Restitution of the NHS breast reconstruction service during the recovery phase of the Covid 19 pandemic.

During the recovery restitution phase of the coronavirus pandemic, breast reconstruction teams have faced particular challenges to restarting this essential service. This is due to the length and complexity of the surgery, along with the demands on healthcare staff. The Royal College of Surgeons have classified immediate breast reconstruction as priority 2 and the National Institute for Health and Care Excellence have provided a pre-operative pathway for resumption of elective procedures. We therefore describe our experience in restarting our service for providing a breast reconstruction service from the 29th June 2020.

Regenerating axons reclaim sensory targets from collateral nerve sprouts.

There is a critical period for the sprouting of intact low-threshold mechanosensory cutaneous nerves in rats; functional invasion of adjacent denervated skin does not occur in animals older than about 20 days of age, and it is largely confined to denervated skin within the "domain" of the parent dermatome. These nerves can regenerate readily in the adult, however, and such regenerating nerves do not respect domain borders; moreover, they functionally displace endings of intact nerves that earlier had sprouted into denervated skin.

Comparing the surgical timelines of military and civilians traumatic lower limb amputations.

The care and challenges of injured service have been well documented in the literature from a variety of specialities. The aim of this study was to analyse the surgical timelines of military and civilian traumatic amputees and compare the surgical and resuscitative interventions. A retrospective review of patient notes was undertaken. Military patients were identified from the Joint Theatre Trauma Registry (JTTR) in 2009. Civilian patients were identified using the hospital informatics database. Patient demographics, treatment timelines as well as surgical and critical care interventions were reviewed. In total 71 military patients sustained traumatic amputations within this time period. This represented 11% of the total injury demographic in 2009. Excluding upper limb amputees 46 patients sustained lower extremity amputations. These were investigated further. In total 21 civilian patients were identified in a 7-year period. Analysis revealed there was a statistically significant difference between patient age, ITU length of stay, blood products used and number of surgical procedures between military and civilian traumatic amputees. This study identified that military patients were treated for longer in critical care and required more surgical interventions for their amputations. Despite this, their time to stump closure and length of stay were not statistically different compared to civilian patients. Such observations reflect the importance of an Orthoplastic approach, as well as daily surgical theatre co-ordination and weekly multi-disciplinary meetings in providing optimal care for these complex patients. This study reports the epidemiological observed differences between two lower limb trauma groups.

Cation effects on chloride fluxes and accumulation levels in barley roots.

Accumulation of Cl(-) by excised barley roots, as of K(+), approaches a maximum level at which the ion influx and efflux rates become equal. The rate of Cl(-) influx at this equilibrium is close to the initial rate while the efflux rate increases with time from zero to equality with influx. The Cl(-) fluxes are independent of simultaneous exchange flux of the cations, but depend on the nature and concentration of the salt solutions from which they originate. The Cl(-) content at equilibrium, however, is largely independent of the external concentrations. The approach to equilibrium reflects the presence of the cation. Cl(-) flux equilibrium is attained more rapidly in KCl than in CsCl or CaCl(2). This is presumably an effect of much slower distribution of Cs(+) and Ca(++) than of K(+) within the roots. Accumulated Cs(+) appears to form a barrier to ion movement primarily within the outermost cells, thereby reducing influx and ultimately efflux rates of both Cl(-) and cations. Slow internal mixing and considerable self-exchange of the incoming ions suggest internal transport over a series of steps which can become rate-limiting to the accumulation of ions in roots.

Development of synaptic connections between muscle sensory and motor neurons: anatomical evidence that postsynaptic dendrites grow into a preformed sensory neuropil.

The anatomical development of muscle sensory arbors and dendrites of brachial motoneurons in the spinal cord of the bullfrog was studied by labeling both types of cells with horseradish peroxidase. Sensory and motoneurons were labeled in tadpoles (stages XV-XVIII) by backfilling the triceps nerve in vivo with HRP throughout the stages in development when functional monosynaptic connections between these cells are first being formed. Individual triceps motoneurons were injected with HRP in other tadpoles at the same developmental stages. By stage XV, triceps sensory afferents already projected to and arborized in the ventral sensory neuropil region of the spinal cord where sensory-motor connections are made. In contrast, the dendrites of triceps motoneurons rarely were present in this region until stage XVI. By stage XVII, triceps dendrites in this region were common and they intermingled with the collaterals of muscle sensory axons. Thus, sensory axons supplying limb muscles grow into the future neuropil region well in advance of the arrival of motoneuronal dendrites. Electrophysiological studies have shown that the connections between triceps sensory and motor neurons are already specific at stage XVII, as soon as monosynaptic potentials between these cells can be detected (Frank and Westerfield: J. Physiol. (Lond.) 343:593-610, '83). The present anatomical results demonstrate that the processes of sensory and motor cells are not in close anatomical proximity before this time; thus the selection of appropriate synaptic partners must occur from the outset.

Temporal and spatial constraints on the collateral sprouting of low-threshold mechanosensory nerves in the skin of rats.

We have studied the collateral sprouting of intact low-threshold mechanosensory nerves into adjacent denervated skin in rats. An "isolated" field was produced by extensive denervations of the surrounding skin; sprouting of the remaining cutaneous nerve supplying the field was looked for in the form of field expansion into the surrounding denervated territory at various postoperative intervals. Such isolated fields failed to expand in the adult rat for periods up to at least 85 days. "Nonfunctional" sprouting is unlikely to explain this failure. However, similar experiments done in very young animals gave a different result. In rat pups aged less than 20 days, isolated fields did expand, but this ceased at about 20 days, and attempts to evoke it after this time were unsuccessful. There seems to be a critical period for sprouting of these touch-sensitive nerves into denervated skin, and our evidence suggests that it may not begin until about 15 days of age. Within this developmental window the sprouting that occurs is spatially constrained, an isolated field expanding preferentially into denervated skin of the parent dermatome; if only skin of neighboring dermatomes is available there is no expansion. In contrast, low-threshold nerves regenerated readily after a crush at all ages studied, and the mechanosensory fields established by regenerating nerves expanded progressively into denervated skin without apparent constraints at dermatomal boundaries. The temporal and spatial constraints found for the sprouting of intact low-threshold axons are in marked contrast to their absence for the well-described sprouting of high-threshold (nociceptive) nerves.

Failure of intact cutaneous mechanosensory axons to sprout functional collaterals in skin of adult rabbits.

The original evidence that spared cutaneous nerves will sprout following partial denervation of skin was obtained in adult rabbits, in which nociceptive function returned to the deprived areas. Recently we reported that in the adult rat intact touch-sensitive (low-threshold mechanosensory) nerves fail to establish new functional endings in adjacent denervated skin. We have now investigated low-threshold mechanosensory nerves in the skin of adult rabbits after partially denervating the ear or hind limb; the sprouting of new functional endings into neighboring skin would be revealed by an expansion of the low-threshold receptive fields of cutaneous nerves (the areas of skin from which impulses could be evoked by stroking with a bristle). The results show that intact low-threshold mechanosensory nerves do not establish functional endings in adjacent denervated skin in the adult rabbit. These findings, together with those now reported for the cat as well as the rat, support the conclusion that possibly in all adult mammals intact low- and high-threshold nerves differ in their ability to respond to the presence of adjacent denervated skin by sprouting.

Normal electrical activity is not required for the formation of specific sensory-motor synapses.

These studies sought to determine the role of stretch-evoked electrical activity in muscle sensory axons on the formation of specific monosynaptic connections made by these neurons onto spinal motoneurons. Normal activity was disrupted by tenotomy during the developmental stages that the central connections are made. The pattern of connections was normal, suggesting that normal activity is not required in this system for the formation of specific sensory-motor connections.

Evaluating the performance of an edge detection algorithm for use in radioisotope imaging.

The criteria are presented for establishing how an edge detection algorithm (EDA) will respond under a variety of imaging situations. Several parameters have been defined to allow comparison of the processed image under varying conditions of count density, target to background ratio, depth of organ, scatter and intra-image motion. These parameters could also be used for intercomparison of EDAs.

Monte Carlo modelling of light propagation in breast tissue.

Light transport in three-dimensional plane-parallel tissue slabs has been modelled by Monte Carlo analogue simulation. The model design has allowed the study of transmission properties that are pertinent to imaging systems for the detection of breast cancer. An important aspect of the investigations is that they make use of data obtained from quantitative measurements of light scattering and absorption in normal and pathological breast tissues. It is shown that an imaging technique which used a raster scanning laser and detector arrangement and plane-parallel compression of the breast could have considerable advantages in terms of improved transmittance, spatial unsharpness and contrast. Time-of-flight gating of images is also found to be beneficial provided that the light intensities after temporal filtering remain adequate.

Optical attenuation characteristics of breast tissues at visible and near-infrared wavelengths.

Optical experiments are described for measuring the attenuation characteristics of breast tissues at visible and near-infrared wavelengths. Total attenuation coefficients post mortem were measured directly in thin tissue sections. They are usually within the range from 10 to 30 mm-1, are rather higher in fat than in fibroglandular specimens and decrease with increasing wavelength. The scattering phase function is strongly forward-peaked with the mean cosine of scattering in the range from 0.85 to 0.97 and appearing more forward-peaked in fat than in fibroglandular tissue. The reduced scattering coefficient is of the order of 1 mm-1 in all tissues. Absorption coefficients were measured indirectly in optically thick sections. They are typically between 0.1 and 0.5 mm-1 at wavelengths around 580 nm and an order of magnitude lower at 850 nm. At 580 nm and shorter wavelengths the absorption in carcinoma is significantly higher than in adjacent uninvolved tissue. Significant differences were observed in the first-order derivatives of the transmission spectra of carcinoma and surrounding tissues at certain infrared wavelengths. Transmission spectra measured in vivo across the wavelength range from 500 to 860 nm have a similar form to the spectra of excised samples. Linear absorption coefficients are generally of the same order of magnitude as those found in vitro although they are lower at green wavelengths.

The potential of phase and amplitude images in determining the boundary of the left ventricle.

The phase and amplitude images derived from multiple gated blood pool studies of the heart have been used to aid the delineation of the boundary of the left ventricle. The results of left ventricular ejection fraction (LVEF) using this method have been compared with those obtained using edge detection algorithms, dual region of interest techniques, and x-ray contrast ventriculography, in a series of patients with well documented left ventricular wall motion. The results indicate that the sole use of phase and amplitude images does not improve the correlation or accuracy of LVEF estimation in relation to those obtained by x-ray contrast ventriculography, and that the dual region of interest technique is likely to remain the preferred method.

Compartmental analysis of cerebrospinal fluid transfer and absorption in simulated hydrocephalus.

A mathematical model of the cerebrospinal fluid (CSF) flow dynamics found in hydrocephalic infants with myelomeningocele lesions was constructed using criteria obtained from analogous clinical situations where 125I-labelled and 131I-labelled ortho-iodobenzoyl-amino-acetic acid (hippuran) had been employed to measure CSF flow dynamics. The quantitative results from this study allowed clinical data to be assessed and the importance of various CSF transfer mechanisms to be discussed. Our mathematical model indicates that the majority of radiopharmaceutical passes from the cerebral reservoir (the ventricles) into the blood. Experimental evidence indicates that the principal mechanism responsible for this movement is the bulk flow of CSF between its sites of production in the choroid plexus and absorption by the arachnoid villi.

An image processing technique for the identification of contact pixels applied to x-ray CT images of implanted hip prostheses.

Uncemented prosthetic joint implants used in orthopaedic surgery are usually coated with a porous surface to encourage bone ingrowth. Better contact between the endosteal bone and the porous surface improves ingrowth, and such contact may be increased if the joint further subsides into position in the first weeks following implantation. An image processing technique has been developed as part of a study undertaken to determine the effect of early subsidence on endosteal contact. The method provides a measure of the degree of contact between the surfaces from transverse x-ray CT images, but is suitable for application to any image with a similar intensity distribution.

Partitioning of water resources among plants of a lowland tropical forest.

Source water used by plants of several species in a semi-evergreen lowland tropical forest on Barro Colorado Island, Panama, was assessed by comparing the relative abundance of deuterium, D, versus hydrogen, H (stable hydrogen isotope composition, δD) in xylem sap and in soil water at different depths, during the dry season of 1992. Ecological correlates of source water were examined by comparing xylem water δD values with leaf phenology, leaf water status determined with a pressure chamber, and rates of water use determined as mass flow of sap using the stem heat balance method. Soil water δD values decreased sharply to 30 cm, then remained relatively constant with increasing depth. Average δD values were-13‰, for 0-30 cm depth and-36.7‰ for 30-100 cm depth. Soil water δD values were negatively associated with soil water content and soil water potential. Concurrent analyses of xylem water revealed a high degree of partitioning of water resources among species of this tropical forest. Xylem water δD of deciduous trees (average=-25.3±1.4‰) was higher than that of evergreen trees (average=-36.3±3.5‰), indicating that evergreen species had access to the more abundant soil water at greater depth than deciduous species. In evergreen shade-tolerant and high-light requiring shrubs and small trees, δD of xylem water was negatively correlated with transpiration rate and leaf water potential indicating that species using deeper, more abundant water resources had both higher rates of water use and more favorable leaf water status.

Ultrasound quantitation of respiratory organ motion in the upper abdomen.

Organ motion can cause artefacts in abdominal imaging particularly with magnetic resonance imaging (MRI), and may often limit the diagnostic quality of an image. If spatial resolution and image quality are to improve in MRI and other imaging techniques, a more detailed understanding of organ motion is required. Despite the importance of organ motion little quantitative information is available to date. This study was the continuation of work instigated to investigate and quantify respiratory movements of upper abdominal organs for a group of healthy volunteers in order to provide the design criteria for a motion test object for use in MRI. A previous phase of the project allowed construction of a test object but refinements were needed to represent respiratory motion more closely as a consequence of the data presented in this paper. Improvements in the scanning technique and the recording procedure have revealed that, contrary to our initial findings, motion of the diaphragm and liver is predominantly in the superior-inferior (SI) direction with an average displacement (+/- SD) (quiet respiration) of 12 +/- 7 mm (range 7-28 mm) and 10 +/- 8 mm (range 5-17 mm), respectively. For some volunteers, motion of the kidneys can be complex, especially during deep inspiration. New data have been provided by this phase of the motion study on the displacement, velocity and acceleration of abdominal organs as a function of time. These data show that MRI motion artefact reduction techniques which assume that either organ displacement, velocity or acceleration are constant are only applicable during certain phases of the respiratory cycle.

New scans from old: digital reformatting of ultrasound images.

Two-dimensional images obtained using ultrasound have been digitized from videotape recordings and stored within a maximum of 240 digital memory planes to form a three-dimensional data set using a commercially available image processing unit. This data set has been manipulated to produce images in planes perpendicular to the original scan set. The reformatted images represent not only the scans that could have been obtained by rotating the scan head but also demonstrate planes that are not accessible by conventional scanning. The system has been evaluated with a tissue-equivalent phantom to determine the geometric accuracy of the reformatting process. Clinical material has also been used to evaluate the practical value of such a technique and to highlight difficulties that may be encountered in its routine use.

The accuracy of digital subtraction angiography for the quantification of atherosclerosis.

Digital subtraction angiography (DSA) allows the degree of arterial patency or stenosis to be rapidly quantified. We have assessed the accuracy with which a single-plane DSA system is able to quantify area patency by densitometric and geometric methods. Arterial phantoms were designed to test for systematic error; intra-arterial DSA images of critical lesions of the carotid bifurcation and the lower abdominal and peripheral vessels were used to determine intra- and interobserver reproducibility. The densitometric method, which was more accurate than the geometric method, had a mean systematic error of up to 4% and a mean intra-observer variability of about 15% (coefficient of variation). We have identified the principal sources of inaccuracy and ways in which it may be reduced.

The development of a system for transillumination computed tomography.

A transillumination computed tomography system has been developed for studies of the breast, testes, neonatal skull and peripheral limbs. Initial experiments on test objects have emphasised the problems of scattering and geometrical dependence of lesion detection that are likely to be encountered in conventional diaphanography, but have demonstrated the feasibility of computed tomography as a means of improving the sensitivity of the transillumination technique. The problems of transillumination computed tomography have been addressed and further areas of research identified.

A comparative study of velocity measurements in major blood vessels using magnetic resonance imaging and Doppler ultrasound.

Velocity measurements in major blood vessels were obtained in studies of volunteers using magnetic resonance imaging (MRI) and compared with Doppler ultrasound (US). The vessels studied were the abdominal aorta, superior mesenteric artery, common carotid artery, superficial femoral artery and middle cerebral artery. Using a paired t-test, no significant difference was found between velocity values estimated by MRI and US (p > 0.08). The relative advantages of each technique in radiological practice are discussed.