(2026) Moeskes | PCCT vs V/Q-SPECT for lobar perfusion in CTEPH

Daniel Stromer

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.

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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.