UC Davis

Purpose: 4-dimensional computed tomography (4D-CT)-based pulmonary ventilation imaging is an emerging functional imaging modality. The purpose of this study was to investigate the physiological significance of 4D-CT ventilation imaging by comparison with pulmonary function test (PFT) measurements and single-photon emission CT (SPECT) ventilation images, which are the clinical references for global and regional lung function, respectively. Methods and Materials: In an institutional review board-approved prospective clinical trial, 4D-CT imaging and PFT and/or SPECT ventilation imaging were performed in thoracic cancer patients. Regional ventilation (V 4DCT) was calculated by deformable image registration of 4D-CT images and quantitative analysis for regional volume change. V 4DCT defect parameters were compared with the PFT measurements (forced expiratory volume in 1second (FEV1; % predicted) and FEV1/forced vital capacity (FVC; %). V 4DCT was also compared with SPECT ventilation (V SPECT) to (1) test whether V 4DCT in V SPECT defect regions is significantly lower than in nondefect regions by using the 2-tailed t test; (2) to quantify the spatial overlap between V 4DCT and V SPECT defect regions with Dice similarity coefficient (DSC); and (3) to test ventral-to-dorsal gradients by using the 2-tailed t test. Results: Of 21 patients enrolled in the study, 18 patients for whom 4D-CT and either PFT or SPECT were acquired were included in the analysis. V 4DCT defect parameters were found to have significant, moderate correlations with PFT measurements. For example, V4DCTHU defect volume increased significantly with decreasing FEV1/FVC (R=-0.65, P<.01). V 4DCT in V SPECT defect regions was significantly lower than in nondefect regions (mean V4DCTHU 0.049 vs 0.076, P<.01). The average DSCs for the spatial overlap with SPECT ventilation defect regions were only moderate (V4DCTHU0.39±0.11). Furthermore, ventral-to-dorsal gradients of V 4DCT were strong (V4DCTHU R2=0.69, P =.08), which was similar to V SPECT (R2=0.96, P<.01). Conclusions: An 18-patient study demonstrated significant correlations between 4D-CT ventilation and PFT measurements as well as SPECT ventilation, providing evidence toward the validation of 4D-CT ventilation imaging. © 2014 Elsevier Inc.