Regulatory and clinical implications of using diagnostic CT in PET/CT

The introduction of combined positron emission tomography (PET) and computed tomography (CT) scanner has made it possible to acquire, in a single study, complementary morpho-structural and functional/metabolic information. In its standard applications hybrid PET/CT imaging, with a low-dose (LD) CT scan without contrast medium administration, can allow attenuation correction and anatomical cross-sectional of functional PET images, while avoiding the increased radiation burden which, instead, is associated with a full-dose (FD) CT. Nevertheless, the association of PET imaging with FDCT and with contrast-enhanced (CE) CT, i.e. diagnostic CT, has been investigated to increase the diagnostic accuracy of PET/CT in some specific clinical scenarios. There are potential clinical and procedural benefits to using single step combined dual imaging PET and FD-CECT. However, radiation protection regulations, guidelines from scientific societies, local provisions, correct clinical decision making and practical considerations, limit the use of PET/CECT to selected patients in which a clinical or procedural justification must be demonstrated, despite current scientific context where there is a lack of significant studies that support its appropriateness.