Abstract
ObjectivesTo investigate whether the increased soft tissue contrast of virtual monoenergetic images (VMIs) obtained from a spectral detector computed tomography (SDCT) system improves washout assessment of arterially hyper-enhancing liver lesions.MethodsFifty-nine arterially hyper-enhancing lesions in 31 patients (age 65 ± 9 years, M/W 20/11) were included in this IRB-approved study. All patients underwent multi-phase SDCT for HCC screening. MRI, CEUS or biopsy within 3 months served as standard of reference to classify lesions as LiRADS 3 or 4/5. VMIs and conventional images (CIs) were reconstructed. Visual analysis was performed on 40, 60, and 80 kiloelectronvolt (keV) and CIs by 3 radiologists. Presence and visibility of washout were assessed; image quality and confidence of washout evaluation were evaluated on 5-point Likert scales. Signal-to-noise ratio (SNR), lesion-to-liver contrast-to-noise ratio (CNR) (|HUlesion–HUliver|/SDliver) and washout (|HUlesion–HUliver|) were calculated. Statistical assessment was performed using ANOVA and Wilcoxon test.ResultsOn subjective lesion analysis, the highest level of diagnostic confidence and highest sensitivity for the detection of lesion washout were found for 40-keV VMIs (40 keV vs. CI, 81.3 vs. 71.3%). Image quality parameters were significantly better in low-kiloelectronvolt VMIs than in CIs (p < 0.05; e.g. SNRliver: 40 keV vs. CIs, 12.5 ± 4.1 vs. 5.6 ± 1.6). In LiRADS 4/5 lesions, CNR and quantitative washout values were significantly higher in 40-keV VMIs compared to CIs (p < 0.05; e.g. CNR and washout in 40 keV vs. CIs, 2.3 ± 1.6 vs. 0.8 ± 0.5 and 29.0 ± 19.1 vs. 12.9 ± 6.9 HU, respectively).ConclusionBy increasing lesion contrast, low-kiloelectronvolt VMIs obtained from SDCT improve washout assessment of hyper-enhancing liver lesions with respect to washout visibility and diagnostic confidence.Key Points• Low-kiloelectronvolt virtual monoenergetic images from spectral detector CT facilitate washout assessment in arterially hyper-enhancing liver lesions.• Image quality and quantitative washout parameters as well as subjective washout visibility and diagnostic confidence benefit from low-kiloelectronvolt virtual monoenergetic images.
Highlights
Hepatocellular carcinoma (HCC) may be diagnosed by contrast-enhanced (CE) magnetic resonance imaging (MRI), computed tomography (CT), ultrasound (CEUS) or a combination of these modalities without the need for a histological confirmation by biopsy [1, 2]
Many studies and metaanalyses investigated and compared the diagnostic performances of the different modalities with the predominant result that MRI provides the highest accuracy, especially in small liver lesions [2,3,4]. These studies slightly favour MRI over CT, both are recommended as modality of choice for the diagnostic evaluation of patients at risk of HCC, due to their high sensitivity and coverage allowing a comprehensive assessment of the entire liver [1, 2]
A structured search in the radiology information system was performed with the following inclusion criteria: (1) older than 18 years of age, (2) multi-phase contrast-enhanced spectral detector computed tomography (SDCT) for HCC workup between May 2016 and November 2018, (3) examination with a standardized imaging protocol as described below, (4) arterially hyper-enhancing liver lesions of 1 cm or greater and (5) MRI, CEUS or biopsy within 3 months
Summary
Hepatocellular carcinoma (HCC) may be diagnosed by contrast-enhanced (CE) magnetic resonance imaging (MRI), computed tomography (CT), ultrasound (CEUS) or a combination of these modalities without the need for a histological confirmation by biopsy [1, 2]. Many studies and metaanalyses investigated and compared the diagnostic performances of the different modalities with the predominant result that MRI provides the highest accuracy, especially in small liver lesions [2,3,4]. These studies slightly favour MRI over CT, both are recommended as modality of choice for the diagnostic evaluation of patients at risk of HCC, due to their high sensitivity and coverage allowing a comprehensive assessment of the entire liver [1, 2]. The assessment of washout, defined as a hypointensity, hypo-density or hypoechogenicity compared to the adjacent liver parenchyma, can be difficult in cases with only subtle differences [7]
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