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Biomedical subjects

D Lui

Publications and source records attributed to D Lui.

33 records · Page 2Linked to original sources
PubMed1991

Combined 67Ga citrate and 99Tcm-human immunoglobulin imaging in human immunodeficiency virus-positive patients with fever of undetermined origin.

Patients infected with the human immunodeficiency virus (HIV) suffer from serious and life-threatening infections. These patients often present with pyrexia but without localizing signs. Despite its high sensitivity in identifying focal infection 67Ga citrate scintigraphy lacks specificity; lymphoma and solid tumours may also be imaged. This presents particular problems in HIV-positive patients with pyrexia where the differential diagnosis is often between infection and lymphoma. In an attempt to improve the specificity of radionuclide imaging in these patients a combination of 67Ga citrate and the new agent 99Tcm-labelled human immunoglobulin (99Tcm-HIG) was used in 25 patients who were sequentially imaged with the two agents. Fourteen patients had 29 sites of microbiologically confirmed infection; 67Ga citrate identified 27 sites and 99Tcm-HIG identified 16 sites. Seven of the nine sites visualized with 99Tcm-HIG, but positive with 67Ga citrate, were intrathoracic. Abnormal concentration of 67Ga citrate, not due to infection, occurred at eight sites; five lymphoma, one gout, one recent fracture and one patient with prominent bone marrow islands. 99Tcm-HIG showed increased concentration of tracer in only one of the patients with lymphoma. A combination of 67Ga citrate and 99Tcm-HIG imaging in HIV-positive patients with pyrexia of unknown origin enables a differentiation between infection and lymphoma to be made more readily. The poor sensitivity of 99Tcm-HIG in the chest will limit its sole use in this patient group.

Adult↗
PubMed1990

99mTc-human immunoglobulin (HIG)--first results of a new agent for the localization of infection and inflammation.

Technetium (99mTc) labelled, polyclonal human immunoglobulin (HIG) is a new agent that detects focal infection and inflammation. This new agent was compared in 40 patients with the accepted standard, namely 111In-oxine-labelled leucocytes. This comparison resulted in a sensitivity of 94% and a specificity of 96% for 99mTc-HIG when 111In-oxine leucocytes were defined as giving the true result. The new agent was shown to localize both sepsis and active inflammatory bowel disease (IBD). There was 100% concordance in the 16 patients with IBD who were imaged with both 99mTc-HIG and 111In-oxine leucocytes. Discordant results were obtained in one case of suspected osteomyelitis, which was false-positive on the 99mTc-HIG scan, and one case of pyrexia of unknown origin when the 99mTc-HIG was false-negative and the 111In-oxine leucocyte scan demonstrated accumulation of tracer in the caecum at 24 h post-injection. Normal distribution for 99mTc-HIG demonstrated activity in the kidneys and bladder and that 50% of the tracer is cleared through the kidneys during the first 24 h post-injection. There were no major or minor side-effects.

Bacterial Infections↗
PubMed1989

Intracellular localization of 99Tcm-d,l-HMPAO and 201Tl-DDC in rat brain.

The intracellular localization and relative distribution of 99Tcm-hexamethylpropyleneamine-oxime (99Tcm-d, l-HMPAO) and 201Tl-diethyldithiocarbamate (201Tl-DDC), which have been used to assess regional cerebral blood flow (rCBF) in man, were investigated in rat brain. 99Tcm-d, l-HMPAO was found attached mainly to cell organelles whilst 201Tl-DDC was localized mainly in free state in the cytosolic fraction. Isolation of neuronal and glial nuclei showed that there is higher uptake of 99Tcm-d, l-HMPAO in neuronal nuclei than in glial nuclei for all the different regions of the rat brain investigated. These data demonstrate a different subcellular localization of the two lipophilic agents studied. In view of their proposed clinical utility, this difference merits further investigation.

Animals↗
PubMed1988

White cells radiolabelled with 111In and 99Tcm--a study of relative sensitivity and in vivo viability.

In this study a comparison between the classical (111In oxine) and the newer (99Tcm HMPAO) technique of labelling leucocytes is reported. The behaviour in vivo and the relative sensitivity in the detection of infection (chest and bone) and inflammatory bowel disease (IBD) is presented. Simultaneous dual-radionuclide gamma camera acquisition methodology was applied to study 99 patients, 18 with chest infection, 26 with bone infection, 41 with IBD and 14 with other pathological conditions. The mean (1 SD) 50% washout time from the lungs was 483.03 (79.10) s for 99Tcm HMPAO-labelled white blood cells and 475.85 (83.79) s for 111In oxine-labelled white cells (r = 0.81). Concordance between the two techniques was 94% in the chest-infection group of patients, 88% in the bone-infection group and 71% in the localization of IBD.

Adolescent↗
PubMed1987

Functional imaging of the brain.

The radionuclide tracer method is unique amongst all other imaging methodologies in its ability to trace organ or tissue function and metabolism. It derives this advantage from the nature of the signal used for image generation, and its single interaction with the organ or system under examination. Physical processes such as electron or proton density assessment or resonance, edge identification, electrical or ultrasonic impedence, do not pertain to the image generation process in nuclear medicine, and if so, only in a rather secondary manner. The nuclear medicine imaging study is primarily a study of the chemical nature, distribution and interaction of the tracer/radiopharmaceutical utilised with the cellular system which requires investigation: the thyroid cells with sodium iodide, the recticular endothelial cells with colloidal particles, the adrenal medulla cells with metaiodobenzylguanidine, and so on. In the two most recent areas of nuclear medicine expansion, oncology (with labelled monoclonal antibodies) and neurology and psychiatry (with a whole new series of lipid soluble radiopharmaceuticals), specific cell systems can also be targeted and hence imaged and investigated. The study of structure as masterly performed by Virchow and all his successors over more than a century, is now definitely the prerogative of such imaging systems which excel with spatial and contrast resolution (x-ray computed transmission tomography, nuclear magnetic resonance imaging, diagnostic ultrasound). However the investigation of function and metabolism (as performed by Claude Bernard, Georg von Hevesy, and so many others), has clearly passed from the laboratory animal protocol and experiment to the direct investigation in man, this being the achievement of the radionuclide tracer methodology. In this article, we review present interest and developments in that part of nuclear medicine activity which is aimed at the study of the neurological or psychiatric patient.

Amines↗
PubMed1985

A 99Tcm-labelled radiotracer for the investigation of cerebral vascular disease.

The first clinical data is given on 99Tcm-hexamethylpropyleneamine oxime (HM-PAO) in normal subjects and patients with established stroke. Regional cerebral blood flow maps (rCBF) have been recorded and displayed in tomographic mode with this new radiopharmaceutical. Good images were obtained, comparable to those achieved with 123I-isopropylamphetamine (IMP).

Amphetamines↗
PubMed1984

The mechanism of diarrhoea resulting from pelvic and abdominal radiotherapy; a prospective study using selenium-75 labelled conjugated bile acid and cobalt-58 labelled cyanocobalamin.

An attempt was made to elucidate the mechanism of diarrhoea resulting from pelvic and abdominal radiotherapy in a prospective study of 10 patients undergoing treatment for curable pelvic malignant tumours using the synthetic trihydroxy 75Se-labelled conjugated bile acid, SeHcat and 58Co-labelled cyanocobalamin (58Co Vit B12). Evidence of malabsorption of vitamin B12 measured as a significant fall in whole body percentage retention of 58Co Vit B12 from baseline levels was found in all nine patients who developed diarrhoea during radiotherapy. Only four out of these nine patients also had malabsorption of the trihydroxy conjugated bile acid, cholic acid, measured as a significant fall in SeHcat whole body percentage retention and these patients had the most severe diarrhoea. The findings are discussed in the light of what is known about the pathophysiology of diarrhoea during pelvic and abdominal radiotherapy and lend support to previous work which implicated increased bowel motility in the pathogenesis of radiation-induced diarrhoea. The hypothesis that local neuroendocrine mechanisms in the gut may be involved is put forward, with possible implications for treatment.

Adult↗
PubMed1983

Cerebral blood flow studies with 123iodine-labelled amines.

The cerebral distribution of a new class of 123I radiopharmaceuticals was determined by emission tomography after the isotope had been injected intravenously into 20 patients with a variety of neurological disorders. Regional cerebral blood flow images of diagnostic quality were obtained in all cases. Early and late ischaemic stroke showed up as areas of impaired perfusion, and gliomas and secondary deposits as areas of increased or reduced blood flow. A hyperaemic focus was clearly seen in an epileptic patient in whom other imaging techniques, including CT scanning and electroencephalography, had been uninformative. This new technique promises to be an extremely useful addition to the range of radioisotope brain scanning methods.

Adult↗
PubMed1978

99mTc-imidodiphosphonate: a superior radio-pharmaceutical for in vivo positive myocardial infarct imaging. I: Experimental data.

99mTc-Imidodiphosphonate (99mTc-IDP) was investigated as an agent for nuclear medicine imaging of acute myocardial infarctions. For this purpose a suitable animal model was found. After coronary artery ligation reproducible myocardial infarcts were obtained with 80% of surviving animals. Scans of the myocardial infarcts were recorded with a high resolution gamma camera and good quality images were obtained. 99mTc-IDP ratios for normal and infarcted tissue were calculated and compared with similar data available from other 99mTc-labelled phosphates. With an infarct/normal ratio of 21:1, 99mTc-IDP is so far the best radiopharmaceutical for nuclear medicine imaging of necrosed heart muscle. Images of the myocardial infarcts have been recorded as early as 6 hours after infarction.

Animals↗
PubMed1977

High-quality, high-throughput, early whole-body bone scanning.

99mTc-IDP allows for high-quality, high-throughput and early whole-body bone scanning. Whole-body bone scans obtained at 30 min after intravenous administration of the tracer were compared with the standard and delayed 180 min p.i images. A subtraction technique allowed for the anlysis of the 30 min scans and it was found that in both types of investigation the same clinical information was present. This procedure will therefore increase considerably the throughput of whole-body bone scans in a busy department of nuclear medicine. It is however inadequate for detailed analysis of the skeleton (evaluation of benign bone disease).

Adult↗
PubMedDate not supplied

Contrast media osmolality and plasma volume changes.

A theoretical and experimental study of the plasma volume expansion consequent on the hyperosmolality of contrast media is presented. In the case of the ratio 1.5 media theory and experiment coincide closely but in the case of the ratio 3 media the observed changes exceed the predicted. It is proposed that this is due partly to the slower diffusion of the ratio 3 media out of the intravascular space and partly due to the fact that the osmotic load presented by these media is greater than would be expected from a study of their commercial solutions in which osmolality is reduced by molecular aggregation. The implications for the relative haemodynamic effects of different contrast media are discussed. The osmotic effects of contrast media also play a part in determining the image quality achievable in intravenous digital subtraction angiography (IV-DSA). It is predicted that ratio 3 contrast media will give better quality images in IV-DSA than ratio 1.5 media.

Contrast Media↗