Alasti Hamideh, Cho Young-Bin, Catton Charles, Berlin Alejandro, Chung Peter, Bayley Andrew, Vandermeer Aaron, Kong Vickie, Jaffray David
Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Canada; Department of Radiation Oncology, University of Toronto, Canada.
Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Canada; Department of Radiation Oncology, University of Toronto, Canada.
Radiother Oncol. 2017 Oct;125(1):118-123. doi: 10.1016/j.radonc.2017.08.012. Epub 2017 Aug 28.
The aim was to determine whether the enhanced soft tissue contrast provided by high-dose volumetric CT (HDVCT) can reduce inter-observer variability in delineating prostate compared to helical conventional CT (CCT) scans and 3T MRI scans for patients undergoing radical prostate cancer radiotherapy. Secondly, to quantify the potential PTV reduction with decreased inter-observer variability.
A 320 slice volumetric CT scanner was used. The wide-detector coverage of 16cm enabled volumetric image acquisition of prostate gland in one rotation. Three imaging studies were performed on ten patients. CCT and HDVCT were performed consecutively at the same coordinate system followed by MRI. Five radiation oncologists delineated the prostate.
The inter-observer variability is 2.0±0.6, 1.9±0.4 and 1.8±0.4mm for CCT, HDVCT and MR respectively with the maximum at the apex region. Comparing inter-observer difference variability between CCT and HDVCT with MR indicates that observers have larger variations in contouring using CCT than HDVCT especially at apex. Jaccard index of HDVCT is significantly higher than CCT with a mean difference of 0.03 (p=0.011). Both MRI and HDVCT provide the opportunity for a 2mm PTV margin reduction at the apex compared to CCT.
Inter-observer variability in delineation remains an important source of systematic error. HDCTV for treatment planning reduces this error without recourse to MRI and permits a PTV reduction of 2mm at the apex. The margins required to account for residual error with any imaging modality are still greater than are used in typical current practice.
旨在确定对于接受根治性前列腺癌放疗的患者，高剂量容积CT（HDVCT）所提供的增强软组织对比度与螺旋式传统CT（CCT）扫描及3T MRI扫描相比，是否能降低观察者间在勾画前列腺轮廓时的变异性。其次，量化随着观察者间变异性降低，计划靶区（PTV）可能缩小的程度。
使用一台320层容积CT扫描仪。16厘米的宽探测器覆盖范围使得一次旋转就能采集前列腺的容积图像。对10名患者进行了三项成像研究。在同一坐标系下连续进行CCT和HDVCT扫描，随后进行MRI扫描。五名放射肿瘤学家勾画前列腺轮廓。
CCT、HDVCT和MR的观察者间变异性分别为2.0±0.6、1.9±0.4和1.8±0.4毫米，在尖部区域最大。将CCT和HDVCT与MR之间的观察者间差异变异性进行比较表明，观察者使用CCT勾画轮廓时的变异性比HDVCT更大，尤其是在尖部。HDVCT的杰卡德指数显著高于CCT，平均差异为0.03（p = 0.011）。与CCT相比，MRI和HDVCT都为在尖部将PTV边界缩小2毫米提供了机会。
观察者间在勾画轮廓时的变异性仍然是系统误差的一个重要来源。用于治疗计划的HDCTV可减少这种误差，无需借助MRI，并允许在尖部将PTV缩小2毫米。对于任何成像方式，考虑残留误差所需的边界仍大于当前典型实践中所使用的边界。
