Alison Noble

The biology of platelet-rich plasma and its application in trauma and orthopaedic surgery: a review of the literature.

Although mechanical stabilisation has been a hallmark of orthopaedic surgical management, orthobiologics are now playing an increasing role. Platelet-rich plasma (PRP) is a volume of plasma fraction of autologous blood having platelet concentrations above baseline. The platelet alpha granules are rich in growth factors that play an essential role in tissue healing, such as transforming growth factor-beta, vascular endothelial growth factor, and platelet-derived growth factor. PRP is used in various surgical fields to enhance bone and soft-tissue healing by placing supraphysiological concentrations of autologous platelets at the site of tissue damage. The easily obtainable PRP and its possible beneficial outcome hold promise for new regenerative treatment approaches. The aim of this literature review was to describe the bioactivities of PRP, to elucidate the different techniques for PRP preparation, to review animal and human studies, to evaluate the evidence regarding the use of PRP in trauma and orthopaedic surgery, to clarify risks, and to provide guidance for future research.

International standards for newborn weight, length, and head circumference by gestational age and sex: the Newborn Cross-Sectional Study of the INTERGROWTH-21st Project

BACKGROUND In 2006, WHO published international growth standards for children younger than 5 years, which are now accepted worldwide. In the INTERGROWTH-21(st) Project, our aim was to complement them by developing international standards for fetuses, newborn infants, and the postnatal growth period of preterm infants. METHODS INTERGROWTH-21(st) is a population-based project that assessed fetal growth and newborn size in eight geographically defined urban populations. These groups were selected because most of the health and nutrition needs of mothers were met, adequate antenatal care was provided, and there were no major environmental constraints on growth. As part of the Newborn Cross-Sectional Study (NCSS), a component of INTERGROWTH-21(st) Project, we measured weight, length, and head circumference in all newborn infants, in addition to collecting data prospectively for pregnancy and the perinatal period. To construct the newborn standards, we selected all pregnancies in women meeting (in addition to the underlying population characteristics) strict individual eligibility criteria for a population at low risk of impaired fetal growth (labelled the NCSS prescriptive subpopulation). Women had a reliable ultrasound estimate of gestational age using crown-rump length before 14 weeks of gestation or biparietal diameter if antenatal care started between 14 weeks and 24 weeks or less of gestation. Newborn anthropometric measures were obtained within 12 h of birth by identically trained anthropometric teams using the same equipment at all sites. Fractional polynomials assuming a skewed t distribution were used to estimate the fitted centiles. FINDINGS We identified 20,486 (35%) eligible women from the 59,137 pregnant women enrolled in NCSS between May 14, 2009, and Aug 2, 2013. We calculated sex-specific observed and smoothed centiles for weight, length, and head circumference for gestational age at birth. The observed and smoothed centiles were almost identical. We present the 3rd, 10th, 50th, 90th, and 97th centile curves according to gestational age and sex. INTERPRETATION We have developed, for routine clinical practice, international anthropometric standards to assess newborn size that are intended to complement the WHO Child Growth Standards and allow comparisons across multiethnic populations. FUNDING Bill & Melinda Gates Foundation.

Contrast enhancement and segmentation of ultrasound images: a statistical method

Ultrasound B-scan images often exhibit intensity inhomogeneities caused by non-uniform beam attenuation within the body. These cause major problems for image analysis, both by manual and computer-aided techniques, particularly the computation of quantitative measurements. We present a statistical model that exploits knowledge of tissue properties and intensity inhomogeneities in ultrasound for simultaneous contrast enhancement and image segmentation. The underlying model was originally proposed for correction of the B1 bias field distortion and segmentation of magnetic resonance (MR) images. A physics-based model of intensity inhomogeneities in ultrasound images shows that the bias field correction method is well suited to ultrasound B-scan images. The tissue class labeling and the intensity correction field are estimated using the maximum a posteriori (MAP) principle, in an iterative, multi-resolution manner. The algorithm has been applied to breast and cardiac ultrasound images. The results demonstrate that it can successfully remove intensity inhomogeneities caused by varying attenuation as well as uninteresting intensity changes of background tissues. With the removal of intensity inhomogeneities, significant improvement is achieved in tissue contrast and segmentation result.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

P4D-7 Nonlinear Propagation of Ultrasound Through Microbubble Clouds: A Novel Numerical Implementation

Nonlinear propagation of ultrasound can cause imaging errors in the context of medical ultrasound with microbubble ultrasound contrast agents. Modelling nonlinear propagation of ultrasound through a microbubble cloud is therefore essential for simulating the phenomenon to understand the causes of these errors and to develop suitable error correction techniques to reduce these imaging errors. Such models do exist but large discrepancies are found when simulation results are compared to experimental data. In this work the reasons for these inaccuracies are examined and a more realistic approach is proposed.

Body composition at birth and its relationship with neonatal anthropometric ratios: the newborn body composition study of the INTERGROWTH-21st project

BackgroundWe aimed to describe newborn body composition and identify which anthropometric ratio (weight/length; BMI; or ponderal index, PI) best predicts fat mass (FM) and fat-free mass (FFM).MethodsAir-displacement plethysmography (PEA POD) was used to estimate FM, FFM, and body fat percentage (BF%). Associations between FFM, FM, and BF% and weight/length, BMI, and PI were evaluated in 1,019 newborns using multivariate regression analysis. Charts for FM, FFM, and BF% were generated using a prescriptive subsample (n=247). Standards for the best-predicting anthropometric ratio were calculated utilizing the same population used for the INTERGROWTH-21st Newborn Size Standards (n=20,479).ResultsFFM and FM increased consistently during late pregnancy. Differential FM, BF%, and FFM patterns were observed for those born preterm (34+0−36+6 weeks’ gestation) and with impaired intrauterine growth. Weight/length by gestational age (GA) was a better predictor of FFM and FM (adjusted R2=0.92 and 0.71, respectively) than BMI or PI, independent of sex, GA, and timing of measurement. Results were almost identical when only preterm newborns were studied. We present sex-specific centiles for weight/length ratio for GA.ConclusionsWeight/length best predicts newborn FFM and FM. There are differential FM, FFM, and BF% patterns by sex, GA, and size at birth.

Ultrasound phase velocities in SonoVue ™ as a function of pressure and bubble concentration

This work investigates the effects of insonating pressure on ultrasound phase velocity in the SonoVue™ microbubble suspension. Ultrasound transmission measurements were carried out using a single element transducer and calibrated needle hydrophone, for a range of SonoVue™ concentrations from 50 to 800µl/l. Phase velocity was calculated using an established method based on the phase difference between pulses transmitted through the contrast agent and reference pulses for a range of insonating pressures from 13 to 128 kPa. Phase velocity was shown to be dependent on frequency, insonating pressure and SonoVue™ concentration. The relationship between pressure and phase velocity was found to be approximately linear, with the pressure-velocity gradient increasing with concentration. These results may have significant implications for contrast-enhanced ultrasonography, for example in understanding artifact generation and quantitative applications such as estimating local bubble concentration.

On computing aspect graphs of smooth shapes from volumetric data

The authors address the problem of computing the aspect graph of an object from volumetric image data, with applications in medical image analysis and interpretation. Anatomical surfaces are assumed to be smooth and are identified as the zero set of a three-dimensional density function (e.g., a CT, MR, or ultrasound image). The orthographic-projection aspect graph is constructed by partitioning the view sphere at infinity into maximal regions bounded by visual event curves. These events are the intersections of the view sphere with surfaces ruled by singular tangent lines that graze the objects surface along a set of critical curves. For each visual event the proposed algorithm constructs a new density function from the original one and its derivatives, and computes the corresponding critical curve as the intersection of the objects surface with the zero set of the new density function. Once the critical curves have been traced, the regions of the sphere delineated by the corresponding visual events are constructed through cell decomposition, and a representative aspect is constructed for each region by computing the occluding contour for a sample viewing direction. A preliminary implementation of the proposed approach has been constructed and experiments with synthetic data and real medical data are presented. Extensions to the sectional imaging case are also discussed.

A passive array technique for cavitation mapping during HIFU treatment

During exposure of tissue to HIFU, cavitation has been shown to enhance the rate of heat deposition in tissue and could provide an effective means of treatment monitoring. However, cavitation activity occurring pre‐focally or growing unstable around the focal region is known to impede safe and effective treatment delivery. A combined computational and experimental approach is being applied to develop a passive array‐based technique for mapping cavitation activity in real‐time, using a novel cross‐correlation algorithm to combine single‐channel information received by an imaging array co‐axial to the HIFU transducer. The cavitation maps produced in this manner were validated using two single‐element 15‐MHz focused PCDs during continuous‐wave insonation of a polyacrylamide‐based tissue mimicking material by 1.1 MHz HIFU. Initial experiments have shown bubble cloud movement towards the HIFU transducer, in agreement with previously reported observations. Future work will involve applications of advanced imagi...

HTX: a tool for the exploration and visualization of high-throughput image assays

High-throughput screening (HTS) techniques have enabled large scale image-based studies, but extracting biological insights from the imaging data in an exploratory setting remains a challenge. Existing packages for this task either require expert annotations, which can bias the outcome of the study, or are completely unsupervised, failing to leverage the information present in the assay design. We present HTX, an interactive tool to aid in the exploration of large microscopy data sets by allowing the visualization of entire image-based assays according to visual similarities between the samples in an intuitive and navigable manner. Underlying HTX are a collection of novel algorithmic techniques for deep texture descriptor learning, 2D data visualization, adversarial suppression of batch effects, and backprop-based image saliency estimation. We demonstrate that HTX can exploit the screen meta-data in order to learn screen-specific image descriptors, which are then used to quantify the visual similarity between samples in the assay. Given these similarities and the different visualization resources of HTX, it is shown that screens of small-molecule libraries on cell data can be easily explored, reproducing the results of previous studies where highly-specific domain knowledge was required.

An approach to the symbolic representation of brain arteriovenous malformations for management and treatment planning

IntroductionThere is currently no standardised approach to arteriovenous malformation (AVM) reporting. Existing AVM classification systems focuses on angioarchitectural features and omit haemodynamic, anatomical and topological parameters intuitively used by therapists.MethodsWe introduce a symbolic vocabulary to represent the state of an AVM of the brain at different stages of treatment. The vocabulary encompasses the main anatomic and haemodynamic features of interest in treatment planning and provides shorthand symbols to represent the interventions themselves in a schematic representation.ResultsThe method was presented to 50 neuroradiologists from14 countries during a workshop and graded 7.34 ± 1.92 out of ten for its usefulness as means of standardising and facilitating communication between clinicians and allowing comparisons between AVM cases. Feedback from the survey was used to revise the method and improve its completeness. For an AVM test case, participants were asked to produce a conventional written report and subsequently a diagrammatic report. The two required, on average, 6.19 ± 2.05 and 5.09 ± 3.01 min, respectively. Eighteen participants said that producing the diagram changed the way they thought about the AVM test case.ConclusionIntroduced into routine practice, the diagrams would represent a step towards a standardised approach to AVM reporting with consequent benefits for comparative analysis and communication as well as for identifying best treatment strategies.