評估頭部電腦斷層於不同體重假體之有效劑量

利用頭部電腦斷層進行不同體重的假體掃描，評估器官與組織的等價劑量與有效劑量。熱發光劑量計Thermoluminescent dosimeters (TLD-100H)佈值於擬人侖道假體與五種自製研發之假體。這自製假體為壓克力(polymethylmethacrylate, PMMA)數學假體，其特性經由ICRU 48號報告設計，體重範圍為10公斤至90公斤重。模擬頭部電腦斷層掃描之範圍為上頷骨至顱頂，經由128切CT掃描。為了減少實驗上的誤差，每個假體實驗各進行三次。侖道假體之有效劑量，由TLD-100H根據國際輻射防護委員會(ICRP) 103號報告書之權重，所推算得知，為1.72±0.28 mSv，略高於經由劑量掃描長度乘積(Dose lehgth product, DLP)所推算的有效劑量1.70 mSv。在實驗中，經由TLD所推算的有效劑量於ICRP 103號報告，從最高的1.85±0.28 mSv (90公斤)至最低的1.47±0.22 mSv (10公斤)。HE,TLD (mSv) = 5.45×10-3 W(kg) + 1.361，R2 為 0.87667。有效劑量利用DLP所評估的方式，是經由劑量掃描單位CTDIvol，於電腦斷層控制台上直接顯示，再乘上轉換因子k來推得之。最後，結果與各國的相關文獻互相比較。臨床工作者應該選擇適當的掃描方式，防止患者接受非必要的輻射，以達合理抑低之原則。研究的數據及發現，將有利於患者、醫師及主管機關參考。

The effective dose (HE) and organ or tissue equivalent dose (HT) of various body weight phantoms during brain computed tomography (CT) examinations were evaluated. Thermoluminescent dosimeters (TLD-100H) were inserted into Rando and five tissue-equivalent phantoms. These phantoms were made of polymethylmethacrylate (PMMA), according to the specifications of ICRU 48, with masses from 10 to 90 kg. Brain CT examinations were conducted, scanning the maxillae from the external auditory meatus to the parietal bone using a 128-slice CT scanner. To reduce errors, three independent trials were conducted. HE,TLD of Rando phantom, based on the weighting factor recommended by ICRP 103, was 1.72±0.28 mSv, which slightly exceeds the HE,DLP, 1.70 mSv, that was calculated from the dose length product (DLP) of the Rando phantom. This experiment yielded HE,TLD values of ICRP 103 from the highest 1.85±0.28 (90 kg) to the lowest 1.47±0.22 (10 kg) mSv. HE,TLD (mSv) = 5.45×10-3 W(kg) + 1.361, with an R2 of 0.87667. Using the DLP method, HE,DLP was estimated from CTDIvol that was recorded directly from the console display of the CT unit and multiplied by the conversion coefficient (k) recommended by the ICRP 103. Finally, the experimental results obtained herein are compared with those in the literature. Physicians should choose and adjust protocols to prevent the exposure of patients to unnecessary radiation, satisfying the as low as reasonably achievable (ALARA) principle. These findings will be valuable to patients, physicians, radiologists, and the public.