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Biomedical subjects

D M Healy

Publications and source records attributed to D M Healy.

13 recordsLinked to original sources
PubMed2006

Ability of rabies vaccine strains to elicit cross-neutralising antibodies.

Two European Bat Lyssaviruses (EBLV-1 and EBLV-2) have been identified (n > 750 cases) in European bat species. In addition, EBLVs have been detected as "spillover" cases in three humans, one stone marten and four sheep. A further concern is the interaction of companion animals with infected bats and the possibility of subsequent lyssavirus infection. Cat-bat interactions represent approximately 32 % (n = 398) of passive lyssavirus surveillance submissions at the Veterinary Laboratories Agency (VLA) (1987-2004). Cats therefore represent a potentially significant spillover host. This study evaluated the ability of rabies vaccine antibodies to neutralise EBLVs using modified fluorescent antibody virus neutralisation (FAVN) assays (EBLV-1, EBLV-2). We examined vaccinated human, dog and cat sera in two classes; (i) FAVN-CVS titres > or = 0.5-5.0 IU/ml (n = 34, 79 and 54, respectively), and (ii) > 5.0 IU/ml (n = 22, 21 and 32 respectively). Most sera (approximately 80 %) with higher titres were able to neutralise both EBLV-1 and -2 regardless of the vaccine received. Only a proportion of those with low titres were capable of neutralising either EBLV-1 (27-92 %) or EBLV-2 (38-92 %) or both EBLVs (27-79 %). The cat sera constitute the lower end of each range. More animals that had received LEP based vaccines were able to neutralise EBLVs than those that had received PV based vaccines. The continuing occurrence of non-classical lyssaviruses in Europe emphasizes the need for continual surveillance of bats and other species.

Animals↗
PubMed2001

Early dissolution of a morsellised impacted silicate-free bioactive glass in metaphyseal defects.

The purpose of this study was to evaluate the biological properties of idealized, morsellised impacted Corglaes, a soluble silicate-free glass. Twenty-two sheep underwent implantation of pellets in six metaphyseal defects in both rear limbs. Particle size distribution of all aggregates (except the autograft) approached the ideal logarithmic grading line and all implants were impacted to a standard compactive effort. Treatment groups consisted of (1) empty defect (negative control), (2) autograft (positive control), (3) allograft (clinical control), (4) allograft idealized with Corglaes, (5) 50/50 allograft/Corglaes and (6) Corglaes. Defects were sealed with polymethylmethacrylate. Healing of the defects was evaluated at 7 weeks (n=6) and 14 weeks (n=16) with computed tomography, histology, and histomorphometry. Remnants of Corglaes were found within one of the defects 7 weeks after implantation. Defects filled with mixtures containing 50% or 100% Corglaes were less dense, contained less bone and more fibrous tissue than defects with allograft, autograft, or allograft idealized with Corglaes. Allograft idealized with Corglaes may be considered for impaction grafting in revision hip arthroplasty, as well as local delivery of antibiotics. However, further studies and potential revision of the agent are required before mixtures containing concentrations of Corglaes equal to or higher than 50% can be recommended.

Animals↗
PubMed1998

Elastic image registration using correlations.

We have developed a multiscale algorithm for elastic registration of images. Rigid registration has many applications but it is often limited by distortions in the images. For example, different views of the same object produce distortions. Common examples of slightly different views producing a distortion can be found in medical imaging, such as matching a current mammogram or chest radiograph with one from a previous year, and in remote sensing, such as matching images taken from different satellite positions. We have developed two methods of elastic registration. Both are multiscale but one used an iterative minimization of the local error and the other uses a windowed correlation. We present preliminary results of the elastic registration method used on windowed correlations.

Algorithms↗
PubMed1998

Biodegradable controlled release glass in the repair of peripheral nerve injuries.

The experiments in this paper were concerned with the recovery of function and ease of application of an entubulation technique using a biodegradable, controlled release glass tube (CRG) for the repair of a transected peripheral nerve. The peroneal nerves of 15 New Zealand White rabbits were repaired with either a CRG tube filled with freeze-thawed muscle, or a conventional freeze thawed muscle graft (FTMG). These were compared with controls in which a CRG was used to enclose the cut ends of a nerve separated by a 1 cm gap. Electrophysiological and morphometric assessment was carried out 6 months after repair. No statistical difference was found in any test between the FTMG and the CRG tube filled with freeze thawed muscle. The CRG tube and 1 cm gap produced inferior levels of recovery of function when compared with the other two repair groups.

Action Potentials↗
PubMed1998

Haemocompatiblity of controlled release glass.

There are many medical applications which benefit from the use of soluble biomaterials, including the sustained release of drugs over a precise period of time, or temporary conduits for controlling nerve regrowth. We have manufactured a series of phosphate-based controlled release glasses (CRGs) in which the solubility could be controlled by varying the concentration of CaO and Na2O. Fibres of the CRG containing iron and cerium were placed into direct contact with human neutrophils and macrophages in tissue culture for 2.5 and 24 h respectively and the responses analysed by scanning electron microscopy (SEM) and confocal microscopy. The supernatants were analysed for the cytokine IL-1beta by enzyme-linked immunosorbent assay (ELISA). Disks of CRG of various compositions were placed in contact with whole blood for 30 min and platelet adhesion assessed by SEM. Activation of platelets, granulocytes and complement were quantified by ELISA for beta-thromboglobulin, elastase and iC3b. Intrinsic coagulation activation was measured by timing the clotting of recalcified plasma. Only the cerium fibre inhibited IL-1beta release from macrophages. No platelet adhesion was observed to any disk composition. Three compositions containing MgO inhibited plasma clotting and showed an insignificant level of complement activation. This study has demonstrated the development of a number of compositions of CRG, which have great potential in a wide variety of biomedical applications.

Journal Article↗
PubMed1998

Soft tissue response to glycerol-suspended controlled-release glass particulate.

Vesicoureteral reflux and urinary incontinence have previously been treated by various means including the endoscopic delivery of injectable bulking materials such as silicone micro-implants, PTFE implants, glass particles, fat and bovine collagen. These first three materials do not degrade and collagen requires frequently repeated injections in order to sustain the restored continence provided. Vesicoureteric reflux in children usually resolves independently before the age of five. Correction is required before this, because treatment by prophylactic antibiotics is frequently unsuccessful in preventing breakthrough infection. The ideal material for injection should have large particles to avoid migration, inject easily and controllably, be non-toxic and dissolve over the period of time by which time the kidney will be mature. Three different controlled-release glass (CRG) granule compositions have been prepared by Giltech Ltd, and suspended in a suitable carrier medium (in this case glycerol). The degradable glasses, which have two different size ranges of 200-300 and <53 microm, and three different solution rates, were injected intramuscularly into the dorso-lumbar region of rats. Histological analysis of cryostat cut section after time periods of 2 d, 4 and 9 wk, and 6 mon has been performed. Histology sections were stained for neutrophils and macrophages using enzyme histochemistry. ED1 (monocytes and immature macrophages), ED2 (mature tissue macrophages), CD4 (helper/inducer T-lymphocytes and macrophages), CD8 (suppressor/cytotoxic T-lymphocytes), Interleukin-1beta, IL-2 (activated T-lymphocytes), Major Histocompatibility Complex (MHC) class II (activated macrophages and activated B-lymphocytes), alpha-beta (T-lymphocytes) and CD45RA (B lymphocytes) antibodies have been used to stain immunohistochemically each sample. This study demonstrates that particulate, degrading glass is stimulating an inflammatory response in soft tissue at time periods up to 6 mon. It should be noted that very small particulate, fast degrading glass is leading to tissue necrosis and should not be considered further for these applications. However, larger particulate, slower degrading materials are demonstrating effective potential for stress incontinence applications.

Journal Article↗
PubMed1998

In vitro nerve repair--in vivo. The reconstruction of peripheral nerves by entubulation with biodegradeable glass tubes--a preliminary report.

Biodegradeable "controlled release" inorganic polymer glass tubes can be manufactured to fit the dimensions of any nerve and their rate of solubility can be adjusted to encompass the time taken for nerve regeneration. They have been used in a number of biological applications. The facial nerve was repaired in a group of five sheep by entubulation with biodegradeable glass tubes. The sheep were assessed 10 months after repair and compared with a similar sized group of normal sheep. It was found that while there was a reduction in the peak velocity of conduction in the repaired nerves and in the range of conduction velocities, the minimum conduction velocity was within normal limits. There was a diminution in all of the measured variables of nerve morphometry but in no case did this reach statistical significance. These findings are consistent with the view that regeneration of the nerves had taken place to a degree at least as effective as that seen in nerves of a similar size repaired by conventional means.

Animals↗
PubMed1998

Multiresolution elastic image registration.

We have developed a multiscale algorithm for elastic (or molded) alignment of images. There is a wide array of medical applications of elastic (as opposed to strictly rigid) alignment: Subtraction of previous images from current ones to identify changes is perhaps the most obvious. We present preliminary results of this molding technique on a variety of images, and conclude with some closing remarks about this and future directions and goals of this work.

Algorithms↗
PubMed1992

Wavelet-encoded MR imaging.

Wavelet encoding is presented and compared to phase encoding. In wavelet encoding a distribution of spins is excited by a slice selective RF pulse; for each repetition time the distribution excited has the profile of a wavelet at different scale and translation. The spin density can be reconstructed with an inverse wavelet transform. Wavelet encoding has three advantages over phase encoding: (1) there is no Gibb's ringing from partial volume effects, (2) the effective repetition time can be 36 times the repetition time for a 256 x 256 image, and (3) motion artifacts are local and dramatically reduced. Using wavelet encoding, a 256 x 256 T2-weighted projection image can be acquired in 33 s.

Artifacts↗
PubMed1991

Filtering noise from images with wavelet transforms.

A new method of filtering MR images is presented that uses wavelet transforms instead of Fourier transforms. The new filtering method does not reduce the sharpness of edges. However, the new method does eliminate any small structures that are similar in size to the noise eliminated. There are many possible extensions of the filter.

Artifacts↗
PubMed1991

Prophylactic minitracheotomy in lung resections. A randomized controlled study.

Thirty consecutive patients undergoing lung resections were randomized into two groups: Group A (n = 15) received minitracheotomy postoperatively and group B (n = 15) were control patients. Postoperative respiratory course was monitored by serial clinical assessments, chest x-ray examination, arterial blood gases, sputa bacterial cultures, and the patient's requirement and response to chest physiotherpy. The two groups were similarly matched in age (mean 58.5 years), smoking habits, pulmonary functions, and surgical procedures. Postoperative pulmonary complications of collapse/consolidation developed in 11 patients (two in group A and nine in group B) (p less than 0.03). Four patients (all in group B) required nimitracheotomy in addition to antibiotics and chest physiotherapy to treat their pneumonia. Chest physiotherapy requirement was less in group A than in group B, with a mean number of sessions of seven in group A and eight in group B and a mean total time of 92 minutes in group A and 112 minutes in group B. The mean duration of minitracheotomy was 4.13 days. Minor temporary symptoms resulted from the minitracheotomy in eight patients (42%) and included discomfort, voice changes, subcutaneous emphysema, and stridor. There was one case of long-term morbidity (5%)-skin scarring from wound infection at the site of the minitracheotomy. No postoperative deaths resulted. We conclude that the prophylactic use of minitracheotomy is safe and effective in decreasing postoperative respiratory complications in patients undergoing lung resections.

Adult↗
PubMedDate not supplied

Two applications of wavelets and related techniques in medical imaging.

We present two applications of wavelet and related techniques to problems arising in medical imaging. Both make considerable use of the edge detection and classification properties of wavelet-type representations. First we describe simple and effective techniques for image denoising and contrast enhancement based on the multiscale edge representation of images. These techniques are sufficiently flexible to successfully address the varying requirements posed by several different medical imaging modalities in common use today. Experimental results are presented to illustrate the application of these techniques to various types of medical images. Next we describe adapted waveform encoding, a technique for magnetic resonance imaging. One advantage of this technique is that it can be used to efficiently encode edge features of the object being imaged. This has a particular diagnostic application in tracking heart wall thickness during the cardiac cycle, which we present along with some experimental results along this line. We also present an analysis of the signal-to-noise ratios of images formed with this technique, as this is a factor of paramount importance in MRI. The fact that wavelet schemes tend to concentrate energy near edge features makes the result rather different than that found in standard Fourier based approaches. We indicate an exciting potential application of our technique: reducing spectral leakage in phosphorus spectroscopy.

Algorithms↗