AbstractThe aim of this study was to investigate the value of fractal dimension in separating no... more AbstractThe aim of this study was to investigate the value of fractal dimension in separating normal and cancerous images, and to examine the relationship between fractal dimension and traditional texture analysis features. Forty-four normal images and 58 cancer images from ...
The degree of myocardial electrical organization during ventricular fibrillation remains unknown.... more The degree of myocardial electrical organization during ventricular fibrillation remains unknown. The aim of this study was to compare the characteristics of the surface ECG on three independent and approximately orthogonal leads. Ten recordings of ventricular fibrillation, each induced at electrophysiology study and successfully terminated by direct current shock, were analyzed. Each recording was divided into 1-second epochs for analysis. Frequency analysis using the Fast Fourier Transform showed that the frequency of the dominant spectral peak increased significantly from a mean of 4.1 +/- 0.8 Hz to 5.2 +/- 0.7 Hz during the first 5 seconds of ventricular fibrillation. In 95% of the epochs analyzed, a similar dominant frequency was observed on either two or three ECG leads. Frequency agreement tended to increase as ventricular fibrillation evolved. This study shows that the rate of ventricular fibrillation increases rapidly during the first 5 seconds but only gradually thereafter, and that similar signal characteristics are observed on independent ECG leads. These findings are not compatible with the traditional view of incoherent myocardial activity during ventricular fibrillation.
Background: There are no data on the pattern of the Korotkoff phases in the normal population. Th... more Background: There are no data on the pattern of the Korotkoff phases in the normal population. This study was designed to describe the pattern of Korotkoff phase distribution in adults and children; to measure the duration of each of the phases; and to describe the differences between adults and children. Methods: A total of 57 children (7 to 8 years old) and 59 adults (median age 47 years, range 30 to 62 years) were studied. The pressure in the arm cuff was deflated using a device to provide a consistent deflation rate. The Korotkoff sounds were recorded to MiniDisc from the bell of a stethoscope and each sound described as phase I, II, III, or IV. Results: The most common pattern of Korotkoff phase distribution was for all five phases to be present (children [23/57; 40%], adults [24/59; 41%]). Phases I and IV were more common in children than in adults (56/57 [98%] v 47/59 [80%]; P ϭ .002 for phase I; 52/57 [91%] v 44/59 [75%]; P ϭ .018 for phase IV). Phases II and III were less common in children than in adults (32/57 [56%] v 50/59 [85%], P ϭ .001 for phase II; 27/57 [47%] v 45/59 [76%], P ϭ .001 for phase III). Phases I and IV were longer in children (median 3.9 [interquartile range, IQR 2.1 to 6.7] and 6.7 [IQR 3.2 to 9.8] sec, respectively) compared with adults (1.3 [IQR 0.7 to 2.7] and 1.7 [IQR 0.3 to 2.6), P Ͻ .001). Conclusions: There are clear differences in the Korotkoff phases between adults and children. The length of phases II and III increase with age with concomitant decrease in phases I and IV. These differences between adults and children remain unexplained.
7th International Conference on Image Processing and its Applications, 1999
ABSTRACT Image analysis for the classification of normal and cancerous colonic mucosa is reported... more ABSTRACT Image analysis for the classification of normal and cancerous colonic mucosa is reported. Pathology samples were taken from human colon mucosa, and 44 normal and 58 cancer images captured to computer via an optical microscope with a CCD camera. Texture analysis was performed using fractal dimension, entropy and correlation. Using non-parametric classification, fractal dimension improved the classification accuracy from 88% to 94% in comparison with the combined entropy and correlation analysis
Background and Purpose— Impaired autonomic function is common in the acute poststroke phase but l... more Background and Purpose— Impaired autonomic function is common in the acute poststroke phase but little is known about the longer term effects, particularly in older people. We sought to determine if autonomic function is impaired after stroke recovery in older patients. Methods— A cross-sectional case-control study comparing autonomic function in 76 nondemented stroke patients with 70 community-living controls aged older than 75 years. Results— Cases were assessed on average 9 months after stroke. From power spectral analysis of heart rate variability, stroke patients had lower total ( P =0.032) and low-frequency ( P =0.014) spectral densities and impaired baroreflex sensitivity (α low-frequency baroreflex sensitivity, P =0.006). From a series of cardiovascular autonomic reflex tests, heart rate variation during forced respiration, Valsalva ratio, and blood pressure overshoot during Valsalva maneuver were significantly lower in stroke patients ( P =0.003, <0.001, and 0.027, respe...
To investigate the effect of different lead exclusion criteria for the manual measurement of QT d... more To investigate the effect of different lead exclusion criteria for the manual measurement of QT dispersion (QTd). Simultaneous 12-lead ECGs from three groups of 25 subjects were studied; healthy normal subjects, subjects with a myocardial infarction, and subjects with arrhythmias. Leads were excluded with (1) small absolute T wave amplitudes, (2) small relative T wave amplitudes, and (3) small and/or large relative QT measurements. QTd was calculated as the QT range and assessed for its ability to differentiate between the normal and pathological groups. With exclusion of no leads or low absolute amplitude T waves (&amp;amp;lt; 50 microV) significant differences were observed only between normal and myocardial infarct groups (P &amp;amp;lt; 0.05). Significant differences between normal and both pathological groups were observed when excluding the lead with the smallest amplitude T wave or shortest QT (P &amp;amp;lt; 0.05), or when two leads of either type were excluded (P &amp;amp;lt; 0.005). There was good agreement between leads excluded by amplitude or QT (P &amp;amp;lt; 0.01). Lead exclusion for QTd is important. Exclusion of the two smallest amplitude or two shortest QT leads from each subject produced the greatest differences between the normal and pathological groups.
Objective: This study prospectively assessed the diagnostic accuracy of a novel bilateral photopl... more Objective: This study prospectively assessed the diagnostic accuracy of a novel bilateral photoplethysmography toe pulse measurement technique for the detection of significant lower limb peripheral arterial disease. Method: Bilateral photoplethysmography toe pulse measurements were compared with the ankle-brachial pressure index (ABPI) gold standard reference. Pulse wave analysis techniques extracted timing, amplitude, and shape characteristics for the great toes and their right-to-left side differences. These characteristics were compared with previously obtained normative ranges, and the accuracy was assessed for all significant disease (ABPI <0.9) and higher-grade disease (ABPI <0.5). Measurements were collected in a controlled environment within a tertiary vascular surgical unit for 111 subjects (age range, 42-91years), of whom 48 had significant lower limb peripheral arterial disease and 63 were healthy. Subjects were matched in age, sex, height, body mass index, and heart rate. Diagnostic performance was assessed using diagnostic sensitivity, specificity, accuracy, negative-predictive and positive-predictive value, and the statistic representing agreement between techniques beyond chance. Results: The degree that pulse shape fell beyond the normal range of normalized pulse shapes was at the threshold of substantial to almost perfect agreement compared with ABPI for significant disease detection (diagnostic accuracy, 91% [ ؍ 0.80]; sensitivity, 93%; specificity, 89%), and with 90% accuracy (؍ 0.65) for higher-grade disease detection. Pulse transit time differences between right and left toes also had substantial agreement with ABPI, with diagnostic accuracy of 86% for significant disease detection (pulse transit time to pulse foot [ ؍ 0.71] and to pulse peak [ ؍ 0.70]) and reached at least 90% for these for the higher-grade disease. The performance ranking for the different pulse features mirrored an earlier pilot study. With the shape and pulse transit time measurements, the negative-predictive values of the 5% disease population screening-prevalence level were at least 99% and had positive-predictive values of at least 98% for the 90% disease-prevalence level for vascular laboratory referrals. Conclusion: This simple-to-use technique could offer significant benefits for the diagnosis of peripheral arterial disease in settings such as primary care where noninvasive, accurate, and diagnostic techniques not requiring specialist training are desirable. Improved diagnosis and screening for peripheral arterial disease has the potential to allow identification and risk factor management for this high-risk group.
Journal of Neurology, Neurosurgery & Psychiatry, 2006
Background: There are no studies of autonomic function comparing Alzheimer's disease (AD), vascul... more Background: There are no studies of autonomic function comparing Alzheimer's disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). Aims: To assess cardiovascular autonomic function in 39 patients with AD, 30 with VAD, 30 with DLB, 40 with PDD and 38 elderly controls by Ewing's battery of autonomic function tests and power spectral analysis of heart rate variability. To determine the prevalence of orthostatic hypotension and autonomic neuropathies by Ewing's classification. Results: There were significant differences in severity of cardiovascular autonomic dysfunction between the four types of dementia. PDD and DLB had considerable dysfunction. VAD showed limited evidence of autonomic dysfunction and in AD, apart from orthostatic hypotension, autonomic functions were relatively unimpaired. PDD showed consistent impairment of both parasympathetic and sympathetic function tests in comparison with controls (all p,0.001) and AD (all p,0.03). DLB showed impairment of parasympathetic function (all p,0.05) and one of the sympathetic tests in comparison with controls (orthostasis; p = 0.02). PDD had significantly more impairment than DLB in some autonomic parameters (Valsalva ratio: p = 0.024; response to isometric exercise: p = 0.002). Patients with VAD showed impairment in two parasympathetic tests (orthostasis: p = 0.02; Valsalva ratio: p = 0.08) and one sympathetic test (orthostasis: p = 0.04). These results were in contrast with AD patients who only showed impairment in one sympathetic response (orthostasis: p = 0.004). The prevalence of orthostatic hypotension and autonomic neuropathies was higher in all dementias than in controls (all p,0.05). Conclusion: Autonomic dysfunction occurs in all common dementias but is especially prominent in PDD with important treatment implications.
Journal of Medical Engineering & Technology, 1986
A new technique using a pre-calibrated magnetometer has been used to investigate the stability of... more A new technique using a pre-calibrated magnetometer has been used to investigate the stability of the human body. Transducer coils were attached to a belt which was worn by the subject. Sway was measured over 30 s periods with eyes open and eyes closed. For 10 normal subjects, the mean sway speed was 3.6 +/- 0.9 mm/s with eyes open, and 5.3 +/- 1.5 mm/s with eyes closed. The mean ratio for eyes open to eyes closed was 0.68 +/- 0.10. The test was simple to perform and gave reproducible results.
IEEE Transactions on Information Technology in Biomedicine, 2002
The aim of this study was to investigate the value of fractal dimension in separating normal and ... more The aim of this study was to investigate the value of fractal dimension in separating normal and cancerous images, and to examine the relationship between fractal dimension and traditional texture analysis features. Forty-four normal images and 58 cancer images from sections of the colon were analyzed. A "leave-one-out" analysis approach was used to classify the samples into each group. With fractal analysis there was a highly significant difference between groups (0 0001). Correlation and entropy features showed greater differences between the groups (0 0001). Nevertheless, the addition of fractal analysis to the feature analysis improved the sensitivity from 90% to 95% and specificity from 86% to 93%.
IEEE Transactions on Information Technology in Biomedicine, 1998
The development of an automated algorithm for the categorization of normal and cancerous colon mu... more The development of an automated algorithm for the categorization of normal and cancerous colon mucosa is reported. Six features based on texture analysis were studied. They were derived using the co-occurrence matrix and were angular second moment, entropy, contrast, inverse difference moment, dissimilarity, and correlation. Optical density was also studied. Forty-four normal images and 58 cancerous images from sections of the colon were analyzed. These two groups were split equally into two subgroups: one set was used for supervised training and the other to test the classification algorithm. A stepwise selection procedure showed that correlation and entropy were the features that discriminated most strongly between normal and cancerous tissue (P < 0:0001). A parametric linear-discriminate function was used to determine the classification rule. For the training set, a sensitivity and specificity of 93.1% and 81.8%, respectively, were achieved, with an overall accuracy of 88.2%. These results were confirmed with the test set, with a sensitivity and specificity of 93.1% and 86.4%, respectively, and an overall accuracy of 90.2%.
The repeatability of commonly used electrocardiographic (ECG) related autonomic function tests wa... more The repeatability of commonly used electrocardiographic (ECG) related autonomic function tests was investigated in 25 diabetic subjects, mean age 44 (range 18-67) years and mean duration of diabetes 10 (&lt; 1-35) years. Tests were based on deep breathing, the Valsalva manoeuvre, relaxed normal breathing, and standing up from a lying position. All tests were repeated twice at each session, with two sessions separated by a mean of 5 (range 3-8) months. ECG and respiratory data were recorded for subsequent analysis. Maximum (max) and minimum (min) RR intervals and instantaneous heart rate (HR) were determined. The mean and repeatability data (within-subject standard deviation) for 21 different test results were calculated, and included deep breathing sitting (max-min)RR 226 +/- 39 ms and (max-min)HR 19.3 +/- 3.2 beats min-1, Valsalva manoeuvre 1.74 +/- 0.18, and lying-to-standing RR ratio 1.19 +/- 0.07. The within-subject repeatability to between-subject variability ratios consistently demonstrated that it is better to perform the deep breathing test sitting (with the smaller mean ratio of 0.37) rather than supine (0.46), with the use of three respiratory cycles rather than a single cycle (0.33 compared with 0.50 for (max-min)RR). A significant (p = 0.037) relationship was found between variability in heart rate changes and variability in air volume breathed during the deep breathing test.
The electrocardiogram is of major importance in the diagnosis of heart disease. Cardiac repolaris... more The electrocardiogram is of major importance in the diagnosis of heart disease. Cardiac repolarisation is the result of the return to a resting state of myocardial cells, and is detected on the surface 12-lead ECG as the T wave. The exact mechanisms responsible for the T wave shape are not completely understood. In this work, using our computer model of
ABSTRACT A recent BBC radio programme highlighted the case of an airline pilot’s wife who died un... more ABSTRACT A recent BBC radio programme highlighted the case of an airline pilot’s wife who died unexpectedly during surgery. The pilot was surprised by the lack of seriousness in investigating the incident. In his review of the programme, Ferner remarked on the many …
The genesis of the U wave in the ECG is still in doubt. This study aimed to investigate the relat... more The genesis of the U wave in the ECG is still in doubt. This study aimed to investigate the relationship between the occurrence of the U wave and both the electrical and mechanical timing sequence in heart beats. The M-mode echocardiography and 12-lead ECG were simultaneously recorded from 4 healthy subjects, with four repeat measurements in each. The ECG for both aortic valve (AV) and mitral valve (MV) were recorded from all four subjects. The timings of QQ interval, the peak and end of T wave, the peak and end of U wave, the AV and MV opening and closing were measured. The relationships between the QQ interval and the other timings were analysed. The MV opening and AV closing preceded the end of T wave (also considered as the start of U wave for healthy subjects) by 9 ± 11ms and 47 ± 15ms, respectively. When compared with the mechanical timings, the timing of the U wave had better correlation with the QQ interval, with the R square increasing from 0.76 to 0.95. Our finding suggest...
Background/Objectives: Older adults in sub-Saharan Africa (SSA) are at greatest risk of an impend... more Background/Objectives: Older adults in sub-Saharan Africa (SSA) are at greatest risk of an impending noncommunicable diseases epidemic, of which cardiac disease is the most prevalent contributor. Thus, it is essential to establish electrocardiographic reference values for a population that is likely to differ genetically and environmentally from others where reference values are established. Methods: Two thousand two hundred thirty-two apparently healthy community-based participants without known cardiac disease aged 70+ in rural Tanzania underwent 12-lead electrocardiography. Electrocardiograms were digitally analyzed and gender-specific reference values for P duration (P D), P amplitude (P AMP), P area (P AREA), P terminal negative force (V 1) (P TNF), PR interval, QRS duration (QRS D), QT/QTc, R amplitude (II, V 5) (R AMP) LVH index (LVHI), R axis and R/S ratio (V 1) reported, following univariate analysis of covariance using a multiple linear regression model, adjusting for age, systolic blood pressure (SBP), body mass index (BMI), and RR interval. Results: Data from 1824 subjects were suitable for analysis. Adjusted mean values for men/women were:
Recent guideline drafts of the International Conference on Harmonisation of Technical Requirement... more Recent guideline drafts of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) underline the necessity to test nonantiarrhythmic drugs for their potential to prolong the QT or the corrected QT (QTc) interval. The implementation of these guidelines requires a large amount of ECG measurements on animals and humans in preclinical and clinical phases of the drug development process. We propose the use of magnetocardiography (MCG) as a complementary method with particular advantages in high-throughput studies, where signal quality and reliability are key factors. Our proposal is based on a review of recent MCG studies investigating the repolarization phase and results of methodological work assessing QT interval parameters from the MCG. The applicability of MCG for pre-clinical in-vivo studies is demonstrated by the ease of measurement in unrestrained non-anesthetized rabbits, guinea pigs, and hamsters..
AbstractThe aim of this study was to investigate the value of fractal dimension in separating no... more AbstractThe aim of this study was to investigate the value of fractal dimension in separating normal and cancerous images, and to examine the relationship between fractal dimension and traditional texture analysis features. Forty-four normal images and 58 cancer images from ...
The degree of myocardial electrical organization during ventricular fibrillation remains unknown.... more The degree of myocardial electrical organization during ventricular fibrillation remains unknown. The aim of this study was to compare the characteristics of the surface ECG on three independent and approximately orthogonal leads. Ten recordings of ventricular fibrillation, each induced at electrophysiology study and successfully terminated by direct current shock, were analyzed. Each recording was divided into 1-second epochs for analysis. Frequency analysis using the Fast Fourier Transform showed that the frequency of the dominant spectral peak increased significantly from a mean of 4.1 +/- 0.8 Hz to 5.2 +/- 0.7 Hz during the first 5 seconds of ventricular fibrillation. In 95% of the epochs analyzed, a similar dominant frequency was observed on either two or three ECG leads. Frequency agreement tended to increase as ventricular fibrillation evolved. This study shows that the rate of ventricular fibrillation increases rapidly during the first 5 seconds but only gradually thereafter, and that similar signal characteristics are observed on independent ECG leads. These findings are not compatible with the traditional view of incoherent myocardial activity during ventricular fibrillation.
Background: There are no data on the pattern of the Korotkoff phases in the normal population. Th... more Background: There are no data on the pattern of the Korotkoff phases in the normal population. This study was designed to describe the pattern of Korotkoff phase distribution in adults and children; to measure the duration of each of the phases; and to describe the differences between adults and children. Methods: A total of 57 children (7 to 8 years old) and 59 adults (median age 47 years, range 30 to 62 years) were studied. The pressure in the arm cuff was deflated using a device to provide a consistent deflation rate. The Korotkoff sounds were recorded to MiniDisc from the bell of a stethoscope and each sound described as phase I, II, III, or IV. Results: The most common pattern of Korotkoff phase distribution was for all five phases to be present (children [23/57; 40%], adults [24/59; 41%]). Phases I and IV were more common in children than in adults (56/57 [98%] v 47/59 [80%]; P ϭ .002 for phase I; 52/57 [91%] v 44/59 [75%]; P ϭ .018 for phase IV). Phases II and III were less common in children than in adults (32/57 [56%] v 50/59 [85%], P ϭ .001 for phase II; 27/57 [47%] v 45/59 [76%], P ϭ .001 for phase III). Phases I and IV were longer in children (median 3.9 [interquartile range, IQR 2.1 to 6.7] and 6.7 [IQR 3.2 to 9.8] sec, respectively) compared with adults (1.3 [IQR 0.7 to 2.7] and 1.7 [IQR 0.3 to 2.6), P Ͻ .001). Conclusions: There are clear differences in the Korotkoff phases between adults and children. The length of phases II and III increase with age with concomitant decrease in phases I and IV. These differences between adults and children remain unexplained.
7th International Conference on Image Processing and its Applications, 1999
ABSTRACT Image analysis for the classification of normal and cancerous colonic mucosa is reported... more ABSTRACT Image analysis for the classification of normal and cancerous colonic mucosa is reported. Pathology samples were taken from human colon mucosa, and 44 normal and 58 cancer images captured to computer via an optical microscope with a CCD camera. Texture analysis was performed using fractal dimension, entropy and correlation. Using non-parametric classification, fractal dimension improved the classification accuracy from 88% to 94% in comparison with the combined entropy and correlation analysis
Background and Purpose— Impaired autonomic function is common in the acute poststroke phase but l... more Background and Purpose— Impaired autonomic function is common in the acute poststroke phase but little is known about the longer term effects, particularly in older people. We sought to determine if autonomic function is impaired after stroke recovery in older patients. Methods— A cross-sectional case-control study comparing autonomic function in 76 nondemented stroke patients with 70 community-living controls aged older than 75 years. Results— Cases were assessed on average 9 months after stroke. From power spectral analysis of heart rate variability, stroke patients had lower total ( P =0.032) and low-frequency ( P =0.014) spectral densities and impaired baroreflex sensitivity (α low-frequency baroreflex sensitivity, P =0.006). From a series of cardiovascular autonomic reflex tests, heart rate variation during forced respiration, Valsalva ratio, and blood pressure overshoot during Valsalva maneuver were significantly lower in stroke patients ( P =0.003, <0.001, and 0.027, respe...
To investigate the effect of different lead exclusion criteria for the manual measurement of QT d... more To investigate the effect of different lead exclusion criteria for the manual measurement of QT dispersion (QTd). Simultaneous 12-lead ECGs from three groups of 25 subjects were studied; healthy normal subjects, subjects with a myocardial infarction, and subjects with arrhythmias. Leads were excluded with (1) small absolute T wave amplitudes, (2) small relative T wave amplitudes, and (3) small and/or large relative QT measurements. QTd was calculated as the QT range and assessed for its ability to differentiate between the normal and pathological groups. With exclusion of no leads or low absolute amplitude T waves (&amp;amp;lt; 50 microV) significant differences were observed only between normal and myocardial infarct groups (P &amp;amp;lt; 0.05). Significant differences between normal and both pathological groups were observed when excluding the lead with the smallest amplitude T wave or shortest QT (P &amp;amp;lt; 0.05), or when two leads of either type were excluded (P &amp;amp;lt; 0.005). There was good agreement between leads excluded by amplitude or QT (P &amp;amp;lt; 0.01). Lead exclusion for QTd is important. Exclusion of the two smallest amplitude or two shortest QT leads from each subject produced the greatest differences between the normal and pathological groups.
Objective: This study prospectively assessed the diagnostic accuracy of a novel bilateral photopl... more Objective: This study prospectively assessed the diagnostic accuracy of a novel bilateral photoplethysmography toe pulse measurement technique for the detection of significant lower limb peripheral arterial disease. Method: Bilateral photoplethysmography toe pulse measurements were compared with the ankle-brachial pressure index (ABPI) gold standard reference. Pulse wave analysis techniques extracted timing, amplitude, and shape characteristics for the great toes and their right-to-left side differences. These characteristics were compared with previously obtained normative ranges, and the accuracy was assessed for all significant disease (ABPI <0.9) and higher-grade disease (ABPI <0.5). Measurements were collected in a controlled environment within a tertiary vascular surgical unit for 111 subjects (age range, 42-91years), of whom 48 had significant lower limb peripheral arterial disease and 63 were healthy. Subjects were matched in age, sex, height, body mass index, and heart rate. Diagnostic performance was assessed using diagnostic sensitivity, specificity, accuracy, negative-predictive and positive-predictive value, and the statistic representing agreement between techniques beyond chance. Results: The degree that pulse shape fell beyond the normal range of normalized pulse shapes was at the threshold of substantial to almost perfect agreement compared with ABPI for significant disease detection (diagnostic accuracy, 91% [ ؍ 0.80]; sensitivity, 93%; specificity, 89%), and with 90% accuracy (؍ 0.65) for higher-grade disease detection. Pulse transit time differences between right and left toes also had substantial agreement with ABPI, with diagnostic accuracy of 86% for significant disease detection (pulse transit time to pulse foot [ ؍ 0.71] and to pulse peak [ ؍ 0.70]) and reached at least 90% for these for the higher-grade disease. The performance ranking for the different pulse features mirrored an earlier pilot study. With the shape and pulse transit time measurements, the negative-predictive values of the 5% disease population screening-prevalence level were at least 99% and had positive-predictive values of at least 98% for the 90% disease-prevalence level for vascular laboratory referrals. Conclusion: This simple-to-use technique could offer significant benefits for the diagnosis of peripheral arterial disease in settings such as primary care where noninvasive, accurate, and diagnostic techniques not requiring specialist training are desirable. Improved diagnosis and screening for peripheral arterial disease has the potential to allow identification and risk factor management for this high-risk group.
Journal of Neurology, Neurosurgery & Psychiatry, 2006
Background: There are no studies of autonomic function comparing Alzheimer's disease (AD), vascul... more Background: There are no studies of autonomic function comparing Alzheimer's disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). Aims: To assess cardiovascular autonomic function in 39 patients with AD, 30 with VAD, 30 with DLB, 40 with PDD and 38 elderly controls by Ewing's battery of autonomic function tests and power spectral analysis of heart rate variability. To determine the prevalence of orthostatic hypotension and autonomic neuropathies by Ewing's classification. Results: There were significant differences in severity of cardiovascular autonomic dysfunction between the four types of dementia. PDD and DLB had considerable dysfunction. VAD showed limited evidence of autonomic dysfunction and in AD, apart from orthostatic hypotension, autonomic functions were relatively unimpaired. PDD showed consistent impairment of both parasympathetic and sympathetic function tests in comparison with controls (all p,0.001) and AD (all p,0.03). DLB showed impairment of parasympathetic function (all p,0.05) and one of the sympathetic tests in comparison with controls (orthostasis; p = 0.02). PDD had significantly more impairment than DLB in some autonomic parameters (Valsalva ratio: p = 0.024; response to isometric exercise: p = 0.002). Patients with VAD showed impairment in two parasympathetic tests (orthostasis: p = 0.02; Valsalva ratio: p = 0.08) and one sympathetic test (orthostasis: p = 0.04). These results were in contrast with AD patients who only showed impairment in one sympathetic response (orthostasis: p = 0.004). The prevalence of orthostatic hypotension and autonomic neuropathies was higher in all dementias than in controls (all p,0.05). Conclusion: Autonomic dysfunction occurs in all common dementias but is especially prominent in PDD with important treatment implications.
Journal of Medical Engineering & Technology, 1986
A new technique using a pre-calibrated magnetometer has been used to investigate the stability of... more A new technique using a pre-calibrated magnetometer has been used to investigate the stability of the human body. Transducer coils were attached to a belt which was worn by the subject. Sway was measured over 30 s periods with eyes open and eyes closed. For 10 normal subjects, the mean sway speed was 3.6 +/- 0.9 mm/s with eyes open, and 5.3 +/- 1.5 mm/s with eyes closed. The mean ratio for eyes open to eyes closed was 0.68 +/- 0.10. The test was simple to perform and gave reproducible results.
IEEE Transactions on Information Technology in Biomedicine, 2002
The aim of this study was to investigate the value of fractal dimension in separating normal and ... more The aim of this study was to investigate the value of fractal dimension in separating normal and cancerous images, and to examine the relationship between fractal dimension and traditional texture analysis features. Forty-four normal images and 58 cancer images from sections of the colon were analyzed. A "leave-one-out" analysis approach was used to classify the samples into each group. With fractal analysis there was a highly significant difference between groups (0 0001). Correlation and entropy features showed greater differences between the groups (0 0001). Nevertheless, the addition of fractal analysis to the feature analysis improved the sensitivity from 90% to 95% and specificity from 86% to 93%.
IEEE Transactions on Information Technology in Biomedicine, 1998
The development of an automated algorithm for the categorization of normal and cancerous colon mu... more The development of an automated algorithm for the categorization of normal and cancerous colon mucosa is reported. Six features based on texture analysis were studied. They were derived using the co-occurrence matrix and were angular second moment, entropy, contrast, inverse difference moment, dissimilarity, and correlation. Optical density was also studied. Forty-four normal images and 58 cancerous images from sections of the colon were analyzed. These two groups were split equally into two subgroups: one set was used for supervised training and the other to test the classification algorithm. A stepwise selection procedure showed that correlation and entropy were the features that discriminated most strongly between normal and cancerous tissue (P < 0:0001). A parametric linear-discriminate function was used to determine the classification rule. For the training set, a sensitivity and specificity of 93.1% and 81.8%, respectively, were achieved, with an overall accuracy of 88.2%. These results were confirmed with the test set, with a sensitivity and specificity of 93.1% and 86.4%, respectively, and an overall accuracy of 90.2%.
The repeatability of commonly used electrocardiographic (ECG) related autonomic function tests wa... more The repeatability of commonly used electrocardiographic (ECG) related autonomic function tests was investigated in 25 diabetic subjects, mean age 44 (range 18-67) years and mean duration of diabetes 10 (&lt; 1-35) years. Tests were based on deep breathing, the Valsalva manoeuvre, relaxed normal breathing, and standing up from a lying position. All tests were repeated twice at each session, with two sessions separated by a mean of 5 (range 3-8) months. ECG and respiratory data were recorded for subsequent analysis. Maximum (max) and minimum (min) RR intervals and instantaneous heart rate (HR) were determined. The mean and repeatability data (within-subject standard deviation) for 21 different test results were calculated, and included deep breathing sitting (max-min)RR 226 +/- 39 ms and (max-min)HR 19.3 +/- 3.2 beats min-1, Valsalva manoeuvre 1.74 +/- 0.18, and lying-to-standing RR ratio 1.19 +/- 0.07. The within-subject repeatability to between-subject variability ratios consistently demonstrated that it is better to perform the deep breathing test sitting (with the smaller mean ratio of 0.37) rather than supine (0.46), with the use of three respiratory cycles rather than a single cycle (0.33 compared with 0.50 for (max-min)RR). A significant (p = 0.037) relationship was found between variability in heart rate changes and variability in air volume breathed during the deep breathing test.
The electrocardiogram is of major importance in the diagnosis of heart disease. Cardiac repolaris... more The electrocardiogram is of major importance in the diagnosis of heart disease. Cardiac repolarisation is the result of the return to a resting state of myocardial cells, and is detected on the surface 12-lead ECG as the T wave. The exact mechanisms responsible for the T wave shape are not completely understood. In this work, using our computer model of
ABSTRACT A recent BBC radio programme highlighted the case of an airline pilot’s wife who died un... more ABSTRACT A recent BBC radio programme highlighted the case of an airline pilot’s wife who died unexpectedly during surgery. The pilot was surprised by the lack of seriousness in investigating the incident. In his review of the programme, Ferner remarked on the many …
The genesis of the U wave in the ECG is still in doubt. This study aimed to investigate the relat... more The genesis of the U wave in the ECG is still in doubt. This study aimed to investigate the relationship between the occurrence of the U wave and both the electrical and mechanical timing sequence in heart beats. The M-mode echocardiography and 12-lead ECG were simultaneously recorded from 4 healthy subjects, with four repeat measurements in each. The ECG for both aortic valve (AV) and mitral valve (MV) were recorded from all four subjects. The timings of QQ interval, the peak and end of T wave, the peak and end of U wave, the AV and MV opening and closing were measured. The relationships between the QQ interval and the other timings were analysed. The MV opening and AV closing preceded the end of T wave (also considered as the start of U wave for healthy subjects) by 9 ± 11ms and 47 ± 15ms, respectively. When compared with the mechanical timings, the timing of the U wave had better correlation with the QQ interval, with the R square increasing from 0.76 to 0.95. Our finding suggest...
Background/Objectives: Older adults in sub-Saharan Africa (SSA) are at greatest risk of an impend... more Background/Objectives: Older adults in sub-Saharan Africa (SSA) are at greatest risk of an impending noncommunicable diseases epidemic, of which cardiac disease is the most prevalent contributor. Thus, it is essential to establish electrocardiographic reference values for a population that is likely to differ genetically and environmentally from others where reference values are established. Methods: Two thousand two hundred thirty-two apparently healthy community-based participants without known cardiac disease aged 70+ in rural Tanzania underwent 12-lead electrocardiography. Electrocardiograms were digitally analyzed and gender-specific reference values for P duration (P D), P amplitude (P AMP), P area (P AREA), P terminal negative force (V 1) (P TNF), PR interval, QRS duration (QRS D), QT/QTc, R amplitude (II, V 5) (R AMP) LVH index (LVHI), R axis and R/S ratio (V 1) reported, following univariate analysis of covariance using a multiple linear regression model, adjusting for age, systolic blood pressure (SBP), body mass index (BMI), and RR interval. Results: Data from 1824 subjects were suitable for analysis. Adjusted mean values for men/women were:
Recent guideline drafts of the International Conference on Harmonisation of Technical Requirement... more Recent guideline drafts of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) underline the necessity to test nonantiarrhythmic drugs for their potential to prolong the QT or the corrected QT (QTc) interval. The implementation of these guidelines requires a large amount of ECG measurements on animals and humans in preclinical and clinical phases of the drug development process. We propose the use of magnetocardiography (MCG) as a complementary method with particular advantages in high-throughput studies, where signal quality and reliability are key factors. Our proposal is based on a review of recent MCG studies investigating the repolarization phase and results of methodological work assessing QT interval parameters from the MCG. The applicability of MCG for pre-clinical in-vivo studies is demonstrated by the ease of measurement in unrestrained non-anesthetized rabbits, guinea pigs, and hamsters..
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Papers by Alan Murray