Taccini G, Cavagnetto F, Coscia G, Garelli S, Pilot A
Department of Medical Physics, S. Martino Hospital, Genoa, Italy.
Med Phys. 1997 Dec;24(12):2034-7. doi: 10.1118/1.598117.
Ruthenium ophthalmic applicators are energetic beta ray sources, supplied in several shapes and dimensions, and used in intraocular tumor therapy. Because of their small dimensions, the determination of dosimetric characteristics represents a technical challenge. We developed a semiautomatic method to define surface dose, dose distribution, and percentage depth dose of such applicators using radiochromic dosimetric media. These detectors consist of a thin (7 microns) radiation sensitive layer on polyester base (100 microns total thickness) changing color as a function of radiation exposure. Transmission images of exposed films were then grabbed with a TV-digitizer system to obtain a gray-level image from which dosimetric characteristics such as isodose distribution, dose values, and homogeneity of nuclide distribution were derived. Good agreement between experimental results and Monte Carlo simulation performed using the GEANT 3 code, appear to be a confirmation of the validity of the method. Moreover while manufacturer specifications of absolute and relative dose rates present a standard deviation error of +/- 30% on dose rate and +/- 6% on accuracy of relative dose values, the proposed method reduces the errors to +/- 10% and +/- 4%, respectively.
钌眼科敷贴器是高能β射线源，有多种形状和尺寸，用于眼内肿瘤治疗。由于其尺寸小，剂量学特征的测定是一项技术挑战。我们开发了一种半自动方法，使用放射变色剂量学介质来确定此类敷贴器的表面剂量、剂量分布和百分深度剂量。这些探测器由聚酯基底（总厚度100微米）上的薄（7微米）辐射敏感层组成，其颜色会随辐射暴露而变化。然后用电视数字化仪系统抓取曝光胶片的透射图像，以获得灰度图像，从中得出剂量学特征，如等剂量分布、剂量值和核素分布的均匀性。实验结果与使用GEANT 3代码进行的蒙特卡罗模拟之间的良好一致性，似乎证实了该方法的有效性。此外，虽然制造商给出的绝对和相对剂量率规格在剂量率上的标准偏差误差为±30%，在相对剂量值的准确性上为±6%，但所提出的方法分别将误差降低到了±10%和±4%。
