[Coronal paranasal sinus CT: using the spiral technique]

Coronal scanning of the paranasal sinuses requires a prone position and hyperextension of the head. As this position is very uncomfortable for the patients, we tried to reduce the duration of the examination by using Spiral-CT. 5 patients were examined with the conventional mode and 5 patients with spiral-CT. Technical factors for the conventional mode were 250 mAs, a slice thickness of 4 mm and an interval of 3 mm. Spiral-CT was performed with 210 mAs, 120 kV, a slice thickness of 4 mm, an increment of 3 mm and a feed of 4 mm/s. The duration of the examination was measured, image quality was compared by using a score, and radiation exposure was measured on the surface of a phantom. Using the conventional mode examination time was 10.3 min, compared with 4.4 min using spiral-CT. Image quality did not differ significantly. Radiation exposure on the surface of a phantom was 29 mGy in conventional mode and 26 mGy in spiral mode. These results were confirmed in 100 further examinations with spiral-CT. The duration of the examination can be significantly reduced by spiral technique without any loss of image quality. The intricate anatomical structures including the important variations can be well defined applying this technique.