Department of Radiation Oncology, Daniel Den Hoed Cancer Center, EA Rotterdam, The Netherlands.
Radiother Oncol. 2011 Feb;98(2):192-7. doi: 10.1016/j.radonc.2010.12.009. Epub 2011 Feb 3.
The aim of this study was to systematically analyse the effect of catheter displacements both on target coverage and normal tissue irradiation in fractionated high dose rate (HDR) prostate brachytherapy, using a simulation study, and to define tolerances for catheter displacement ensuring that both target coverage and normal tissue doses remain clinically acceptable. Besides the effect of total implant displacement, also displacements of catheters belonging to selected template rows only were evaluated in terms of target coverage and normal tissue dose, in order to analyse the change in dose distribution as a function of catheter dwell weight and catheter location.
Five representative implant geometries, with 17 catheters each, were selected. The clinical treatment plan was compared to treatment plans in which an entire implant displacement in caudal direction over 3, 5, 7 and 10 mm was simulated. Besides, treatment plans were simulated considering a displacement of either the central, most ventral or most dorsal catheter rows only, over 5 mm caudally.
Due to displacement of the entire implant the target coverage drops below the tolerance of 93% for all displacements studied. The effect of displacement of the entire implant on organs at risk strongly depended on the patient anatomy; e.g., for 80% of the implant geometries the V(80) of the rectum exceeded its tolerance for all displacements. The effect of displacement of catheters belonging to selected template rows depended strongly on the relative weight of each catheter row when considering the target coverage and on its location when considering the dose in the organs at risk.
This study supports the need for a check of the catheter locations before each fraction and correction of deviations of the catheter position exceeding 3mm.
本研究旨在通过模拟研究系统分析分次高剂量率（HDR）前列腺近距离治疗中导管移位对靶区覆盖和正常组织照射的影响，并确定导管位移的容限，以确保靶区覆盖和正常组织剂量仍保持临床可接受水平。除了总植入物移位的影响外，还评估了仅属于选定模板行的导管的移位对靶区覆盖和正常组织剂量的影响，以分析剂量分布随导管驻留权重和导管位置的变化。
选择了 5 种具有代表性的植入物几何形状，每个形状均有 17 根导管。将临床治疗计划与模拟整个植入物在尾向方向上移位 3、5、7 和 10mm 的治疗计划进行了比较。此外，还模拟了仅在尾向方向上移位中央、最腹侧或最背侧导管行 5mm 的治疗计划。
由于整个植入物的移位，所有研究的位移都导致靶区覆盖率低于 93%的耐受水平。整个植入物移位对危及器官的影响强烈依赖于患者的解剖结构；例如，对于 80%的植入物几何形状，直肠的 V（80）超过了所有位移的耐受水平。考虑到靶区覆盖，属于选定模板行的导管移位对危及器官剂量的影响强烈取决于各导管行的相对权重；考虑到危及器官的剂量时，取决于其位置。
本研究支持在每次分次治疗前检查导管位置并纠正导管位置偏差超过 3mm 的需要。
