Abstract
ObjectivesTo 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.MethodsIntraindividual, 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. Dose-length product (DLP) and CTDIvol were extracted for dose comparison.ResultsDespite 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.ConclusionsDLCTlow 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.
Highlights
The introduction of dual-layer detector technology in computed tomography (CT) enabled the acquisition of spectral data for all performed scans without the need of an additional CT x-ray tube or additional acquisitions
While patient radiation exposure has long been a topic of interest in CT, as CT accounts for 49–66% of overall patient radiation exposure, this interest has recently led to new regulations in the European Union via the EURATOM directive, with the deadline for implementation into federal law in 2018 [7, 8]
Similar to CTDIvol and Doselength product (DLP), the Size-specific dose estimates (SSDEs) was lowest for SLCTlow while SSDE of DLCTlow was significantly less than DLCThigh for all body regions (p < 0.0001)
Summary
The introduction of dual-layer detector technology in computed tomography (CT) enabled the acquisition of spectral data for all performed scans without the need of an additional CT x-ray tube or additional acquisitions. Dual-layer spectral CT (DLCT) acquisitions allow material decomposition (virtual non-contrast, iodine-only imaging, and effective atomic numbers) as well as the calculation of virtual monoenergetic images. For the image acquisition of such data, a tube potential of either 140 kVp or 120 kVp is necessary to allow for spectral decomposition under the exploitation of the energy-specific x-ray absorption of different materials. Acquisition protocols for the thorax, abdomen, and pelvis have been previously optimized to reduce patient radiation exposure beyond these legal requirements This was achieved, in part, by reducing tube potential from 120 to 100 kVp for single-layer CT (SLCT), resulting in an average patient dose 60% below the federal DRL for the thorax, abdomen, and pelvis, which is a DLP of 1000 mGy·cm and a CTDIvol of 13 mGy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
