Song William Y, Chiu Bernard, Bauman Glenn S, Lock Michael, Rodrigues George, Ash Robert, Lewis Craig, Fenster Aaron, Battista Jerry J, Van Dyk Jake
Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.
Int J Radiat Oncol Biol Phys. 2006 Jun 1;65(2):595-607. doi: 10.1016/j.ijrobp.2006.01.049.
To evaluate the image-guidance capabilities of megavoltage computed tomography (MVCT), this article compares the interobserver and intraobserver contouring uncertainty in kilovoltage computed tomography (KVCT) used for radiotherapy planning with MVCT acquired with helical tomotherapy.
Five prostate-cancer patients were evaluated. Each patient underwent a KVCT and an MVCT study, a total of 10 CT studies. For interobserver variability analysis, four radiation oncologists, one physicist, and two radiation therapists (seven observers in total) contoured the prostate and seminal vesicles (SV) in the 10 studies. The intraobserver variability was assessed by asking all observers to repeat the contouring of 1 patient's KVCT and MVCT studies. Quantitative analysis of contour variations was performed by use of volumes and radial distances.
The interobserver and intraobserver contouring uncertainty was larger in MVCT compared with KVCT. Observers consistently segmented larger volumes on MVCT where the ratio of average prostate and SV volumes was 1.1 and 1.2, respectively. On average (interobserver and intraobserver), the local delineation variability, in terms of standard deviations [Deltasigma = radical(sigma2MVCT-sigma2KVCT)], increased by 0.32 cm from KVCT to MVCT.
Although MVCT was inferior to KVCT for prostate delineation, the application of MVCT in prostate radiotherapy remains useful.
为评估兆伏级计算机断层扫描（MVCT）的图像引导能力，本文比较了用于放射治疗计划的千伏级计算机断层扫描（KVCT）与螺旋断层放射治疗获得的MVCT在观察者间和观察者内轮廓勾画的不确定性。
对5例前列腺癌患者进行了评估。每位患者均接受了KVCT和MVCT检查，共10次CT检查。对于观察者间变异性分析，4名放射肿瘤学家、1名物理学家和2名放射治疗师（共7名观察者）在10次检查中对前列腺和精囊（SV）进行了轮廓勾画。通过要求所有观察者重复对1例患者的KVCT和MVCT检查进行轮廓勾画来评估观察者内变异性。使用体积和径向距离对轮廓变化进行定量分析。
与KVCT相比，MVCT的观察者间和观察者内轮廓勾画不确定性更大。观察者在MVCT上一致分割出更大的体积，其中平均前列腺和SV体积之比分别为1.1和1.2。平均而言（观察者间和观察者内），就标准差而言[Δσ = √(σ²MVCT - σ²KVCT)]，从KVCT到MVCT局部勾画变异性增加了0.32 cm。
虽然在前列腺勾画方面MVCT不如KVCT，但MVCT在前列腺放射治疗中的应用仍然是有用的。
