Mohamed S. Hefny

A prospective, randomized assessment of a spatial orientation device in natural orifice transluminal endoscopic surgery

BACKGROUND One of the challenges in natural orifice transluminal endoscopic surgery (NOTES) is spatial orientation. The Queens NOTES group has devised a novel method of orientation by using a magnetic device that passes within an endoscope channel allowing for 3-dimensional imaging of the shape and orientation of the endoscope. OBJECTIVE To assess the feasibility and utility of a novel orientation device. DESIGN Randomized, controlled trial. SETTING Animal research laboratory study on four 25-kg pigs. INTERVENTION The device was tested by 6 endoscopists and 6 laparoscopic surgeons. Starting at the gastrotomy, the time to identify 4 targets was recorded. Participants were required to identify and touch the gallbladder, the fallopian tube, a clip on the abdominal wall, and the liver edge. Use of the orientation device was randomized for each session. MAIN OUTCOME MEASUREMENTS Time to identify targets with and without the device. Secondary analysis assessed differences between medical specialties and level of training. RESULTS The mean time to identify all 4 targets with the device was 75.08 ± 42.68 seconds versus 100.20 ± 60.70 seconds without the device (P <.001). The mean time to identify all 4 targets on the first attempt was 102.29 ± 61.36 seconds versus 72.99 ± 40.19 seconds on the second attempt (P <.001). No differences based on specialty or level of training were identified. LIMITATIONS Small sample size and simplicity of tasks. CONCLUSION Regardless of randomization order, both groups were faster with the device. These encouraging results warrant further study using more complex scenarios.

A Liver Atlas Using the Special Euclidean Group

An atlas is a shape model derived using statistics of a population. Standard models treat local deformations as pure translations and apply linear statistics. They are often inadequate for highly variable anatomical shapes. Non-linear methods has been developed but are generally difficult to implement.

A statistical shape model of femoral head-neck cross sections using principal tangent components

Diagnosis of orthopedic conditions, such as femoroacetabular impingement, is difficult to automate. Current methods rely on human analysis of contours that are derived from planar cross-sections of volumetric data. We propose a statistical shape model for analyzing proximal femoral contours. Current frameworks, based on principal component analysis, appear inadequate for analyzing femoral contours because of the complex deformations in diseased patients. We present an analysis based on principal tangent components as a new method for shape description. This model represents deformations as a flow on a manifold, then performs calculations on the associated tangent spaces through exponential mapping, which is appealing because computations on the tangent spaces are Euclidean even if the actual deformations are highly nonlinear. The new model recovered 98% of the contour shapes using only two components, whereas the conventional method needed 48 components to achieve the same reconstruction.

Computer-assisted hip resurfacing planning using Lie group shape models

IntroductionHip resurfacing is a surgical option for osteoarthritis young and active patients. Early failures has been reported due to improper implant placement. Computer-assisted surgery is a promising avenue for more successful procedures.PurposeThis paper presents a novel automatic surgical planning for computer-assisted hip resurfacing procedures. The plan defined the femoral head axis that was used to place the implant. The automatic planning was based on a Lie group statistical shape model.MethodsA statistical shape model was constructed using 50 femurs from osteoarthritis patients who underwent computer-assisted hip resurfacing. The model was constructed using product Lie groups representation of shapes and nonlinear analysis on the manifold of shapes. A surgical plan was drawn for the derived base shape. The base shape was transformed to 14 femurs with known manual plans. The transformed base plan was used as the computed plan for each femur. Both actual and computed plans were compared.ResultsThe method showed a success by computing plans that differ from the actual plans within the surgical admissible ranges. The minimum crossing distance between the two plans had a mean of 0.75 mm with a standard deviation of 0.54 mm. The angular difference between the two plans had the mean of 5.94

Quantification of Edematic Effects in Prostate Brachytherapy Interventions

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The aspherical human hip: implication for early osteoarthritis.

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Analysis of Discrete Shapes Using Lie Groups

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