Biomedical subjects
M A Macleod
Publications and source records attributed to M A Macleod.
Cerebral perfusion deficits in dysbaric illness.
Decompression sickness (DCS) is usually categorised as type I (mild; peripheral pain, non-neurological) or type II (serious; neurological). Type II is regarded as predominantly a spinal cord disease with infrequent cerebral involvement. Cerebral perfusion was studied by injection of 99Tcm-hexamethylpropyleneamine oxime and single photon emission tomography in 28 divers with confirmed incidents of DCS and cerebral arterial gas embolism (CAGE). Cerebral perfusion deficits were present in all 23 cases of type II DCS and in all 4 cases of CAGE. No deficits were present in the single case of type I DCS. Type II DCS should be recognised as a diffuse, multifocal, central nervous system disease.
Factor analysis of dynamic structures (FADS) in the diagnosis of renal disease.
Factor analysis of dynamic structures (FADS) has been used in the interpretation of dynamic scintigraphic studies since the technique was described by Bazin et al. (1980). This study was designed to analyse to what extent, if any, does physiological factor analysis of dynamic renal data really help the clinician and by how much the method improves the diagnostic accuracy when compared to deconvolution analysis and parenchymal transit time (PTT) measurements. One hundred and fifty patients who were clinically, biochemically and radiologically investigated for renal disease were included in the study. Fifty of these were found to have no clinical evidence of renal disease, 50 were diagnosed as having non obstructive kidney disease and 50 had evidence of renal obstruction. Data obtained from 99mTc-DTPA renography were processed using deconvolution (with PTTs) and physiological factor analysis and the results compared by ROC analysis. Clinically the information gained from factor analysis was superior to that obtained from deconvolution with PTT measurements in that a more accurate differentiation between an obstructive nephropathy and an obstructive uropathy was obtained. It is considered that physiological factor analysis enhanced the clinical information obtained from renography, increases diagnostic accuracy and obviates the need for diuresis renography.
A perception experiment to assess the clinical accuracy of various methods of obtaining cardiac phase images.
Five methods of obtaining cardiac phase (and phase-like) images are compared. These are single-harmonic Fourier phase imaging; time-to-minimum using a two-harmonic fit to each dixel; time-to-minimum using four weighted harmonics; composite factorial phase imaging; and individual factorial phase imaging. Polaroid prints of phase images for both gated equilibrium studies (using all methods) and first-pass studies (first and last methods only) were shown to observers who were asked to rate the images according to their confidence of an abnormality presenting. A receiver operating characteristic (ROC) analysis was performed. For gated studies composite factorial phase imaging appears to be best, while all methods are significantly better than single-harmonic Fourier phase imaging. For first-pass studies individual factorial phase imaging appears to be superior to single-harmonic Fourier phase imaging.
99Tcm-HMPAO single photon emission tomography in the diagnosis of cerebral barotrauma.
Cerebral barotrauma, or the neurological manifestation of the "bends", is a relatively common disease of divers and aviators. To date, however, no-one has succeeded in demonstrating a cerebral or spinal cord lesion in vivo following a decompression incident, despite the presence of definitive clinical signs and symptoms of central nervous system involvement. This paper describes the use of 99Tcm-labelled hexamethylpropyleneamine oxime (99Tcm-HMPAO) with single photon emission tomography in a study of three individuals involved in driving accidents. All three suffered cerebral barotrauma during decompression and all exhibited clinical signs and symptoms of dysbarism to a varying degree. Imaging was performed at time intervals ranging from 2 h to several days following the incidents. The results showed well defined cerebral ischaemic lesions in all three subjects. We conclude that 99Tcm-HMPAO imaging provides a significant advance in locating and demonstrating cerebral lesions following barotrauma and will contribute greatly to our understanding of the pathophysiological processes involved.
Functional imaging in nuclear medicine--clinical aspects.
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Functional imaging in the early diagnosis of dysbaric osteonecrosis.
Eight divers who developed permanent scintigraphic bone changes following dives to various depths took part in a study to determine the nature of these lesions. Only one of these divers had radiologically evident bone changes in his scintigraphic lesion. Dynamic scintigrams of the bones containing the lesions were obtained from all eight divers and functional images generated of both amplitude (osteoblastic activity) and accretion (microvasculature) rate constants. All had increased amplitude in the area of the scintigraphic lesion indicating continuing osteoblastic activity. Three divers showed a decreased accretion rate in the lesions, indicating impairment or absence of local microcirculation; one of these was the diver who showed radiological changes prior to the study and the other two subsequently developed radiologically evident osteonecrosis. It is concluded that functional images, generated from dynamic bone scintigrams, can successfully predict dysbaric osteonecrosis.
A comparison of three methods of assessing renal function.
In a study of 100 patients referred for assessment of renal function a comparison is made between gamma camera computer assisted displays of 99mTc-DTPA(Sn) nephrograms, intra-venous urography (I.V.U.) and triple probe 131I-Hippuran renography. The computer processed data displays renal morphology and activity/time curves which are deconvolved enabling quantitative assessment of glomerular function to be made. Pattern recognition techniques for feature extraction are employed to facilitate classification of the curves. It is concluded that the computer processed data gives better results both in the recognition of morphological defects and in the indication and measurement of renal damage.
External monitoring of kidney transplant function using Tc-99m(Sn)DTPA.
The purpose of this study was to evaluate the use of an external counting technique to provide daily monitoring of kidney transplant function by measuring the renal clearance of Tc-99m(Sn)DTPA. During the first few weeks following transplant, 15 patients had their renal clearance of Tc-99m DTPA measured daily over periods of 5-24 hr. Clearance rates were compared with daily plasma creatinine levels, and the effects of diurnal variation, drug treatment, and physical activity noted. The results show that any significant fall in clearance rate of chelate, indicating a rejection episode, preceded a rise in plasma creatinine levels by at least 24 hr. One episode of transplant failure presented as a sudden deterioration in clearance rate of chelate; in the others the change was more gradual but was still apparent within hours. It is considered that this noninvasive, low-dose, easy-to-perform technique is of considerable value in extended daily monitoring of renal function and is superior to standard daily or twice-weekly renography for the early detection of transplant rejection.
The influence of age and plasma glucagon on renal clearance of 99mTc-DTPA (Sn).
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The advantages of 99mTc DTPA(Sn) in dynamic renal scintigraphy and measurement of renal function.
The results of excretion urography (IVU) and dynamic renal scintigraphy using 99mTc DTPA(Sn) were compared in 109 urological patients. Computer analysis of the gamma camera data provided a reproducible, accurate, qualitative and quantitative assessment of renal function and was found to be superior to urography in the detection of morphological defects of the renal parenchyma and in the identification of early upper tract obstruction. The radio-isotope study is a safe, non-invasive investigation, easily performed on an out-patient basis, requires no prior preparation and is without significant radiation hazard to the patient.
Processing of liver dynamic studies with technetium-labelled sulphur colloid.
The uptake of technetium-labelled sulphur colloid by the liver was investigated by monitoring 69 patients on a gamma camera/computer system. Following an intravenous injection 30 half-minute frames were collected and summed to give a composite view. Regions of interest were drawn round the liver and over the aorta and corresponding activity-time curves were formed. A simple physiological model has been assumed and two parameters, namely total uptake and rate of uptake, were shown to give fairly good separation between the classes of normal, cirrhosis, space occupying lesions, reticulosis and hepatitis. Furthermore the uptake rate-constant was also shown to be a useful indication of whether or not a reticulosis or hepatitis was in an acute phase. Principal components analysis was also applied to the liver curves producing two relevant components. However, a plot of the first against the second yielded no better separation of classes than that obtained by the model.
Principal components analysis as an aid to classification of renal dynamic studies.
Four hundred renal dynamic studies obtained using 99mTc-(Sn) DTPA were classified clinically into four classes (normal, pre-renal lesion, intrarenal lesion and urinary tract obstruction). Principal components analysis was then applied to the kidney activity/time curves and yielded good class separation using only three components. The separation of normal and obstructed or damaged kidneys using only the first component was better than that obtained using the calculated mean transit time.
A compartmental model for the distribution of 113mIn-DTPA and 99mTc-(Sn)DTPA in man following intravenous injection.
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An intercomparison of computer assisted image processing and display methods in liver scintigraphy.
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UVL induced changes in calcium absorption and excretion and in serum vit D3 levels measured in black-skinned and caucasian males.
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The influence of glucose and crude fibre (wheat bran) on the rate of intestinal 47Ca absorption. The influence of glucose and wheat bran on calcium absorption.
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Urinary clearance of 113m In-DTPA and 99mTc-(Sn)DTPA measured by external arm counting.
Single shot glomerular filtration rate measurements involving chelates (113mIn-DTPA, 99mTc-DTPA etc) assume direct loss from the plasma to urine via glomerular filtration and excretion. Inherent errors, due to considerable uptake of activity in tissue and uncertainty of complete bladder emptying are ignored and taking of half-hourly blood and urine samples involves patient discomfort. This paper describes a simple method of measuring urinary clearance of chelates using serial external arm counting which entails only an initial injection and takes into account tissue loss from plasma. The resultant plotted curve exhibits three phases, the first two depicting input and equilibration between plasma and tissue and the third and exponential part, which is a measure of the biological half-life of the chelate, being representative of the efficiency of renal glomerular filtration, the parameter to be measured. Results obtained, compared with single shot glomerular filtration rate measurements performed simultaneously, gave better correlation with clinical data including renography.