Comparison of radiation dose and image quality between fast kVp switching dual-energy CT and routine single-energy CT for whole abdomen at King Chulalongkorn Memorial Hospital

Abstract

Abdominal computed tomography (CT) using a single energy protocol is a common imaging procedure in hospitals. As CT technology has continued to evolve, dual-energy protocols (DECT) have emerged as a new option. A spectral CT scanner with fast kVp switching was installed at King Chulalongkorn Memorial Hospital in 2017, and its clinical utility in emergency patients has not yet been studied. This study aims to compare the radiation dose and image quality between DECT and SECT in abdominal CT for emergency patients. The study retrospectively collected CT data from 130 standard-sized adult patients who underwent contrast-enhanced using the 256-slice MDCT. CT Contrast media was intravenously injected of iobitridol at a dose of 2.0 mL/kg with a flow rate of 2 mL/s through the median cubital vein. After the contrast medium was administered for 90 s, fast kVp-switching DECT (80/140 kVp,) and SECT (120 kVp) enhanced abdominal CT was performed. The scanning parameters for fast kVp-switching between 80 and 140-kVp were as follows: tube current, GSI Assist; detector collimation 80 x 0.625 mm; rotation speed 0.6 s; pitch factor 0.992:1. The scanning parameters for single-energy CT were as follows: 120 kVp, tube current 3D mA modulation; detector collimation 80 x 0.625 mm; rotation speed 0.5 s; pitch factor 0.992:1. The radiation dose was evaluated for both protocols in terms of CTDIvol. Objective analysis was performed by measuring the region of interest (ROI) at 5 abdominal structures: aorta, main portal vein, liver, spleen, and psoas muscle in order to evaluate signal (HU), noise (SD), and signal-to-noise ratio (SNR). Subjective image quality was evaluated by two radiologists who have similar experience in terms of diagnostic acceptability on a 4-point scale and image noise on a 3-point scale following the European Guidelines on Quality Criteria. There was no statistically significant difference in average CTDIvol between SECT (10.7±2.3 mGy) and DECT (10.3±2.8 mGy) (p>0.05). The objective image quality analysis indicated that DECT had significantly higher signal and noise values compared to SECT for all measured structures (p<0.05), but there was no significant difference in SNR except MPV between the two groups (p>0.05). The subjective image quality analysis showed no significant difference in diagnostic acceptability and image noise between SECT and DECT as evaluated by both radiologists (p>0.05). In conclusion, the fast kV switching DECT protocol used in this study provides similar objective image quality and equivalent subjective image quality with a similar level of radiation dose as SECT. Therefore, the results of this study could be implemented as a routine protocol in the emergency room to reduce patient radiation dose while maintaining image quality and accelerating patient diagnostic workflow.