Evaluation of a module for the fusion of data on blood vessels from multiple sources.
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Carotid Arteries↗
Biomedical subjects
A C Colchester
Publications and source records attributed to A C Colchester.
A new algorithm for deriving pulsatile blood flow waveforms tested using stimulated dynamic angiographic data.
In vascular pathology the assessment of disease severity and monitoring of treatment requires quantitative and reproducible measurements of arterial blood flow. We have developed a new technique for processing sequences of dynamic digital X-ray angiographic images. We have tested it using computer simulated angiographic data which includes the effect of pulsatile blood flow and X-ray quantum noise. A parametric image was formed in which the image grey-level represents dye concentration as a function of time and distance along a vessel segment. Adjacent concentration--distance profiles in the parametric image were re-registered along the vessel axis until a match occurred. A match was defined as the point where the sum of squares of the differences in the two profiles was a minimum. The distance translated per frame interval is equal to the bolus velocity. We have tested several contrast medium injection methods including constant flow and a range of discrete pulses per second. The technique proved to be robust and independent of injection technique. Average blood flow was measured for simulated pulsatile waveforms with mean flows of up to 650 ml/min (peak velocities up to 186 cm/s) in a range of diameters from 2 mm to 6 mm. The standard deviation of the error in the mean flow estimates over the whole range of velocities and vessel sizes was +/- 1.4 cm/s.
Algorithms↗
Prediction of neurological damage after cardiopulmonary bypass surgery. Use of the cerebral function analysing monitor.
Sixty-five patients who had coronary artery graft surgery were subjected to detailed neuropsychometric assessment before operation and twice again within 7 days after operation. They were monitored continuously with a cerebral function analysing monitor during the operation. The results of the peroperative cerebral monitoring were compared on completion of the study with the neuropsychometric assessments. Seventy-six percent of the patients with a significant neuropsychometric deficit after operation also showed significant peroperative changes on the analysing monitor; the majority occurred immediately after the start of perfusion. Twenty-eight patients failed to demonstrate any evidence of neuropsychometric deficit and six (21%) of these also showed significant peroperative changes. All patients whose traces demonstrated more than one significant change during the peroperative course had a significant neuropsychometric deficit afterwards.
Brain↗
Evidence for involvement of hypocapnia and hypoperfusion in aetiology of neurological deficit after cardiopulmonary bypass.
Arterial and jugular bulb pressures and blood gas tensions were recorded for later analysis in 65 patients having coronary artery graft surgery. In the first 35 (group A) routine peroperative monitoring was used; and in the next 30 (group B), similar in age and other characteristics, special measures were adopted to maintain normocapnia (PaCO2 35-45 mm Hg) by continuous monitoring during surgery. On the third postoperative day clinical neurological deficits were observed in 46% of group A and 27% of group B, and psychometric deficits in 71% and 40%, respectively. On analysis of the records, more than half of group A proved to have been hypocapnic immediately before onset of cardiopulmonary bypass, and those with postoperative deficits differed from the others in this group in having had greater changes in PaCO2 after onset of bypass and lower cerebral perfusion pressures in the first 10 minutes of bypass, usually because of a rise in cerebral venous pressure.
Carbon Dioxide↗
Tuberculosis of the central nervous system.
We report on the clinical features, management, and outcome of 27 patients with tuberculous disease of the central nervous system admitted to the London Hospital over six years. Seventeen presented with meningitis, and in nine of these there was bacteriological confirmation of tuberculous disease although acid fast bacilli were only found in the CSF of four patients. This appeared to carry a poor prognosis. There was a high incidence of rifampicin-induced hepatitis. The outcome was satisfactory in six out of seven patients in whom no AFBs were cultured. Eleven patients presented with intracranial tuberculomas but without evidence of systemic TB. The CT scan revealed mass lesions, but only in three patients was the appearance pathognomonic of tuberculoma. However, biopsy can be a hazardous procedure and led to the death of two of our patients. Where possible, surgical intervention should be avoided, and the response to medical treatment assessed by CT scan.
Adolescent↗
Treatment of hyperlipidaemia retards progression of symptomatic femoral atherosclerosis. A randomised controlled trial.
The effect of plasma lipid reduction on the progression of femoral atherosclerosis was studied in hyperlipidaemic patients with stable intermittent claudication. 24 patients were randomly assigned to treatment and usual-care groups, the former receiving dietary advice and cholestyramine, nicotinic acid, or clofibrate depending on their lipoprotein phenotype. Biplanar arteriography was performed when the study began and after a mean period of 19 months. Angiograms were assessed visually, with blinding, and by computerised image analysis. Therapy reduced mean plasma total cholesterol by 25%, mean low density lipoprotein (LDL) cholesterol by 28%, and mean plasma triglycerides by 45%. Significantly fewer arterial segments showed detectable progression of atherosclerosis in the treatment group. The mean increase in plaque area (mm2/segment/year) in the treatment group was only one third of that in the usual-care group. The mean increase in edge irregularity index (a measure of the severity of disease) in the treatment group was only 40% of that in the usual care group. Twice as many arterial segments showed improvement in the treatment group. In both groups changes in edge irregularity index were directly related to plasma LDL cholesterol concentration. This study, the first randomised controlled trial of its type, provides evidence that effective treatment of hyperlipidaemia favourably influences the natural history of symptomatic peripheral atherosclerosis.
Angiography↗
A geometry-and intensity-based partial volume correction for MRI volumetric studies.
Segmentation of objects of interest in magnetic resonance imaging is a necessary procedure for volumetric calculations. However, these direct measurements tend to be inaccurate due to the intrinsic MRI partial volume effects. In this paper, a general method for correcting these effects based on the geometry and grey level intensity of the segmented objects is presented. This method is independent of the segmentation strategy used to extract the objects of interest. An evaluation for three different segmentation methods is presented and it is shown that the proposed partial volume correction can improve the volume estimation of all three methods.
Brain↗
Computer-aided interpretation of SPECT images of the brain using an MRI-derived 3D neuro-anatomical atlas.
Nuclear medicine images have comparatively poor spatial resolution, making it difficult to relate the functional information which they contain to precise anatomical structures. A 3D neuro-anatomical atlas has been generated from the MRI data set of a normal, healthy volunteer to assist in the interpretation of nuclear medicine scans of the brain. Region growing and edge-detection techniques were used to semi-automatically segment the data set into the major tissue types within the brain. The atlas was then labelled interactively by marking points on each 2D slice. Anatomical structures useful in the interpretation of SPECT images were labelled. Additional, more detailed information corresponding to these structures is provided via an interactive index which allows access to images, diagrams and explanations. Registration of patient SPECT studies with the atlas is accomplished by using the position of the skull vertex and four external fiducial markers attached to the skin surface. The 3D coordinates determined from these points are used to calculate the transformation required to rotate, scale and translate the SPECT data, in 3D, to match the atlas. Corresponding 2D slices from the two 3D data sets are then displayed side-by-side on a computer screen. A cursor linking the two images allows the delineation of regions of interest (ROIs) in the SPECT scan based on anatomical structures identified from the atlas. Conversely regions of abnormal isotope distribution in the SPECT image can be localized by reference to corresponding structures in the atlas.
Brain↗