有效劑量的定義是為了量化輻射對人體造成的風險，但有效劑量卻無法直接經由量
測得到，因此需要透過模擬計算來評估。輻射防護實務上，最方便的方式是透過劑量轉換係數將輻射場的描述物理量(通量)轉換為有效劑量。通量劑量轉換係數一般建立在預設的照射幾何與擬人假體模型，但幾乎文獻中所有通量劑量轉換係數的假體模型都是固定直立站姿的型式，無法配合輻射工作人員的實際姿態而改變，此一限制可能導致劑量評估誤差。因此，本研究引進PIMAL程式輔助，深入探討假體姿態對轉換係數的影響。PIMAL允許使用者產生各種不同手臂與腿部姿態的擬人假體模型，可接續利用 MCNP程式進行完整的輻射遷移計算。基於此特性，本研究先是利用標準直立姿態的假體進行模擬，計算光子和中子的全身有效劑量轉換係數，與其他文獻的結果比較作為驗證，增加本研究的可信度並彙整不同能量光子和中子轉換係數的合理計算方式，特別是高能量光子和中子在MCNP中的劑量計算。其次，本研究再利用彎曲姿態的假體進行模擬，探討彎曲姿態與直立姿態的轉換係數差異，此部分中低能量的轉換係數亦與相關文獻比較驗證，增加本研究建立之模型的可信度，最後再延伸到高能量範圍，建立彎曲假體在標準曝露條件下之全能量範圍的有效劑量轉換係數。此外，本研究亦將轉換係數的計算模式應用於台灣參考人假體，也深入探討有效劑量定義中的其餘器官劑量計算方式的差異。

Effective dose was defined to quantify the risk of radiation to human, but it cannot be measured directly. Hence, it is convenient to use dose conversion coefficients (DCC) transforming fluence which can be measured directly into effective dose. Generally, DCC were built in ideal situations, including specific radiation type, energy, irradiation geometry, and anthropomorphic phantom. Most anthropomorphic phantoms were built in a fixed upright standing posture that can not be easily adapted to realistic postures of a radiation worker. This limitation may result in errors or uncertainties in dose assessment in certain circumstances. Therefore, this study induce PIMAL to discuss the influence of phantom postures to dose conversion coefficients. PIMAL (Phantom wIth Moving Arms and Legs) software allow users to adjust the posture of computational phantom, generate a corresponding MCNP input file, and perform accurate radiation transport simulations for estimating organ doses and effective dose. Based on this feature, first this study use PIMAL with upright standing posture to calculate the effective dose conversion coefficients from external photon and neutron exposure, and compare the results with reference to convince this study. Then organize the calculating mode of photon and neutron conversion coefficients in MCNP, especially for high energy photon and neutron sources. Next, use PIMAL with bent postures to simulate and discuss the difference of dose conversion coefficients between upright and bent postures. Low to medium energy range conversion coefficients can be compare with reference, increasing the credibility of the model established in this study, and then extend to high energy conversion coefficients, building effective dose conversion coefficients of bent posture phantom with all energy range. In addition, this study utilize the conversion coefficient calculation mode on Taiwan Reference Man/Woman phantoms, and also discuss the difference on effective dose by dealing with tissue weighting factors of the remainders in different methods.

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