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Biomedical subjects

P Tothill

Publications and source records attributed to P Tothill.

At least 73 records · Page 4Linked to original sources
PubMed1983

Normal levels of total body sodium and chlorine by neutron activation analysis.

In vivo neutron activation analysis was used to measure total body sodium and chlorine in 18 male and 18 female normal adults. Corrections for body size were developed. Normalisation factors were derived which enable the prediction of the normal levels of sodium and chlorine in a subject. The coefficient of variation of normalised sodium was 5.9% in men and 6.9% in women, and of normalised chlorine 9.3% in men and 5.5% in women. In the range examined (40-70 years) no significant age dependence was observed for either element. Total body sodium was correlated with total body chlorine and total body calcium. Sodium excess, defined as the amount of body sodium in excess of that associated with chlorine, also correlated well with total body calcium. In females there was a mean annual loss of sodium excess of 1.2% after the menopause, similar to the loss of calcium.

Adult↗
PubMed1983

Comparison between 153Gd and 241Am, 137Cs for dual-photon absorptiometry of the spine.

The bone mineral content (BMC) of the spine can be measured from the attenuation of two photon beams. An equation was derived for the theoretical precision of BMC measurement and validated experimentally. Though 153Gd was found to possess the better energy combination, the precision due to the photon energy levels using 241Am, 137Cs was only 1.5 times the value obtained from 153Gd. The available photon outputs from 241Am and 153Gd were investigated and with a 12 mm diameter disc source a theoretical precision of 1% could be obtained with source strengths 20 GBq 241Am or 5GBq 153Gd in a 40 min and 20 min patient scan respectively. There was no great advantage in either energy combination when the problems of fat or patient dose were considered. Given the disadvantages of 153Gd, its cost and availability, 241Am, 137Cs can be used as a practical alternative to measure spine BMC from a reconstructed bone mineral image.

Americium↗
PubMed1983

Dual photon absorptiometry of the spine with a low activity source of gadolinium 153.

Apparatus and data-processing techniques were developed to measure the bone mineral content (BMC) of the lumbar spine. 153Gd was used as the dual photon source with an activity down to 7 GBq, lower than that adopted by other workers. The compromise between resolution and sensitivity was optimised. A reproducibility in normal subjects of 1.5% (coefficient of variation) was obtained. Normalisation procedures using parameters of the scan image and other indicators of body size such as span were developed, and reduced the coefficient of variation between normal subjects to 10% for men and 8% for pre-menopausal women. The absolute values of BMC are similar to those reported by others. Cross-sectional studies in women demonstrated an accelerated loss of BMC after the menopause.

Adult↗
PubMed1982

Total body calcium in rheumatoid arthritis: effects of disease activity and corticosteroid treatment.

Rheumatoid arthritis may be associated with generalised as well as periarticular osteoporosis. To assess the extent of bone loss and the influence of corticosteroid treatment total body calcium was measured by in-vivo neutron activation analysis in 63 patients with rheumatoid arthritis treated with non-steroidal anti-inflammatory drugs alone and 31 treated with additional low-dose corticosteroids. The results were compared with those in 40 normal controls matched for age, sex, and menopausal state. There were significant reductions in mean total body calcium in the group treated with non-steroidal anti-inflammatory drugs (5.3% in men; 6.8% in women) and greater reductions in the corticosteroid-treated patients (11.5% in men, 15.5% in women). The reduction was correlated with disease duration and activity in the patients treated with non-steroid anti-inflammatory drugs alone. Measured total body calcium was significantly less than the values predicted when this relation was used in the corticosteroid-treated patients. The data suggest that increased bone loss in patients with rheumatoid arthritis treated with corticosteroids is attributable to drug treatment rather than disease activity. Many patients with rheumatoid arthritis treated with low-dosage corticosteroids and some postmenopausal women with the disease are likely to be at risk from the complications of osteoporosis.

Adult↗
PubMed1982

Total body neutron activation analysis of calcium: calibration and normalisation.

An irradiation system has been designed, using a neutron beam from a cyclotron, which optimises the uniformity of activation of calcium. Induced activity is measured in a scanning, shadow-shield whole-body counter. Calibration has been effected and reproducibility assessed with three different types of phantom. Corrections were derived for variations in body height, depth and fat thickness. The coefficient of variation for repeated measurements of an anthropomorphic phantom was 1.8% for an absorbed dose equivalent of 13 mSv (1.3 rem). Measurements of total body calcium in 40 normal adults were used to derive normalisation factors which predict the normal calcium in a subject of given size and age. The coefficient of variation of normalised calcium was 6.2% in men and 6.6% in women, with the demonstration of an annual loss of 1.5% after the menopause. The narrow range should make single measurements useful for diagnostic purposes.

Adult↗
PubMed1982

Gastric emptying of solids in man.

The influence of the type and size of solid particles on their emptying from the stomach was studied using isotopically labelled chicken liver and inert particles in normal subjects and in patients who had undergone gastric surgery. In normal subjects, initial emptying of the liver was slower than that of inert particles both for large liver cubes (1 cm) and small cubes (0.3 cm). Liver emptying subsequently accelerated to be faster than emptying of the inert particles. Overall emptying of the liver given as small cubes was faster than large cubes; 50% emptied in 50 minutes and 70 minutes respectively. In the postoperative subjects, emptying of the liver and of the inert particles was identical. The findings are consistent with the hypothesis that solid foods such as liver are ground down and 'liquified' by the action of gastric peristalsis before being discharged to the duodenum. Ingested particle size appears to influence the rapidity of this process, which should be distinguished from the propulsive function of the stomach where small solid particles are concerned.

Adult↗
PubMed1981

An evaluation of 99mTc pertechnetate scanning for the detection of coeliac disease and Crohn's disease.

To investigate the use of abdominal scintiscanning in the detection of small bowel pathology, the accumulation of pertechnetate (99mTc), following intravenous injection, has been studied in 21 patients with coeliac disease, 13 patients with Crohn's disease and in 83 control subjects without known small bowel disease. Although a trend for a greater accumulation of 99m Tc was noted in patients with coeliac disease and Crohn's disease compared with controls (P less than 0.025) there was a large overlap in individual studies. Under the conditions of this study the accumulation of 99mTc by the small bowel did not provide a reliable diagnostic test for coeliac disease or Crohn's disease of the small intestine. The accumulation of 99mTc pertechnetate by normal small bowel suggests that scintiscanning with this radiopharmaceutical does not provide a consistently reliable method for the detection of small bowel pathology.

Adult↗
PubMed1981

Acetaminophen absorption and metabolism in celiac disease and Crohn's disease.

To investigate further the conflicting results in reports of drug absorption in patients with small intestinal mucosal disease, gastric emptying and the disposition of acetaminophen were assessed simultaneously in 41 subjects (13 controls, 12 patients with Crohn's disease, and 16 with celiac disease). Acetaminophen absorption as judged by plasma concentrations and gastric emptying were slower in patients with celiac disease and Crohn's disease. Total drug absorption as indicated by urinary recovery did not differ, but plasma acetaminophen half-life was shorter and glucuronide conjugation was enhanced in the patients with Crohn's disease. Contrary to expectation, the mean rate constant for acetaminophen absorption from the small intestine was not decreased in Crohn's disease and celiac disease. The abnormally slow acetaminophen absorption in the patients with Crohn's or celiac disease could be explained by slower gastric emptying of the drug solution.

Acetaminophen↗
PubMed1981

The comparison of neutron activation analysis and photon absorptiometry at the same part-body site.

Two non-invasive methods of bone measurement were, for the first time, compared at the dame part-body site. Bone calcium, using in vivo neutron activation analysis, and bone mineral, using photon absorptiometry, were measured in the forearm in a group of renal patients. A highly significant correlation was obtained from absolute values (r = 0.91) which was reduced after normalisation (r = 0.75). Percentage changes, over periods totalling 31.3 patient years, were also highly significantly correlated (r = 0.61, P less than 0.001). The precision of the techniques accounts for the spread of the bivariate data and the estimated line of the true relationship was not significantly different from the line described if the percentage changes measured by the two techniques were equal. The two basic techniques were shown to be equally sensitive in vivo methods for monitoring calcified bone in patients suffering from metabolic bone disease.

Absorption↗
PubMed1980

Limitations of radioactive microspheres as tracers for bone blood flow and extraction ratio studies.

Radioactive microspheres have been used for measuring bone blood flow and the extraction ratios of bone-seeking radionuclides, but we have shown that the technique is not completely valid. Bone uptake of 18F and 85Sr was compared with that of microspheres simultaneously injected into the heart or aorta of rats and rabbits under a variety of conditions. In single-passage experiments with quick killing to avoid recirculation, attention was focused on the tibiae and femora which could be dissected quickly to avoid post-mortem migration. For the rest of the skeleton, the effect of the latter was minimized by allowing recirculation for 5 min and comparing blood flow determinations in conjunction wit a cardiac output measurement. The apparent extraction ratio of 18F was variable and always exceeded unity in the single-passage experiments. With recirculation, there were significant differences between the extraction ratios for some bones, and the ratios sometimes exceeded unity. Extraction ratios for 85Sr were similarly variable, but lower. When 85Sr was compared directly with 18F, the relative extraction ratio was 0.8, with little variation between bones or animals. It is concluded that the flux of microspheres entering the vasculature of bone is not representative of blood flow, owing to the removal of some microspheres in pre-osseous capillary beds. Microspheres are therefore not a satisfactory standard for the determination of extraction ratios.

Animals↗
PubMed1980

The effect of posture on errors in gastric emptying measurements.

Scintigraphic gastric emptying measurements were made with subjects supine and upright using a dual-detector rectilinear scanner. Previously reported variations of the depth of activity during the course of a study were again found with both postures. Although there was no significant mean depth change in the group when upright, some individual variations were substantial. Measurements with a gamma camera demonstrated similar changes of depth of stomach contents with seated subjects. The resulting variations of attenuation of the emergent radiation lead to appreciable errors in the emptying rates determined by unilateral detection. In about half the cases the mean movement of a 99Tcm-labelled solid phase marker exceeded 1 cm; such a movement led to an average 20% error in emptying rate determination by an anterior detector. Depth changes of a liquid marker were less marked, exceeding 0.5 cm in half the subjects; this movement gave rise to an average 6% error when 113Inm was used as the tracer.

Diagnostic Errors↗
PubMed1980

Gastric emptying in diabetic autonomic neuropathy.

Gastric emptying was studied in 12 diabetic patients, six with and six without objective evidence of autonomic neuropathy and in 20 nondiabetic controls, using a double isotope scintiscanning technique which differentiated between solid and liquid emptying. Three patients with autonomic neuropathy exhibited gastric stasis, although this was detected by conventional radiology in only one. Neither the patients with stasis nor those without exhibited abnormally rapid early gastric emptying. In patients without stasis, the normal differentiation between solid and liquid emptying was impaired, suggesting an abnormality of antral peristalsis not attributable to vagal denervation. Both intravenous and oral metoclopramide produced symptomatic improvement in two patients with gastric stasis and restored their gastric emptying to normal.

Adult↗
PubMed1979

Effect of gel fibre on gastric emptying and absorption of glucose and paracetamol.

To determine the part played by altered gastric emptying in the modification of glucose absorption by gel fibres, glucose tolerance tests were done in seven healthy volunteers with and without the addition of pectin to the ingested glucose solution and after pharmacological inhibition of gastric emptying with propantheline. Compared with the controls, pectin significantly reduced blood-glucose. Propantheline had a similar but more pronounced effect. Pectin and guar gum did not substantially alter glucose tolerance in a patient who had had total gastrectomy. In a further investigation, gastric emptying and paracetamol absorption were studied simultaneously in fourteen subjects. In eight of these the study was repeated after addition of guar gum and pectin to the ingested paracetamol. Both gastric emptying and paracetamol absorption were slower after gel fibre but the total absorption of the drug, reflected in urinary recovery, was not significantly reduced. The results suggest that the effects of guar gum and pectin on glucose tolerance and paracetamol absorption could be due simply to alteration in the rate of gastric emptying.

Absorption↗
PubMed1979

Iodine 131 labelled ioglycamic acid (Biligram) for scintiscanning in hepatobiliary disorders.

Iodine-131 labelled Biligram has been evaluated as a radiopharmaceutical for dynamic scintiscanning of the liver and biliary tract. In 10 normal subjects there was good visualisation of the liver and gallbladder. In 18 patients 131I Biligram was found to be unsatifactory for differentiating parenchymal liver disease from biliary tract obstruction owing to inability to demonstrate the gallbladder when liver function was more than mildly deranged. Quantitative analyses of blood clearance and hepatic activity curves for 131I Biligram were not clinically helpful. Urinary excretion of 131I Biligram increased with the degree of hepatic dysfunction.

Biliary Tract Diseases↗
PubMed1979

Development of apparatus to measure calcium changes in the forearm and spine by neutron activation analysis using californium-252.

Techniques were developed to measure small changes of calcium in the forearm and spine in vivo by neutron activation analysis using two sources of 252Cf in a hospital environment. Using purpose-built part-body counters and bilateral irradiation with 7.5 cm premoderation between the sources and the bone, peripheral bone was measured with a total source strength eventually as low as 50 mCi. Two methods of spectral analysis were used and compared. Patient studies of the forearm were successfully undertaken, with a precision of 2.6% which included patient movement, and an annual bone dose of less than 10 rem and skin dose of 35 rem from six measurements. Two 100 mCi sources were used for measurements of the lumbar spine. Care was taken to minimise the problems of non-uniformity of activation which are present using unilateral irradiation. Emphasis was placed on measuring the bodies of the vertebrae with adequate sensitivity and uniformity, and the spinous processes and arches with low sensitivity. A whole body counter was used for the bilateral detection of the induced activity. The precision of the method was 3.0% with an annual peak bone dose of 2.1 rem and skin dose of 18 rem from three measurements.

Activation Analysis↗