Low-dose non-contrast examination of the temporal bone using volumetric 320-row computed tomography

Background 320-row volume computed tomography (CT) allows CT dose to be reduced while maintaining image quality. Purpose To evaluate image quality of low-dose non-contrast temporal bone CT using single volumetric 320-row multidetector CT technique. Material and Methods A total of 125 patients were included in our study. Two low-dose protocols, including 135 kV tube voltage with 5 mAs tube current and 80 kV tube voltage with 5 mAs tube current, were chosen based on results of present phantom study. For evaluating subjective image quality, conspicuity of anatomic landmarks were assigned a score using a five-point scale. Objective image quality analysis was performed by analyzing regions of interest on axial soft-tissue and bone reconstructions. Effective dose was calculated from dose-length product. Results Mean effective radiation dose for 120 kV and 75 mAs protocol (control group) was 0.29 +/- 0.04 mSv; for 135 kV and 5 mAs protocol (study group A), this value was 0.02 +/- 0. 003 mSv; and for 80 kV and 5 mAs protocol (study group B), this value was 0.005 +/- 0. 0009 mSv. Mean effective radiation doses of study group A and B were significantly lower than the control group (P < 0.001). Study group A and control group images showed no significant difference in image quality except for some anatomic landmarks. Study group B images had lower image quality than control group images. Conclusions Temporal bone CT with 135 kVp and 5 mAs can be performed at very low radiation exposure while maintaining high image quality.