小兒全脊椎攝影之劑量降低與風險評估

Dose Reduction and Risk Estimation of Whole Spine Examination in Pediatrics

本篇目的為評估小兒全脊椎攝影之劑量與風險於使用前後（AP）投照、AP投照並以鉍屏蔽覆蓋乳房區域檢查（AP+Bi）與後前（PA）投照之分布。本研究使用蒙地卡羅模擬軟體PCXMC計算10歲與15歲小兒使用三種方式的有效劑量，並評估肺、胃、乳房、肝與甲狀腺的器官劑量與曝露導致死亡風險（risk of exposure-induced death, REID）。10歲與15歲小兒以AP投照接受的有效劑量各為0.43 mSv與0.34 mSv，PA投照可較AP投照各下降55％與53％的有效劑量，而AP+Bi則可分別降低15％與10％的有效劑量。器官劑量分布中，在AP投照與AP+Bi時乳房的器官劑量皆為五種器官中最大者（10歲小兒各為1.12 mGy與0.80 mGy，15歲小兒各為0.88 mGy與0.78 mGy），PA投照時則為肺的器官劑量最大（10歲與15歲小兒分別為0.42 mGy與0.36 mGy），而REID與器官劑量正相關，故在AP投照與AP +Bi時罹患乳癌致死的風險最高，而PA投照則以罹患肺癌致死的風險最高。建議臨床優先考慮以PA投照方式進行檢查，若遇無法採PA投照時，可採用AP+Bi方式，以降低乳房器官劑量與有效劑量。 Whole spine examination is often used as a diagnostic approach for scoliosis in pediatrics. Since children and adolescents are keen to be radiosensitive, it is necessary to take actions to reduce the radiation dose of whole spine examination. The aim of the study was to evaluate the radiation dose and risk of whole spine examination for pediatrics in anteroposterior (AP) projection, AP projection with bismuth shielding covered the breast (AP+Bi), and posteroanterior (PA) projection. Two age groups: 10 year-old group and 15 year-old group were included in the study. The effective dose was calculated by PCXMC Monte Carlo simulation software first, then the organ doses and the risk of exposure-induced death (REID) of lung, stomach, breast, liver and thyroid were further calculated. The effective doses in AP projection of 10-year-old children and 15-year-old adolescents were 0.43 mSv and 0.34 mSv, respectively. In PA projection, the effective dose could be reduced to 55% and 53% of the dose absorbed in AP projection for 10-year-old children and 15-year-old adolescents, respectively. As for the AP+Bi setting, the effective doses of two age groups could be decreased to almost 15% and 10% of the dose absorbed in AP projection for 10-year-old children and 15-year-old adolescents, respectively. . In both AP projection and AP+Bi setting, the organ doses of breast were the highest one among the 5 interested organs (1.12 mGy and 0.80 mGy for 10-year-old children, and 0.88 mGy and 0.78 mGy for 15-year-old children). In PA projection, the organ doses of lung (0.42 mGy for 10-year-old children, and 0.36 mGy for 15-year-old children) were the highest one among the 5 interested organs. The radiation risk was correlated with the organ dose, and the REID of the breast cancer was the highest one in both AP projection and AP+Bi setting, and the REID of the lung cancer was the highest one PA projection. It is thus recommended the routine use of PA projections during the whole spine examinations. While using AP projection instead of PA projection in some situations, the bismuth shielding could be used to reduce the effective doses and breast doses.