利用影像導引定位系統分析前列腺癌患者在放射治療中的擺位誤差

Measurement and Analysis of Setup Error in Image Guided Radiation Therapy for Prostate Cancer Patients

康誠麟(Chen-Lin Kang) ； 蔡正祥(Cheng-Hsiang Tasi) ； 張軒銘(Hsuan-Ming Chang) ； 陳文凱(Wen-Kai Chen) ； 廖宗義(Tzung-Yi Liao) ； 阮國榮(Kuo-Jung Juan)

《中華放射線技術學雜誌》 32卷2期 (2008/12) Pp. 173-180

https://doi.org/10.30045/CJRT.200812.0005

摘要

在放射治療過程中，患者的擺位誤差(setup errors)是影響精確治療的關鍵因素。本研究針對使用諾力刀(Novalis)治療機治療的前列腺癌患者，用其搭配影像導引定位系統(Exact Trac X-ray positioning system)將X-ray和治療計畫中的數位重組影像(Digital Reconstructed Radiography, DRR)進行校正比對，測定患者分次間(inter-fraction)的擺位誤差。擺位誤差可主要分爲系統誤差(systematic error)和隨機誤差(random error)，系統誤差可能在患者治療前就已存在，隨機誤差可能是來自每日治療時的擺位誤差或者病患呼吸，器官移動所引起的。收集共21名利用即時影像系統來測定擺位偏差的患者資料進行分析，三維各軸的平移誤差，所測得平均位移在左右，頭腳，及前後三個方向分別爲2.61mm、6.97mm、4.92mm。Σ值分別爲1.02mm、3.44mm、2.89mm。σ值分別爲0.6mm、2.36mm、1.92mm。藉著所測得的擺位誤差，利用國外文獻所提出計畫靶體積(Planning Target Volume, PTV)設定方法，來分析外擴邊緣的大小，最後評估三軸PTV外擴邊緣爲分別爲3mm、10mm、8.5mm是可行的。

關鍵字

分次間 ； 擺位誤差 ； 系統誤差 ； 隨機誤差

並列摘要

In external beam radiotherapy, patient setup error is a key factor affecting the precision of treatment. The current study was designed to investigate inter-fraction setup errors of prostate cancer patients treated with Novalis, coupled with Exact Trac X-ray positioning system, by comparing X-ray images with Digital Reconstructed Radiography (DRR) generated by the treatment planning system. Setup error primarily could be divided into systematic error and random error. Systematic error could exist before the treatment, and random error may result from the setup error in daily treatment or the movement of internal organs associated with respiration. We collected twenty-one patients and used the Exact Trac X-ray positioning system to analyze the setup data. The mean translation in X (LR), Y (SI), and Z (AP) directions were 2.61mm, 6.97mm, and 4.92mm, respectively. The standard deviations of systematic error (Σ) were 1.02mm, 3.44mm, and 2.89mm, and that of the random error (σ) were 0.6mm, 2.36mm, 1.92mm, respectively. We checked the setup errors with the settings of planning target volume (PTV) suggested in the literature to determine the proper size of margin. The final results revealed that it was feasible to set the PTV margin (MPTV) to 3 mm, 10 mm, and 8.5 mm in treating prostate cancer patients.

並列關鍵字

inter-fraction ； setup error ； systematic error ； random error