PCCT virtual non-contrast (VNC) reconstructions differentiated adrenal adenomas from metastases on portal-venous contrast-enhanced imaging, with adenomas showing significantly lower attenuation on both conventional VNC (VNCConv) and calcium-preserving PureCalcium VNC (VNCPC) (p = 0.007).
VNC nevertheless systematically overestimated attenuation compared with true non-contrast (TNC) imaging: mean differences were 17.67 HU for VNCConv and 14.85 HU for VNCPC, indicating that the conventional 10-HU TNC threshold cannot simply be transferred to PCCT VNC.
Diagnostic performance was particularly strong for VNCPC (AUC 0.931) and when combining all available spectral information (AUC 0.938). For VNCConv, a higher threshold of 26 HU achieved 86.7% sensitivity and 75.6% specificity, supporting a PCCT-specific VNC threshold for adrenal lesion characterization.
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Figure 1. Example of semiautomatic segmentation of a left adrenal adenoma using 3D Slicer.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Application | Contrast-enhanced abdominal CT / adrenal lesion characterization |
Study design | Retrospective, single-center |
Acquisition mode | Abdomen QuantumPlus with spectral information |
Contrast phase | Portal venous |
Scan direction | Craniocaudal |
Patient position | Supine |
Breath-hold | Single breath-hold |
Tube voltage | 120 kV |
Rotation time | 0.5 s or 0.25 s |
Collimation | 144 × 0.4 mm |
Slice thickness | 1.0 mm |
Reconstruction increment | 0.5 mm |
Reconstruction kernel | Qr40 |
Iterative reconstruction | QIR 3 |
Reconstruction software | ReconCT 16.0 |
TNC reconstruction software | Syngo.via VB60A |
VNC reconstructions | Conventional VNC (VNCConv) and PureCalcium VNC (VNCPC) |
VNC energy | 70 keV |
Virtual monoenergetic images | 40–90 keV in 10-keV increments |
Additional spectral reconstruction | Iodine maps |
Contrast agent | Ultravist 300 mg I/mL |
Contrast volume | 100 mL |
Flow rate | 4.0 mL/s |
Saline chaser | 30 mL |
Scan delay | Fixed 75 s after contrast injection |
True non-contrast imaging | Available in 49/90 patients; obtained either within the same protocol or from a separate CT acquisition |
Lesion analysis | Semiautomatic whole-lesion 3D segmentation |
Segmentation software | 3D Slicer |
Primary comparison | VNCConv and VNCPC vs TNC; spectral imaging for adenoma vs metastasis differentiation |
Key Results
Parameter | Main finding |
|---|
Study population | 90 patients; 45 adrenal adenomas and 45 metastases |
VNCConv attenuation | Adenomas 18.15 HU [12.92–24.26] vs metastases 31.28 HU [26.00–35.89]; p = 0.007 |
VNCPC attenuation | Adenomas 16.00 HU [11.02–21.56] vs metastases 27.22 HU [22.59–30.64]; p = 0.007 |
VNCConv vs TNC | VNCConv overestimated attenuation by a mean 17.67 HU |
VNCPC vs TNC | VNCPC overestimated attenuation by a mean 14.85 HU |
All spectral features | AUC 0.938 for adenoma/metastasis discrimination |
VNCPC alone | AUC 0.931 |
VNCConv alone | AUC 0.857 |
TNC alone | AUC 0.762 |
VNCConv 26-HU cutoff | 86.7% sensitivity, 75.6% specificity |
Feature importance | VNCConv and VNCPC were the most important discriminators in random-forest feature selection |
Main implication | PCCT VNC may enable adrenal lesion characterization from contrast-enhanced scans, potentially reducing additional dedicated adrenal CT/MRI examinations, but requires a higher VNC-specific HU threshold rather than direct application of the conventional 10-HU TNC cutoff. |
Source:
Bette S, Risch F, Canalini L, Becker J, Leithner EV, Huber A, Haerting M, Jehs B, Wollny C, Schwarz F, Tehlan K, Scheurig-Muenkler C, Wendler T, Kroencke T, Decker JA. Diagnostic performance of photon-counting detector CT for differentiation between adrenal adenomas and metastases. European Radiology. 2024;34:5944–5953.
