Validation of Registration-based Dynamic Ventilation Imaging

1. Validation of Registration-based Dynamic Ventilation Imaging using Xenon-CT Measures of Specific Ventilation Kai Ding, Kunlin Cao, Matthew L. Moehlmann, Gary E. Christensen, Eric A.Hoffman, Joseph M. Reinhardt Iowa Institute of Biomedical Imaging, The University of Iowa Introduction • Consistent Linear Elastic Image Registration • Cost Minimization: • Regional volume change: Jacobian determinant Results • The correlation coefficients from linear regression of Xe-CT derived specific ventilation and registration-based specific ventilation • The landmark error • Registration also reveals expansion heterogeneity in tidal breathing. • Background • Lung diseases can change tissue properties, e.g., Emphysema (COPD): Increased compliance, Idiopathic Pulmonary Fibrosis (IPF): Decreased compliance • Traditional pulmonary function measurements (e.g. spirometry) only give global information and cannot show regional difference. • Goal • Use image registration to estimate regional ventilation as an indicator of regional lung function. • Evaluate of the accuracy of the result by two standards: Xe-CT derived measures of regional ventilation (functional) and 20 manually picked landmarks (anatomical). g h Template, T Target, S Method • Xe-CT Analysis • Observed time-intensity data is fit to compartment model using least squares curve fit. • Pulmonary Analysis Software Suite • Reg.-based vs. Xe-CT derived Spec. Ventilation • Track the deformed slab and calculate the average registration derived and Xe-CT derived Spec. Ventilation within the slab. • Manually Picked Landmarks • 20 landmarks (airway branchpoints) were manually picked by one observer and matched across different pressures and phases. For each landmark, the actual landmark position was compared to the registration-derived landmark position. • Experiments • Siemens Sensation 64 MDCT scanner. • Four adult sheep were used in this experiment. • The sheep were oriented in the supine position, anesthetized and mechanically ventilated. • Dynamic scans: retrospectively reconstructed at 0, 25, 50, 75 and 100% phase points of inspiration portion and 75, 50 and 25% of the expiration portion of the respiratory cycle (denoted as the T0, T1, T2 … and T7 images). • Xe-CT scans: acquired at the end expiratory point during the respiratory cycle (about 45 breaths) at PEEP of 10 for each sheep. Slice thickness = 2.4 mm (about 3.2 times thicker than the volumetric CT slices). 12 contiguous slices = 3 cm of coverage along the axial direction. Before registration After registration 1.13 Apex Expansion Contraction Base 0.88 0%IN-25%IN 25%IN-50%IN 50%IN-75%IN 75%IN-100%IN y Conclusions • Inverse consistent linear elastic registration shows good estimation of specific ventilation as evaluated by Xe-CT derived specific ventilation. • Registration also reveals expansion heterogeneity in tidal breathing. Lung Height x 100%IN 0%IN Acknowledgement • This work was supported in part by the grant HL079406 from National Institute of Health. • Thanks to Matthew Fuld and Dr. Deokiee Chon Contact • Kai Ding, Email: kai-ding@uiowa.edu