This pilot study demonstrates that spectral information from photon-counting detector CT (PCD-CT) can help differentiate hyperdense renal cysts from vascular renal lesions when conventional portal-venous images are indeterminate. In 26 patients with 42 hyperdense renal lesions, attenuation on standard 70-keV VMI substantially overlapped between vascular and non-vascular lesions.
Iodine quantification maps provided the strongest differentiation: non-vascular lesions measured 5.7 ± 7.8 HU versus 33.3 ± 19.0 HU for vascular lesions. A threshold of >20.3 HU identified vascular lesions with 87.5% sensitivity and 88.2% specificity, correctly identifying 7/8 vascular lesions.
VNC was less specific: a 52-HU threshold achieved 100% sensitivity but only 55.9% specificity. The results suggest that routinely available spectral PCD-CT data—particularly iodine maps—could potentially reduce additional true non-contrast or multiphasic imaging when an incidental hyperdense renal lesion is encountered, although validation in larger cohorts is required.
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Figure 3. (A): Axial 70 keV reconstruction as well as VNC and iodine maps of a left renal mass in a portal venous CT scan of the abdomen. The lesion shows elevated HU in 70 keV (75 HU), VNC values of 66 HU (B) and 13 HU for iodine map CT values (C). (D,E): Contrast-enhanced ultrasound confirmed that there was no contrast medium uptake. (F–H): Example of a renal mass without solid components and elevated CT values in iodine maps in comparison to the first patient (52 HU) and similar values in 70 keV reconstructions (86 HU) compared to the confirmed renal cyst (A). Contrast-enhanced ultrasound confirmed a contrast enhancement (green arrow in (I,J)) and histopathology revealed the diagnosis of a renal cell carcinoma.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Application | Contrast-enhanced abdominal CT / characterization of hyperdense renal lesions |
Study population | 26 patients, 42 hyperdense renal lesions (>20 HU) |
Acquisition mode | QuantumPlus with spectral information |
Scan phase | Portal venous phase |
Scan area | Lung apex or diaphragm to symphysis |
Scan direction | Craniocaudal |
Patient position | Supine |
Breath-hold | Single breath-hold |
Tube voltage | 120 kVp |
Tube current modulation | CARE Dose4D |
Rotation time | 0.25 s |
Pitch | 0.8 |
Collimation | 144 × 0.4 mm |
Slice thickness | 1.0 mm |
Reconstruction increment | 1.0 mm |
Reconstruction kernel | Qr40 |
Iterative reconstruction | QIR 3 |
Spectral postprocessing | SPP |
VMI | 70 keV |
Spectral reconstructions | VNC and iodine quantification maps |
Workstation | Syngo.Via VB60A |
Contrast agent | Iopromide (Ultravist 300 mgI/mL) |
Contrast volume | 120 mL |
Saline chaser | 30 mL |
Flow rate | 4.0 mL/s |
Bolus triggering | 120 HU in ascending aorta |
Post-trigger delay | 45 s |
Image analysis | Three ROI measurements per renal lesion; mean value used |
Reference standard | TNC CT, ultrasound/CEUS, MRI/PET-CT, or histopathology |
Key Results
Parameter | Main finding |
|---|
Study cohort | 26 patients with 42 hyperdense renal lesions |
70-keV VMI | Substantial overlap between non-vascular (61.4 ± 19.4 HU) and vascular lesions (65.5 ± 17.4 HU); p = 1.000 |
Iodine maps | Non-vascular 5.7 ± 7.8 HU vs vascular 33.3 ± 19.0 HU; p = 0.002 |
Iodine-map threshold | >20.3 HU |
Iodine-map performance | 87.5% sensitivity, 88.2% specificity |
Vascular lesions detected | 7/8 (87.5%) |
VNC values | Non-vascular 55.7 ± 24.2 HU vs vascular 32.2 ± 11.1 HU; p = 0.034 |
VNC threshold | 52 HU |
VNC performance | 100% sensitivity, 55.9% specificity |
70-keV threshold | 74 HU |
70-keV performance | 76.5% sensitivity, 50% specificity |
Best spectral feature | Iodine quantification maps were the most important discriminator in random-forest feature selection |
Potential implication | Spectral iodine information from routine PCD-CT may reduce the need for additional TNC or follow-up examinations in indeterminate hyperdense renal lesions, pending validation in larger studies |
Source:
Becker J, Feitelson L-M, Risch F, Canalini L, Kaufmann D, Wudy R, Jehs B, Haerting M, Wollny C, Scheurig-Muenkler C, et al. Spectral Differentiation of Hyperdense Non-Vascular and Vascular Renal Lesions Without Solid Components in Contrast-Enhanced Photon-Counting Detector CT Scans—A Pilot Study. Diagnostics. 2025;15(1):79. https://doi.org/10.3390/diagnostics15010079
