Quantitative Assessment of Postural Influence on Lung Function Using Deformable Image Registration-Based Breath-Hold CT Ventilation Imaging.

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Purpose This study aimed to clarify which positions are beneficial for patients with pathological lung diseases, such as acute respiratory distress syndrome, by obtaining lung ventilation and deformable vector field (DVF) images using Deformable Image Registration (DIR). Methods Thirteen healthy volunteers (5 female, 8 male) provided informed consent to participate to observe changes in normal lungs. DIR imaging was processed using the B-spline algorithm to obtain BH-CTVI (inhale, exhale) in four body positions (supine, prone, right lateral, left lateral) using DIR-based breath-hold CT ventilation imaging (BH-CTVI). DVF imaging was created through DIR-based BH-CTVI, which obtained the displacement vector from expiration to inspiration for each lung lobe. Results In the DIR images for each body position, the areas with Jacobian values in the 75th percentile or higher, indicating highly functional areas, were distributed on the side of the patient in contact with the ground. DVF images showed the abdominal displacement vector to be oriented from dorsal to ventral in the supine position. However, in the prone position, the displacement vectors were nearly parallel to the ground, directed from head to feet, indicating that lung motion was unaffected by gravity. Conclusion We demonstrated that the prone position allows for lung ventilation with the least gravitational load compared with the supine, right lateral decubitus, and left lateral decubitus positions, based on a comparison of DIR-based BH-CTVI when the positions were converted. It is important to include the evaluation of DVF images, in addition to ventilation images, when assessing lung function using DIR-based BH-CTVI.