Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran.
J Appl Clin Med Phys. 2010 Dec 2;12(1):3360. doi: 10.1120/jacmp.v12i1.3360.
High dose rate (HDR) brachytherapy is one of the accepted treatment modalities in gastro-intestinal tract and bladder carcinomas. Considering the shortcoming of contact brachytherapy routinely used in gastrointestinal tract in treatment of big tumors or invasive method of bladder treatment, an intraluminal applicator with the capability of insertion into the tumor depth seems to be useful. This study presents some dosimetric evaluations to introduce this applicator to the clinical use. The radiation attenuation characteristics of the applicator were evaluated by means of two dosimetric methods including well-type chamber and radiochromic film. The proposed 110 cm long applicator has a flexible structure made of stainless steel for easy passage through lumens and a needle tip to drill into big tumors. The 2mm diameter of the applicator is thick enough for source transition, while easy passage through any narrow lumen such as endoscope or cystoscope working channel is ensured. Well-chamber results showed an acceptably low attenuation of this steel springy applicator. Performing absolute dosimetry resulted in a correlation coefficient of R = 0.9916 (p-value ≈ 10-7) between standard interstitial applicator and the one proposed in this article. This study not only introduces a novel applicator with acceptable attenuation but also proves the response independency of the GAFCHROMIC EBT films to energy. By applying the dose response of the applicator in the treatment planning software, it can be used as a new intraluminal / interstitial applicator.
高剂量率（HDR）近距离治疗是胃肠道和膀胱癌的一种公认的治疗方法。考虑到胃肠道常规使用的接触近距离治疗在治疗大肿瘤或侵袭性膀胱治疗方法方面的缺点，一种能够插入肿瘤深处的腔内施源器似乎很有用。本研究通过两种剂量学方法（包括井型室和光致变色胶片）对该施源器进行了一些剂量学评估，以将其引入临床应用。通过井型室和光致变色胶片两种剂量学方法评估了施源器的辐射衰减特性。所提出的 110cm 长施源器采用不锈钢制成，具有灵活的结构，易于通过管腔，并且针尖可钻入大肿瘤。施源器的 2mm 直径足以进行源转换，同时确保易于通过任何狭窄的管腔，如内窥镜或膀胱镜工作通道。井型室结果表明，这种钢弹簧式施源器的衰减可以接受。进行绝对剂量学测量得到了标准间质施源器和本文提出的施源器之间相关系数 R = 0.9916（p 值≈10-7）。本研究不仅介绍了一种具有可接受衰减的新型施源器，还证明了 GAFCHROMIC EBT 胶片对能量的响应独立性。通过在治疗计划软件中应用施源器的剂量响应，可以将其用作新型腔内/间质施源器。
