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Biomedical subjects

S Webb

Publications and source records attributed to S Webb.

At least 271 records · Page 15Linked to original sources
PubMed1987

Three-dimensional display of data obtained by single photon emission computed tomography.

Three-dimensional display of radioactive distributions has been achieved using data generated by single photon emission computed tomography (SPECT). Computer techniques for constructing images are presented and the special problems associated with manipulating SPECT data are reviewed. The potential role of three-dimensional imaging in nuclear medicine is discussed and SPECT studies from several illustrative cases are presented.

Adult↗
PubMed1985

Comparison of data-processing techniques for the improvement of contrast in SPECT liver tomograms.

Techniques for improving image contrast in liver single-photon emission computed tomography (SPECT) are discussed. It is shown that by suitable choice of reconstruction method combined with subsequent image processing, image contrast can be improved without the generation of artefactual mottle. The use of this technique is illustrated with clinical data from a rotating gamma camera.

Electronic Data Processing↗
PubMed1985

An x-ray detector system and modified simulator providing CT images for radiotherapy dosimetry planning.

A high count rate position-sensitive detector was developed in order to obtain CT information using a modified radiotherapy simulator. The detector is attached to one arm of the simulator gantry and acquires projection data from a fan beam of X-rays derived from the simulator X-ray tube. The scanner is designed principally for planning the dosimetry of breast cancer radiotherapy. During the collection of transmission projection data, suitable for the digital reconstruction of patient cross sections, the simulator gantry rotates continuously through about 360 degrees. A film cassette holder can be positioned above the detector to provide conventional simulator check films. Cross sections through patients receiving post-operative radiotherapy for breast cancer were reconstructed from projections acquired with the patient lying in the treatment position. These scans are an average over the breathing cycle. The outlines of internal anatomy and the patient external contour were used to produce treatment plans which include tissue inhomogeneity corrections. The data produced by this wide aperture CT scanner are suitable for planning those conditions in which radiotherapy is delivered to an organ such as the breast or the whole body, rather than to a localised lesion.

Breast Neoplasms↗
PubMed1985

Vicky.

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Female↗
PubMed1985

Autonomic regulation of postprandial plasma somatostatin, gastrin, and insulin.

To evaluate the neural regulation of postprandial somatostatin release we studied the effect of blockade of (a) alpha-adrenergic and beta-adrenergic and (b) cholinergic receptors on the plasma somatostatin, gastrin and insulin responses to a standard meal in two groups of five fasting healthy male volunteers. Thymoxamine (0.1 mg/kg iv over two minutes then 10 mg/hour for two hours) and propranolol (0.15 mg/kg iv over two minutes, then 0.75 mg/kg/hour for two hours) were started just before eating while atropine (0.04 mg/kg/im) was given at 15 minutes on completion of the meal. There was a prompt and sustained rise in plasma somatostatin after a control meal in all experiments. This rise was arrested by atropine but not altered by either thymoxamine or propranolol. The plasma gastrin response to a meal was moderately enhanced by thymoxamine and markedly enhanced by atropine. Postprandial insulin release was not affected by alpha- or beta-adrenergic blockade but was abolished by atropine. The effect of atropine on the postprandial plasma somatostatin rise might have been mediated through reduction in gastric acidity or delay in gastric emptying. Hence we gave five fasting male volunteers and intraduodenal infusion of fat emulsion (25 calories in 30 minutes) on two occasions both alone and after atropine. Plasma somatostatin rose during the fat infusion alone and this rise was abolished by atropine. These data suggest that (a) cholinergic but not adrenergic mechanisms are important modulators of plasma somatostatin release after orally ingested and intraduodenally infused nutrients (b) atropine abolishes plasma somatostatin release independently of its effects on gastric acidity and motility and (c) are consistent with the hypothesis that atropine potentiates postprandial gastrin release through reduction of somatostatin mediated inhibition.

Adult↗
PubMed1985

High resolution SPECT using divergent geometry.

A special-purpose collimator with holes which converge in the plane of rotation has been used together with an IGE 400A gamma camera and STAR computer system in order to achieve high-resolution single-photon emission computed tomography (SPECT). The variation in width and shape of the reconstructed line-spread function with position in the field of view was quantified. A comparison with parallel-geometry SPECT showed an improved resolution and sensitivity.

Mathematics↗
PubMed1985

Somatostatin and counterregulatory hormone responses to hypoglycaemia in diabetics with and without autonomic neuropathy.

Blood glucose, somatostatin and counterregulatory hormone responses to an i.v. bolus of insulin were studied in insulin-dependent diabetics with different degrees of autonomic neuropathy, after 24 hours of optimised control with an artificial pancreas. There was no plasma catecholamine response in patients with a sympathetic autonomic neuropathy. A normal somatostatin response to hypoglycemia was absent in patients with autonomic neuropathy. Glucagon did not respond in diabetics, independently of the degree of neuropathy. In all diabetics, cortisol and GH were stimulated. Absence of warning symptoms was observed in patients with catecholamine deficiency. Despite different hormone behaviour, blood glucose fall and recovery were similar in all diabetic groups. It is concluded that the glucagon response to insulin hypoglycaemia is reduced in all type 1 longstanding diabetics, whereas catecholamine and somatostatin responses are only abolished in those with autonomic neuropathy. Patients with sympathetic neuropathy would be considered at increased risk severe hypoglycaemia.

Adult↗
PubMed1985

Cohort study of internal malignancy in genetic hemochromatosis and other chronic nonalcoholic liver diseases.

The risk of hepatocellular carcinoma (HCC) and other internal malignancies was examined in patients with genetic hemochromatosis (GH) by following 208 patients from the time of diagnosis to June 1983 and by comparing the numbers of cancers they developed with expected values constructed from cancer registry incidence data by means of actuarial methods. In addition, cancers occurring in a comparison group of 148 subjects with other chronic nonalcoholic liver diseases (CLD) were determined. Among the GH group, 16 new cases of HCC occurred subsequent to the diagnosis of GH, together with 8 other malignancies. The 16 cases of HCC reflect a 200-fold excess risk, which from all indications represents the first quantitation of the risk of this tumor in GH. There appears to be no increased risk of other malignancies in this disease. Among the CLD group only 1 HCC and 1 other malignancy occurred.

Adolescent↗
PubMed1984

Possible mechanisms of TSH--independent thyroid growth.

Considerable evidence has been accumulated which indicates the participation of the autonomic nervous system in the growth of adrenals, ovaries, testes and thyroid lobes. Results have been gathered indicating that the pituitary is not required for the growth of the thyroid, adrenals and ovaries; interest is currently focused on the involvement of the pineal gland in the control of growth not only of the gonads, but also of the thyroid. This paper summarizes the data currently available on the concepts of thyroid hypertrophic and hyperplastic mechanisms, which occur independently of thyrotropin (TSH), and which suggest the existence of a reciprocal relationship between the pineal and the thyroid.

Animals↗
PubMed1984

Distribution of F-actin during cleavage of the Drosophila syncytial blastoderm.

The process of cleavage during the syncytial blastoderm stage of the Drosophila embryo was studied in fixed whole-mounts using a triple-staining technique. Plasmalemma was stained with Concanavalin A conjugated to tetramethylrhodamine isothiocyanate, the underlying cortical F-actin with a fluorescein derivative of phalloidin, and nuclei with 4',-6 diamidine-2-phenylindole dihydrochloride. The surface caps, which overlie the superficial nuclei at this stage, were found to be rich in F-actin as compared with the rest of the cortex. After the caps formed, they extended over the surface and flattened. Whilst this was occurring the F-actin network within the caps became more diffuse. By the end of the expansion process F-actin had become concentrated at both poles of the caps. The caps then split in two. The cleavage was not accompanied by the formation of any apparent contractile ring of microfilaments across the cap, rather the break region was depleted in F-actin. The cortical actin associated with each half of the old cap then became reorganized around a nucleus to form a new daughter cap, and the cycle began again.

Actins↗