The patient dose from whole-body CT examination depends on a number of parameters including the technical features of the CT, the selected acquisition parameters and the size of the patient [41]. Thus, patient doses from CT differ significantly among study sites and CT systems. Dose depends strongly on the selected X-ray spectrum (i.e. the tube potential and the filtration), the tube current (mA) and examination time. Compared with CT as an imaging technique, spinal single-slice 2D QCT examinations use low-exposure parameters, i.e. 80-kV tube voltage and 120–140 mAs. This may be attributed to the fact that the high contrast between bone and surrounding structures allows BMD evaluation even with high noise levels. Table 3 shows radiation doses of optimised QCT protocols derived from the literature [9, 30, 42–44].
Table 3 Radiation doses associated with QCT protocols
Examination Voltage (kV) X-ray tube load (mAs) Effective dose (mSv) References
2D QCT spine, scout image and 3 slices of 10-mm thickness 80 125 0.06–0.3 [30, 41]
3D MDQCT spine, L1–L2, pitch 1 120 100 1.5 [9]
3D MDQCT hip, pitch 1 120 150–200 2.5–3.0 [9]
3D MDQCT radius, pitch 1 120 100 <0.01 [43]
Patient dose may differ significantly between institutions because of the variability in acquisition protocols and differences in the CT system characteristics