Dynamic Chest Radiography: Clinical Validation Of Ventilation And Perfusion Metrics Derived From Changes In Radiographic Lung Density Compared To Nuclear Medicine Imaging

Background: Dynamic chest radiography (DCR) is a type of non-contrast-enhanced functional lung imaging with a dynamic flat-panel detector (FPD). This study aimed to assess the clinical significance of ventilation and perfusion metrics derived from changes in radiographic lung density on DCR in comparison to nuclear medicine imaging-derived metrics.Methods: DCR images of 42 lung cancer patients were sequentially obtained during respiration using a dynamic FPD imaging system. For each subdivided lung region, the maximum change in the averaged pixel value (Delta(max)), i.e., lung density, due to respiration and cardiac function was calculated, and the percentage of Amax relative to the total of all lung regions (Delta(max)%) was computed for ventilation and perfusion, respectively. The Delta(max)% was compared to the accumulation of radioactive agents such as Tc-99m gas and Tc-99m macro aggregated albumin (radioactive agents%) on ventilation and perfusion scans in the subdivided lung regions, by Spearman's correlation coefficient (r) and the Dice similarity coefficients (DSC). To facilitate visual evaluation, Delta(max)% was visualized as a color scaling, where larger Delta(max) values were indicated by higher color intensities.Results: We found a moderate correlation between Delta(max)% and radioactive agents% on ventilation and perfusion scans, with perfusion metrics (r=0.57, P<0.001) showing a higher correlation than ventilation metrics (r=0.53, P<0.001). We also found a good or strong correlation (r >= 0.5) in 80.9% (34/42) of patients for perfusion metrics (r=0.60 +/- 0.16) and in 52.4% (22/42) of patients for ventilation metrics (r=0.53 +/- 0.16). DSC indicated a moderate correlation for both metrics. Decreased pulmonary function was observed in the form of reduced color intensities on color-mapping images.Conclusions: DCR-derived ventilation and perfusion metrics correlated reasonably well with nuclear medicine imaging findings in lung subdivisions, suggesting that DCR could provide useful information on pulmonary function without the use of radioactive contrast agents.