A prospective study to validate pulmonary blood mass changes on non-contrast 4DCT in pulmonary embolism patients.

ABSTRACT

PURPOSE: Limited diagnostic options exist for patients with suspected pulmonary embolism (PE) who cannot undergo CT-angiogram (CTA). CT-ventilation methods recover respiratory motion-induced lung volume changes as a surrogate for ventilation. We recently demonstrated that pulmonary blood mass change, induced by tidal respiratory motion, is a potential surrogate for pulmonary perfusion. In this study, we examine blood mass and volume change in patients with PE and parenchymal lung abnormalities (PLA). METHODS: A cross-sectional analysis was conducted on a prospective, cohort-study with 129 consecutive PE suspected patients. Patients received 4DCT within 48 h of CTA and were classified as having PLA and/or PE. Global volume change (VC) and percent global pulmonary blood mass change (PBM) were calculated for each patient. Associations with disease type were evaluated using quantile regression. RESULTS: 68 of 129 patients were PE positive on CTA. Median change in PBM for PE-positive patients (0.056; 95% CI 0.045, 0.068; IQR 0.051) was smaller than that of PE-negative patients (0.077; 95% CI 0.064, 0.089; IQR 0.056), with an estimated difference of 0.021 (95% CI 0.003, 0.038; p = 0.0190). PLA was detected in 57 (44.2%) patients. Median VC for PLA-positive patients (1.26; 95% CI 1.22, 1.30; IQR 0.15) showed no significant difference from PLA-negative VC (1.25; 95% CI 1.21, 1.28; IQR 0.15). CONCLUSIONS: We demonstrate that pulmonary blood mass change is significantly lower in PE-positive patients compared to PE-negative patients, indicating that PBM derived from dynamic non-contrast CT is a potentially useful surrogate for pulmonary perfusion.