PCCT-derived virtual non-contrast (VNC) images provided renal cyst attenuation measurements comparable to true non-contrast imaging, with no significant difference across true non-contrast, arterial VNC, and portal-venous VNC (p = 0.301).
In contrast, dual-energy EID-CT VNC showed a significant difference from true non-contrast attenuation (p = 0.02) and produced false-positive enhancement >20 HU in 5/19 lesions (26.3%).
With PCCT, all evaluated cysts remained below the 20-HU enhancement threshold on both arterial and portal-venous VNC, supporting VNC as a potential replacement for true non-contrast imaging in uncomplicated renal cyst characterization.
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Figure 2. Example of Density-measurements in a simple renal cyst on EID DE-CT and PCCT images using true non-contrast, portal venous and virtual non-contrast derived images (from left to right). While true enhancement is < 20 HU, EID DE-CT VNC-derived values are remarkably low leading to false-positive enhancement > 20 HU. PCCT = photon-counting CT; DE EID-CT = dual-energy integrating detector CT.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Scan area | Abdomen |
Acquisition | Multiphase PCCT |
Scan mode | QuantumPlus |
Phases | True non-contrast, arterial, portal venous |
Tube voltage [kVp] | 120 |
Tube current | Automated attenuation-based modulation |
IQ level | 100 (non-contrast & arterial); 145 (portal venous) |
Effective mAs [mAs] | 99 (non-contrast); 100 (arterial & portal venous) |
Rotation time [s] | 0.5 |
Pitch | 0.8 |
Collimation | 144 × 0.40 mm |
Contrast agent | Iopromide (Ultravist 370 mg iodine/mL) |
Contrast amount | Body-weight adapted, 1.2 mg/kg as reported |
Injection / saline flush | 4.0 mL/s; 40 mL saline |
Arterial timing | Bolus tracking, descending aorta, 100-HU threshold |
Portal venous timing | 80 s after contrast administration |
Reconstruction | 70-keV virtual monoenergetic images |
Kernel | Br40 |
Slice thickness [mm] | 3.0 |
Increment [mm] | 3.0 |
Iterative reconstruction | QIR 4 |
Spectral reconstruction | Arterial VNC + portal-venous VNC |
Reference imaging | MRI and/or ultrasound |
Key Results
Parameter | Main finding |
|---|
Study cohort | 19 patients / 19 simple renal cysts |
PCCT true non-contrast attenuation | 13.7 ± 11.6 HU |
PCCT arterial VNC | 9.27 ± 10.1 HU |
PCCT portal-venous VNC | 12.3 ± 9.9 HU |
PCCT attenuation comparison | No significant difference, p = 0.301 |
PCCT arterial VNC enhancement | 4.5 ± 5.0 HU, range −6.2 to 14.2 |
PCCT portal-venous VNC enhancement | 2.4 ± 5.3 HU, range −6.4 to 13.5 |
PCCT false-positive enhancement >20 HU | 0/19 (0%) |
DE EID-CT false-positive enhancement >20 HU | 5/19 (26.3%) |
Portal-venous CTDIvol | PCCT 8.66 mGy vs DE EID-CT 10.95 mGy, p < 0.001 |
Clinical implication | PCCT VNC may potentially substitute true non-contrast imaging for simple renal cyst characterization |
The authors conclude that PCCT VNC provided reliable characterization comparable to true non-contrast imaging, while DE EID-CT VNC falsely characterized 26% of lesions; consequently, PCCT VNC could potentially reduce true non-contrast acquisitions, radiation exposure, and unnecessary follow-up imaging.
Source:
Rau S, Rau A, Stein T, et al. Value of virtual non-contrast images to identify uncomplicated cystic renal lesions: photon-counting detector CT vs. dual-energy integrating detector CT. La Radiologia Medica. 2024;129:669–676. doi:10.1007/s11547-024-01801-2.
