The authors found strong agreement between PCCT-derived PBV maps and V/Q-SPECT for whole-lung and lobar perfusion, supporting PCCT as a feasible quantitative perfusion tool in CTEPH work-up.
Best-practice implication: PCCT may enable combined assessment of pulmonary perfusion, vasculature, and parenchyma in one examination, especially where both functional and anatomical information are needed.
The authors highlight important protocol considerations: vessel masking, z-score normalisation, right-arm injection where feasible, and awareness of venous inflow artefacts and V/Q-SPECT respiratory misregistration.
Access to publication
Figure 1. Image processing workflow for quantification of lobar mean perfusion and perfusion defect percentage from PCCT and V/Q-SPECT images. Lung and lobar segmentation were performed on inspiratory PCCT virtual non-contrast (VNC) and attenuation-correction CT (AC-CT) images using TotalSegmentator. Pulmonary vessels were excluded from PBV maps using a threshold-based vessel mask to enable comparison with V/Q-SPECT-derived perfusion. For inter-modal comparison, perfusion data from both imaging techniques were standardised using z-score normalisation (95% confidence interval). Mean PBV as a surrogate for lung perfusion was calculated for each lobe and the entire lung and used to derive lobar and whole-lung perfusion defect volumes.
Protocol
Detail | VQCT | CTPA |
|---|
Scanner | NAEOTOM Alpha | NAEOTOM Alpha |
Scan area | Chest / lung perfusion | Chest / pulmonary angiography and perfusion |
Scan mode | VQCT, inspiration/expiration | CTPA, single inspiratory acquisition |
Scan direction | Transverse | Transverse |
Tube voltage [kV] | 120 | 120 |
IQ level | 67 | 40 |
Dose modulation | CARE Dose4D | CARE Dose4D + CARE keV |
CTDIvol [mGy] | 15.2 ± 7.5 overall PCCT cohort | 15.2 ± 7.5 overall PCCT cohort |
DLP [mGy*cm] | 262.5 ± 93.1 overall PCCT cohort | 262.5 ± 93.1 overall PCCT cohort |
Effective dose [mSv] | 3.68 ± 1.30 overall PCCT cohort | 3.68 ± 1.30 overall PCCT cohort |
Rotation time [s] | 0.25 | 0.25 |
Pitch | 1.4 | 1.5 |
Slice collimation [mm] | n.a. | n.a. |
Slice width [mm] | 1.0 | 1.0 |
Reconstruction increment [mm] | 0.7 | 0.7 |
Reconstruction kernel | Qr40 | Qr40 |
Iterative reconstruction | QIR 2 | QIR 2 |
keV level [keV] | n.a. | n.a. |
Contrast agent | Iomeron 400 mgI/mL | Iomeron 400 mgI/mL |
Contrast volume | 50 mL contrast + 50 mL NaCl | 50 mL contrast + 50 mL NaCl |
Flow rate | 3.5 mL/s | 3.5 mL/s |
Saline chaser | Yes | Yes, plus additional 50 mL NaCl |
ECG technique | n.a. | n.a. |
Acquisition phase | Inspiration trigger delay 10 s; expiration delay 300 s | Inspiration trigger delay 10 s |
Publication reference: Moeskes MMV, Derlin T, Hunkemöller AM, et al. Photon-counting CT vs V/Q SPECT for lobar perfusion quantification in chronic thromboembolic pulmonary hypertension. European Radiology. Published 2026.
