Rosen I I, Khan K M, Lane R G, Kelsey C A
Med Phys. 1982 Mar-Apr;9(2):220-3. doi: 10.1118/1.595075.
In the treatment of tumors using interstitial implants of radioactive seeds, the accuracy of computed dose distributions depends upon the accuracy with which the three-dimensional source geometries are reconstructed from radiographs of the implants. The effect of geometric reconstruction errors in iridium-192 seed implants were studied, using tumor dose as the measure. Tumor dose was defined as the average dose around the periphery of the treatment volume. Three ideal mathematical implants and five actual patient implants were used. The implants were distorted by randomly moving a specified number of seeds a specified distance. Tumor doses were directly calculated for the ideal implants. For the actual implants, isodose distributions were plotted and were read by a radiotherapist. For both types of implants, percentage errors in the tumor doses were calculated for the distorted reconstructions relative to the correct reconstructions. It was found that the tumor dose was accurate to within 5% if all the seeds were reconstructed to within 0.5 cm of their actual positions. Furthermore, up to 5% of the seeds could be mismatched between films, or otherwise incorrectly reconstructed, with position errors as large as 20 cm, and not change the tumor dose by more than 5%.
在使用放射性种子间质植入物治疗肿瘤时，计算剂量分布的准确性取决于从植入物的X光片重建三维源几何形状的准确性。以肿瘤剂量为衡量标准，研究了铱-192种子植入物中几何重建误差的影响。肿瘤剂量定义为治疗体积周边的平均剂量。使用了三个理想的数学植入物和五个实际患者植入物。通过将指定数量的种子随机移动指定距离来使植入物变形。直接计算理想植入物的肿瘤剂量。对于实际植入物，绘制等剂量分布并由放射治疗师读取。对于两种类型的植入物，计算相对于正确重建的变形重建的肿瘤剂量百分比误差。结果发现，如果所有种子重建位置在其实际位置的0.5厘米范围内，则肿瘤剂量的误差在5%以内。此外，胶片之间高达5%的种子可能不匹配，或以其他方式重建错误，位置误差高达20厘米，且肿瘤剂量变化不超过5%。
