TH‐D‐L100J‐04: Dose and Image Quality of Flat‐Panel Detector Volume Computed Tomography for Sinus Imaging

Purpose: CT of the sinuses is commonly used for diagnosis and assessment of chronic sinusitis and preoperative planning for otolaryngological and dental procedures. Sinus imaging is a high‐contrast procedure requiring high spatial resolution. The purpose of this study is to compare the dose and image quality for typical sinus CT clinical protocols using conventional 16‐ and 64‐slice CT scanners with a flat‐panel volume CT scanner. Method and Materials: Three systems were chosen: a MiniCAT (Xoran Technologies, Inc.) flat‐panel detector unit, a Lightspeed 16 Pro, and a Lightspeed VCT (GE Medical Systems). A typical sinus technique of 120 Kvp, 150 mAs, and 2.5 mm slice thickness was selected for the GE scanners. The MiniCAT used a preset sinus technique of 120 kVp, 45 mAs, and 0.4 mm voxel size. The doses from 20 TLDs (Landauer, Inc.) inserted in a Rando head phantom were used to estimate the effective dose for each technique. The spatial resolution and slice sensitivity profiles (SSP) were measured for these same techniques. Results: The flat‐panel detector volume CT scanner gave an effective dose of 0.17 mSv while the 16‐ and 64‐slice scanners gave 0.96 and 0.87 mSv, respectively. The Lightspeed scanners had a trans‐axial spatial resolution of 7 lp/mm (standard filter) and 11 lp/cm (bone filter). The flat‐panel CT scanner had isotropic spatial resolution of 12 lp/cm. The FWHM of the SSP along the z‐axis was 0.49 mm for the MiniCAT, and 2.32 and 2.34 mm for the 16‐ and 64‐slice scanners, respectively. Conclusion: Flat‐panel volume CT with submillimeter isotropic spatial resolution is a low dose alternative for high‐contrast sinus imaging. While the conventional CT scanners have advantages for low‐contrast resolution, this can be sacrificed for a five‐fold dose reduction and increased spatial resolution in a volume image. Conflict of Interest: Research sponsored by Xoran Technologies, Inc.