Rijkhorst Erik-Jan, Lakeman Annemarie, Nijkamp Jasper, de Bois Josien, van Herk Marcel, Lebesque Joos V, Sonke Jan-Jakob
Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2009 Nov 15;75(4):1254-60. doi: 10.1016/j.ijrobp.2009.04.034.
To quantify and evaluate the accumulated prostate, rectum, and bladder dose for several strategies including rotational organ motion correction for intensity-modulated radiotherapy (IMRT) of prostate cancer using realistic organ motion data.
Repeat computed tomography (CT) scans of 19 prostate patients were used. Per patient, two IMRT plans with different uniform margins were created. To quantify prostate and seminal vesicle motion, repeat CT clinical target volumes (CTVs) were matched onto the planning CTV using deformable registration. Four different strategies, from online setup to full motion correction, were simulated. Rotations were corrected for using gantry and collimator angle adjustments. Prostate, rectum, and bladder doses were accumulated for each patient, plan, and strategy. Minimum CTV dose (D(min)), rectum equivalent uniform dose (EUD, n = 0.13), and bladder surface receiving >or=78 Gy (S78), were calculated.
With online CTV translation correction, a 7-mm margin was sufficient (i.e., D(min) >or= 95% of the prescribed dose for all patients). A 4-mm margin required additional rotational correction. Margin reduction lowered the rectum EUD(n = 0.13) by approximately 2.6 Gy, and the bladder S78 by approximately 1.9%.
With online correction of both translations and rotations, a 4-mm margin was sufficient for 15 of 19 patients, whereas the remaining four patients had an underdosed CTV volume <1%. Margin reduction combined with online corrections resulted in a similar or lower dose to the rectum and bladder. The more advanced the correction strategy, the better the planned and accumulated dose agreed.
使用真实的器官运动数据，对几种策略（包括前列腺癌调强放射治疗（IMRT）的旋转器官运动校正）的前列腺、直肠和膀胱累积剂量进行量化和评估。
使用了19例前列腺癌患者的重复计算机断层扫描（CT）图像。为每位患者创建了两个具有不同均匀边界的IMRT计划。为了量化前列腺和精囊的运动，使用可变形配准将重复CT扫描的临床靶区（CTV）与计划CTV进行匹配。模拟了从在线摆位到完全运动校正的四种不同策略。使用机架和准直器角度调整来校正旋转。计算每位患者、每个计划和每种策略的前列腺、直肠和膀胱剂量。计算最小CTV剂量（D(min)）、直肠等效均匀剂量（EUD，n = 0.13）以及膀胱表面接受≥78 Gy的剂量（S78）。
对于在线CTV平移校正，7 mm的边界就足够了（即所有患者的D(min)≥处方剂量的95%）。4 mm的边界需要额外的旋转校正。边界缩小使直肠EUD（n = 0.13）降低了约2.6 Gy，膀胱S78降低了约1.9%。
对于19例患者中的15例，通过在线平移和旋转校正，4 mm的边界就足够了，而其余4例患者的CTV剂量不足体积<1%。边界缩小与在线校正相结合，可使直肠和膀胱接受的剂量相似或更低。校正策略越先进，计划剂量和累积剂量的一致性越好。
