Biomedical subjects
Publications and source records attributed to H Baddeley.
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Magnetic resonance imaging is a new, but expensive, modality that is being introduced into clinical use in Australia. While it promises increased safety and accuracy in many situations, its precise role when compared with computed tomography and other modalities is not fully established. Therefore, a Government financed evaluation of costs and efficacy of magnetic resonance imaging units in five teaching hospitals is to be conducted over two years (1986-1988). Experience with the introduction of computed tomography to Australia and other nations has revealed difficulties in the evaluation by conventional methods of a diagnostic technology that is improving rapidly; it is to be hoped that a systematic evaluation of the clinical applications of magnetic resonance imaging will be more achievable and useful. Open cooperation between the Commonwealth and State Governments and the medical profession in this evaluation should lead to a rational policy for the clinical availability of magnetic resonance imaging within Australia in the future.
The use of magnetic resonance imaging, in the demonstration of internal human anatomy and in the diagnosis of disease, has the major advantages that the technique is noninvasive, does not require the use of ionizing radiation and that it can demonstrate neurological and cardiovascular lesions that cannot be diagnosed easily by other imaging methods. Magnetic resonance imaging is derived from the principle that certain atomic nuclei in a strong magnetic field will absorb pulses of radiofrequency energy; when the pulse is finished the nuclei will emit radiowaves at the same frequency. These radiowaves are received by specially designed aerials or coils and the information is collected by a computer which reconstructs an image of internal anatomy in a similar way to that of x-ray computed tomography (CT). By changing the strength of the magnetic fields and the frequency of the radiowave pulses, it is possible to examine different sections within the body. The first magnetic resonance images of humans were obtained in Australia in October 1985 on the research instrument of the Queensland Medical Magnetic Resonance Research Centre, which is based at the Mater Hospital in Brisbane, and is part of the University of Queensland's Department of Radiology.
A new approach to volume-selected in vivo NMR spectroscopy uses two frequency-shifted sinc pulses, in conjunction with pulsed field gradients, to destroy the coherence of the unwanted signals. A hard pi/2 pulse can then be used to read the z magnetization in the region of interest. This method is independent of T2, provides complete volume selection in a single acquisition, and can be readily implemented on most high-field commercial imaging/spectroscopy systems.
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Indices of past lead absorption were measured and compared in patients with chronic renal failure from many causes, including some with chronic lead nephropathy. X-ray fluorescence (XRF) yielded finger bone lead concentrations by a new in vivo method. These correlated significantly with excess urinary lead following calcium di-sodium EDTA (ethylenediamine tetra-acetate) and erythrocyte lead concentration. Discriminant function analysis demonstrated that the patients in the study could be separated into two groups without any reference to the EDTA lead excretion test using the following variables, all of which contributed significantly to the discrimination. In order of importance, these were: a childhood history of acute lead poisoning, a history of gout, a family history of gout and detectable XRF finger bone lead. Although the XRF finger bone lead measurement is convenient and non-invasive, its lack of sensitivity (48%) limits its usefulness as a screening test for chronic lead nephropathy.
A modification of the method of Carr et al. [1976] for the ultrasonic assessment of liver volume was devised for use with a UI Octoson water delay B mode echoscope, and 32 subjects without clinical history or signs of liver disease were examined. In 9 subjects the measurements were repeated by a separate observer. Comparison of the variance between observers and that between subjects showed that the precision of the method is within acceptable limits, the variance ratio (F) being 13.7 (p less than 0.001). The mean liver volume was 1,545.4 +/- (SD) 255 ml. This finding is in close agreement with previously published data. The liver volume was correlated with body weight, height, body surface area, and body mass index. The liver volume was found to correlate best with body weight using partial correlation analysis. This was in accordance with previously published data, with the exception of that of Koischwitz [1979]. However, variations in weight could only account for 0.43 of the variation in liver volume.
One hundred twenty-five patients investigated at the Royal Brisbane Hospital, who underwent both hepatic ultrasonography and liver biopsy between 1980 and 1983, were scored quantitatively for ultrasound features of loss of detail, echogenicity, and attenuation, as well as for histologic features of fat, fibrosis, and inflammation. Strong correlations were found between the score for fat content and each of the three ultrasound features, and between the score for hepatic fibrosis and loss of detail and echogenicity, but there was no strong correlation with attenuation. Hepatic inflammation did not correlate with any of the ultrasound features. The correlations for fat were strongest when the interval between ultrasonography and liver biopsy was less than or equal to 7 days. Although ultrasonography had a positive predictive value of 98% in the diagnosis of diffuse parenchymal abnormality, it did not distinguish fat from fibrosis nor reliably diagnose cirrhosis. Ultrasonography gave false-positive results in only 2 patients, but in 17 patients, false-negative ultrasound examinations were encountered. These findings indicate that ultrasound is not a useful screening investigation for parenchymal liver disease, nor is it useful in gauging hepatic pathology. However, abnormal hepatic ultrasonography in patients with suspected liver disease strongly suggests the presence of diffuse liver disease.
X-ray mammography was performed on 446 patients with suspected breast disease and 23 breast carcinomas were detected of 26 (sensitivity: 88.5%) that were ultimately diagnosed in the 12-24 months' period following examination. Ultrasound mammography was used as an additional procedure in 183 patients because the radiographic findings were considered to be indeterminate and it detected an additional two carcinomas, to give an overall sensitivity of 96%. X-ray mammography identified 40 benign lesions and subsequent ultrasound mammography characterised 38 of these as being either cystic or solid. Ultrasound also detected an additional 32 benign lesions (28 cysts and 4 fibroadenomas) which had not been evident on X-ray mammography. It is concluded that ultrasound mammography is a useful complementary procedure for those patients who have radiodense breasts or indeterminate radiographic findings on X-ray mammography.
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EDTA (calcium disodium edetate) lead mobilization and x-ray fluorescence (XRF) finger bone lead tests were done in 42 patients with chronic renal failure and without persisting lead intoxication. Nineteen of 23 patients with gout and 8 of 19 without gout had positive EDTA lead mobilization tests. Those patients with gout excreted significantly more excess lead chelate than those without gout. In the gout group 17 patients denied any childhood or industrial exposure to lead. They had a greater number of positive tests and excreted significantly more excess lead chelate than 14 patients with neither gout nor lead exposure. These results confirm that gout in the presence of chronic renal failure is a useful marker of chronic lead poisoning. Of 27 patients with positive lead mobilization tests, only 13 had elevated XRF finger bone lead concentrations (sensitivity 48%). Three of 15 patients with negative lead mobilization tests had elevated XRF finger bone lead concentrations (specificity 80%). Although the XRF finger bone lead test is a convenient noninvasive addition to the diagnostic evaluation of patients with chronic renal failure and gout, its application is limited due to the lack of sensitivity of the method.
A group of 200 Queensland adults without known health problems had in-vivo estimation of finger bone lead concentrations using X-ray fluorescence analysis (XRF). Forty of these subjects had elevated levels of bone lead of 25 ppm or more, consistent with exposure to the metal. Although the correlation between Queensland residence during childhood and raised bone lead levels was not significant, there were significant correlations between childhood residence in a painted wooden house and raised levels, and between occupational exposure and raised levels. Of the 40 subjects with elevated lead levels only two had neither a history of occupational exposure or childhood residence in a wooden house, whereas 11 of the 25 who had a history of both occupational and residential exposure were positive. The data are consistent with lead in housepaint, or absorbed during occupational exposure, being the two major sources of raised bone lead concentrations.
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In vivo neutron activation analysis of liver cadmium concentration was performed in 285 metal workers, 130 of whom had been exposed to cadmium in the workplace. Only two workers showed pathological levels in excess of 50 ppm. However, mean liver, urine and blood cadmium levels were significantly different as between the exposed and the unexposed workers. In vivo neutron activation analysis of liver cadmium concentration is easy to perform and can readily be used for industrial screening whenever a hazard is suspected.
The usefulness of hepatobiliary echography was assessed prospectively in 32 patients with cholestatic jaundice. The predictive reliability of the method for detecting major bile duct obstruction was 93% and for excluding this possibility was 88%. Echography altered diagnostic thinking significantly in 22 patients (69%). Correct management decisions were made promptly in all but 1 patient who underwent unnecessary laparotomy for acute hepatitis. Laparotomy was correctly avoided in 2 patients and invasive investigations were not required in a further 12. It is concluded that hepatobiliary echography is a useful and cost-effective method in the diagnosis and management of the jaundiced patient.
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