Evaluation the Interfractional dose Difference Using Cone-beam CT in Prostate Patients

利用錐體體積電腦斷層影像評估前列腺腫瘤病人分次間的劑量差異

何秀雯(Hsiu-Wen Ho) ； 林裕為(Mark Lin) ； 林立青(Li-Ching Lin) ； 李淞維(Sung-Wei Li) ； 林秀滿(Hsiu-Man Lin) ； 周振宇(Chen-Yu Chou) ； 黃俊喬(Joe Huang)

《放射治療與腫瘤學》 21卷1期 (2014/03) Pp. 43-53

https://doi.org/10.6316/TRO/201421(1)43

摘要

目的：立體定位放射線治療是一種可精準且有效達到低分次放射線治療的方式。本研究的目的旨在利用錐體體積電腦斷層影像，進行劑量重建並評估其腫瘤包覆性與正常組織的劑量分布。材料與方法：本文利用3位早期前列腺癌病人為研究對象。每位病人在治療前先接受金屬標誌物的植入。定位與治療時病人都接受特殊的直腸與膀胱事前準備工作。在每次治療之前病人會先接受以金屬植入物為對位依據的正交X光影像，再接著以軟組織為對位依據的錐體體積電腦斷層影像。治療總劑量為37.5 Gy分5個分次給予。治療計畫須滿足95%的腫瘤體積須包覆95%的處方劑量。結果：以軟組織為對位依據的錐體體積電腦斷層影像條件下，所有病人的計畫皆可達到95%的腫瘤體積包覆95%的處方劑量。以金屬植入物為對位依據的正交X光影像條件下，只有86%的病人計畫可達到95%的腫瘤體積包覆95%的處方劑量。正常組織方面，86.66%的病人計畫其膀胱劑量可達到V50少於50%；60%的病人計畫可達到V100少於5 cc。86.66 %的病人計畫其直腸劑量可達到V50少於50%；94%的病人計畫其直腸劑量可達到V80少於20%；60% 的病人計畫其直腸劑量可達到V90少於10%；60%的病人計畫其直腸劑量可達到V100少於5%。結論：研究結果顯示錐體體積電腦斷層影像可提供正確的病人對位資訊，雖然對於病人在定位與治療時皆配合膀胱與直腸的特殊準備，但仍無法有效減少其體積變化因而反應在劑量的變異性上。在未來我們希望可以增加樣本數以提供更客觀與顯著的結果。

關鍵字

攝護腺癌 ； 立體定位放射線治療 ； 錐體體積電腦斷層影像

並列摘要

Purposes: Stereotactic body radiation therapy (SBRT) is a method for the precise and efficient administration of hypofractionated radiotherapy. The aim of this study was to utilize the cone beam computed tomography (CBCT) scans acquired before treatment for dose reconstruction and hereby to assess target volume coverage during prostate SBRT.Materials and Methods: Three patients with early stage prostate cancer were included in this study. All patients had implanted two golden fiducial markers under transrectal ultrasound for image-guided localization. The rectum and bladder in-house preparation protocols were used in this study. Before each treatment, the patient was first set up with a pair of orthogonal kilovoltage (kV) portal images based on fiducial markers and subsequently adjusted to the treatment position with CBCT for soft tissue alignment. A CBCT image set acquired prior to each treatment for patient positioning was employed for the dose reconstruction calculation. The prescription dose was 37.5 Gy in 5 fractions. The criterion of plan is to satisfy at least the 95% of prescription dose to cover 95% of PTV (V95 greater than 95%).Results: All the patients can meet the V95 greater than 95% criterion if we corrected the patient position base on CBCT image. There was only 86% of all fractions can meet the V95 greater than 95% when the patient position was corrected with kV portal images. For bladder, 86.66% and 60% of all fractions could meet the criteria of V50 of bladder less than 50%, and V100 less than 5 c.c respectively. For rectum, 86.66%, 94%, 60%, and 60% of all fractions could meet the criteria of V50 of rectum less than 50%, V80 less than 20%, V90 less than 10%, and V100 less than 5% respectively. Furthermore, there are less than 5cc of rectum receiving 100% of dose for all cases.Conclusion: The correct dose delivered to the correct location is the most important goal of radiation therapy especially for SBRT. The tighter margin than other conventional treatment was applied to this study. Our results show the CBCT registration provides the opportunity to improve the dose delivery accuracy. Although the dose and volume variations of bladder and rectum still cannot be controlled well even if we used in house special protocols in this study. In conclusion, the margin apply to this study is sufficient to achieve the PTV coverage if applying CBCT base on soft tissue matching for patient position registration. We plan to expend our sample size to get more statistically significant results in near future.

並列關鍵字

Prostate ； SBRT (stereotactic body radiation therapy) ； CBCT (cone beam computed tomography)