Spectral imaging of photon-counting detector CT (PCD-CT) scanners allows for generating
virtual non-contrast (VNC) reconstruction. By analyzing 12 abdominal organs, we aimed
to test the reliability of VNC reconstructions in preserving HU values compared to
real unenhanced CT images.Our study included 34 patients with pancreatic cystic neoplasm
(PCN). The VNC reconstructions were generated from unenhanced, arterial, portal, and
venous phase PCD-CT scans using the Liver-VNC algorithm. The observed 11 abdominal
organs were segmented by the TotalSegmentator algorithm, the PCNs were segmented manually.
Average densities were extracted from unenhanced scans (HUunenhanced), postcontrast
(HUpostcontrast) scans, and VNC reconstructions (HUVNC). The error was calculated
as HUerror=HUVNC-HUunenhanced. Pearson's or Spearman's correlation was used to assess
the association. Reproducibility was evaluated by intraclass correlation coefficients
(ICC).Significant differences between HUunenhanced and HUVNC[unenhanced] were found
in vertebrae, paraspinal muscles, liver, and spleen. HUVNC[unenhanced] showed a strong
correlation with HUunenhanced in all organs except spleen (r = 0.45) and kidneys (r
= 0.78 and 0.73). In all postcontrast phases, the HUVNC had strong correlations with
HUunenhanced in all organs except the spleen and kidneys. The HUerror had significant
correlations with HUunenhanced in the muscles and vertebrae; and with HUpostcontrast
in the spleen, vertebrae, and paraspinal muscles in all postcontrast phases. All organs
had at least one postcontrast VNC reconstruction that showed good-to-excellent agreement
with HUunenhanced during ICC analysis except the vertebrae (ICC: 0.17), paraspinal
muscles (ICC: 0.64-0.79), spleen (ICC: 0.21-0.47), and kidneys (ICC: 0.10-0.31).VNC
reconstructions are reliable in at least one postcontrast phase for most organs, but
further improvement is needed before VNC can be utilized to examine the spleen, kidneys,
and vertebrae.