Preliminary Results Comparing Thin Plate Splines with Finite Element Methods for Modeling Brain Deformation during Neurosurgery using Intraoperative Ultrasound.

Brain shift compensation attempts to model the deformation of the brain which occurs during the surgical removal of brain tumors to enable mapping of presurgical image data into patient coordinates during surgery and thus improve the accuracy and utility of neuro-navigation. We present preliminary results from clinical tumor resections that compare two methods for modeling brain deformation, a simple thin plate spline method that interpolates displacements and a more complex finite element method (FEM) that models physical and geometric constraints of the brain and its material properties. Both methods are driven by the same set of displacements at locations surrounding the tumor. These displacements were derived from sets of corresponding matched features that were automatically detected using the SIFT-Rank algorithm. The deformation accuracy was tested using a set of manually identified landmarks. The FEM method requires significantly more preprocessing than the spline method but both methods can be used to model deformations in the operating room in reasonable time frames. Our preliminary results indicate that the FEM deformation model significantly out-performs the spline-based approach for predicting the deformation of manual landmarks. While both methods compensate for brain shift, this work suggests that models that incorporate biophysics and geometric constraints may be more accurate.

Incidence of surgical site infection in postoperative patients at a tertiary care centre in India.

OBJECTIVE: A prospective observational was carried out to calculate the incidence of surgical site infections (SSI) along with the main risk factors and causative organisms in postoperative patients at a tertiary care setting in Mumbai. METHOD: A total number of 1196 patients between June 2011 to March 2013 admitted to the general surgical ward or surgical ICU of our hospital were included in the study. Post laproscopy patients and organ space SSIs were excluded. Patient data were collected using a preformed pro forma and a wound Southampton score tabulated and checked repeatedly until suture removal of patient. Regular follow-up was maintained until at least 30 days postoperatively. RESULTS: The study showed a SSI rate of 11%. Risk factors associated with a higher incidence of SSI were found to be age (>55 years), diabetes mellitus (especially uncontrolled sugar in the perioperative period), immunocompromised patients (mainly HIV and immunosuppressive therapy patients), surgeon skill (higher in senior professors compared with junior residents), nature of the cases, (emergency surgeries), placement of drains, wound class (highest in dirty wounds), type of closure (multilayer closure), prolonged duration of hospital stay, longer duration of surgery (>2 hours), type of surgery (highest in cholecystectomy). The highest rates of causative organisms for SSIs found were Staphylococcus aureus, Escherichia coli and Klebsiella ssp. CONCLUSION: Prevention of SSIs requires a multipronged approach with particular emphasis on optimising preoperative issues, adhering religiously to strict protocols during the intraoperative period and addressing and optimising metabolic and nutritional status in postoperative period.

The detection of varicella zoster antibodies by simultaneous competitive EIA and its comparison with radioimmunoassay, latex agglutination and antiglobulin type EIA.

A rapid and simultaneous competitive enzyme immunoassay (EIA) for the detection of human antibodies to varicella zoster virus (VZV) which utilises complement fixing (CF) VZV antigen and peroxidase labelled human antibodies to VZV as reagents is described. The competitive EIA was compared with competitive radioimmunoassay (RIA) in a selection of sera from 501 blood donors and 115 patients. The competitive EIA was comparable in sensitivity and specificity to the RIA, but had the advantage of not requiring radiolabelling or facilities for radioactive handling and disposal, and also had an enhanced stability. The competitive EIA was compared with competitive RIA, a commercially available latex agglutination assay and an antiglobulin type EIA on sera from 100 patients. The competitive EIA and RIA appeared to be the most sensitive tests.

New rapid latex agglutination test for diagnosing Trichomonas vaginalis infection.

A newly developed latex agglutination test for Trichomonas vaginalis infection was compared for sensitivity, specificity, efficiency, and positive and negative predictive values with microscopy, culture, and an enzyme linked immunosorbent assay (ELISA) in the diagnosis of 395 women attending a genitourinary medicine clinic. T vaginalis infection was diagnosed in 42 (11%) women. The sensitivities of both the latex agglutination test and the ELISA were 95% compared with 74% for microscopy and 76% for culture. The latex test was specific and showed no cross reaction with a wide range of other genital tract infections. The latex agglutination test can detect antigen in both soluble and insoluble forms, and as it is simple to perform, can be undertaken during routine examination without recourse to special equipment or training. Further evaluation is required.