[Radiation exposure in low dose computerized tomography of the thorax]

Computed tomography accounts for a high percentage of the populations exposure to radiation. Every possible means of reducing patient exposure must be considered. Exposure reduction will be most appropriate for organs with large absorption differences, since the accompanying decrease in signal-to-noise ratio will have a smaller effect. It has been shown in the literature that high-contrast details in the lung can be depicted, even with the lowest exposure rates. Therefore, experimental data are presented by means of thermoluminescence dosimetry and calculations using conversion factors to determine the technical parameters to be adopted for achieving the effective equivalent dose close to that of a conventional chest X-ray in two projections. With helical CT (pitch 2, 50 mAs, 120 kV, 5-mm slice thickness) it was possible to reduce the equivalent dose from 9.6 mSv to 0.6 mSv, which is comparable with the exposure in a conventional chest X-ray, measured to be 0.2 mSv.