The influence of spinal venous blood pressure on cerebrospinal fluid pressure.

In Alligator mississippiensis the spinal dura is surrounded by a venous sinus; pressure waves can propagate in the spinal venous blood, and these spinal venous pressures can be transmitted to the spinal cerebrospinal fluid (CSF). This study was designed to explore pressure transfer between the spinal venous blood and the spinal CSF. At rest the cardiac-related CSF pulsations are attenuated and delayed, while the ventilatory-related pulsations are amplified as they move from the spinal venous blood to the spinal CSF. Orthostatic gradients resulted in significant alterations of both cardiac- and ventilatory-related CSF pulsations. Manual lateral oscillations of the alligator's tail created pressure waves in the spinal CSF that propagated, with slight attenuation but no delay, to the cranial CSF. Oscillatory pressure pulsations in the spinal CSF and venous blood had little influence on the underlying ventilatory pulsations, though the same oscillatory pulsations reduced the ventilatory- and increased the cardiac-related pulsations in the cranial CSF. In Alligator the spinal venous anatomy creates a more complex pressure relationship between the venous and CSF systems than has been described in humans.

Measuring College Students' with Disabilities Attitudes Toward Taking COVID-19 Vaccines.

This survey explores attitudes of 245 currently enrolled college students with disabilities regarding their comfort taking a COVID-19 vaccine. Results suggest most college students with disabilities are willing to take a COVID-19 vaccine if their institution requires it to return to campus in subsequent semesters. However, many students with disabilities would not feel comfortable with a vaccine mandate mid-semester and would consider withdrawing, especially among older students with disabilities and first generation college students with disabilities. Implications for postsecondary policy and leadership are addressed.

Gene Expression Differences Between Young Adults Based on Trauma History and Post-traumatic Stress Disorder.

Background: The purpose of this study was to identify gene expression differences associated with post-traumatic stress disorder (PTSD) and trauma exposure (TE) in a three-group study design comprised of those with and without trauma exposure and PTSD. Methods: We conducted gene expression and gene network analyses in a sample (n = 45) composed of female subjects of European Ancestry (EA) with PTSD, TE without PTSD, and controls. Results: We identified 283 genes differentially expressed between PTSD-TE groups. In an independent sample of Veterans (n = 78) a small minority of these genes were also differentially expressed. We identified 7 gene network modules significantly associated with PTSD and TE (Bonferroni corrected p ≤ 0.05), which at a false discovery rate (FDR) of q ≤ 0.2, were significantly enriched for biological pathways involved in focal adhesion, neuroactive ligand receptor interaction, and immune related processes among others. Conclusions: This study uses gene network analyses to identify significant gene modules associated with PTSD, TE, and controls. On an individual gene level, we identified a large number of differentially expressed genes between PTSD-TE groups, a minority of which were also differentially expressed in the independent sample. We also demonstrate a lack of network module preservation between PTSD and TE, suggesting that the molecular signature of PTSD and trauma are likely independent of each other. Our results provide a basis for the identification of likely disease pathways and biomarkers involved in the etiology of PTSD.

Organellomic data sets confirm a cryptic consensus on (unrooted) land-plant relationships and provide new insights into bryophyte molecular evolution.

PREMISE: Phylogenetic trees of bryophytes provide important evolutionary context for land plants. However, published inferences of overall embryophyte relationships vary considerably. We performed phylogenomic analyses of bryophytes and relatives using both mitochondrial and plastid gene sets, and investigated bryophyte plastome evolution. METHODS: We employed diverse likelihood-based analyses to infer large-scale bryophyte phylogeny for mitochondrial and plastid data sets. We tested for changes in purifying selection in plastid genes of a mycoheterotrophic liverwort (Aneura mirabilis) and a putatively mycoheterotrophic moss (Buxbaumia), and compared 15 bryophyte plastomes for major structural rearrangements. RESULTS: Overall land-plant relationships conflict across analyses, generally weakly. However, an underlying (unrooted) four-taxon tree is consistent across most analyses and published studies. Despite gene coverage patchiness, relationships within mosses, liverworts, and hornworts are largely congruent with previous studies, with plastid results generally better supported. Exclusion of RNA edit sites restores cases of unexpected non-monophyly to monophyly for Takakia and two hornwort genera. Relaxed purifying selection affects multiple plastid genes in mycoheterotrophic Aneura but not Buxbaumia. Plastid genome structure is nearly invariant across bryophytes, but the tufA locus, presumed lost in embryophytes, is unexpectedly retained in several mosses. CONCLUSIONS: A common unrooted tree underlies embryophyte phylogeny, [(liverworts, mosses), (hornworts, vascular plants)]; rooting inconsistency across studies likely reflects substantial distance to algal outgroups. Analyses combining genomic and transcriptomic data may be misled locally for heavily RNA-edited taxa. The Buxbaumia plastome lacks hallmarks of relaxed selection found in mycoheterotrophic Aneura. Autotrophic bryophyte plastomes, including Buxbaumia, hardly vary in overall structure.

Highly integrated workflows for exploring cardiovascular conditions: Exemplars of precision medicine in Alzheimer's disease and aortic dissection.

For precision medicine to be implemented through the lens of in silico technology, it is imperative that biophysical research workflows offer insight into treatments that are specific to a particular illness and to a particular subject. The boundaries of precision medicine can be extended using multiscale, biophysics-centred workflows that consider the fundamental underpinnings of the constituents of cells and tissues and their dynamic environments. Utilising numerical techniques that can capture the broad spectrum of biological flows within complex, deformable and permeable organs and tissues is of paramount importance when considering the core prerequisites of any state-of-the-art precision medicine pipeline. In this work, a succinct breakdown of two precision medicine pipelines developed within two Virtual Physiological Human (VPH) projects are given. The first workflow is targeted on the trajectory of Alzheimer's Disease, and caters for novel hypothesis testing through a multicompartmental poroelastic model which is integrated with a high throughput imaging workflow and subject-specific blood flow variability model. The second workflow gives rise to the patient specific exploration of Aortic Dissections via a multi-scale and compliant model, harnessing imaging, computational fluid-dynamics (CFD) and dynamic boundary conditions. Results relating to the first workflow include some core outputs of the multiporoelastic modelling framework, and the representation of peri-arterial swelling and peri-venous drainage solution fields. The latter solution fields were statistically analysed for a cohort of thirty-five subjects (stratified with respect to disease status, gender and activity level). The second workflow allowed for a better understanding of complex aortic dissection cases utilising both a rigid-wall model informed by minimal and clinically common datasets as well as a moving-wall model informed by rich datasets.

Who's challenging who training for staff empathy towards adults with challenging behaviour: cluster randomised controlled trial.

BACKGROUND: One in five adults with intellectual disabilities (ID) known to services display challenging behaviours (CBs), and these individuals are at risk for restrictive practices and poor care. Staff attitudes may contribute to the development and/or maintenance of CBs. We investigated the effectiveness of co-produced Who's Challenging Who? training delivered by people with ID to staff. METHOD: This study involved a cluster randomised controlled trial (RCT) of Who's Challenging Who? training with follow-up at six and 20 weeks post-randomisation. PARTICIPANTS: two staff from each of 118 residential care settings for adults with ID at least one of whom displayed aggressive CB. PRIMARY OUTCOME: Self-reported Staff Empathy for people with Challenging Behaviour Questionnaire. ANALYSIS: intention to treat of all randomised settings. ISCRTN registration: ISRCTN53763600. RESULTS: 118 residential settings (including 236 staff) were randomised to either receive training (59 settings) or to receive training after a delay (59 settings). The primary analysis included data from 121 staff in 76 settings (51% of staff, 64% of settings). The adjusted mean difference on the transformed (cubed) Staff Empathy for people with Challenging Behaviour Questionnaire score at the primary end point was 1073.2 (95% CI: -938.1 to 3084.5, P = 0.296) in favour of the intervention group (effect size Cohen's d = .19). CONCLUSIONS: This is the first large-scale RCT of a co-produced training course delivered by people with ID. Findings indicated a small positive (but statistically non-significant) effect on increased staff empathy at 20 weeks, and small to moderate effects for staff reported secondary outcomes in favour of the intervention group.

Breast milk transmission of flaviviruses in the context of Zika virus: A systematic review.

BACKGROUND: Since the Zika virus epidemic in the Americas began in 2015, Zika virus transmission has occurred throughout the Americas. However, limited information exists regarding possible risks of transmission of Zika virus and other flaviviruses through breast feeding and human milk. We conducted a systematic review of the evidence regarding flaviviruses detection in and transmission through milk, specifically regarding Zika virus, Japanese encephalitis virus, tick-borne encephalitis virus, Powassan virus, West Nile virus, dengue virus, and yellow fever virus. METHODS: Medline, Embase, Global Health, CINAHL, Cochrane Library, Scopus, Popline, Virtual Health Library, and WorldCat were searched through June 2017. Two authors independently screened potential studies for inclusion and extracted data. Human and nonhuman (animal) studies describing: 1) confirmed or suspected cases of mother-to-child transmission through milk; or 2) the presence of flavivirus genomic material in milk. RESULTS: Seventeen studies were included, four animal models and thirteen observational studies. Dengue virus, West Nile virus, and Zika virus viral ribonucleic acid was detected in human milk, including infectious Zika virus and dengue virus viral particles. Human breast-feeding transmission was confirmed for only yellow fever virus. There was evidence of milk-related transmission of dengue virus, Powassan virus, and West Nile virus in animal studies. CONCLUSIONS: Because the health advantages of breast feeding are considered greater than the potential risk of transmission, the World Health Organization recommends that mothers with possible or confirmed Zika virus infection or exposure continue to breast feed. This review did not identify any data that might alter this recommendation.

An examination of the elastic properties of tissue-mimicking phantoms using vibro-acoustography and a muscle motor system.

Tissue hardness, often quantified in terms of elasticity, is an important differentiating criterion for pathological identity and is extensively used by surgeons for tumor localization. Delineation of malignant regions from benign regions is typically performed by visual inspection and palpation. Although practical, this method is highly subjective and does not provide quantitative metrics. We have previously reported on Vibro-Acoustography (VA) for tumor delineation. VA is unique in that it uses the specific, non-linear properties of tumor tissue in response to an amplitude modulated ultrasound beam to generate spatially resolved, high contrast maps of tissue. Although the lateral and axial resolutions (sub-millimeter and sub-centimeter, respectively) of VA have been extensively characterized, the relationship between static stiffness assessment (palpation) and dynamic stiffness characterization (VA) has not been explicitly established. Here we perform a correlative exploration of the static and dynamic properties of tissue-mimicking phantoms, specifically elasticity, using VA and a muscle motor system. Muscle motor systems, commonly used to probe the mechanical properties of materials, provide absolute, quantitative point measurements of the elastic modulus, analogous to Young's modulus, of a target. For phantoms of varying percent-by-weight concentrations, parallel VA and muscle motor studies conducted on 18 phantoms reveal a negative correlation (p < - 0.85) between mean signal amplitude levels observed with VA and calculated elastic modulus values from force vs. indentation depth curves. Comparison of these elasticity measurements may provide additional information to improve tissue modeling, system characterization, as well as offer valuable insights for in vivo applications, specifically surgical extirpation of tumors.

The Complete Moss Mitochondrial Genome in the Angiosperm Amborella Is a Chimera Derived from Two Moss Whole-Genome Transfers.

Sequencing of the 4-Mb mitochondrial genome of the angiosperm Amborella trichopoda has shown that it contains unprecedented amounts of foreign mitochondrial DNA, including four blocks of sequences that together correspond almost perfectly to one entire moss mitochondrial genome. This implies whole-genome transfer from a single moss donor but conflicts with phylogenetic results from an earlier, PCR-based study that suggested three different moss donors to Amborella. To resolve this conflict, we conducted an expanded set of phylogenetic analyses with respect to both moss lineages and mitochondrial loci. The moss DNA in Amborella was consistently placed in either of two positions, depending on the locus analyzed, as sister to the Ptychomniales or within the Hookeriales. This agrees with two of the three previously suggested donors, whereas the third is no longer supported. These results, combined with synteny analyses and other considerations, lead us to favor a model involving two successive moss-to-Amborella whole-genome transfers, followed by recombination that produced a single intact and chimeric moss mitochondrial genome integrated in the Amborella mitochondrial genome. Eight subsequent recombination events account for the state of fragmentation, rearrangement, duplication, and deletion of this chimeric moss mitochondrial genome as it currently exists in Amborella. Five of these events are associated with short-to-intermediate sized repeats. Two of the five probably occurred by reciprocal homologous recombination, whereas the other three probably occurred in a non-reciprocal manner via microhomology-mediated break-induced replication (MMBIR). These findings reinforce and extend recent evidence for an important role of MMBIR in plant mitochondrial DNA evolution.

Detection and modelling of contacts in explicit finite-element simulation of soft tissue biomechanics.

PURPOSE: Realistic modelling of soft tissue biomechanics and mechanical interactions between tissues is an important part of biomechanically-informed surgical image-guidance and surgical simulation. This submission details a contact-modelling pipeline suitable for implementation in explicit matrix-free FEM solvers. While these FEM algorithms have been shown to be very suitable for simulation of soft tissue biomechanics and successfully used in a number of image-guidance systems, contact modelling specifically for these solvers is rarely addressed, partly because the typically large number of time steps required with this class of FEM solvers has led to a perception of them being a poor choice for simulations requiring complex contact modelling. METHODS: The presented algorithm is capable of handling most scenarios typically encountered in image-guidance. The contact forces are computed with an evolution of the Lagrange-multiplier method first used by Taylor and Flanagan in PRONTO 3D extended with spatio-temporal smoothing heuristics for improved stability and edge-edge collision handling, and a new friction model. For contact search, a bounding-volume hierarchy (BVH) is employed, which is capable of identifying self-collisions by means of the surface-normal bounding cone of Volino and Magnenat-Thalmann, in turn computed with a novel formula. The BVH is further optimised for the small time steps by reducing the number of bounding-volume refittings between iterations through identification of regions with mostly rigid motion and negligible deformation. Further optimisation is achieved by integrating the self-collision criterion in the BVH creation and updating algorithms. RESULTS: The effectiveness of the algorithm is demonstrated on a number of artificial test cases and meshes derived from medical image data. It is shown that the proposed algorithm reduces the cost of BVH refitting to the point where it becomes a negligible part of the overall computation time of the simulation. It is also shown that the proposed surface-normal cone computation formula leads to about 40 % fewer BVH subtrees that must be checked for self-collisions compared with the widely used method of Provot. The proposed contact-force formulation and friction model are evaluated on artificial test cases that allow for a comparison with a ground truth. The quality of the proposed contact forces is assessed in terms of trajectories and energy conservation; a [Formula: see text]0.4 % drop off in total energy and highly plausible trajectories are found in the experiments. The friction model is evaluated through a benchmark problem with an analytical solution and a maximum displacement error of 8.2 %, and excellent agreement in terms of the stick/slip boundary is found. Finally, we show with realistic image-guidance examples that the entire contact-modelling pipeline can be executed within a timeframe that is of the same order of magnitude as that required for standard FEM computations.

Leptin may play a role in bone microstructural alterations in obese children.

CONTEXT: Bone mass is low and fracture risk is higher in obese children. Hormonal changes in relation to skeletal microstructure and biomechanics have not been studied in obese children. OBJECTIVE: The objective of the study was to ascertain the relationships of obesity-related changes in hormones with skeletal microstructure and biomechanics. DESIGN: High resolution peripheral quantitative computed tomography (HR-pQCT) was used to compare three-dimensional cortical and trabecular microstructure and biomechanics at load-bearing and nonload bearing sites in obese and lean children. The relationship between leptin, adiponectin, testosterone, estrogen, osteocalcin and sclerostin and skeletal microstructure was also determined. SETTING: The study was conducted at a tertiary pediatric endocrine unit in the United Kingdom. PARTICIPANTS: Obese and lean children were matched by gender and pubertal stage. RESULTS: Radial cortical porosity (mean difference -0.01 [95% CI: -0.02, -0.004], P = .003) and cortical pore diameter (mean difference -0.005 mm [95% CI: -0.009, -0.001], P = .011) were lower in obese children. Tibial trabecular thickness was lower (mean difference -0.009 mm [95% CI: -0.014, -0.004], P = .003), and trabecular number was higher (mean difference 0.23 mm(-1) [95% CI: 0.08, 0.38], P = .004) in obese children. At the radius, fat mass percentage negatively correlated with cortical porosity (r = -0.57, P < .001) and pore diameter (r = -0.38, P = .02) and negatively correlated with trabecular thickness (r = -0.62, P < .001) and trabecular von Mises stress (r = -0.39, P = .019) at the tibia. No difference was observed in the other biomechanical parameters of the radius and tibia. Leptin was higher in obese children (805.3 ± 440.6 pg/ml vs 98.1 ± 75.4 pg/ml, P < .001) and was inversely related to radial cortical porosity (r = 0.60, 95% CI: [-0.80, -0.30], P < .001), radial cortical pore diameter (r = 0.51, 95% CI [-0.75, -0.16], P = .002), tibial trabecular thickness (r = 0.55, 95% CI: [-0.78, -0.21], P = .001) and tibial trabecular von Mises stress (r = -0.39, 95% CI: -0.65, 0.04, P = .02). CONCLUSION: Childhood obesity alters radial and tibial microstructure. Leptin may direct these changes. Despite this, the biomechanical properties of the radius and tibia do not adapt sufficiently in obese children to withstand the increased loading potential from a fall. This may explain the higher incidence of fracture in obese children.

Landscape models for nuclear genetic diversity and genetic structure in white-footed mice (Peromyscus leucopus).

Dramatic changes in the North American landscape over the last 12 000 years have shaped the genomes of the small mammals, such as the white-footed mouse (Peromyscus leucopus), which currently inhabit the region. However, very recent interactions of populations with each other and the environment are expected to leave the most pronounced signature on rapidly evolving nuclear microsatellite loci. We analyzed landscape characteristics and microsatellite markers of P. leucopus populations along a transect from southern Ohio to northern Michigan, in order to evaluate hypotheses about the spatial distribution of genetic heterogeneity. Genetic diversity increased to the north and was best approximated by a single-variable model based on habitat availability within a 0.5-km radius of trapping sites. Interpopulation differentiation measured by clustering analysis was highly variable and not significantly related to latitude or habitat availability. Interpopulation differentiation measured as FST values and chord distance was correlated with the proportion of habitat intervening, but was best explained by agricultural distance and by latitude. The observed gradients in diversity and interpopulation differentiation were consistent with recent habitat availability being the major constraint on effective population size in this system, and contradicted the predictions of both the postglacial expansion and core-periphery hypotheses.

Synergistic activity of rapamycin and dexamethasone in vitro and in vivo in acute lymphoblastic leukemia via cell-cycle arrest and apoptosis.

Activation of the mTOR pathway subsequent to phosphatase and tensin homolog (PTEN) mutation may be associated with glucocorticoid (GC) resistance in acute lymphoblastic leukemia (ALL). The combination activity of rapamycin and dexamethasone in cell lines and xenograft models of ALL was determined. Compared with either drug alone, dexamethasone+rapamycin showed significantly greater apoptosis and cell cycle arrest in some cell lines, and was more frequently seen in T-lineage cell lines with PTEN mutation. The combination significantly extended the event-free survival of mice carrying PTEN mutated xenografts. Our data suggest that PI3K/mTOR pathway inhibitors could benefit patients with PTEN mutated T-ALL.

Prescribing competence of junior doctors: does it add up?

BACKGROUND: Prescribing errors complicate a significant number of paediatric admissions. Ongoing training and monitoring of prescribing competency in junior doctors has occurred in Cardiff since 2001, alongside national measures aimed at improving training and competency. AIM: Ongoing monitoring of junior doctors' prescribing competency to assess the effect of these national and local initiatives. METHODS: Junior doctors receive training and subsequent assessment on prescribing competency at induction. A 1 h bleep-free session concerning paediatric prescribing precedes completion of four prescribing tasks. British National Formulary for children and calculators are provided. Those scoring 0 or 1 are retrained before prescribing is permitted. Our previously published data of doctors between 2001 and 2004 was compared with assessment in 2007. RESULTS: 30 junior doctors were assessed in 2007 (32 in 2001-2004). All four questions were answered correctly by 22/30, compared to 10/32 (31%) in 2001-2004. The mean score in 2007 was 93.3% compared to 57.8% previously (see table 1). Comparison of means with previous results demonstrated statistically significant improvement with a mean difference of 36% (95% CI 24 to 47). In 2007, eight (27%) doctors got just one question wrong and no doctor answered all questions incorrectly. In 2001-2004, 22/32 (67%) made at least one error during previous assessment, and one doctor answered all questions incorrectly. Table 1Prescribing assessment scores in 2001-2004 and 2007 Answer scores2001-2004 (n=32)2007 (n=30)All questions correct10 (31%)22 (73%)One incorrect08 (27%)Two incorrect13 (41%)0Three incorrect8 (25%)0All questions incorrect1 (3%)0 CONCLUSION: Ongoing monitoring of junior doctors' prescribing ability has demonstrated improvements which may be due to local and national training initiatives.

Toward a 1550 nm InGaAs photoconductive switch for terahertz generation.

We report a terahertz (THz) photoconductive switch made from a composite of metal ErAs nanoparticles embedded in In(0.53)Ga(0.47)As and coupled to a square spiral antenna. The THz output power was measured in a 77 K cryostat by using a standard hyperhemisphere-lens package, a Golay cell outside the cryostat, and a quasi-optical filter bank for spot frequency spectral measurements. Results indicate an average output power of approximately 12 microW at 22 V bias using 140 mW of optical pump power from a subpicosecond fiber mode-locked laser. In addition, the THz spectra displayed invariance to bias voltage despite operating near impact ionization.

On modelling of anisotropic viscoelasticity for soft tissue simulation: numerical solution and GPU execution.

Efficient and accurate techniques for simulation of soft tissue deformation are an increasingly valuable tool in many areas of medical image computing, such as biomechanically-driven image registration and interactive surgical simulation. For reasons of efficiency most analyses are based on simplified linear formulations, and previously almost all have ignored well established features of tissue mechanical response such as anisotropy and time-dependence. We address these latter issues by firstly presenting a generalised anisotropic viscoelastic constitutive framework for soft tissues, particular cases of which have previously been used to model a wide range of tissues. We then develop an efficient solution procedure for the accompanying viscoelastic hereditary integrals which allows use of such models in explicit dynamic finite element algorithms. We show that the procedure allows incorporation of both anisotropy and viscoelasticity for as little as 5.1% additional cost compared with the usual isotropic elastic models. Finally we describe the implementation of a new GPU-based finite element scheme for soft tissue simulation using the CUDA API. Even with the inclusion of more elaborate constitutive models as described the new implementation affords speed improvements compared with our recent graphics API-based implementation, and compared with CPU execution a speed up of 56.3 x is achieved. The validity of the viscoelastic solution procedure and performance of the GPU implementation are demonstrated with a series of numerical examples.

A simplified gentamicin dosing chart is quicker and more accurate for nurse verification than the BNFc.

BACKGROUND: At least 5% of paediatric admissions are complicated by medication error. Nurses can prevent some errors by correctly verifying prescriptions before administering drugs, which requires adequate drug calculation skills and familiarity with the BNFc. We wished to explore whether a newly devised chart would improve nurses' dose calculation ability and thus potentially reduce doctors' prescription errors. AIMS: To explore nurses' ability to calculate doses of gentamicin for neonates and children using a new simple dosing chart compared with the BNFc. METHODS: Two gentamicin dosing charts (paediatric and neonatal) devised by a multidisciplinary group to simplify dose calculation and selection of frequency were compared with the BNFc using four questions (two neonatal, two paediatric) asking ward nurses to calculate gentamicin doses. Answers were scored for both the correct dosage and correct frequency. RESULTS: 51 nurses participated. 11 nurses (22%) answered all four questions correctly. A higher proportion correctly answered both the dosage and frequency questions simultaneously when using the chart compared with the BNFc: paediatric questions 100% (51/51 chart) versus 80% (41/51 BNFc) (OR 0.20) and neonatal questions 55% (28/51 chart) versus 35% (18/51 BNFc) (OR 0.2). Errors when using the BNFc were due to selection of the incorrect regimen (23%), wrong frequency (17%) and one 10-fold dosing error. When using the chart, there were no dosing errors, only frequency errors for the neonatal regimen. CONCLUSION: The chart was more reliable, quicker and may be useful for patient safety. Revising the format of the BNFc may be beneficial for nurses.

Reflective terahertz imaging of porcine skin burns.

A reflective pulsed terahertz imaging system based on direct detection was developed and used to obtain high-resolution images of a porcine skin specimen with superficial partial-thickness (second-degree) burns. Images were also obtained of the sample through ten layers of dry medical (cotton) gauze with minimal image degradation. The burned and unburned regions of skin had large differences in terahertz reflectivity, displaying clear delineation [20 dB signal-to-noise ratio (SNR) difference signal] between both regions in the images. The terahertz images also exhibited a "halo" surrounding the burn areas that may correlate to the extent of burn injury. The system operated at a center frequency of 500 GHz with 125 GHz of 3 dB bandwidth and used whiskbroom scanning to generate images with a spatial resolution of 1.5 mm. Each pixel was acquired with a 16 ms integration time, resulting in a 40 dB postdetection SNR. The simplicity and high SNR of the reflective terahertz system are promising steps toward real-time terahertz medical imaging.

High-speed nonlinear finite element analysis for surgical simulation using graphics processing units.

The use of biomechanical modelling, especially in conjunction with finite element analysis, has become common in many areas of medical image analysis and surgical simulation. Clinical employment of such techniques is hindered by conflicting requirements for high fidelity in the modelling approach, and fast solution speeds. We report the development of techniques for high-speed nonlinear finite element analysis for surgical simulation. We use a fully nonlinear total Lagrangian explicit finite element formulation which offers significant computational advantages for soft tissue simulation. However, the key contribution of the work is the presentation of a fast graphics processing unit (GPU) solution scheme for the finite element equations. To the best of our knowledge, this represents the first GPU implementation of a nonlinear finite element solver. We show that the present explicit finite element scheme is well suited to solution via highly parallel graphics hardware, and that even a midrange GPU allows significant solution speed gains (up to 16.8 x) compared with equivalent CPU implementations. For the models tested the scheme allows real-time solution of models with up to 16,000 tetrahedral elements. The use of GPUs for such purposes offers a cost-effective high-performance alternative to expensive multi-CPU machines, and may have important applications in medical image analysis and surgical simulation.