Improving Monte Carlo Program for Light Transport in Tissue

Monte Carlo Simulations use random number generators and aggregation in order to numerically solve various real-world problems that are too difficult to solve analytically. They are currently the gold standard for simulating photon transport through tissues, and with the adoption of GPU computing, a program by the name of Monte Carlo eXtreme can run these simulations faster than ever. However, this program still lacks several features that would be useful to researchers, such as fluorescent material support and easy simulation of multiple wavelengths. I have added the multi-wavelength feature to MCX, and I have started the process of adding a feature that will allow researchers to easily model fluorescence materials. Although more testing is required, I have laid the foundations of a program that is more readily useful and robust while retaining the speed increases afforded by GPU computing

Environmental factors influencing benthic macrofaunal invertebrate community structure in the Flower Gardens East Bank

The Flower Garden Banks consist of two salt domes raised above the continental shelf in the Gulf of Mexico roughly 190 km southeast of Galveston, Texas. With mean annual temperature variations of 18 to 32°C and relatively low-turbidity water, the shallower portions of both banks provide ideal substrates for scleractinian coral growth, resulting in the formation of the two northernmost coral reefs in the continental U.S (Bright et al., 1984; Teague et al., 2013). Factors affecting macroinfaunal organism communities within the shallowest portions of these banks have so far been neglected, with the nearest assessments being conducted by Yingst and Rhoads in waters over 90 m deep and adjacent to the Banks, not within the Bank tops (1985). The objectives of this study were twofold: to determine if there are statistically significant differences in composition between the polychaete communities of the coastal northwestern Gulf of Mexico and the East Flower Garden Bank (EFGB), and to look for correlations between the environmental parameters of percent carbonate content, particulate organic carbon (POC) content, and sediment grain size, and the community parameters of biomass, density, species richness, species evenness, and diversity of all macroinfaunal invertebrates at a depth of ~25 meters in the EFGB. Eight box core samples were taken off the coast of Louisiana from August 21-September 9, 1978, and box core samples were taken from the EFGB on August 28-29, 2013. There was no overlap in species composition between the Louisiana samples and the EFGB samples, and the Louisiana samples were more diverse in general. Amphipod and isopod crustaceans dominated the EFGB macrofauna numerically in most samples, but polychaete worms comprised the largest percentage of biomass in all EFGB samples. Mean sediment grain size was positively and significantly correlated with species count, Margalef’s richness, and biomass. Particulate organic carbon content was positively and significantly correlated with every diversity measurement except species count and individual density. Sediment carbonate content was not significantly correlated with any biotic variable. No significant correlations were detected between the environmental variables

Cerebellar hemorrhage after spine fixation misdiagnosed as a complication of narcotics use -A case report-

Cerebellar hemorrhage occurs mainly due to hypertension. Postoperative cerebellar hemorrhage is known to be associated frequently with frontotemporal craniotomy, but quite rare with spine operation. A 56-year-old female received spinal fixation due to continuous leg tingling sensation for since two years ago. Twenty-one hours after operation, she was disoriented and unresponsive to voice. Performed computed tomography showed both cerebellar hemorrhage. An emergency decompressive craniotomy was carried out to remove the hematoma. On the basis of this case, we reported this complications and reviewed related literature

Structural and mechanical evaluations of a topology optimized titanium interbody fusion cage fabricated by selective laser melting process

A topology optimized lumbar interbody fusion cage was made of Ti-Al6-V4 alloy by the rapid prototyping process of selective laser melting (SLM) to reproduce designed microstructure features. Radiographic characterizations and the mechanical properties were investigated to determine how the structural characteristics of the fabricated cage were reproduced from design characteristics using micro-computed tomography scanning. The mechanical modulus of the designed cage was also measured to compare with tantalum, a widely used porous metal. The designed microstructures can be clearly seen in the micrographs of the micro-CT and scanning electron microscopy examinations, showing the SLM process can reproduce intricate microscopic features from the original designs. No imaging artifacts from micro-CT were found. The average compressive modulus of the tested caged was 2.97 ± 0.90 GPa, which is comparable with the reported porous tantalum modulus of 3 GPa and falls between that of cortical bone (15 GPa) and trabecular bone (0.1–0.5 GPa). The new porous Ti-6Al-4V optimal-structure cage fabricated by SLM process gave consistent mechanical properties without artifactual distortion in the imaging modalities and thus it can be a promising alternative as a porous implant for spine fusion. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57400/1/31231_ftp.pd

Changes in circulating microRNA levels associated with prostate cancer

BACKGROUND: The aim of this study was to investigate the hypothesis that changes in circulating microRNAs (miRs) represent potentially useful biomarkers for the diagnosis, staging and prediction of outcome in prostate cancer. METHODS: Real-time polymerase chain reaction analysis of 742 miRs was performed using plasma-derived circulating microvesicles of 78 prostate cancer patients and 28 normal control individuals to identify differentially quantified miRs. RESULTS: A total of 12 miRs were differentially quantified in prostate cancer patients compared with controls, including 9 in patients without metastases. In all, 11 miRs were present in significantly greater amounts in prostate cancer patients with metastases compared with those without metastases. The association of miR-141 and miR-375 with metastatic prostate cancer was confirmed using serum-derived exosomes and microvesicles in a separate cohort of patients with recurrent or non-recurrent disease following radical prostatectomy. An analysis of five selected miRs in urine samples found that miR-107 and miR-574-3p were quantified at significantly higher concentrations in the urine of men with prostate cancer compared with controls. CONCLUSION: These observations suggest that changes in miR concentration in prostate cancer patients may be identified by analysing various body fluids. Moreover, circulating miRs may be used to diagnose and stage prostate cance

Biomechanical effects of polyaxial pedicle screw fixation on the lumbosacral segments with an anterior interbody cage support

BACKGROUND: Lumbosacral fusion is a relatively common procedure that is used in the management of an unstable spine. The anterior interbody cage has been involved to enhance the stability of a pedicle screw construct used at the lumbosacral junction. Biomechanical differences between polyaxial and monoaxial pedicle screws linked with various rod contours were investigated to analyze the respective effects on overall construct stiffness, cage strain, rod strain, and contact ratios at the vertebra-cage junction. METHODS: A synthetic model composed of two ultrahigh molecular weight polyethylene blocks was used with four titanium pedicle screws (two in each block) and two rods fixation to build the spinal construct along with an anterior interbody cage support. For each pair of the construct fixed with polyaxial or monoaxial screws, the linked rods were set at four configurations to simulate 0°, 7°, 14°, and 21° lordosis on the sagittal plane, and a compressive load of 300 N was applied. Strain gauges were attached to the posterior surface of the cage and to the central area of the left connecting rod. Also, the contact area between the block and the cage was measured using prescale Fuji super low pressure film for compression, flexion, lateral bending and torsion tests. RESULTS: Our main findings in the experiments with an anterior interbody cage support are as follows: 1) large segmental lordosis can decrease the stiffness of monoaxial pedicle screws constructs; 2) polyaxial screws rather than monoaxial screws combined with the cage fixation provide higher compression and flexion stiffness in 21° segmental lordosis; 3) polyaxial screws enhance the contact surface of the cage in 21° segmental lordosis. CONCLUSION: Polyaxial screws system used in conjunction with anterior cage support yields higher contact ratio, compression and flexion stiffness of spinal constructs than monoaxial screws system does in the same model when the spinal segment is set at large lordotic angles. Polyaxial pedicle screw fixation performs nearly equal percentages of vertebra-cage contact among all constructs with different sagittal alignments, therefore enhances the stabilization effect of interbody cages in the lumbosacral area

Biomechanical comparison of a new stand-alone anterior lumbar interbody fusion cage with established fixation techniques – a three-dimensional finite element analysis

<p>Abstract</p> <p>Background</p> <p>Initial promise of a stand-alone interbody fusion cage to treat chronic back pain and restore disc height has not been realized. In some instances, a posterior spinal fixation has been used to enhance stability and increase fusion rate. In this manuscript, a new stand-alone cage is compared with conventional fixation methods based on the finite element analysis, with a focus on investigating cage-bone interface mechanics and stress distribution on the adjacent tissues.</p> <p>Methods</p> <p>Three trapezoid 8° interbody fusion cage models (dual paralleled cages, a single large cage, or a two-part cage consisting of a trapezoid box and threaded cylinder) were created with or without pedicle screws fixation to investigate the relative importance of the screws on the spinal segmental response. The contact stress on the facet joint, slip displacement of the cage on the endplate, and rotational angle of the upper vertebra were measured under different loading conditions.</p> <p>Results</p> <p>Simulation results demonstrated less facet stress and slip displacement with the maximal contact on the cage-bone interface. A stand-alone two-part cage had good slip behavior under compression, flexion, extension, lateral bending and torsion, as compared with the other two interbody cages, even with the additional posterior fixation. However, the two-part cage had the lowest rotational angles under flexion and torsion, but had no differences under extension and lateral bending.</p> <p>Conclusion</p> <p>The biomechanical benefit of a stand-alone two-part fusion cage can be justified. This device provided the stability required for interbody fusion, which supports clinical trials of the cage as an alternative to circumferential fixations.</p

Total disc replacement for chronic back pain in the presence of disc degeneration

Scientific Assessment and Innovation in Neurosurgical Treatment Strategie