Weiss Elisabeth, Wijesooriya Krishni, Ramakrishnan Viswanathan, Keall Paul J
Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Int J Radiat Oncol Biol Phys. 2008 Feb 1;70(2):572-581. doi: 10.1016/j.ijrobp.2007.09.035. Epub 2007 Dec 19.
To evaluate the implications of differences between contours drawn manually and contours generated automatically by deformable image registration for four-dimensional (4D) treatment planning.
In 12 lung cancer patients intensity-modulated radiotherapy (IMRT) planning was performed for both manual contours and automatically generated ("auto") contours in mid and peak expiration of 4D computed tomography scans, with the manual contours in peak inspiration serving as the reference for the displacement vector fields. Manual and auto plans were analyzed with respect to their coverage of the manual contours, which were assumed to represent the anatomically correct volumes.
Auto contours were on average larger than manual contours by up to 9%. Objective scores, D(2%) and D(98%) of the planning target volume, homogeneity and conformity indices, and coverage of normal tissue structures (lungs, heart, esophagus, spinal cord) at defined dose levels were not significantly different between plans (p = 0.22-0.94). Differences were statistically insignificant for the generalized equivalent uniform dose of the planning target volume (p = 0.19-0.94) and normal tissue complication probabilities for lung and esophagus (p = 0.13-0.47). Dosimetric differences >2% or >1 Gy were more frequent in patients with auto/manual volume differences > or =10% (p = 0.04).
The applied deformable image registration algorithm produces clinically plausible auto contours in the majority of structures. At this stage clinical supervision of the auto contouring process is required, and manual interventions may become necessary. Before routine use, further investigations are required, particularly to reduce imaging artifacts.
评估手动绘制轮廓与通过可变形图像配准自动生成的轮廓之间的差异对四维（4D）治疗计划的影响。
对12例肺癌患者进行调强放射治疗（IMRT）计划，在4D计算机断层扫描的呼气中期和呼气峰值期分别使用手动轮廓和自动生成（“自动”）轮廓，以吸气峰值期的手动轮廓作为位移矢量场的参考。分析手动计划和自动计划对手动轮廓的覆盖情况，假定手动轮廓代表解剖学上正确的体积。
自动轮廓平均比手动轮廓大9%。计划靶体积的客观评分、D(2%)和D(98%)、均匀性和适形指数以及在规定剂量水平下正常组织结构（肺、心脏、食管、脊髓）的覆盖情况在两种计划之间无显著差异（p = 0.22 - 0.94）。计划靶体积的广义等效均匀剂量（p = 0.19 - 0.94）以及肺和食管的正常组织并发症概率（p = 0.13 - 0.47）的差异无统计学意义。自动/手动体积差异≥10%的患者中剂量差异>2%或>1 Gy更为常见（p = 0.04）。
所应用的可变形图像配准算法在大多数结构中产生临床上合理的自动轮廓。在此阶段，需要对自动轮廓绘制过程进行临床监督，可能需要进行手动干预。在常规使用之前，需要进一步研究，特别是要减少成像伪影。
