Lung ventilation analysis using deformable registration in Xe-enhanced CT images

To analyze lung regional ventilation using two-phase Xe-enhanced CT with wash-in and wash-out periods, we propose an accurate and fast deformable registration and ventilation imaging. To restrict the registration to the lung parenchyma, the left and right lungs are segmented. To correct position difference and local deformation of the lungs, affine and demon-based deformable registrations are performed. The lungs of wash-out image are globally aligned to the wash-in image by narrow-band distance propagation based affine registration and nonlinearly deformed by a demon algorithm using a combined gradient force and active cells. To assess the lung ventilation, color-coded ventilation pattern map is generated by deformable registration and histogram analysis of xenon attenuation. Experimental results show that our accurate and fast deformable registration corrects not only positional difference but also local deformation. Our ventilation imaging helps the analysis of lung regional ventilation.