| Abstract: | 本研究探討三種兒童年齡層(1、5、10歲)實施臨床電腦斷層掃描時，劑量 長度積(DLP)轉換有效劑量因數(k 值)。k 值會隨不同的掃描部位而有不同，此值 可有效評估電腦斷層掃描造成的有效劑量。但目前並無公認的權威機構以 ICRP 103號報告為基礎，發佈 k值以供臨床應用於實際電腦斷層掃描，尤其是兒童的 建議值。本研究將使用 1, 5, 10歲三種類人形假體模擬兒童，內填充熱發光劑量 計於 ICRP 建議的組織加權器官，計算器官劑量與有效劑量。我們預計評估六種 身體部位的有效劑量轉換因數(k值)，以利實際掃描兒童之有效劑量換算。此外， 依六種掃描部位得到各器官的有效劑量貢獻，參考 BEIR VII [Committee on the Biological Effects of Ionizing Radiations, BEIR 2006]報告，使用 BEIR VII報告計 算九種致死癌症的機率。我們將提出二種 CT掃描對應風險的轉換值，即(1)傳 統的有效劑量(1 Sv)對應的風險(REID, risk of exposure-induced cancer death)；與 (2)每 1 Gycm造成的風險。相較於較其它文章或報告(EUR 16262報告、AAPM 96 號報告)，本研究俱有以下的優勢，(1)使用新 ICRP 103 號報告，(2)使用 TLD實 驗度量，(3)配合臨床常掃描長度與範圍，(4)提供風險數據。
The conversion factors (k values) of the dose length product (DLP) transfer to effective doses for three kinds of ages (1, 5, and 10 years old) undergoing clinical CT scans will be studied. The k value that varied with different scan range on the body can easily evaluate the effective dose caused by a CT scan. Unfortunately, there is no any k value recommended by recognized authority base on the ICRP 103 report for clinical CT scans, especially recommended value of children. Three kinds of anthropomorphic phantom embedded with thermoluminescent dosimeters (TLDs) in the tissue weighted organs recommended by ICRP 103 report to evaluate the effective doses of 1-year, 5-year and 10-year old pediatric phantoms scanned by CT examinations. We will evaluate six conversion factors (k values) for six scanned ranges of body to consistent with the clinical needs on the translation from DLP to pediatric effective dose. In addition, the risks (REID, risk of exposure-induced cancer death) of nine fatal cancers induced by the radiation exposure of CT scan will evaluated in the study. The risk based on the BEIR VII report could be calculated while the effective dose contributions of several organs be measured base on the of risk. We will propose two risk recommended values corresponding to different CT scanning index, i.e., (i) the risk corresponding to the traditional effective dose (per 1 Sv), and (ii) the risk corresponding to the dose length product (per 1 Gycm). Compared to other articles or well-known reports (EUR 16262 report, AAPM Report No. 96), the study has the following advantages: (i) using the new ICRP 103 Report, (ii) using TLDs measurements instead of Monte Carlo simulation, (iii) with clinical scanned ranges, (iv) provide the risk assessment for application. |
