是：（i）使用 导管末端的放射性源，（ii）永久 闭塞部位的放射性支架的植入。 第一个是 临时腔内近距离放射治疗的例子 被放置在靶病变附近的体腔中；另一个是一个例子 永久性近距离放射疗法，放射性源植入 靶病变。 众所周知，直接剂量梯度 由于几何形状，放射性来源附近很高 和组织衰减效果。 传统上，目标的剂量是 指定距离源1厘米的距离。 在此参考距离 近距离放射治疗来源的剂量学相当合理地确定。 但是，血管内近距离放射治疗的辐射的预期靶标 小得多，范围为1-3毫米。 在这些短距离处 剂量法是高度不确定的，需要改善。 专业之一 短途剂量不确定性的原因可能是 低能次级辐射，例如荧光X射线，β颗粒， 辅助电子等，主要被吸收在源 封装或源周围的前几毫米组织。 他们的 在传统的近距离放射治疗剂量法中，效果在很大程度上被忽略了，因为 目标体积的一小部分受其影响。 这是， 但是，对于整个靶标的血管内近距离放射治疗并不正确 可能在源的毫米内。 目前有许多调查 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，但重要的是也确定 剂量在短距离内交付。 这个剂量法很可能是 明显不同，具体取决于特定的放射性核素和设计 来源和涂药者。 在这个项目中，血管内物理 将研究用于治疗再狭窄的近距离放射治疗剂量测定法 使用热发光的剂量计碎片和床单，放射性膜， 聚合物凝胶剂量计，rossi型比例室的微尺度法， 和蒙特卡洛模拟。 最后，组织异质性和 导管和支架对光子和beta的自我屏蔽效果 还将研究颗粒。