Patient movement compensation for 3D echocardiography fusion.

Limited field of view (FOV) is a major problem for 3D real-time echocardiography (3DRTE), which results in an incomplete representation of cardiac anatomy. Various image registration techniques have been proposed to improve the field of view in 3DRTE by fusing multiple image volumes. However, these techniques require significant overlap between the individual volumes and rely on high image resolution and high signal-to-noise ratio. Changes in the heart position due to patient movement during image acquisition can also reduce the quality of image fusion. In this paper, we propose a multi-camera based optical tracking system which 1) eliminates the need for image overlap and 2) compensates for patient movement during acquisition. We compensate for patient movement by continuously tracking the patient position using skin markers and incorporating this information into the fusion process. We fuse volumes acquired during R-R wave peaks based on Electrocardiogram (ECG) data to account for retrospective image acquisition. The fusion technique was validated using a heart phantom (Shelley Medical Imaging Technologies) and on one healthy volunteer. The fused ultrasound volumes could be generated in within 2 seconds and were found to have complete myocardial boundaries alignment upon visual assessment. No stitching artefacts or movement related artefacts were observed in the fused image.

An economic evaluation of perioperative adverse events associated with spinal surgery.

BACKGROUND CONTEXT: Besides their clinical impact, the economic impact of health care-related adverse events (AEs) is significant. Although a number of studies have attempted to estimate the economic impact of AEs, few have directly linked costs to clinician-reported event severity. PURPOSE: To estimate the economic impact in terms of the incremental cost and length of stay (LOS), attributable to different severity grades of AEs that occurred during perioperative spinal surgery. STUDY DESIGN: Health economic evaluation of data from a prospective observational study from the perspective of an academic hospital. PATIENT SAMPLE: Consecutive patients at a single, tertiary-quaternary care institution who have undergone inpatient spinal surgery. OUTCOME MEASURES: The cost and LOS impacts with respect to the severity of the AEs. METHODS: We analyzed 4 years of patient discharges between January 1, 2007 and December 31, 2010. The Spine Adverse Events Severity instrument was completed by the surgical team at discharge. Clinical impacts of the AEs were graded as I (requires no/minimal treatment), II (requires treatment and is not likely to cause long-term [>6 months] sequelae), III (requires treatment and is most likely to cause long-term sequelae), and IV (death). A total of 1,815 records were linked with the patient-level costing information. We matched each AE case with four control cases based on their propensity score for the risk of experiencing an AE, regressed against case characteristics. We estimated an incremental cost and LOS for each severity grade by calculating the differences in means across cases and controls. We conducted a sensitivity analysis by estimating the alternate models using generalized linear model (GLM) regression with a gamma log link. RESULTS: Adverse events were reported in 316 (17.4%) cases, with 126 of these patients (40.2%) experiencing multiple events. The incremental cost/LOS for each severity grade are as follows: I=$4,224 (p=.0351)/3.63 days (p=.0001); II=$23,500 (p<.0001)/14.03 days (p<.0001); III=$147,285 (p=.0036)/74.50 days (p=.0018); and IV=$121,366 (p=.0323)/46.44 days (p=.0036). The total cost in millions/LOS (days) associated with each grade over the 4-year study period are as follows: I=$0.66 million/569.9 days; II=$2.96 million/1,767.8 days; III=$4.27 million/2,160.5 days; and IV=$0.49 million/185.8 days. Our sensitivity analysis produced comparable overall results using alternate modeling techniques. Overall, AEs contributed an estimated $8.38 million (16.0% of the total costs for all patients in the sample) in incremental costs and 4,684 additional bed days over the 4-year study period. CONCLUSIONS: In this surgical spine cohort, AEs accounted for 16% of the total cost of in-hospital care. Higher severity AEs were progressively more costly on a per-case basis; however, the more frequent lower severity events (ie, Grade I and II) also had a substantial aggregate cost (43%). These results suggest that a strong business case exists for patient safety strategies focused not only on severe AEs but also on the reduction of lower severity events that may be more amenable to prevention efforts.