Abstract Rationale CT:VQ software quantifies and generates 3D ventilation (V) and perfusion (Q) images from non-contrast inspiratory/expiratory chest CT scans. To demonstrate consistency in reader performance, CT:VQ perfusion images were directly compared to corresponding single-photon emission CT (SPECT) perfusion images using a standardized reader study platform simulating clinical interpretation conditions, in cohorts with subacute pulmonary embolism, chronic lung conditions (e.g. COPD and small airways disease), or undergoing lung volume reduction therapy. Methods A prospective reader study with N = 6 readers (Avg.=24.3 years clinical experience) who routinely review V/Q studies were enrolled. 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 (USA, AUS, UK) who had paired inspiratory/expiratory chest CT and SPECT V/Q scans. CT:VQ (4D Medical, Melbourne, AUS) software analysed all paired chest CTs. Coronal format perfusion images from both modalities were uploaded to an online DICOM viewer (Flywheel, Minneapolis, MN, USA) for reporting findings within an embedded survey. For each subject, lung perfusion magnitude was evaluated on a monotonic scale (1=absent to 5=well perfused) for each of six lung zones for both modalities by each reader. Inter-modality correlation of regional perfusion was assessed using Kendall’s Tau (τ) across six lung zones. The similarities in perfusion intensity distributions across modalities were also compared by readers in a side-by-side view (1=no agreement to 5=excellent agreement) for each lung zone and reported as mean ± standard deviation (SD). Results All τ values ranged from 0.702 to 0.765 and were statistically significant (p 0.001), indicating very strong, positive ordinal agreement between CT:VQ and SPECT across all zones and readers (Table 1), indicating good to excellent agreement between SPECT and CT:VQ perfusion distributions across all lung zones. Conclusions These findings collectively demonstrate that CT:VQ generates high-fidelity perfusion images that are both interpretable by clinicians and closely aligned with SPECT, supporting its use as a viable, non-nuclear alternative for regional lung perfusion assessment. This abstract is funded by: 4D Medical
Hatt et al. (2026) studied this question.