D109-06 CT:VQ Software Performance Validation Against Spect V/Q and Pulmonary Function Tests

Abstract Rationale CT:VQ software quantifies and generates 3D ventilation (V) and perfusion (Q) images from non-contrast inspiratory/expiratory chest CT scans. The software was validated against clinical-standard, single-photon emission CT for ventilation-perfusion (SPECT V/Q) and pulmonary function tests (PFT) in cohorts with subacute pulmonary embolism, chronic lung conditions (e.g. COPD and small airways disease), or undergoing lung volume reduction therapy. Methods N = 77 subjects (25F, 29M, 23 unknown; 59.5±13.0 years, 29 unknown; 28.2±6.9 BMI, 29 unknown) from four clinical sites (2xUSA, AUS, UK) with paired inspiratory/expiratory chest CT and SPECT V/Q scans. N = 46 subjects with spirometry and diffusing capacity of carbon monoxide (DLCO). Image registration between SPECT CT and paired chest CT performed to spatially align CTs and SPECT. Lobar mask generated from expiratory CT. CT:VQ (4D Medical, Melbourne, AUS) software analysed all paired chest CTs. Pearson linear regression analysis performed on lobar-level V and Q distributions between the software’s outputs and SPECT; reported as a percentage of lung total. Pearson linear regression analyses performed on the software’s regional lung Q and V variability metrics (coefficient of variation (CV=SD/mean) and heterogeneity (H=IQR/mean)) vs. PFT measurements (Forced Expiratory Volume in one second/Forced Vital Capacity (FEV1/FVC)). Results Strong lobar-level correlations between CT:VQ and SPECT were observed for V (ρ = 0.842,p0.001) and Q (ρ = 0.872,p0.001) as seen in Figure 1. CT:VQ perfusion heterogeneity metrics produced greater negative correlations with DLCO % predicted than SPECT (CVQ: ρ=-0.778 vs. ρ=-0.617; HQ: ρ=-0.766 vs. ρ=-0.542; all p 0.001). Additionally, CT:VQ ventilation heterogeneity metrics produced moderate negative correlations with FEV1/FVC % predicted (CVV: ρ=-0.553; HV: ρ=-0.551; both p 0.001). Conclusions CT:VQ demonstrated strong agreement with SPECT for lobar perfusion and ventilation distributions, indicating consistent regional measurements. CT:VQ perfusion heterogeneity metrics showed stronger inverse correlations with DLCO than SPECT suggesting improved sensitivity to gas exchange impairment. Moderate correlations between CT:VQ- and SPECT-based heterogeneity metrics were observed, with a systematic offset indicating lower heterogeneity in CT:VQ outputs—potentially reflecting higher spatial resolution and reduced artifact susceptibility. Furthermore, CT:VQ ventilation heterogeneity was significantly associated with FEV1/FVC % predicted, a standard clinical indicator of obstructive lung disease, demonstrating the CT:VQ’s capacity to provide physiologically meaningful, spatially resolved assessments of regional ventilation and perfusion. This abstract is funded by: 4D Medical