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M A Macleod

Publications and source records attributed to M A Macleod.

At least 19 recordsLinked to original sources
PubMed2001

Geographical distribution of variant Creutzfeldt-Jakob disease in Great Britain, 1994-2000.

BACKGROUND: Geographical variation in the distribution of variant Creutzfeldt-Jakob disease (vCJD) might indicate the transmission route of the infectious agent to man. We investigated whether regional incidences of vCJD were correlated with regional dietary data. METHODS: The National CJD Surveillance Unit prospectively identified 84 people with vCJD up to Nov 10, 2000, in Great Britain. Their lifetime residential histories were obtained by interviews with a close relative. Cumulative incidences of vCJD by standard region were calculated. Grid references for places of residence in 1991 were identified and evidence of geographical clusters were sought. Data on diet in the 1980s were analysed for regional correlations with vCJD incidence. The socioeconomic status of the places of residence of people with vCJD was compared with that of the general population. FINDINGS: vCJD incidence was higher in the north of Great Britain than the south. The rate ratio (north vs south) was 1.94 (95% CI 1.27-2.98). The mean Carstairs' deprivation score for areas of residence of people with vCJD was -0.09 (-0.73 to 0.55), which is close to the national average of zero. Regional rates of vCJD were correlated with consumption of other meat or meat products as classified and recorded by the Household Food Consumption and Expenditure Survey (r=0.72), but not with data from the Dietary and Nutritional Survey of British Adults. Five people with vCJD in Leicestershire formed a cluster (p=0.004). INTERPRETATION: Regional differences in vCJD incidence are unlikely to be due to ascertainment bias. We had difficulty determining whether regional variations in diet might cause these differences, since the results of dietary analyses were inconsistent.

Adult↗
PubMed2000

The pulvinar sign on magnetic resonance imaging in variant Creutzfeldt-Jakob disease.

BACKGROUND: There is a need for an accurate non-invasive diagnostic test for variant Creutzfeldt-Jakob disease (vCJD). We investigated the sensitivity and specificity of bilateral pulvinar high signal on magnetic resonance imaging (MRI) for the diagnosis of vCJD. METHODS: MRI from patients with vCJD and controls (patients with suspected CJD) were analysed. Scans were reviewed on two separate occasions by two neuroradiologists and scored for the distribution of changes, and likely final diagnosis. Scans from vCJD cases were reassessed to reach a consensus on all abnormalities. FINDINGS: We analysed 36 patients and 57 controls. vCJD patients were correctly identified based on bilateral pulvinar high signal in 29 of 36 and 32 of 36 cases on the first assessment by the two radiologists, and 32 of 36 and 31 of 36 on their second assessment. Bilateral increased pulvinar signal was identified in one of 57 and one of 57 controls on the first assessment and two of 57 and three of 57 controls on the second assessment. These reported changes in controls were graded as minimal/equivocal in six of seven patients and moderate in one (<0.5% of all control assessments). 80% of the assessments in vCJD cases were graded as moderate or substantial. On consensus review, 28 of 36 cases and none of 57 controls had prominent bilateral pulvinar signal-sensitivity 78% (95% CI 60-90%) and specificity 100% (95% CI 94-100%). Other common MRI features of vCJD were medial thalamic and periaqueductal grey matter high signal, and the notable absence of cerebral atrophy. Pulvinar high signal correlated with histological gliosis. INTERPRETATION: In the appropriate clinical context the MRI identification of bilaterally increased pulvinar signal is a useful non-invasive test for the diagnosis of vCJD.

Adolescent↗
PubMed2000

Diagnosis of new variant Creutzfeldt-Jakob disease.

As of December 31, 1998, 35 deaths had been attributed to new variant Creutzfeldt-Jakob disease (nvCJD) in the United Kingdom, of which 33 cases had been neuropathologically confirmed and 2 classified as probable nvCJD. Fifteen cases were male and 20 female. The median illness duration was 14 months (range, 8-38 months) and the median age at death was 29 years (range, 18-53 years). The dinical features were consistent with previous descriptions. In nearly all cases, there were early psychiatric symptoms after a median period of 6 months ataxia developed, followed by involuntary movements and cognitive impairment. Electroencephalograms did not show the "typical" appearances found in sporadic CJD, about half the cases tested had a positive 14-3-3 immunoassay, and over 70% of cases had bilateral pulvinar high signal on magnetic resonance brain scanning. Prion protein gene analysis showed that all cases were homozygous for methionine at codon 129. Diagnostic criteria for nvCJD have been formulated, which have a high sensitivity and specificity.

Adolescent↗
PubMed1999

[111Indium-DTPA-D-phe] octreotide scintigraphy in the diagnostic assessment of palpable breast lumps.

It has been suggested that [111Indium-DTPA-D-Phe] octreotide scintigraphy may be useful in the staging of breast cancer. We evaluated its role in the diagnostic assessment of 40 female patients with palpable breast lumps. All were clinically assessed and imaged by ultrasound or mammography. Thirty patients had adequate FNA cytology performed. Histological examination following core or excision biopsy showed 31 lumps to be benign and 9 to be malignant. All patients with invasive cancer proceeded to wide local excision or mastectomy with an axillary clearance. The mean diameter of malignant lesions was 2.4 cm (SEM 0.3 cm). The sensitivity (22%), specificity (81%) and positive predictive value (25%) of octreotide scintigraphy in the detection of breast cancer was inferior to that of clinical assessment (56%, 90% and 71%), radiological imaging(77%, 96% and 100%) and FNA cytology (88%, 95% and 88%). No axillary uptake of isotope was seen in 4 patients with nodal metastases. Four scans showed uptake of isotope at one or more sites remote from the clinically or radiologically significant lesion. [111Indium-DTPA-D-Phe] octreotide scintigraphy provided no additional diagnostic information to that given by triple assessment and does not appear to have a role in the evaluation of breast lumps.

Adult↗
PubMed1998

An assessment of two methods for generating automatic regions of interest.

Two fully automatic methods for generating regions of interest (ROIs) for nuclear medicine images are described and assessed. One of these, involving registration of a previously defined ROI onto a new image, uses spatial information and is appropriate for two- and three-dimensional images which may be static or dynamic. The other method is based on artificial neural networks and uses temporal information. It is appropriate for dynamic images only. The registration method has been tested using 10 pairs of stress and redistribution images obtained from cardiac perfusion SPET. Regions of interest of the left ventricular muscle, defined on the stress images, were registered onto the redistribution images, where they were compared with reproducibility of manually drawn ROIs. Both methods were tested on 17 99Tcm-MAG3 kidney dynamic studies, where the original ROIs corresponding to both kidneys and the bladder were defined using the COST B2 hybrid phantom. Our results indicate that neither method is as reliable as having ROIs redrawn by the operator, although there are indications that an artificial neural network which combines the use of the spatial and temporal information could prove useful for dynamic studies.

Automation↗
PubMed1998

Use of significance image to determine patterns of cortical blood flow abnormality in pathological and at-risk groups.

UNLABELLED: The purpose of this work was to determine whether certain pathological groups and other groups at risk for neurological damage exhibited distinctive patterns of regional cerebral blood flow (rCBF) abnormality. METHODS: HMPAO SPECT images obtained from six groups of subjects were compared with a normal cortical rCBF atlas, based on multivariate, voxel-by-voxel methods. In each case, a significance image was outputted, highlighting voxels with deficits of > or =3 s.d. of normal. Abnormal patterns were examined for the six groups, which comprised a further 40 normal volunteers, 18 diver controls, 50 divers with decompression illness (DCI), 34 boxers, 23 schizophrenics and 21 subjects with Alzheimer's disease. RESULTS: The percentages of abnormal cortical voxels for each group were 0.41%, 0.53%, 1.38%, 1.05%, 0.56% and 2.24%, respectively. The percentages of images in each group with at least one lesion of 10 or more connected abnormal voxels and at least 10 lesions of two or more connected voxels, respectively, were 8% and 8% (normal volunteers), 17% and 11% (diver controls), 38% and 38% (divers with DCI), 41% and 29% (boxers), 26% and 13% (schizophrenics) and 90% and 48% (subjects with Alzheimer's disease). This suggests that multiple small lesions are as common as single large lesions for divers with DCI but not for patients with Alzheimer's disease or schizophrenia. Large lesions are located predominantly in the parietal and inferior temporal regions for Alzheimer's disease, in the parietal and occipital regions for divers with DCI and boxers and in the inferior frontal region for schizophrenia. CONCLUSION: It appears that the groups considered here do have different rCBF patterns and that the significance image is a useful way of demonstrating this fact.

Adult↗
PubMed1998

Cerebral perfusion and psychometric testing after exposure to high altitude in the mountains.

Exposure to hypobaric hypoxia is known to cause reductions in mental performance and decision-making and it has been reported that these effects are not fully reversed following descent from altitude. Eight climbers had cerebral perfusion scans performed and undertook a battery of psychometric tests prior to, and upon return from, an expedition to climb the eleventh highest mountain in the world, Gasherbrum 1. No decrements were found in either their performance on the psychometric tests nor to their cerebral perfusion following the expedition. Two subjects had significant cerebral perfusion abnormalities prior to the expedition, which had improved immediately following their return from the expedition. Repeat scans four months later showed the lesion of one of the subjects had returned and there were indications that the lesion in the other subject was beginning to return. These findings are in contrast to previous studies which have suggested that altitude exposure leads to permanent reductions in brain function, this could be because in those studies factors other than hypobaric hypoxia per se lead to the reductions in brain function.

Adult↗
PubMed1996

Optimization of factors affecting the state of normality of a medical image.

The purpose of this paper is to examine the first stage of the diagnostic process in medical imaging, namely determination of the state of normality, and to attempt to optimize factors contributing to this stage. An image of a given type is defined as abnormal if it does not belong to the appropriate class of normal images. All images must be pre-processed involving image registration and normalization to align and scale the images with respect to each other. Normal ranges may be determined for each voxel (or other appropriate region) from a representative normal sample using univariate analysis, obtaining mean and standard deviation images, or multivariate analysis, which accounts also for normal patterns of variation (represented as principal components). For a new image, the variation from normality (in SDs) for each region may be determined. Since the spatial distribution of this parameter is thought to be relevant, connectivity of abnormal voxels was considered as a possible factor. For the purposes of this study, SPECT images indicating regional cerebral blood flow were used. Images from 50 normal subjects formed the normal sample. A further 40 normal subjects and 200 patients referred with suspected dementia were then analyzed using the normal ranges. ROC analysis, using number of SDs as a variable threshold, was used to optimize the factors. Normalization to global values followed by multivariate analysis using four or five principal components provided optimal discrimination. Connectivity of voxels emerged as an important factor, around 10 connected voxels being optimal for this study.

Adolescent↗
PubMed1996

A voxel-by-voxel multivariate analysis of cerebral perfusion defects in divers with 'bends'.

Past analysis of dysbaric-induced cerebral perfusion defects, demonstrated by 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) single photon emission tomography in divers using quantitative and/or univariate techniques, has resulted i considerable controversy regarding the significance of these lesions compared to those seen in control subjects, correlations with clinical findings and the role of 99Tcm-HMPAO as a prognostic indicator in decompression sickness. We tried to address these problems by using a multivariate approach to a voxel-by-voxel analysis, involving the use of principal components, to determine ranges of normality in 50 reference controls. In subsequent images, abnormality was defined as 10 spatially connected voxels at an appropriate significance level of three standard deviations. The images of 50 divers with clinically diagnosed 'bends' were compared with those of a further 40 normal population controls with no previous history of loss of consciousness, head injury or dysbarism. The results showed that 19 of 50 divers with 'bends' and 3 of 40 population controls had significant perfusion defects, representing a significant difference between divers with dysbarism and population controls at the level P < 0.002. It is concluded that dysbarism causes significant cerebral cortical perfusion defects in affected divers both in 'silent' and symptomatic (clinically correlated) areas.

Adolescent↗
PubMed1995

Cerebral perfusion and psychometric testing in military amateur boxers and controls.

The objective was to compare two neurophysiological variables in active amateur boxers with non-boxing sportsmen. 41 boxers and 27 controls were given psychometric tests: 34 boxers and 34 controls underwent technetium-99m hexamethylpropyleneamineoxime single photon emission computerised tomography (Tc-99m HMPAO SPECT) cerebral perfusion scans. The controls performed better at most aspects of the psychometric tests. Boxers who had fought fewer bouts had a tendency to perform better at psychometric tests than those boxers who had fought more bouts. Tc-99m HMPAO SPECT cerebral perfusion scanning showed that controls had less aberrations in cerebral perfusion than the boxers. In conclusion, significant differences were shown in two neurophysiological variables between young amateur sportsmen who box and those who do not. The long term effects of these findings remain unknown.

Adolescent↗
PubMed1994

A method for assessing the significance of abnormalities in HMPO brain SPECT images.

METHODS: A normal atlas for HMPAO rCBF SPECT images was obtained from images of 53 normal controls. Following image registration and normalization, a mean image was extracted, while images representing correlated normal deviants were identified using principal component analysis. These images formed the "building blocks" of the atlas. For subsequent images, the atlas was used to create a "nearest normal equivalent" image, which was compared to a residual standard deviation image to determine the significance of deviations in the new image. RESULTS: Images from 30 patients (10 with Alzheimer's disease; 12 with single or multiple infarcts; and 8 normals) were analyzed. CONCLUSION: Using an optimal decision level, 10/10 patients with Alzheimer's disease and 11/12 patients with infarcts were correctly identified, with only one false-positive resulting. We utilized a database of images obtained from normal controls to create a normal atlas.

Alzheimer Disease↗
PubMed1991

The use of induction in the design of an expert system for thyroid function studies.

In this study, the role of induction in the design of an expert system for diagnosing thyroid disorders is evaluated. An expert system was first designed conventionally, based on interaction between a knowledge engineer and a thyroid specialist. This involved weighting three tests (T3, free T4 and TSH) according to the reliability of the test and the presence or otherwise of influencing factors. Compatibility was then tested with known ranges for the parameter values, and a diagnosis made of one of three possible outcomes (euthyroid; hypothyroid; hyperthyroid). Two expert systems were then induced using, firstly, a set of rules and, secondly, a sample set chosen from a database. These systems were then tested against the expert designed system. Both induced systems produced results which were superior to the expert designed system and, in addition, provided insight into the decision-making process. It is concluded that induction is very useful in the design of expert systems of this nature.

Expert Systems↗