本研究目的為評估寬射束電腦斷層(computed tomography, CT)掃描儀的輻射劑量，研究分為三個部分：(1)傳統CT劑量指標(CT dose index, CTDI)在寬射束CT劑量低估情形並且建立不同劑量計的量測方法；(2)根據美國醫學物理師學會工作小組第111號報告，在320切CT掃描儀進行實驗，使用套管游離腔(thimble ionization chamber)與更長的CTDI假體串接，根據報告計算新的劑量指標：平衡劑量(equilibrium dose, )、平衡劑量–螺距比乘積(equilibrium dose-pitch product, )與平衡劑量常數(equilibrium dose constant, )；(3)探討新的CT劑量最佳化技術，包含自動管電流調控(automatic tube current modulation, ATCM)、疊代演算法在劑量降低與雜訊抑低技術與新的動態體積掃描模式在臨床常規檢查的輻射劑量分佈情形。將寬射束電腦斷層輻射劑量的研究成果提供國內外相同研究領域的團隊作為參考依據，以期改善寬射束電腦斷層的劑量評估方法。

The purpose of the study was to (1) estimate the amount of underestimation of radiation dose using conventional CT dose index theory; (2) to implement the methodology of wide beam CT dosimetry suggested by report of AAPM task group 111 on a 320-detector row CT scanner. The derived values of equilibrium dose, equilibrium dose-pitch product, and equilibrium dose constant and related dose indexes using a thimble ionization chamber and 600 mm length cylindrical phantom were provided as reference tables for users who has the same CT scanner. (3) to assess the radiation dose distribution of clinical CT examinations with latest CT dose and image quality optimization techniques which included automatic tube current modulation (ATCM) techniques, adaptive iterative dose reduction 3D (AIDR3D), and dynamic wide volume scan mode. The database of our study can be an reference for improving the radiation dose measurement for wide collimation width computed tomography.

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