Correlation of Dose-reporting Parameters in Two-dimensional and Three-dimensional Image-guided Brachytherapy for Cancer of the Cervix Uteri: a Single-Institution Experience

Full Article

SWK Siu, AMK Chow, TMC Ng, FNF Tang, PPY Ho, WWL Chan, MHM Szeto, PWK Kwong, TW Leung

Hong Kong J Radiol 2016;19:256-61

DOI: 10.12809/hkjr1616398

Objective: Different dose-reporting parameters are suggested for two-dimensional and three-dimensional image-guided brachytherapy for cancer of the cervix uteri. We aimed to determine if there is any correlation between these dose-reporting parameters in three-dimensional image-guided brachytherapy plans.

Methods: A computed tomographic (CT) scanner has been installed in the brachytherapy room in our department so that patients can undergo imaging in the same room immediately following insertion of applicators while being maintained under anaesthesia or sedation. Between January 2014 and September 2015, 34 patients underwent CT-based brachytherapy (number of plans, 136). High-risk clinical target volume (HR-CTV) and rectum were contoured according to GEC-ESTRO guidelines. Point A and ICRU rectal points were also determined. The correlations of D90 of HR-CTV with Point A, and also of D2cc of rectum with ICRU rectal points were determined. Two-sided paired t-test was used to determine if there were any statistically significant differences between HR-CTV D90 and Point A, and also between D2cc of rectum and ICRU rectal points.

Results: Comparison of the dose of Point A and D90 of HR-CTV revealed a statistically significant difference (p < 0.001) with a weak negative correlation (R = –0.32; p < 0.0001). Comparison of the dose of ICRU reference rectal point and D2cc of rectum revealed a statistically significant difference (p < 0.01) with a positive correlation (p < 0.001).

Conclusion: HR-CTV D90 and Point A appear to show a random relationship. ICRU rectal point, however, may tend to underestimate the dose to the rectum in a plan that is CT imaging-based compared with D2cc.


Authors’ affiliation:
Department of Clinical Oncology, Queen Mary Hospital, Pokfulam, Hong Kong








方法:本院的近距離放射治療室安裝了電腦斷層掃描儀器(CT),方便患者仍在麻醉或鎮靜的狀況下插入敷料器後立即進行CT成像。2014年1月至2015年9月期間共34名患者接受CT引導下近距離放射治療(計劃數量為136)。根據GEC-ESTRO指南勾劃出高危靶區(HR-CTV)和直腸體積,並確定參考點A和國際輻射單位與測量委員會(ICRU)直腸參考點。找出HR-CTV D90與參考點A,以及直腸D2cc與ICRU直腸參考點的相關性。使用雙側配對t檢驗來確定以上兩組是否有任何統計學顯著差異。

結果:HR-CTV D90與參考點A具統計學顯著差異(p<0.001),但呈弱負相關性(R = –0.32; p<0.0001)。比較直腸D2cc與ICRU直腸參考點具統計學顯著差異(p<0.01),並呈正相關性(p<0.001)。

結論:HR-CTV D90與參考點A似乎有隨機關係。與D2cc相比,CT引導下近距離放射治療的ICRU直腸參考點卻可能低估了直腸劑量。