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題名 | The Differences between EPI and 4D-CBCT in Evaluating Inter-fraction Setup Errors for Breast Cancer Radiotherapy=EPI與4D-CBCT影像導引於評估乳癌放射治療的分次間擺位誤差之差異 |
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作者 | 蔡旻軒; 潘家鵬; 劉文山; | 書刊名 | 放射治療與腫瘤學 |
卷期 | 24:4 2017.12[民106.12] |
頁次 | 頁303-313 |
分類號 | 416.226 |
關鍵詞 | 乳癌; 影像導引; 電子式影像驗證系統; 四維錐狀射束電腦斷層; 擺位誤差; Breast cancer; Image-guided radiotherapy; IGRI; Electronic portal image; EPI; 4-dimensional cone-beam computerized tomography; 4D-CBCT; Setup error; |
語文 | 英文(English) |
中文摘要 | 目的:現今對於四維錐狀射束電腦斷層運用於乳癌放射治療的角色,相較於傳統電子式影像驗 證系統,是否能帶來更多的益處仍不確定。本研究主要目的為比較四維錐狀射束電腦斷層與傳 統電子式影像驗證於偵測擺位的系統及隨機誤差之差異。次要目的為分析各種病人相關因子對 於擺位誤差是否有顯著的影響。 材料與方法:自西元 2013 至 2016 年本研究共納入 17 位乳癌術後的患者;每位患者於頭十次放 射治療前,接受電子式影像驗證與四維錐狀射束電腦斷層這兩種影像導引技術校正,由醫師當 場記錄兩種影像導引技術,評估所得到的三軸誤差數據(包含左右、頭腳及前後方向),並依據 各軸數據計算出不同影像導引條件下擺位之平均誤差、系統性誤差(Σ)及隨機誤差(σ)。理想 的 PTV 邊界是以 van Herk 公式來計算,進一步再比較電子式影像驗證與四維錐狀射束電腦斷 層,這兩種導引技術下所測得之三軸的系統誤差及隨機誤差是否有統計上的差異;同時分析病 人相關因子對擺位誤差的影響性。 結果:本研究共分析 170 組電子式驗證系統影像及 170 組四維錐狀射束電腦斷層影像。電子 式影像驗證與四維錐狀射束電腦斷層的擺位誤差平均值(mm)及標準差(mm)分別為:左 右方向 -0.24 ± 0.73 、0.02 ± 1.17;頭腳方向 0.75 ± 1.40 、1.54 ± 1.78;前後方向 0.27 ± 1.10 、-0.15 ± 1.32。分析發現:兩者的擺位誤差於左右及前後方向均無顯著差異;然而兩者 頭腳方向的系統誤差有顯著差異(1.40 mm vs. 1.78 mm; p= 0.005)。兩種影像導引方法所推估 的最佳計畫靶體積邊界(mm),分別是 EPI:左右方向 2.63 、頭腳方向 6.09 、前後方向 3.85; 4D-CBCT:左右方向 3.85 、頭腳方向 6.68 、前後方向 4.34。經過分析,沒有特定的病人相關因 子與擺位誤差有顯著關聯性。 結論:此研究發現,若使用電子式影像驗證作為乳癌術後放射治療的影像導引,與四維錐狀射 束電腦斷層相比,需特別注意電子式影像驗證會明顯低估頭腳方向的系統誤差,且其於各軸向 所推估出的計畫靶體積邊界均較窄。因此我們建議,臨床實務上應該採用四維錐狀射束電腦斷 層所計算出的最佳計畫靶體積邊界較為適當。 |
英文摘要 | Purpose : There remains uncertainty whether utilization of 4-dimensional cone-beam computerized tomography (4D-CBCT) has additional benefit over electronic portal image (EPI) in breast radiotherapy. The primary goal of this study was to compare the differences between EPI and 4D-CBCT in evaluating setup errors for breast cancer patients. The secondary aim was to assess the relationship between patient-related factors and setup errors. Materials & Methods : A prospective study with a total of 17 post-operative breast cancer patients was conducted between July 2013 and May 2016. All patients received two kinds of image-guided methods, EPI and 4D-CBCT, before each treatment in the first ten fractions of radiation. The translations in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions under different image-guided techniques were measured by physicians on-line. Group systematic (Σ) and random errors (σ) for each axis of EPI and 4D-CBCT were calculated. The optimal PTV margins were computed based on van Herk’s formula. Differences in daily positioning errors were examined using Wilcoxon singed-ranks test to compare the results between EPI and 4D-CBCT. The Mann-Whitney U-test was used to distinguish the significance between the setup errors and the following patient-related factors: age, height, weight, BMI, laterality of breast cancer and the chest ratio of maximal anterior-posterior to lateral diameter measured from simulation images. Results : The total serial images were 170 EPIs and 170 4D-CBCTs. The mean (mm) and standard deviation (mm) of setup errors of EPI and 4D-CBCT were -0.24 ± 0.73 and 0.02 ± 1.17 in LR direction; 0.75 ± 1.40 and 1.54 ± 1.78 in SI direction; 0.27 ± 1.10 and -0.15 ± 1.32 in AP direction, respectively. The systemic (Σ) and random errors (σ) for 4D-CBCT (ΣLR= 1.17 mm, ΣAP= 1.32 mm and σLR= 1.32 mm, σAP= 1.49 mm) and EPI (ΣLR= 0.73 mm, ΣAP= 1.10 mm and σLR= 1.15 mm, σAP= 1.57 mm) were not significant difference in the LR and AP directions. In the SI direction, the systemic setup errors were significantly different between EPI vs. 4D-CBCT (1.40 mm vs. 1.78 mm; p= 0.005). The calculated PTV margins (mm) measured by EPI and 4D-CBCT were 2.63 and 3.85 in LR direction; 6.09 and 6.68 in SI direction; 3.85 and 4.34 in AP direction, respectively. None of the patient-related factors have conclusive influence on these setup errors. Conclusion : This study found that EPI would significantly underestimate the setup errors in the SI direction compared to 4D-CBCT, which in-turn generates a narrower PTV margin by van Herk’s formula. Thus we should be careful when using EPI for correction of inter-fraction setup errors in the SI direction of breast cancer patients. We suggest applying the optimal PTV margins calculated from the 4D-CBCT method for clinical application. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。