利用田口方法及Helios QA phantom評估腹部電腦斷層模擬定位儀影像品質之最佳化參數

Optimization of The Image Quality for Abdominal Computed Tomography Simulator Using Taguchi Methodology and Helios QA Phantom

葉文瑜(WEN-YU YEH)

指導教授 ： 張振榮

中臺科技大學/健康科學院/醫學影像暨放射科學系暨研究所/碩士(2017年)

摘要

電腦斷層模擬定位掃描儀在放射腫瘤科是一項重要的定位工具，它是具有模擬定位功能的電腦斷層掃描儀，搭配可動式雷射定位系統，可同時取得醫學影像並且定出腫瘤精確的治療位置。透過其強大的影像重組功能所重組的影像，將有助於設計腫瘤治療的部位及射束照野的方向。當電腦斷層影像品質愈好時，放射治療計畫所計算出的劑量會更加準確。本研究利用田口實驗設計法尋找影響腹部電腦斷層模擬定位掃描儀影像品質的重要因子以及參數條件之最佳化設定。實驗設備使用放射治療專用電腦斷層模擬定位掃描儀，搭配GE原廠校正假體；實驗方法為利用直交表進行實驗，設計四個研究因子，分別為管電壓尖峰、管電流、照野大小以及螺距率，每個因子分別設定兩個水準；實驗掃描壓克力假體內之縷空線對，執行掃描24次，再經由四位放腫科資深放射師進行影像品質分析與評估，再利用變異數分析進行數據分析，最後需驗證極限值，找出本實驗最佳掃描組合。結果顯示本實驗最佳化參數組合為：A1B1C2D2，分別是管電流尖峰為120kVp、管電流為300mA、照野大小為25cm與螺距率(Pitch)為0.75。利用變異數分析重要因子結果顯示，FOV因子重要性大於kVp因子，其F檢定分別為103.95和13.05，信心水準為99.98%和98.47%，具有統計上的意義。

關鍵字

電腦斷層模擬定位掃描儀 ； 實驗設計方法 ； 原廠校正假體 ； 影像品質 ； 變異數分析

並列摘要

The computed tomography simulator (CT-simulator) in Radiation Oncology Department has become an important tool for tumor localization. It is a computed tomography with simulated localizing function, with moving laser system, which can obtain medical image and set the exact location of the tumor.After the image reorganization, will help define the treatment site and the direction of the beam irradiation. When the CT image quality is better, the dose calculation of the treatment plan will be more accurate. This study use Taguchi method to find the important factor and the optimized parameters of abdominal CT simulation. The equipment used GE Light speed 4 CT-simulator and GE Helios QA phantom. The experimental method was setting the change range of each parameter with Taguchi L8 orthogonal array. The four factors were kVp, mAs, FOV and Pitch; furthermore, each was assigned 2 levels, respectively to scan the Helios QA phantom in obtaining the optimal result. Each combination of the CT-simulation scan protocol was repeated three times to ensure the reproducibility that was also an essential data in running the ANOVA. The scanned imaging was scored by fore well-trained radiologists to reduce the biased judgements. The results show that the combination of the optimization parameters of this experiment was A1B1C2D2. The optimized parameters setting were 120kVp, 300mA, field of view 250mm, 0.75 Pitch. The results of ANOVA important factors show that the FOV factor was more important than the kVp factor, the F test was 103.95 and 13.05 respectively, the confidence level was 99.98% and 98.47%, which was statistically significant.

並列關鍵字

CT simulator ； Taguchi method ； Helios QA phantom ； image quality ； variance analysis

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