Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting
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COMPUTED TOMOGRAPHY
Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting Thuy Duong Do 1 & Stephan Rheinheimer 1 & Hans-Ulrich Kauczor 1,2 & Wolfram Stiller 1,2 & Tim Weber 1 & Stephan Skornitzke 1 Received: 31 December 2019 / Revised: 6 March 2020 / Accepted: 14 April 2020 # The Author(s) 2020
Abstract Objectives To quantitatively and qualitatively evaluate image quality in dual-layer CT (DLCT) compared to single-layer CT (SLCT) in the thorax, abdomen, and pelvis in a reduced-dose setting. Methods Intraindividual, retrospective comparisons were performed in 25 patients who received at least one acquisition of all three acquisition protocols SLCTlow (100 kVp), DLCThigh (120 kVp), and DLCTlow (120 kVp), all covering the venous-phase thorax, abdomen, and pelvis with matched CTDIvol between SLCTlow and DLCTlow. Reconstruction parameters were identical between all scans. Image quality was assessed quantitatively at 10 measurement locations in the thorax, abdomen, and pelvis by two independent observers, and subjectively with an intraindividual forced choice test between the three acquisitions. Doselength product (DLP) and CTDIvol were extracted for dose comparison. Results Despite matched CTDIvol in acquisition protocols, CTDIvol and DLP were lower for SLCTlow compared to DLCTlow and DLCThigh (DLP 408.58, 444.68, 647.08 mGy·cm, respectively; p < 0.0004), as automated tube current modulation for DLCTlow reached the lower limit in the thorax (mean 66.1 mAs vs limit 65 mAs). Noise and CNR were comparable between SLCTlow and DLCTlow (p values, 0.29–0.51 and 0.05–0.20), but CT numbers were significantly higher for organs and vessels in the upper abdomen for SLCTlow compared to DLCTlow. DLCThigh had significantly better image quality (Noise and CNR). Subjective image quality was superior for DLCThigh, but no difference was found between SLCTlow and DLCTlow. Conclusions DLCTlow showed comparable image quality to SLCTlow, with the additional possibility of spectral post-processing. Further dose reduction seems possible by decreasing the lower limit of the tube current for the thorax. Key Points • Clinical use of reduced-dose DLCT is feasible despite the required higher tube potential. • DLCT with reduced dose shows comparable objective and subjective image quality to reduced-dose SLCT. • Further dose reduction in the thorax might be possible by adjusting mAs thresholds. Keywords Tomography, X-ray computed . Radiation exposure . Thorax . Abdomen
Abbreviations AP Anterior-posterior CNR Contrast-to-noise ratio * Stephan Skornitzke [email protected] 1
Clinic for Diagnostic and Interventional Radiology (DIR), Heidelberg University Hospital, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany
2
Translational Lung Research Center (TLRC), Member of the German Center for Lung Research (DZL), Heidelberg, Germany
CT CTDIvol DLCT DLP DRI DRL ICC ROI SD SLCT SSDE VMSI
Computed tomography Volumetric computed tomography dose index Dual-layer spectral CT Do
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