Purpose:To compare the accuracy of several magnetic resonance (MR) imaging-based methods for hepatic proton-density fat fraction (FF) estimation at 3.0 T, with spectroscopy as the reference technique. Materials and Methods:This prospective study was institutional review board approved and HIPAA compliant. Informed consent was obtained. One hundred sixty-three subjects (39 with known hepatic steatosis, 110 with steatosis risk factors, 14 without risk factors) underwent proton MR spectroscopy and non-T1-weighted gradient-echo MR imaging of the liver. At spectroscopy, the reference FF was determined from frequency-selective measurements of fat and water proton densities. At imaging, FF was calculated by using two-, three-, or six-echo methods, with single-frequency and multifrequency fat signal modeling. The three-and sixecho methods corrected for T2 * ; the two-echo methods did not. For each imaging method, the fat estimation accuracy was assessed by using linear regression between the imaging FF and spectroscopic FF. Binary classifi cation accuracy of imaging was assessed at four reference spectroscopic thresholds (0.04, 0.06, 0.08, and 0.10 FF). Results:Regression intercept of two-, three-, and six-echo methods were 2 0.0211, 0.0087, and 2 0.0062 ( P , .001 for all three) without multifrequency modeling and 2 0.0237 ( P , .001), 0.0022, and 2 0.0007 with multifrequency modeling, respectively. Regression slope of two-, three-, and six-echo methods were 0.8522, 0.8528, and 0.7544 ( P , .001 for all three) without multifrequency modeling and 0.9994, 0.9775, and 0.9821 with multifrequency modeling, respectively. Signifi cant deviation of intercept and slope from 0 and 1, respectively, indicated systematic error. Classification accuracy was 82.2%-90.1%, 93.9%-96.3%, and 83.4%-89.6% for two-, three-, and six-echo methods without multifrequency modeling and 88.3%-92.0%, 95.1%-96.3%, and 94.5%-96.3% with multifrequency modeling, respectively, depending on the FF threshold. T2 * -corrected (three-and six-echo) multifrequency imaging methods had the overall highest FF estimation and classifi cation accuracy. Among methods without multifrequency modeling, the T2 * -corrected threeecho method had the highest accuracy.

The results of robotic-assisted surgery compare favorably with those of conventional laparoscopy with respect to mortality, complications, and length of stay. Robotic-assisted surgery is safe and effective and is a new reality for American surgery. The role of these devices in surgery will expand as the technology evolves.

This early experience suggests that robotic surgery is a safe and effective alternative to conventional laparoscopic surgery. We believe that robotic surgery, with its ability to restore the hand-eye coordination and three-dimensional view lost in laparoscopic surgery, will allow us to perform complex procedures with greater precision and confidence and better results.

Hypothesis:A bioabsorbable tissue scaffold of porcine submucosal small intestine extracellular matrix (Surgisis Gold [SIS]; Cook Biotech Inc, West Lafayette, Ind) mesh is safe and effective for ventral hernia repair.Design: Retrospective case series at a university teaching hospital.Patients: Fifty-three consecutive patients having 8-ply SIS mesh repair of ventral abdominal hernias. Main Outcome Measures:Early complications, reoperation, hernia recurrence, mesh or wound infection, or reaction. Outcomes reported and compared on an intention-to-treat basis.Results: Patients were stratified by wound class: clean, clean-contaminated and contaminated, or dirty. Median follow-up was 14 months (range, 2-29 months) during which there were 22 complications (41%), 17 early reoperations (32%), 13 partial dehiscences (21%), 6 mesh re-

The more complex the task, the more 3D vision accelerates task completion compared with 2D vision. The gain in task performance is independent of the surgical method.