Rationale and Objectives
To investigate the impact of virtual monoenergetic images (VMI) from photon-counting
detector CT (PCD-CT) on the enhancement and classification of renal cysts.
Materials and Methods
Adults with renal cysts (≥7 mm) who received a triphasic examination on a clinical
PCD-CT (120 kVp; IQ level 68) between July 2021 and March 2022 were retrospectively
identified. Only non-enhancing cysts (enhancement<10 HU between unenhanced and venous
phase at 70 keV) were included. VMI from 40 to 190 keV with increments of 10 keV were
reconstructed from the venous phase. Enhancement was measured to classify each lesion
as non-enhancing (<10 HU), equivocally enhancing (10–19 HU), and definitely enhancing
(≥20 HU). Classification changes as a function of VMI were assessed. Pearson correlation
coefficient, the Kruskal-Wallis and the Chi-square test were used.
Results
A total of 86 patients (mean age, 74 ± 9 years; 74 male) with 160 non-enhancing renal
cysts (17.6 ± 10 mm) were included. CT attenuation of the cysts increased from higher
to lower VMI levels with a mean attenuation of 4 ± 11 HU at 190 keV to 36 ± 17 HU
at 40 keV. Mean attenuation of the renal parenchyma was 43 ± 4 HU at 190 keV and 414 ± 71 HU
at 40 keV. No cyst exhibited enhancement from 70 keV to 190 keV. At 40, 50, and 60 keV,
35% (56/160), 29% (47/160) and 9% (15/160) of cysts showed equivocal and 46% (74/160),
10% (16/160), and 0% (0/160) definite enhancement, respectively. There was no significant
influence of size (P=.13), cyst location (P=.9) and BMI (P=.19) on enhancement classification.
Conclusion
VMI has a relevant impact on enhancement and classification of renal cysts with misclassification
in a large number of cases at energy levels below 70 keV.
Abbreviations:
VMI (virtual monoenergetic images), PCD-CT (photon-counting detector CT), CNR (contrast-to-noise ratio), EID-CT (energy-integrating detector CT), TNC (true non-contrast images), ROI (region of interest)Key Words
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Article info
Publication history
Published online: May 05, 2023
Accepted:
April 3,
2023
Received in revised form:
March 30,
2023
Received:
March 7,
2023
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved All rights reserved.
