Low kV versus dual-energy virtual monoenergetic CT imaging for proven liver lesions: what are the advantages and trade-offs in conspicuity and image quality? A pilot study

Abstract

Purpose Single-energy low tube potential (SE-LTP) and dual-energy virtual monoenergetic (DE-VM) CT images both increase the conspicuity of hepatic lesions by increasing iodine signal. Our purpose was to compare the conspicuity of proven liver lesions, artifacts, and radiologist preferences in dose-matched SE-LTP and DE-VM images. Methods Thirty-one patients with 72 proven liver lesions (21 benign, 51 malignant) underwent full-dose contrast-enhanced dual-energy CT (DECT). Half-dose images were obtained using single tube reconstruction of the dual-source SE-LTP projection data (80 or 100 kV), and by inserting noise into dual-energy projection data, with DE-VM images reconstructed from 40 to 70 keV. Three blinded gastrointestinal radiologists evaluated half-dose SE-LTP and DE-VM images, ranking and grading liver lesion conspicuity and diagnostic confidence (4-point scale) on a per-lesion basis. Image quality (noise, artifacts, sharpness) was evaluated, and overall image preference was ranked on per-patient basis. Lesion-to-liver contrast-to-noise ratio (CNR) was compared between techniques. Results Mean lesion size was 1.5 ± 1.2 cm. Across the readers, the mean conspicuity ratings for 40, 45, and 50 keV half-dose DE-VM images were superior compared to other half-dose image sets (p < 0.0001). Perlesion diagnostic confidence was similar between halfdose SE-LTP compared to half-dose DE-VM images (p ≥ 0.05; 1.19 vs. 1.24–1.32). However, SE-LTP images had less noise and artifacts and were sharper compared to DE-VM images less than 70 keV (p < 0.05). On a per-patient basis, radiologists preferred SE-LTP images the most and preferred 40–50 keV the least (p < 0.0001). Lesion CNR was also higher in SE-LTP images than DE-VM images (p < 0.01). Conclusion For the same applied dose level, liver lesions were more conspicuous using DE-VM compared to SE-LTP; however, SE-LTP images were preferred more than any single DE-VM energy level, likely due to lower noise and artifacts.

Triple‐Phase Computed Tomography May Replace Dual‐Energy X‐ray Absorptiometry Scan for Evaluation of Osteoporosis in Liver Transplant Candidates

“…Dual‐energy CT is used at many institutions for HCC screening because dual‐energy images can increase the iodine signal at contrast‐enhanced CT, thereby increasing the conspicuity of key imaging features of HCC such as arterial enhancement and tumor washout. ( 22‐25 ) The current study was able to demonstrate this validation especially with regard to sensitivity and NPV and it suggests little impact on test performance when delayed‐phase images are used.…”

Postablation assessment of hepatocellular carcinoma using dual-energy CT: Comparison of half versus standard iodine contrast medium

“…The VMI of DECT has the potential to improve image metrics such as the CNR and image noise [18, 24–26]. Hanson et al [21] compared the VMI and low-kVp images of DECT and found that low-keV VMI has more contrast enhancement and lesion conspicuity but with trade-offs for image quality and noise. They concluded that using both low- and high-keV VMI can ensure optimal lesion conspicuity and image quality in abdominal CT.…”

“…However, no study has investigated diagnostic performance in VMI. Although the introduction of nMERA in the dual-source dual-energy system has improved the CNR and conspicuity of low-contrast objects at low energy levels [18–21, 27, 28], no study has investigated the nMERA images of DECT with a reduced CM dose in abdominal CT. To the best of our knowledge, this is the first study to investigate the usefulness of nMERA images of dual-source DECT for CM dose reduction in multiphasic hepatic CT by evaluating image quality and diagnostic performance.…”

“…Several studies have demonstrated various advantages of DECT for imaging and assessment of patients with vascular and oncologic lesions [14–17]. In DECT, a novel monoenergetic reconstruction algorithm (nMERA) was introduced to optimize image quality at low keV levels, providing markedly increased iodine contrast with moderate noise [18–21]. However, this application has not been investigated for CM dose reduction in abdominal CT.…”

Improving iodine contrast to noise ratio using virtual monoenergetic imaging and prior-knowledge-aware iterative denoising (mono-PKAID)

“…The MTF was determined for a 50 keV VMI before and after mono-PKAID processing. The 50 keV was chosen because it is routinely used in our clinical practice (Hanson et al 2018). To generate an MTF, edge spread functions across the boundary of a circular iodine insert were extracted and differentiated to yield line spread functions.…”