The scans were performed using a 16-detector-row CT scanner (Somatom Sensation 16; Siemens, Germany), with 16 .75-mm collimation, 120 kVp, 50 effective mAs, 500-msec gantry rotation time, 18 mm table feed per rotation, 1-mm slice thickness, and 0.7 mm reconstruction increment. CT images were reconstructed with a field of as known, effective dose is the protection quantity, and its main use is to assess dose for planning and optimization in radiological protection. 29 on the other hand, besides the magnitude of the A Siemens Biograph™ 16 Horizon PET/CT system and a Siemens Somatom Sensation 64, both employing the Siemens CAREDose 4D AEC system, were used for acquisition of a range of phantoms. Canada [8, 16]. In addition, we also assessed the relevance of the various published na-tional diagnostic reference levels from Euro-pean countries. Materials and Methods Site, Scanner, and Software Specifications The institutional review board of the Univer - sity Hospital of Basel approved this retrospective