醫學影像輻射劑量之探討

Investigation of the Radiation Dose For Medical Image

本文目的是希望透過醫學影像中輻射劑量的介紹，提供民眾正確認識醫用輻射與輻射防護的觀念。首先以輻射特性與輻射生物效應來建構出輻射基礎的觀念，其次說明各種醫學影像的平均輻射劑量。透過醫療的角度認識輻射給人類帶來的益處以及可能產生的傷害。醫用輻射來源包含X光（如電腦斷層攝影及透視攝影）以及放射性物質示蹤劑。透視攝影包括侵入性檢查（如血管攝影）和其他傳統攝影如使用鋇劑腸道攝影。核子醫學檢查是將放射性示蹤劑注射進入人體，在體內進行衰變時放出加瑪射線後完成照影檢查。電腦斷層攝影、透視攝影、核子醫學檢查是一般大眾最主要接受輻射取得人體影像的醫學檢查。輻射對人體健康影響而言一次接受劑量需要超過250毫西弗(mSv)以上才有可能對身體產生影響，對於醫學影像輻射造成的劑量而言，醫學影像檢查其劑量並未達到250毫西弗(mSv)，對於人體並沒有健康的影響。醫學影像所接受到的輻射劑量並不會對人體產生傷害，透過影像更可以知道身體健康資訊以及對於疾病治療的決策。臺灣地區民眾接受天然輻射年劑量為1.62毫西弗(mSv)。

The purpose of this paper is to introduce the concept of radiation dose in medical imaging and to provide the public with correct information about medical radiation. Most ionizing radiation from medical imaging comes from X-rays such as computerized tomography and interventional radiology and from radioactive tracer material. Fluoroscopic procedures include angiography and traditional procedures such as barium enemas. Nuclear medicine procedures introduce a radioactive tracer into the body by intravenous injection. The tracer then emits gamma rays detected by a gamma camera. Computerized tomography, fluoroscopy, and nuclear medicine studies represent the vast majority of imaging-related radiation exposure for the general population in most developed country. When the human body receives an effective dose over 250 mSv, it could affect health. An effective dose from a medical imaging procedure that was not over 250 mSv would have no influence on the human body. As a point of reference, the annual effective dose from natural radiation was 1.62 mSv in Taiwan. Medical imaging procedures are safe and are important not only in acquiring information about human health but also in making decisions about the treatment of disease.