Preliminary Experience of Reducing Bowel Irradiation Volume in the Treatment of Rectal Cancer: Two Cases Study

治療直腸癌時減低小腸腸道照射體積之經驗：兩案例報告

劉瑞燦(Jui-Tsan Liu) ； 林芳仁(Fang-Jen Lin) ； 陳尚文(Shang-Wen Chen) ； 吳學鼎(Hsieh-Ting Wu) ； 梁基安(Ji-An Liang) ； 楊世能(Shin-Neng Yang)

《放射治療與腫瘤學》 6卷2期 (1999/06) Pp. 141-148

https://doi.org/10.6316/TRO/199906(2)141

摘要

目的：骨盆腔部位放射治療常受限於小腸的耐受劑量。本篇乃評估直腸癌病患在仰臥與俯臥姿勢下，藉由組織劑量分佈圖(dose-volume histogram)的分析，顯示腸道受照體積在兩種姿勢下的改變情形，並對胖瘦不同體型病患進行評估。
村料與方法：每位病患均接受兩組電腦斷層掃描，其中一組，病患以俯臥姿勢躺在腹部支持器(belly board)上，另一組則採仰躺姿勢進行掃描。將影像輸入治療計畫電腦中，分析積分(cumulatlve)與微分(differential)組織劑量分佈圖，評估小腸照射體積與劑量的變化。
結果：積分組織劑量分佈圖可被用以表示正常組織可能受到的傷害，此分析表示在俯臥姿勢時70%至95%的百分劑量範圍內，小腸受照射體積比仰躺姿勢減少15%~18%。而評估腫瘤及組織接受劑量均勻度的微分組織劑量分佈圖，可以看到小腸所受劑量由較高的劑量範圍分佈移到較低的劑量範圍。
結論：經由腹部支持器的使用，使小腸移出照射範圍之外是十分可行的，無論胖或瘦的病人均可藉此減低腸道照射體積。以此方式治療時，一個固定模具是不可或缺的，可使病人在整個治療過程中，具有相同的位置及姿勢，確保治療部位的正確性。

關鍵字

小腸 ； 直腸癌 ； 腹部支持器 ； 組織劑量分佈圖

並列摘要

Purpose: The dosage of radiotherapy to the pelvis is always limited by the tolerance of small bowel. This study is to evaluate the dose volume histogram (DVH) of the irradiated bowel volume by prone position with belly board in comparison to treatment in supine position technique. Two patients with rectal cancer were analyzed.
Materials and Methods: Two groups of sequential computerized tomography (CT) scans were performed with 8-mm slice thickness for each patient. One group of the scans was obtained for patient with a belly board in a prone position, and the other one was in a supine position for comparing the bowel irradiation volume with the previous scan. Hard copies of CT scan slices for both patients were produced. The contours of small bowel volumes were outlined on each CT slice hard copy and the information was then digitized and entered into treatment planning computer. The cumulative and the differential DVHs were performed for evaluating the bowel irradiation volume.
Results: The cumulative DVH, which is used in assessing potential damage to normal tissue, shows that from 70% to 95% of the percentage dose in prone position has a 15% to 18% volume reduction compared to supine position. The differential DVH, which is useful in assessing uniformity of dose to tumors. shows that the irradiated bowel volume has been moved to a region of rower percentage dose.
Conclusion: Displacement of bowel loops out of the true pelvis is done by using a belly board in the prone position for thin and obese patients instead of supine position to decrease the volume of the intestine under irradiation because of external compression. The pelvic board and a half-body cast can be applied to immobilize patient for precise positioning and repositioning throughout the entire treatment.

並列關鍵字

Bowel ； Rectal cancer ； Belly board ； Dose volume histogram