科研之友
微信
新浪微博
Facebook
分享链接
摘要
We conducted a multivariate analysis to determine relationships between prostate radiation dose and the state of surrounding organs, including organ volumes and the internal angle of the levator ani muscle (LAM), based on cone-beam computed tomography (CBCT) images after bone matching. We analyzed 270 CBCT data sets from 30 consecutive patients receiving intensity-modulated radiation therapy for prostate cancer. With patients in the supine position on a couch with the HipFix system, data for center of mass (COM) displacement of the prostate and the state of individual organs were acquired and compared between planning CT and CBCT scans. Dose distributions were then recalculated based on CBCT images. The relative effects of factors on the variance in COM, dose covering 95% of the prostate volume (D-95%), and percentage of prostate volume covered by the 100% isodose line (V-100%) were evaluated by a backward stepwise multiple regression analysis. COM displacement in the anterior-posterior direction (COMAP) correlated significantly with the rectum volume (delta Vr) and the internal LAM angle (delta theta; R = 0.63). Weak correlations were seen for COM in the left-right (R = 0.18) and superior-inferior directions. (R = 0.31). Strong correlations between COMAP and prostate D-95% and V-100% were observed (R >= 0.69). Additionally, the change ratios in delta Vr and delta theta remained as predictors of prostate D-95% and V-100%. This study shows statistically that maintaining the same rectum volume and LAM state for both the planning CT simulation and treatment is important to ensure the correct prostate dose in the supine position with bone matching.
- 出版日期2014
