Multidetector CT of the paranasal sinus: Potential for radiation dose reduction

The aim of the study was to retrospectively determine the potential for radiation dose reduction at multidetector computed tomography (CT) of the paranasal sinus by using computer simulation of the effect of low-radiation dose acquisition on diagnostic image quality. This HIPAA compliant study was approved by the institutional human research committee. The need for informed patient consent was waived. Twenty patients underwent four-section CT at 120 kV, 170 mAs, and 4 x 1-mm collimation. Artificial image noise was added to the CT raw data by using a dedicated software platform. Acquisitions with effective tube currents of 134, 100, 67, and 33 mAs were simulated. Each raw data set was reconstructed with bone and soft-tissue algorithms, and two radiologists independently rated the images in blinded fashion. A two-sided paired Student t test was used for statistical analysis. The lowest radiation dose that still provided diagnostic quality was <= 67 effective mAs for osseous structures and <= 134 effective mAs for the optic nerve and the inferior rectus muscle. On the basis of the results, tube currents can be lowered and radiation dose reduced by 20%.