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Biomedical subjects

R Allen

Publications and source records attributed to R Allen.

At least 19 recordsLinked to original sources
PubMed2006

Long-term nipple shrinkage following augmentation by an autologous rib cartilage transplant in free DIEP-flaps.

Aesthetically pleasing nipple-areola reconstruction is a satisfying part of a two-stage breast reconstruction. The up to 50% [Banducci DR, Le TK, Hughes KC. Long-term follow-up of a modified Anton-Hartrampf nipple reconstruction. Ann Plast Surg 1999;43(5):467-9; discussion 469-70] postoperative shrinkage following a conventional nipple reconstruction is a well-known problem. Augmentation of the nipple with autologous banked cartilage seems to be a promising solution. From 2000-2003, 17 patients underwent a nipple-areola-complex reconstruction following secondary breast reconstruction using free perforator flaps. The rib cartilage harvested during the preparation of the internal thoracic vessels was banked subcutaneously and six months later replanted under the 'arrow flap' after contouring it in a 'mushroom' shape. One year later the shrinkage of the nipple in comparison to the intraoperative status was measured. In addition, patients were asked about their personal palpation impression and the aesthetic outcome. The average height decreased one year postoperatively about 25%. Thirteen of 17 patients judged the aesthetic outcome as very good, 16 nipples healed without cartilage protrusion and no patient felt discomfortable stiffness of the nipple. Our concept of a nipple augmentation with rib cartilage improves the projection and allows a more correct judgement of the later nipple shrinkage. We consider this technique to be an aesthetically satisfying and safe method, which could be used with any kind of breast reconstruction.

Cartilage↗
PubMed2006

Training of staff for the delivery of PET/CT services in the UK.

Evidence for the cost effectiveness of PET/CT imaging is now driving the widespread introduction of PET/CT services throughout the UK. The provision of PET/CT facilities will require a workforce of medical, scientific, technical and engineering staff who are adequately trained and fit for purpose. Suitably trained staff in this speciality are scarce. The development and accreditation of training courses and other educational resources for training programmes in all disciplines will therefore be required at a national and regional level. The implementation of PET/CT training can be achieved more cost-effectively by developing multi-professional learning resources whenever possible. It is intended that the recommendations would be implemented by close co-operation of both public and private healthcare providers together with educational establishments.

Curriculum↗
PubMed2005

A simulation model of the surface EMG signal for analysis of muscle activity during the gait cycle.

This work describes a model able to synthetize the surface EMG (electromyography) signal acquired from tibialis anterior and gastrocnemious medialis muscles during walking of asymptomatic adult subjects. The model assumes a muscle structure where the volume conductor is represented by multiple layers of anisotropic media. This model originates from analysis of the single fiber action potential characterized by the conduction velocity. The surface EMG of voluntary contraction is calculated by gathering motor unit action potentials estimated by the summation of all activities of muscle fibers assumed to have a uniformly parallel distribution. The parameters related to the gait cycle, such as onset and cessation timings of muscle activation, amplitude of muscle contraction, periods and sequences of motor units' recruitment, are included in the model presented. In addition, the relative positions of the electrodes during gait can also be specified in order to adapt the simulation to the different acquisition settings.

Computer Simulation↗
PubMed2005

High spontaneous fluctuation in arterial blood pressure improves the assessment of cerebral autoregulation.

Cerebral autoregulation maintains a relatively constant blood flow despite changes of blood pressure in the brain. Linear models have been extensively applied to identify this mechanism, using spontaneous arterial blood pressure (ABP) fluctuation as input and cerebral blood flow velocity (CBFV) change as output. Although valuable measurements have been achieved by these models, accuracy and consistency are of great concern due to the large variability of results. We therefore investigated whether more reliable measurements can be achieved by selecting only those recordings (or parts of recordings) with relatively high spontaneous variability of ABP. Twenty-four recordings, 7 from hypercapnia and 17 from normocapnia, of ABP and CBFV from 9 healthy adults were analyzed. Two conventional autoregulatory parameters were used to assess cerebral autoregulation. In the absence of a 'gold' standard for the study of dynamic cerebral autoregulation, lower variability of the parameters and higher correlation with pCO(2) were considered as criteria for identifying improved measures of autoregulation. Both significantly lower variability of the parameters, and higher correlation between the parameters and pCO(2) were achieved from the data with higher variability of blood pressure. We therefore conclude that ABP with high variability may effectively stimulate regulatory response in blood flow resulting in improved assessment of cerebral autoregulation.

Arteries↗
PubMed2005

Demystifying biomedical signals: a student centred approach to learning signal processing.

The processing and analysis of physiological signals has become firmly established in clinical medicine and biomedical research. Many of the users of this technology however do not come from an engineering or science background, and traditional approaches in teaching signal processing are thus not appropriate for them. We have therefore developed a series of modular courses that are aimed specifically at an audience with a background in medicine, health-care or the life-sciences. In these courses, we focus on the concepts, principles and rationale of applying signal processing methods, rather than the mathematical foundations of the techniques. Thus, we aim to remove some of the perceived 'mystery' often surrounding this subject. The very practical approach, with hands-on experience using the MATLAB software, has been well received, with strong evidence that students have learnt to apply their knowledge. This paper describes the learning and teaching approach taken, and some of the experience acquired.

Algorithms↗
PubMed2004

Volatilisation of crop protection chemicals from crop and soil surfaces under controlled conditions--prediction of volatile losses from physico-chemical properties.

Volatilisation of crop protection chemicals from soil and crop surfaces is one of a number of processes that may contribute to their dissipation in the environment. Therefore, information on the potential of a chemical to volatilise from these surfaces is required by international and national registration authorities. This paper reports the results of more than 190 experiments, which were carried out with 80 different crop protection chemicals under controlled conditions (laboratory and/or greenhouse) according to the BBA guideline. Percent loss values observed during 24 h after application are reported for 123 soil and 71 crop volatility studies. Generally, volatile losses from crop surfaces were found to be greater than from soil surfaces under comparable experimental conditions. It has been previously proposed that volatile losses from soil surfaces, from crops, and from aqueous systems can be estimated from physico-chemical parameters. The data are therefore analysed to determine whether a correlation exists between volatilisation and physico-chemical parameters, such as vapour pressure, Henry's law constant, water/air and soil/air distribution coefficients. It was found that these parameters can be used to make reasonable predictions of volatile losses from crop and soil surfaces, which can be expected for crop protection chemicals under controlled conditions. Vapour pressure was the best predictor of losses from soil and crops. The use of the soil/air distribution coefficient is an alternative for predicting/estimating the volatility potential of a chemical from soil. Based on direct measurements, no noticeable volatility can be expected from compounds with a vapour pressure below 10(-3) Pa from soil and 10(-4) Pa from crops, this is fully confirmed by indirect measurements. A tiered volatility testing scheme including appropriate trigger values is proposed.

Agrochemicals↗
PubMed2004

Noise reduction in spine videofluoroscopic images using the undecimated wavelet transform.

Videofluoroscopy permits using sequences of low quality images to study the spine movement. In this work the problem of enhancing the quality of these images is considered in order to facilitate the extraction of kinematic parameters. The method is based on the undecimated wavelet transform and on a preliminary training of a sub-set of images. The anatomical features are preserved using a mask. Key element of the method is its fast and automated implementation. The concept of improving the extraction of kinematic parameters by improving the image representation instead of the technique to extract these is also innovative. The technique has been tested on two sequences of images and the results demonstrates that the method enhances images not related with training sub-set.

Algorithms↗
PubMed2004

Molecular characterisation and developmental expression of a cellulose-binding protein gene in the soybean cyst nematode Heterodera glycines.

Secretory proteins encoded by 'parasitism genes' expressed in the oesophageal gland cells of plant-parasitic nematodes play key roles in nematode infection and parasitism of host plants. A cellulose-binding protein-encoding cDNA, designated Hg-cbp-1, was cloned from a Heterodera glycines oesophageal gland-cell long-distance PCR cDNA library. The cDNA hybridised to genomic DNA of H. glycines in Southern blots, and the genomic sequence of Hg-cbp-1 contained only one intron. The Hg-cbp-1 cDNA contained an open reading frame encoding 132 amino acids, with a predicted signal peptide sequence for secretion and a cellulose-binding domain. Bacterial expressed recombinant HG-CBP-1, minus the signal peptide sequence, had no hydrolytic activity on carboxymethyl-cellulose but was able to bind to cellulose. The developmental expression of Hg-cbp-1, determined by real-time reverse transcriptase PCR, showed that Hg-cbp-1 is expressed throughout the parasitic cycle of H. glycines, with a relatively higher expression level in developing parasitic stages.

Amino Acid Sequence↗
PubMed2004

Effect of gait cycle selection on EMG analysis during walking in adults and children with gait pathology.

This paper presents the results of a project to evaluate different methods of gait cycle selection on the analysis of electromyography recorded during gait. Electromyography (EMG) describes the electrical activity associated with the muscle and is often interpreted in gait analysis using a simultaneously obtained signal to identify phases of the gait cycle. Phase transitions are often selected manually from reference signals derived from additional instrumentation, such as pressure platforms, footswitches and video cameras. We propose two methods (automatic and semi-automatic) as an alternative to the more traditional manual selection, and analyse how the gait cycle selection affects the EMG analysis. To quantify the differences between the gait cycles obtained using each method and to classify each cycle, three indices have been introduced. The effect of the gait cycle selection has been evaluated with respect to the EMG step profiles and temporal gait descriptors. An asymptomatic adult, an asymptomatic child and two children with cerebral palsy were examined using telemetric EMG devices and pressure footswitches. The results obtained showed that the method of gait cycle selection did not have a major influence for the adult, but it altered considerably the analysis in the case of the children with cerebral palsy.

Adult↗
PubMed2004

Long-term safety and tolerability of pimecrolimus cream 1% and topical corticosteroids in adults with moderate to severe atopic dermatitis.

OBJECTIVE: This randomized, double-blind, multi-centre study compared the long-term safety and tolerability of pimecrolimus cream 1% and topical corticosteroids (TCS) in 658 adults with moderate-severe atopic dermatitis (AD). METHODS: Patients applied either pimecrolimus or TCS (i.e. 0.1% triamcinolone acetonide cream and/or 1% hydrocortisone acetate cream) twice daily to all affected areas until complete clearance or for up to 1 year. The study was approved by the institutional review board or ethics committee at each centre. RESULTS: A majority of patients treated with either pimecrolimus or TCS used the drug on a continuous basis over 1 year. In patients who had >30% of the body surface involved by AD, the incidence rate of all skin infections was significantly lower in the pimecrolimus group than in the TCS group (95% CI of the treatment difference: -25.3% to -3.4%). The most frequent application site reaction was burning (25.9% of patients on pimecrolimus and 10.9% on TCS), which was transient and mild-moderate in most cases. Three TCS-treated patients reported skin striae. There were no treatment-related serious or clinically significant systemic adverse events. Efficacy was better in patients on continuous TCS therapy, although patients completing the study were similarly well-controlled in both groups. About 42% of the pimecrolimus-treated patients were maintained for 1 year without TCS. CONCLUSION: Pimecrolimus demonstrated a favourable safety profile when used to treat adult patients with moderate-severe AD for up to 1 year. A significant proportion of patients could be maintained without TCS for a year.

Administration, Cutaneous↗
PubMed2004

The LILR family: modulators of innate and adaptive immune pathways in health and disease.

Leukocyte immunoglobulin (Ig)-like receptors [LILRs, also known as Ig-like transcripts (ILTs)] are a family of inhibitory and stimulatory receptors encoded within the leukocyte receptor complex and are expressed by immune cell types of both myeloid and lymphoid lineage. Several members of the LILR family recognize major histocompatibility complex class I. The immunomodulatory role of LILR receptors indicates that they may exert an influence on signaling pathways of both innate and adaptive immune systems. LILR activity can also influence the antigen-presenting properties of macrophages and dendritic cells and may thus play a role in T-cell tolerance. The wide-ranging effects of LILR signaling on immune cell activity imply that these receptors are likely to play an important role in a range of clinical situations including pregnancy, transplantation, and arthritis (including the human leukocyte antigen B27-associated spondyloarthropathies). In this review, we summarize current knowledge on the nature and function of LILRs, focusing on their regulation of immune cell activity and their potential role in disease.

Animals↗
PubMed2004

Validation of the Eczema Area and Severity Index for atopic dermatitis in a cohort of 1550 patients from the pimecrolimus cream 1% randomized controlled clinical trials programme.

OBJECTIVE: To validate the Eczema Area and Severity Index (EASI) by assessing its internal consistency, reliability and sensitivity to change and by correlating it to other efficacy parameters. DESIGN: Three short-term and two long-term double-blind, randomized, controlled trials, performed in 138 study centres in Europe, South Africa, Australia, New Zealand, and North and South America. PATIENTS AND METHODS: In total, 1550 paediatric patients with atopic dermatitis were studied. Pimecrolimus cream 1% was used twice daily to treat atopic dermatitis. The three short-term studies were placebo controlled. The two long-term studies evaluated the efficacy and safety of early intervention with pimecrolimus to prevent progression to disease flare requiring topical corticosteroid treatment, compared with reactive treatment with topical corticosteroids to treat flares of atopic dermatitis. MAIN OUTCOME MEASURES: Five parameters were measured: (i) the EASI (range of score 0-72); (ii) Investigators' Global Assessment (IGA), using a six-point (0-5) scale; (iii) patients' assessment, using a four-point (0-3) scale; (iv) severity of pruritus assessment, using a four-point (0-3) scale; and (v) a quality-of-life evaluation. RESULTS: The EASI score varied in parallel and in correlation with the IGA, pruritus and patients' assessment. All correlation coefficients were statistically different from 0 (P < 0.05). The EASI correlated well with each of its components, and all paired comparisons were within agreed limits. The EASI showed good sensitivity to changes in severity. CONCLUSION: In a large, multinational patient population with atopic dermatitis, the EASI showed good validity, reliability and sensitivity to change and correlated well with other measures of severity. It therefore qualifies as a valid method of assessment in clinical studies of atopic dermatitis.

Adolescent↗
PubMed2003

Lumbar spine visualisation based on kinematic analysis from videofluoroscopic imaging.

Low back pain is a significant problem and its cost is enormous to society. However, diagnosis of the underlying causes remains problematic despite extensive study. Reasons for this arise from the deep-rooted situation of the spine and also from its structural complexity. Clinicians have to mentally convert 2-D image information into a 3-D form to gain a better understanding of structural integrity. Therefore, visualisation and animation may be helpful for understanding, diagnosis and for guiding therapy. Some low back pain originates from mechanical disorders, and study of the spine kinematics may provide an insight into the source of the problem. Digital videofluoroscopy was used in this study to provide 2-D image sequences of the spine in motion, but the images often suffer due to noise, exacerbated by the very low radiation dosage. Thus determining vertebrae position within the image sequence presents a considerable challenge. This paper describes a combination of spine kinematic measurements with a solid model of the human lumbar spine for visualisation of spine motion. Since determination of the spine kinematics provides the foundation and vertebral extraction is at the core, this is discussed in detail. Edge detection is a key feature of segmentation and it is shown that phase congruency performs better than most established methods with the rather low-grade image sequences from fluoroscopy. The Hough transform is then applied to determine the positions of vertebrae in each frame of a motion sequence. In the Hough transform, Fourier descriptors are used to represent the vertebral shapes. The results show that the Hough transform is a very promising technique for vertebral extraction from videofluoroscopic images. A dynamic visualisation package has been developed in order to view the moving lumbar spine from any angle and viewpoint. Wire frame models of the vertebrae were built by using CT images from the Visible Human Project and these models are scaled to match the fluoroscopic image data. For animation, the spinal kinematic data from the motion study is incorporated.

Algorithms↗
PubMed2003

Dynamic cerebral autoregulation assessment using an ARX model: comparative study using step response and phase shift analysis.

Middle cerebral arterial blood velocity (MCAv) response to spontaneous and manipulated changes of arterial blood pressure (ABP) was studied in eight subjects using a linear autoregressive with exogenous input (ARX) model. ABP and MCAv were measured non-invasively by photoplethysmograph and transcranial Doppler ultrasound, respectively. Data were recorded at rest (spontaneous changes in ABP) and during thigh cuff (step-wise changes) and lower body negative pressure (sinusoidal changes of 1/12 Hz) tests in both normocapnia and hypercapnia (5% CO2). Since autoregulation is modulated by CO2, respiratory CO2 was simultaneously monitored to allow comparison of cerebral autoregulation status with different CO2 levels. ABP and MCAv were fitted by ARX models and dynamic cerebral autoregulation was estimated by analysing both the step responses and phase shift at the 1/12 Hz of the corresponding ARX models. The ARX model consistently modelled the phase lead of MCAv to ABP and it showed that the phase shift at 1/12 Hz of ARX model is consistent with the real phase shift of the data (p=0.59). Strong linear relationships between pCO2 and gradient of the step response (r=-0.58, p<0.0001) and between pCO2 and phase shift (r=-0.76, p<0.0001) were observed, which suggests that cerebral autoregulation can be assessed by step response or phase shift analysis of the ARX model fitted to ABP and MCAv data with spontaneous changes.

Adaptation, Physiological↗