Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions

• Published in: European radiology Vol. 31; no. 5; pp. 3468 - 3477
• Main Authors: Reimer, R. P., Große Hokamp, N., Fehrmann Efferoth, A., Krauskopf, A., Zopfs, D., Kröger, J. R., Persigehl, T., Maintz, D., Bunck, A. C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2021; Springer Nature B.V
• Subjects: Aged; Biopsy; Carcinoma, Hepatocellular; Computed tomography; Confidence; Diagnostic Radiology; Diagnostic systems; Evaluation; Hepatobiliary-Pancreas; Humans; Image classification; Image contrast; Image enhancement; Image quality; Image reconstruction; Imaging; Internal Medicine; Interventional Radiology; Lesions; Liver; Liver cancer; Liver Neoplasms - diagnostic imaging; Magnetic resonance imaging; Medical diagnosis; Medical imaging; Medicine; Medicine & Public Health; Middle Aged; Neuroradiology; Parameters; Quality assessment; Radiographic Image Interpretation, Computer-Assisted; Radiography, Dual-Energy Scanned Projection; Radiology; Retrospective Studies; Sensors; Signal to noise ratio; Soft tissues; Spectra; Tomography; Tomography, X-Ray Computed; Ultrasound; Variance analysis; Carcinoma, hepatocellular; Tomography, X-ray computed; Diagnostic imaging
• ISSN: 0938-7994; 1432-1084
• DOI: 10.1007/s00330-020-07379-3

Objectives
To 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.
Methods
Fifty-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) (|HU
lesion
–HU
liver
|/SD
liver
) and washout (|HU
lesion
–HU
liver
|) were calculated. Statistical assessment was performed using ANOVA and Wilcoxon test.
Results
On 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. SNR
liver
: 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).
Conclusion
By 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.