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Biomedical subjects

C Deane

Publications and source records attributed to C Deane.

At least 19 recordsLinked to original sources
PubMed2005

Development of educational image databases and e-books for medical physics training.

Medical physics education and training requires the use of extensive imaging material and specific explanations. These requirements provide an excellent background for application of e-Learning. The EU projects Consortia EMERALD and EMIT developed five volumes of such materials, now used in 65 countries. EMERALD developed e-Learning materials in three areas of medical physics (X-ray diagnostic radiology, nuclear medicine and radiotherapy). EMIT developed e-Learning materials in two further areas: ultrasound and magnetic resonance imaging. This paper describes the development of these e-Learning materials (consisting of e-books and educational image databases). The e-books include tasks helping studying of various equipment and methods. The text of these PDF e-books is hyperlinked with respective images. The e-books are used through the readers' own Internet browser. Each Image Database (IDB) includes a browser, which displays hundreds of images of equipment, block diagrams and graphs, image quality examples, artefacts, etc. Both the e-books and IDB are engraved on five separate CD-ROMs. Demo of these materials can be taken from www.emerald2.net.

Biomedical Engineering↗
PubMed2003

Patient and hospital delays in acute ischaemic stroke in a Dublin teaching hospital.

A limiting factor for thrombolysis in ischaemic stroke is delayed presentation to hospital. Prolonged A&E stay and delayed rehabilitation affects care. We evaluated the delay in presentation, A&E stay and rehabilitation delivery in 117 consecutive stroke patients. The mean presentation delay was 16.0 +/- 23.7 hours. A prior history of TIA or stroke, a reduced Glascow Coma Scale and larger strokes were associated with shorter delays to presentation. Longer delays occurred in patients living alone. The mean time spent in A&E was 11 hours, those with larger strokes spent shorter time. There were significant delays in referral to, and assessment by certain rehabilitation disciplines. Delayed presentation in stroke is a barrier to thrombolysis. Increasing public awareness may reduce this delay. In addition, prolonged A&E stay and delayed rehabilitation may adversely affect management, outcome and duration of hospital stay. Further study is required to investigate the reasons and possible solutions for such deficiencies.

Aged↗
PubMed2000

The effect of the nitric oxide donor glyceryl trinitrate on global and regional cerebral blood flow in man.

Despite their potential use as cerebral vasodilatory agents there are few studies of the effect of nitric oxide (NO) donors on the cerebral circulation in non-anaesthetised man. We determined the effect of the NO donor glyceryl trinitrate (GTN) at clinically relevant doses on global and regional cerebral blood flow (CBF) in healthy non-anaesthetised volunteers, using H(2)(15)O PET, ultrasonic colour velocity flow imaging of carotid artery flow, and transcranial Doppler (TCD) of middle cerebral artery velocities (MCAv). Three rates of GTN infusion (0.1, 0.4, 1.0 microg/kg/min) were used. There was no significant change in common or internal carotid artery flow following GTN administration although a dose dependent fall in MCAv post GTN was observed. There was no significant change in either global or regional CBF following GTN. Thus intravenous GTN at therapeutic doses in awake humans does not alter global or regional CBF. However it does produce basal cerebral artery vasodilatation as evidenced by a fall in MCAv in the absence of a change in internal carotid artery flow.

Adult↗
PubMed2000

Doppler obstetric ultrasound: a graphical display of temporal changes in safety indices.

OBJECTIVE: To investigate ultrasound use and exposure in pregnant women undergoing Doppler ultrasound investigation of the maternal and fetal circulation using Doppler ultrasound techniques. METHODS: Sample graphical displays were generated showing duration of each mode, thermal and mechanical index levels and overall elapsed time of scan and modes. RESULTS: The displays revealed combinations of scanner settings which delivered higher output intensity levels and which we subsequently altered in our practice to reduce ultrasound exposure. CONCLUSION: A display of this type would enable monitoring of output levels and exposures, especially for operators undergoing training in Doppler applications. It would also identify poor practice where there is prolonged exposure at high output levels. Such a display, in combination with accurate output measurement from manufacturers and independent laboratories, would help to ensure the safe use of ultrasound in fetal assessment.

Body Temperature↗
PubMed1999

Assessment of umbilical arterial and venous flow using color Doppler.

OBJECTIVE: To estimate the umbilical artery and vein blood volume flow using B-mode and Doppler ultrasound in the second and third trimesters of pregnancy. DESIGN: This was a cross-sectional study of 129 singleton, healthy pregnancies at 23-33 weeks' gestation. The umbilical artery and vein cross-sectional area, time-averaged velocity and pulsatility index were measured in a free loop of cord, and the fetal weight was estimated. Ranges for each parameter were obtained; from these the blood flow for the vein and artery was calculated, and the average flow corrected for fetal weight was derived. RESULTS: The median time for examination was 6 min. The mean cross-sectional area and time-averaged velocity for both the vein and artery increased linearly with gestation. The umbilical artery flow correlated closely with the average vein flow (r = 0.9, p < 0.001). There was a significant, though poor, inverse correlation between the umbilical artery pulsatility index and the average umbilical flow (r = -0.25, p < 0.05). The average umbilical flow (calculated from the mean of arterial and venous flow), corrected for estimated fetal weight, decreased from 189.2 ml/kg per min at 23 weeks to 176.2 ml/kg per min at 33 weeks' gestation. CONCLUSION: The estimates of fetal umbilical flow obtained by this Doppler method are consistent with previously published data. Averaging the arterial and venous flow is theoretically advantageous in reducing the inherent errors in estimating either the arterial or the venous flow. This method of measuring umbilical flow may have clinical potential in assessing fetal health and disease processes.

Blood Flow Velocity↗
PubMed1998

Protein three-dimensional structural databases: domains, structurally aligned homologues and superfamilies.

This paper reports the availability of a database of protein structural domains (DDBASE), an alignment database of homologous proteins (HOMSTRAD) and a database of structurally aligned superfamilies (CAMPASS) on the World Wide Web (WWW). DDBASE contains information on the organization of structural domains and their boundaries; it includes only one representative domain from each of the homologous families. This database has been derived by identifying the presence of structural domains in proteins on the basis of inter-secondary structural distances using the program DIAL [Sowdhamini & Blundell (1995), Protein Sci. 4, 506-520]. The alignment of proteins in superfamilies has been performed on the basis of the structural features and relationships of individual residues using the program COMPARER [Sali & Blundell (1990), J. Mol. Biol. 212, 403-428]. The alignment databases contain information on the conserved structural features in homologous proteins and those belonging to superfamilies. Available data include the sequence alignments in structure-annotated formats and the provision for viewing superposed structures of proteins using a graphical interface. Such information, which is freely accessible on the WWW, should be of value to crystallographers in the comparison of newly determined protein structures with previously identified protein domains or existing families.

Amino Acid Sequence↗
PubMed1998

Nitric oxide synthase inhibition in humans reduces cerebral blood flow but not the hyperemic response to hypercapnia.

BACKGROUND AND PURPOSE: Animal studies suggest that nitric oxide (NO) is important in basal cerebral blood flow (CBF) regulation and that it may mediate the vasodilatory response to carbon dioxide. We investigated its role in the human circulation using the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA). METHODS: L-NMMA was administered as an intravenous bolus at three doses (1, 3, and 10 mg/kg). CBF was assessed by color velocity ultrasonic imaging of internal and common carotid artery volume flow (ICA flow and CCA flow) and transcranial Doppler ultrasound measurement of middle cerebral artery flow velocity (MCAv). The pressor effect of L-NMMA was controlled for by comparison with noradrenaline titrated to effect an equivalent blood pressure elevation. RESULTS: L-NMMA produced a dose-dependent reduction in basal mean+/-SD CCA flow from 415.2+/-51.9 to 294+/-56.2 mL/min (at 10 mg/kg) and ICA flow from 268.8+/-59.4 to 226.2+/-72.6 mL/min (P<.005 and P<.05, respectively, comparing areas under the dose-response curve). This was reversed by L-arginine. Mean+/-SD systemic blood pressure rose from 85.2+/-6.4 to 100.8+/-9.6 mm Hg (P<.01). There was no significant reduction in MCAv. There was no significant change in the CBF response to either 6% or 8% carbon dioxide after L-NMMA. Noradrenaline produced a lesser fall in basal CCA flow (12.0%) but had a similar effect on the hypercapnic response. CONCLUSIONS: Basal NO release is important in controlling human CBF, but intravenously administered L-NMMA does not inhibit the hypercapnic hyperemic response in humans. The discrepancy between CBF and MCAv after L-NMMA administration is consistent with MCA vasoconstriction. Neuronal NO synthase inhibition may be protective in stroke. However, our results suggest that nonselective NO synthase inhibitors such as L-NMMA should be used with caution because they reduce CBF.

Adult↗
PubMed1996

Transplant renal artery stenosis in 77 patients--does it have an immunological cause?

Transplant renal artery stenosis (TRAS) is a common complication after transplantation and is an important cause of graft dysfunction. Damage from graft rejection, trauma, and atherosclerosis have been implicated as possible causes. We reviewed all 917 patients transplanted in our unit since 1978 to study the prevalence, clinical features, and possible causes of TRAS. Seventy-seven patients with TRAS were identified. The detected incidence was 2.4% before the introduction of color doppler ultrasonography (CDU) and rose to 12.4% after CDU was introduced in 1985, giving an overall incidence of 8.4% during a mean follow-up period of 6.9 years. The TRAS group was compared with a control group of 77 transplanted patients matched for age, year of transplant, sex, and number of previous grafts. Mean ages for the study and control groups were 43.6 +/- 15 and 44.8 +/- 13.7 yr. A total of 25% of cases of TRAS were diagnosed within the first 8 wk of transplantation and in 60% within the first 30 wk (median = 23 wk). All patients were treated with angioplasty, 28 patients had recurrence of TRAS requiring multiple angioplasties (maximum 5) and 1 went on to have surgery. Angioplasty resulted in a significant fall in plasma creatinine. Patient and graft survival were significantly worse in the TRAS group: 69% vs. 83% (P < 0.05) and 56% vs. 74% (P < 0.05) (TRAS vs. Control), respectively. There was a significantly higher incidence of rejection, especially cellular rejection in the TRAS group, 0.67 vs. 0.35 episodes per patient (P < 0.01) (TRAS vs. Control). Recurrence but not occurrence of TRAS was associated with the use of cyclosporine.

Adult↗
PubMed1996

Measurement of volume flow with time domain and M-mode imaging: in vitro and in vivo validation studies.

Color velocity imaging quantification is a commercially available technique that estimates volume flow within vessels by combining velocity data, acquired by time domain correlation, with vessel diameter measurements obtained by M-mode imaging. By integrating the velocity profile over time, quantitative volume flow calculations may be made. To investigate the accuracy of this system, we used two flow phantoms over a range of steady and pulsatile flows for in vitro evaluation, and the common carotid artery of 10 women on five consecutive occasions was insonated for in vivo assessment. In flow phantom studies, accuracy was within 8% for flows above 200 ml/min, but decreased at lower flows depending on the depth, beam-vessel angle used, and steering of the beam. At angles greater than 70 degrees, velocity errors made quantitative measurement of flow unreliable, whereas at angles less than 30 degrees, the increased error in calculating vessel diameter led to large errors of area estimation, and hence made flow measurements unreliable. For the in vivo studies on the carotid artery the intraoperator repeatability values for the three operators were 9.92% (A), 13.74% (B), and 13.24% (C). The interoperator repeatability for the group was 15.30%. This study suggests that the color velocity imaging quantification technique is an accurate and reproducible method of assessing volume flow in vessels. However, in our experience, obtaining volume flow data is more time consuming and operator dependent than traditional Doppler techniques. The color velocity imaging quantification system may be of use in monitoring conditions in which changes in volume flow in a vessel or to an organ is an important part of the disease process.

Blood Flow Velocity↗
PubMed1994

Artery-to-artery anastomosis in monochorionic twins.

We describe Doppler signals in artery-to-artery anastomoses of two monochorionic twin pregnancies. Flow velocity waveforms demonstrated cyclic changes in systolic velocities with intermittent reversal of end-diastolic velocities. A computer model showed that this was the result of two opposing pulsatile blood flow waveforms with different velocities and frequencies.

Arterio-Arterial Fistula↗
PubMed1994

Evaluation of Doppler ultrasound in primary non-function of renal transplants.

Doppler ultrasound investigation was performed in the renal grafts of 86 patients with primary non-function following cadaveric renal transplantation. Pulsatility Index, defined as: [formula: see text] was assessed to examine its predictive use in the diagnosis of rejection episodes as judged by a retrospective analysis of histological data. Altogether 415 Doppler examinations and 228 renal biopsies were performed. In our population the incidence of rejection was 57%. Using a pulsatility index (PI) > 1.8 to be indicative of rejection, the sensitivity of our test was 68% for vascular rejection and 65% for all rejection episodes. The specificity was 25%. We conclude that Doppler ultrasound cannot replace the need for transplant renal biopsy in patients with primary non-function.

Graft Rejection↗
PubMed1992

Doppler and color Doppler ultrasonography in renal transplants: chronic rejection.

Although Doppler and color Doppler ultrasonography has been used extensively to examine acute changes in renal allograft function, there have been few reports on the role of Doppler ultrasonography in the assessment of chronic rejection. In those studies that have addressed chronic rejection, there is agreement that changes in renal function are not accompanied by consistent changes in flow wave-form shape. The pathology of chronic rejection may be very different from the changes seen in acute rejection and its onset is usually gradual. Some authors have suggested that the decline in function is accompanied by lower Doppler frequency shifts (corresponding to lower velocities) in intra-renal arteries. In a preliminary study comparing grafts with normal renal function and with biopsy-proven chronic rejection, it has been shown that for grafts with chronic rejection, observed intra-renal velocities are lower, especially at segmental and interlobar levels. This may be a more reliable reflection of reduced renal blood flow in chronic rejection than conventional Doppler ultrasound analysis of flow waveform shape. However, the diagnostic use of changes to intra-renal flow velocities in chronic rejection is currently very limited.

Graft Rejection↗
PubMed1992

Arteriovenous fistulas in renal transplants: color Doppler ultrasound observations.

One hundred twenty-six new renal transplants were scanned regularly with color Doppler ultrasound (CDU). In 22 (17.5%) of the grafts there was evidence of postbiopsy arteriovenous (AV) fistula during the first 6 months postoperatively. In 14 cases the fistula closed spontaneously. In the remaining eight, the fistula was still present up to 24 months later (four cases) or until the graft failed (four cases). Additionally, 163 established grafts were scanned for evidence of vascular abnormality. AV fistulas were observed in 15 grafts (8%). Circulatory complications of fistulas observed include vascular steal and a possible association with graft vein and artery stenosis.

Arteriovenous Fistula↗
PubMed1992

Short term effect of oxygen on renal haemodynamics in patients with hypoxaemic chronic obstructive airways disease.

BACKGROUND: Oxygen therapy is effective in the prevention and treatment of oedematous exacerbations of cor pulmonale. As renal blood flow is reduced in cor pulmonale a study was designed to investigate whether one of the beneficial effects of oxygen was to increase renal blood flow. The effect of oxygen therapy on renal haemodynamics measured noninvasively was examined in patients with chronic obstructive airways disease and previous episodes of oedema. METHODS: Renal blood flow waveforms were recorded in a single vessel by colour flow Doppler ultrasound in nine hypoxaemic patients (PaO2) (arterial oxygen tension < 8 kPa while they were breathing air) with chronic obstructive airways disease and previous oedema and eight age matched normoxaemic volunteers (arterial oxygen saturation (SaO2) 97% or more when breathing air) while they were breathing air and oxygen. SaO2 and transcutaneous PaO2 (TcPO2) and PaCO2 (TcPCO2) were monitored. Five renal velocity profile recordings were made from the same segmental vessel with the patient breathing room air for one hour followed by oxygen titrated to achieve an oxygen saturation of 95% or more without a rise in TcPCO2 for 15 minutes. Control subjects breathed 35% oxygen. RESULTS: No significant change in the pulsatility index (a measure of distal vascular resistance) or mean height of the waveform (Tamx, a measure of renal blood flow) occurred in the control subjects while they were breathing air or oxygen. The pulsatility index of the patients with chronic obstructive airways disease was significantly greater than that in the control subjects breathing air (1.44 (SD 0.28) v 1.03 (0.14). Breathing oxygen was associated with an increase in TcPO2 in the patients (from 6.9 (1.9) to 11.5 (0.7) kPa), a fall in pulsatility index (from 1.44 (0.28) to 1.26 (0.14) and an increase in Tamx (from 0.187 (0.055) to 0.234 (0.087) m/s). CONCLUSIONS: The results suggest that renal vascular resistance is increased in patients with chronic obstructive airways disease and hypoxaemia and that short term oxygen therapy reduces renal vascular resistance and increases blood flow. Some of the benefits of oxygen therapy in cor pulmonale may be due to improvements in renal haemodynamics.

Aged↗
PubMed1991

Renal transplant vein stenosis: demonstration and percutaneous venoplasty of a new vascular complication in the transplant kidney.

Stenosis of the renal transplant vein has been demonstrated in eight patients undergoing investigation for renal dysfunction arising 3 weeks to 3 years after transplantation. The stenoses were diagnosed by duplex Doppler ultrasound in three cases and by angiography in the presence of arterio-venous fistula in five cases. In four patients percutaneous venous dilatation was performed with technical success in three. In two patients this was repeated for recurrent stenosis but sustained improvement in renal function was not observed. Progression of the venous stenoses was documented with one patient suffering graft loss due to complete venous occlusion.

Adult↗
PubMed1990

Detection of occult nodal metastases in patients with colorectal carcinoma.

Immunohistochemical study may be used for detecting micrometastases by their expression of tumor-associated antigens. In 48 specimens of colorectal cancer from 47 patients, 49 of 249 lymph nodes (median, five per patient; range, 2-11) examined by light microscopic study contained tumor deposits. Sections of all lymph nodes were also examined by immunohistochemical study for carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA) expression using the indirect immunoperoxidase staining method. All 49 lymph node metastases (100%) from 20 patients stained positively for CEA and 45 (92%) expressed EMA. Of the 200 lymph nodes without metastases on light microscopic examination, anti-CEA revealed a single micrometastasis in a patient staged as Dukes' B. No additional metastases were detected with anti-EMA. In this series of patients immunohistochemical study has, therefore, influenced the histologic staging in only one patient (2%) and thus does not offer a significant benefit over conventional histologic staging.

Antibodies, Monoclonal↗