Waterman F M, Mansfield C M, Komarnicky L, Anne P R, Corn B, Suntharalingam N
Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
Int J Radiat Oncol Biol Phys. 1997 Jan 1;37(1):229-35. doi: 10.1016/s0360-3016(96)00472-5.
192Ir interstitial breast implants performed at the time of lumpectomy present a unique problem because they cannot be preplanned, and yet they are expected to produce a treatment dose rate (TDR) from 0.3 to 0.5 Gy/h using sources already procured. The purpose of this work is to describe a system of dosimetry that works within these constraints and has been used to perform more than 600 such implants.
The underlying principle is to fix the ribbon spacing, the interplaner separation, and the linear activity (1 mCi/cm) so that the TDR will depend only on the area (L x W) implanted. The ribbons are spaced 1.5 cm and 2.0 cm apart in single plane and double implants, respectively. Idealized implants were used to study the TDR as a function of the implant dimensions, and to study the effects of varying the ribbon spacing and interplanar separation. Volume-dose histograms were generated to study the homogeneity of dose.
The TDRs of single plane implants range from 0.3 Gy/h for small 4 x 4 cm2 implants to 0.4 Gy/h for large 10 x 10 cm2 implants. The TDRs for double plane implants are similar for the same range of dimensions.
Implants with a TDR between 0.3 and 0.5 Gy/h can be performed for a wide range of geometries without preplanning using fixed ribbons spacings of 1.5 and 2.0 cm for single and double plane implants, respectively, and a linear activity of 1 mCi/cm.
在乳房肿瘤切除术中进行的192Ir组织间植入存在一个独特问题，因为无法预先规划，然而却期望使用已采购的放射源产生0.3至0.5 Gy/h的治疗剂量率（TDR）。这项工作的目的是描述一种在这些限制条件下起作用的剂量测定系统，该系统已用于进行600多次此类植入。
基本原理是固定丝带间距、平面间间距和线性活度（1 mCi/cm），以便TDR仅取决于植入的面积（长×宽）。在单平面和双平面植入中，丝带间距分别为1.5 cm和2.0 cm。使用理想化的植入模型来研究TDR作为植入尺寸的函数，并研究改变丝带间距和平面间间距的影响。生成体积剂量直方图以研究剂量的均匀性。
单平面植入的TDR范围从小的4×4 cm²植入的0.3 Gy/h到10×10 cm²大植入的0.4 Gy/h。相同尺寸范围内双平面植入的TDR相似。
对于广泛的几何形状，可以在不预先规划的情况下进行TDR在0.3至0.5 Gy/h之间的植入，单平面植入和双平面植入分别使用固定的丝带间距1.5 cm和2.0 cm以及1 mCi/cm的线性活度。
