由於之前報章雜誌報導過做一次正子電斷層掃描(positron emission tomography/computer tomography scan, PET/CT scan)相當於在距離原子彈爆炸1.5英哩處所接受的輻射劑量，造成一般民眾的恐慌，所以本文由各種儀器的成像原理、各種檢查所接受的風險及風險評估等三方面來探討，就此評估正子電斷層掃描是否危險。就醫療檢查而言，合理性是最重要的一點，要了解哪種醫療影像檢查技術可以對某些疾病提供最多的訊息，以避免浪費無謂的醫療資源及讓病患承受更多的醫療風險。我們建議病患在確定或高度懷疑罹患某種癌症時，才去作正子電斷層掃描檢查，讓癌症的分期、治療方式及預後評估等可以更加正確。

People were frightened by the report saying that the radiation dose of every single PET/CT scan is equal to the dose 1.5 miles away from the atomic bomb explosion. We thus discuss the imaging principles, associated risks and risk assessment of different imaging examination modalities, The rationality of choicing proper imaging modality according to different disease process is important to reduce the unnecessary patient risk and waste of medical resources, and to obtain the best diagnostic yield. We recommend that PET/CT scan should be reserved for those patient known to have or highly suspicious having cancer to facilitate the disease staging, treatment planning and prognosis evaluation.