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Biomedical subjects

J K Haywood

Publications and source records attributed to J K Haywood.

At least 19 recordsLinked to original sources
PubMed1984

Body elemental composition, with particular reference to total and exchangeable sodium and potassium and total chlorine, in untreated and treated primary hyperaldosteronism.

The whole body content of sodium, potassium, chlorine, calcium, phosphorus and nitrogen was measured by neutron activation analysis in 13 patients with untreated primary hyperaldosteronism (Conn's syndrome; aldosterone-secreting adenoma). Concurrently, exchangeable sodium and potassium were estimated by isotope dilution. Results were compared with values in the same patients during treatment with potassium-conserving diuretics and again after removal of the adenoma; and also with those in a series of 30 patients having untreated essential hypertension. Both total body and exchangeable sodium were high in Conn's syndrome before treatment and were reduced by spironolactone or amiloride and by subsequent surgery. There was no evidence of alteration in the proportion of non-exchangeable sodium in this disease, in contrast to earlier reports. Total body and exchangeable potassium were low in untreated Conn's syndrome and increased to normal after therapy: the proportion of non-exchangeable potassium was similar before and after treatment, and also similar to that in essential hypertension. Total body chlorine was increased before treatment in Conn's syndrome and returned to normal with therapy; body calcium, phosphorus and nitrogen were normal throughout.

Adult↗
PubMed1984

Whole-body elemental composition in patients with renal failure and after transplantation studied using total-body neutron-activation analysis.

Whole body elemental composition in seventy-five patients with either renal failure or a kidney transplant was measured by neutron-activation analysis and whole-body counting. Comparison was made with expected normal values and with a control group; between undialysed, dialysed and transplanted patients; and between those receiving dialysis treatment for various periods. A frequent finding was low body calcium, reflecting the prevalence of renal osteodystrophy. Sodium and chlorine were increased in undialysed patients, a consequence of their renal disease. Patients with transplanted kidneys had reduced amounts of most elements, indicating decreased lean body mass, but increased body weight, probably due to excess fat.

Body Composition↗
PubMed1982

Whole body elemental composition in patients with essential hypertension.

The whole body content of sodium, chlorine and potassium has been measured in 30 patients with essential hypertension, using the techniques of in vivo neutron activation analysis and whole body counting. Total exchangeable sodium and potassium were also measured, and found to be well correlated with the total body amounts of these elements. Comparable measurements on normotensive subjects could not be obtained, but results for both elements were similar to those expected on the basis of published values for healthy normal body composition. Similarly, no abnormality was found in the average body content of the other major elements (chlorine, calcium, phosphorus and nitrogen). We therefore have no evidence that essential hypertension is associated with any abnormality in the mean body content of these elements. However, there was some evidence of a relationship between body sodium and blood pressure in this study group.

Adult↗
PubMed1981

Reliability of absolute and relative measurement of total body nitrogen by the 14N(n, 2n)13N reaction.

Measurements of total body nitrogen by in vivo neutron activation analysis using the 14N(n, 2n)13N reaction, may conveniently be calibrated using phantoms in which nitrogen is uniformly distributed. However, the response of the method varies considerably in the thickest body sections and in order to validate the calibration, it is necessary also to consider the spatial distributions both of nitrogen and of the major interfering element, oxygen. The effects of these spatial distributions have been calculated for the experimental conditions obtained at the East Kilbride facility for total body in vivo neutron activation analysis. The response for total body nitrogen was found to depend strongly on body weight (in the rang e 40 to 100 kg) but only weakly on total body content of adipose tissue (0 to 65% of body weight). It differed little from the response calculated for the nitrogen distributed uniformly within the body. The calculation was tested successfully against measured changes in the net response for nitrogen resulting from 'homogenisation' of inhomogeneous phantoms.

Body Composition↗
PubMed1981

Simplification of simultaneous measurement of the total body content of five elements using only one 14 MeV neutron generator.

Measurement of body composition by total body in vivo neutron activation analysis is a valuable tool for clinical research but use of this technique has been largely restricted to medical units near existing neutron irradiation facilities. A facility for total body in vivo neutron activation analysis was purpose-built at low cost and has performed well. The methods of scanned bilateral neutron irradiation and scanned bilateral measurement of induced activity have been subject to continuous development. It has been found possible to dispense with one of the original complement of two 14 MeV neutron generators, without significantly impairing measurement of any of the elements for which the system was designed (phosphorus, calcium, nitrogen, chlorine and sodium). Thus a hospital department with access to a whole-body counter capable of measuring total body 40K can now extend its investigation of body composition to these five important elements at a cost of 75 m2 of floor space and less than 30 000 pounds.

Body Composition↗
PubMed1980

Whole body calcium deficit in cadmium-exposed workers with hypercalciuria.

Whole body elemental composition of 15 men occupationally exposed to cadmium was determined by total body in vivo neutron activation analysis and whole body counting. A significant deficit (P less than 0.01) in calcium was observed, compared with two groups of control subjects. The deficit increased with length of time exposed to cadmium.

Adult↗
PubMed1980

Whole body aluminium in chronic renal failure and dialysis encephalopathy.

Whole body calcium, phosphorus and nitrogen have been measured by in vivo neutron activation analysis in patients with chronic renal failure, including 9 with dialysis encephalopathy. Aluminium was also activated by this procedure, but to the same radioactive product as that from phosphorus: its presence was therefore detected as an increase in the apparent total body phosphorus above that expected for a person with the same calcium content. Patients with dialysis encephalopathy had slightly more apparent phosphorus than others with chronic renal failure, although the difference was not statistically significant. This difference corresponded to an excess of aluminium not greater than 3.3 g(95% confidence limit) which places an upper limit on excess aluminium accumulation in this condition.

Adult↗
PubMed1979

Whole body elemental composition during drug treatment of rheumatoid arthritis: a preliminary study.

Thirty-two female patients with rheumatoid arthritis were divided into 3 groups and treated for 6 months with prednisolone, depot tetracosactrin, or indomethacin. Their whole body content of calcium, phosphorus, and nitrogen was measured before and after 3 and 6 months' treatment by in-vivo neutron activation analysis. No significant changes in these body elements were observed as a result of the treatments. The average amounts of calcium, phosphorus, and nitrogen were lower than normal in these patients, a finding consistent with the frequent observation of osteoporosis and muscle wasting in rheumatoid arthritis.

Adult↗
PubMed1979

A less empirical method of representing megavoltage beams for use in rapid radiotherapy dose calculations.

A large number of initial measurements are needed for accurate computation of radiotherapy dose distributions directly from stored data on the dose distribution of single radiation beams. Because of this, interest has been shown in alternative methods which use empirical formulae to represent the dose distributions of single beams. These can be easier to implement but are less directly related to measured quantities and may be of limited validity. A method of representing radiotherapy beams is proposed which closely approximates their radiation physics, in order to calculate the dose at any point by a simple algorithm directly from a small number of initial dose measurements. The method is of wide validity, probably including all megavoltage radiations for which Compton scattering is the dominant interaction in tissue. The accuracy of the method is demonstrated by application to an 8 MV linear accelerator and a cobalt 60 machine.

Humans↗
PubMed1978

Concurrent estimation of total body and exchangeable body sodium in hypertension.

1. Total-body neutron-activation analysis in vivo was carried out in 11 hypertensive subjects to measure simultaneously the total body content of sodium, chlorine, calcium, phosphorus and nitrogen. 2. There was a highly significant correlation between total body sodium measured by activation analysis and total exchangeable sodium measured by a standard isotope-dilution technique (r = 0.92, P less than 0.001). Exchangeable sodium averaged 80.3% of total body sodium. 3. The measured values of chlorine, calcium, phosphorus and nitrogen were similar to those for healthy subjects reported by others. 4. Activation analysis in vivo appears promising as an additional tool for investigating sodium metabolism in hypertension, as it is the only method available for determining the total body content of this element. The radiation dose (1 rem) is sufficiently low to permit repeated measurements in the same subject.

Adult↗
PubMed1978

Neutron uniformity studies related to clinical total body in vivo neutron activation analysis.

Methods of assessing the uniformity of thermal and fast neutron fluence in relation to total body in vivo neutron activation analysis are described. Results are presented for 14 MeV neutrons emitted by sealed tube generators housed in a massive concrete shield, representing a substantial source of neutrons degraded in energy. Optimisation of conditions for patient irradiations is discussed and it is shown that acceptable uniformity of fluence can be achieved with little or no premoderation of the incident neutrons.

Activation Analysis↗
PubMed1978

Calibration and evaluation of a system of total body in vivo activation analysis using 14 MeV neutrons.

A system has been established for determining the total body contents of calcium, phosphorus, sodium, chlorine and nitrogen by neutron activation analysis using sealed-tube neutron generators and a shadow-shield whole-body counter. The system was calibrated using three anthropomorphic phantoms of different sizes, filled with various mixtures of the activatable elements in amounts similar to those in man. The reproducibility determined from replicate measurements, was on average +/- 2.9% (SD). The average uncertainty in absolute measurements was estimated to be +/- 4.2% (68% confidence interval).

Activation Analysis↗
PubMed1978

A two-way scanning method for total body in vivo neutron activation analysis.

When determining the total body content of many elements by neutron activation analysis, irradiation and whole body counting by scanning along the length of the body has significant advantages. A neutron source of lower output and a whole body counter using smaller detectors and shielding (than otherwise needed) can provide a high, uniform response for many elements throughout the body. This was previously achieved by making the speed and direction of scanning identical in irradiation and counting (one-way scanning). A simple theoretical model for scanned irradiation and counting is described. The model is used to show that a scanning regime in which both scanning directions are used (two-way scanning) can provide acceptably uniform response for elements having induced activities of a wide range of half-life. This is supported by measurements made using an existing scanning facility for total body in vivo neutron activation analysis. The two-way scanning regime offers the advantages of increased patient comfort, simpler operation and more efficient use of the time available for counting induced activity.

Activation Analysis↗