A four-dimensional deformable image registration (4D DIR) algorithm, referred to as 4D local trajectory modeling (4DLTM), is presented and applied to thoracic 4D computed tomography (4DCT) image sets. The theoretical framework on which this algorithm is built exploits the incremental continuity present in 4DCT component images to calculate a dense set of parameterized voxel trajectories through space as functions of time. The spatial accuracy of the 4DLTM algorithm is compared with an alternative registration approach in which component phase to phase (CPP) DIR is utilized to determine the full displacement between maximum inhale and exhale images. A publically available DIR reference database (http://www.dir-lab.com) is utilized for the spatial accuracy assessment. The database consists of ten 4DCT image sets and corresponding manually identified landmark points between the maximum phases. A subset of points are propagated through the expiratory 4DCT component images. Cubic polynomials were found to provide sufficient flexibility and spatial accuracy for describing the point trajectories through the expiratory phases. The resulting average spatial error between the maximum phases was 1.25 mm for the 4DLTM and 1.44 mm for the CPP. The 4DLTM method captures the long-range motion between 4DCT extremes with high spatial accuracy.

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Area Deprivation Index (ADI) is a marker of neighborhood deprivation. This study investigates utilization of coronary bare-metal stent (BMS) and drug-eluting stent (DES) in Medicare patients across hospitals with varying ADI. Data were abstracted using Diagnosis-Related Group (DRG) codes 249 (BMS without major complications or comorbidities [MCC]), 246, and 247 (DES with and without MCC, respectively) from the 2011-2012 Medicare Provider Utilization and Payment Data Inpatient File, which was linked to American Hospital Association data (to determine bed size, location, ownership, teaching status), and ADI for each hospital zip code was obtained. Hospitals were divided into quintiles using ADI values: Quintile 1 (privileged) to Quintile 5 (deprived). Logistic regression was conducted to determine odds ratios (ORs) for DES utilization across ADI quintiles. There were 313,739 discharges with DRG codes 246 (52,839), 247 (203,928), and 249 (56,972). DES utilization was lower in the deprived quintile, irrespective of teaching status. It was lower in larger hospitals and hospitals with more annual stent discharges, urban locations and nongovernment not-for-profit institutes. Lower odds of DES utilization were found in Quintile 2 (OR-0.9, 95% confidence interval [CI] 0.87-0.93, P < 0.001), Quintile 3 (OR-0.89, 95% CI 0.86-0.92, P < 0.001), and Quintile 4 (OR-0.95, 95% CI 0.92-0.98, P = 0.001) versus Quintile 1 and there was no difference in utilization of DES in Quintile 5 (OR-1.01, 95% CI 0.98-1.04, P = 0.6) versus Quintile 1. Significant differences exist in DES utilization in a large, uniformly insured cohort based on neighborhood deprivation.

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