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Biomedical subjects

D R Chettle

Publications and source records attributed to D R Chettle.

At least 91 records · Page 5Linked to original sources
PubMed1979

Birmingham Medical Research Expeditionary Society 1977 Expedition: effect of a Himalayan trek on whole body composition, nitrogen and potassium.

The body composition of the 17 members of the BMRES was studied using body weight and fat fold calipers, with measurements of whole body potassium and nitrogen. The full assessment was made just before departure from Birmingham and immediately on return. Daily observations of body weight and fat folds were made during the trek to high altitude. During the ascent all subjects lost body fat but there was little change in lean body mass. After return it was found that there had been further loss of body fat and some loss of lean tissue also. One subject who took methandienone retained potassium but had no increase in body nitrogen. There was no correlation between changes in body composition and acute mountain sickness.

Adult↗
PubMed1978

In vivo measurement of calcium by the 37Ar method: a study of the effect of recirculating breath collection systems on the exhalation rate.

A study has been made of the effect that different methods of breath collection have on the measurement of calcium in vivo by the 40Ca(n,alpha) 37Ar method. The effect of open and rebreathing breath collection methods has been examined by using intravenous injections of 133Xe. This study has indicated that comparison of calcium measurements between individuals and between centres is likely to be accurate only if breath is collected on 'open circuit'.

Argon↗
PubMed1978

Problems in the interpretation of the in vivo measurement of calcium by the argon-37 method: an investigation of inert-gas elimination in humans.

An investigation has been made of some physiological problems associated with the interpretation of in-vivo measurements of calcium by the argon-37 method. Inert-gas elimination in humans over a period of several days was studied using i.v. injections of Xe-133. The results imply that the exhalation rate of A-37 formed in bone will be affected by the individual's composition, in particular body fat. Comparison of calcium measurements between individuals and between laboratories is meaningful only if corrections are made for differing individual composition.

Argon↗
PubMedDate not supplied

In vivo neutron activation analysis of organ cadmium burdens. Referent levels in liver and kidney and the impact of smoking.

In vivo neutron activation measurements of liver and kidney cadmium have been made in 77 exposed workers and 101 referents. Cadmium levels were higher in exposed workers than in referents; both in liver, 25.7 cf. 0.6 micrograms/g, and kidney, 17.9 cf. 2.7 mg. The 19 referents who never smoked had lower mean organ cadmium burdens than the other referents, the difference achieving statistical significance in the kidney, p less than .01. Cigarette smoking was estimated to increase cadmium body burden by 370 +/- 140 micrograms/pack year. These referent cadmium levels are similar to, although slightly below, previous in vivo and autopsy data.

Body Burden↗
PubMedDate not supplied

Performance appraisals of digital spectroscopy systems for the measurement of bone lead.

The performances of two new digital spectroscopy systems are compared to a conventional analogue amplifier ADC system for the 109Cd based K X-ray fluorescence in vivo measurement of bone lead. Canberra's DSA-2000 and ORTEC's DSPEC(PLUS) were found to show 27.3 and 10.8% improvements in measurement precision respectively, when compared to an optimized conventional system. The resulting improvements in minimum detection limit, compared with the conventional limit of 6-10 microg Pb/g bone mineral, were reductions of 1.5-2.5 microg Pb/g bone mineral for the DSA-2000, and 0.5-1.0 microg Pb/g bone mineral for the DSPEC(PLUS).

Bone and Bones↗
PubMedDate not supplied

System design for in vivo neutron activation analysis measurements of manganese in the human brain: based on Monte Carlo modeling.

Manganese is an essential nutrient required by the human body, but conversely, over exposure to the element may cause central nervous system damage. The technique of in vivo neutron activation analysis, using the McMaster KN-accelerator, is being investigated as a possible method of noninvasively determining manganese concentrations within the human body. Since the brain is the primary target of damage from exposure it would be the ideal site for measurements. Thus, Monte Carlo simulations have been undertaken to define the optimum experimental parameters for such a measurement, examining the use of possible moderator, reflector and collimator materials.

Basal Ganglia↗
PubMedDate not supplied

Monte Carlo design study for in vivo bone aluminum measurement using a low energy accelerator beam.

The need for aluminum monitoring exists in occupational medicine, as well as for the clinical monitoring of patients with renal dysfunction. After the development of an appropriate neutron source card, Monte Carlo simulations were made to design moderator/reflector assembly consisting of a polyethylene moderator (2 cm) and graphite reflector (30 cm), surrounded by a boronated (5%) wax (20 cm) and lead (1 cm) shield. This design should allow for the bone aluminum measurement of healthy subjects, but prior to that detailed microdosimetry is necessary to address a noticed disagreement between theoretical and experimental dose data.

Aluminum↗
PubMedDate not supplied

Improving the in vivo X-ray fluorescence (XRF) measurement of renal mercury.

In vivo polarised X-ray fluorescence (XRF) measurements of renal mercury have previously been reported (Börjesson J, Barregård L, Sällsten G, Schütz A, Jonson R, Alpsten M, Mattsson S, 1995. In vivo XRF analysis of mercury: the relation between concentrations in the kidney and the urine. Phys. Med. Biol. 40, 413-426). However, with the detection limit reported therein, this system is limited to measurements in cases of significant mercury exposure. An improvement in detection limit is desirable to produce a tool capable of occupational monitoring in cases of mild to moderate exposure. Therefore, design changes have been investigated to improve system performance. Through Monte Carlo simulation and experiment, optimal parameters were determined with respect to polarisation and filtration, as well as the ideal X-ray tube voltage. The optimal configuration will be discussed. A preliminary comparison in terms of minimum detectable limit (MDL) will be made with the preceding polarised XRF renal mercury system.

Filtration↗
PubMedDate not supplied

In vivo X-ray fluorescence (XRF) measurement of uranium in bone.

This study investigates the applicability of X-ray fluorescence (XRF) to measuring bone uranium concentrations, using a 57Co source to excite the uranium X-rays, with the source and detector in an approximate 180 degrees backscatter geometry relative to the sample position. It is demonstrated, by experiment and Monte Carlo simulation, that the X-ray to coherent peak ratio is linearly related to concentration and is independent of variations in source-sample geometry, thickness of overlying tissue and tibia size. Preliminary in vivo measurements indicate a minimum detectable concentration (MDC) of approximately 20 micrograms/g, which may not be sufficiently sensitive for monitoring occupational workers. However, a larger study of occupationally exposed individuals as well as work with subjects with known significant accidental uranium exposures is necessary to assess the clinical usefulness of this system.

Bone and Bones↗
PubMedDate not supplied

Improvements to the in vivo measurement of cadmium in the kidney by neutron activation analysis.

The McMaster University in vivo cadmium measurement system has been upgraded. Two large surface area hyperpure germanium planar detectors (51 mm diameter x 21 mm depth) are now employed for the detection of the 559 keV gamma-ray signal from cadmium. Phantom studies indicate that the new detectors have significantly improved the system. The detection limit in kidney phantoms has been reduced from 8.9 to 3.8 mg for the same dose and measurement time.

Cadmium↗