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Biomedical subjects

R G Bessent

Publications and source records attributed to R G Bessent.

At least 55 records · Page 3Linked to original sources
PubMed1981

A critical assessment of bone scan quantitation (bone to soft tissue ratios) in the diagnosis of metabolic bone disease.

Accurate quantitation from the bone scan image of skeletal uptake of radiopharmaceutical would be of value in the assessment of patients with metabolic bone disease. Repeat measurements of bone to soft tissue (B/ST) ratios on the one set of images were made for 103 subjects, a) by the same observer using lumbar vertebra 2 for the area of bone; b) by the same observer using lumbar vertebra 2 then lumbar vertebra 4; c) by two observers both using lumbar vertebra 2. The median difference between repeat measurements by the same observer was well under 1% but the 5-95 percentile range was -13 to +14%. Between the two observers there was a median difference of 10.6% with a 5-95 percentile range of -11 to +44%. We also measured B/ST ratios in 150 control subjects and 139 patients with various metabolic bone disorders. While statistically significant differences for B/ST ratios were found between the osteomalacia, renal osteodystrophy, Paget's groups, and the control population (P less than 0.001 in all cases), there was appreciable overlap between individual patient results and the control range. It is concluded, therefore, that measurement of B/ST ratios for the individual is of limited value in clinical practice.

Adult↗
PubMed1981

Bayesian analysis of stress thallium-201 scintigraphy.

The variation of the diagnostic value of stress Tl-201 scintigraphy with prevalence of coronary heart disease (CHD) in the population has been investigated using Bayesian reasoning. From scintigraphic and arteriographic data obtained in 100 consecutive patients presenting with chest pain, the sensitivity of stress Tl-201 scintigraphy for the detection of significant CHD was 90% and the specificity was 88%. From Bayes' Theorem, the posterior probability of having CHD for a given test result was calculated for prevalences of CHD ranging from 1% to 99%. The discriminant value of stress Tl-201 scintigraphy was best when the prevalence of CHD lay between 30% and 70% and maximum for a prevalence of 52%. Thus, stress Tl-201 scintigraphy would be an unsuitable diagnostic test where the prior probability of CHD is low, e.g., population screening programmes, and would add little where the clinical probability of having CHD is already high. However, where the prior probability of having CHD is intermediate stress Tl-201 scintigraphy may provide valuable diagnostic information.

Bayes Theorem↗
PubMed1981

Assessment of synthetic steroid (Org OD 14): effect on skeletal metabolism by 24-h whole-body retention of diphosphonate.

Using a 24-h whole-body retention (WBR) of Tc99m hydroxyethylidene diphosphonate (HEDP), a sensitive measure of skeletal metabolism, 24 women receiving the synthetic steroid hormone Org OD 14 were studied. OD 14 was found to have a powerful suppressive effect on skeletal metabolism in both oophorectomized and non-oophorectomized women when compared with control subjects (P less than 0.001 and P less than 0.01, respectively). The degree of suppression was similar to that found with oestrogen therapy. While it has previously been shown that OD 14 prevents bone mineral loss (as measured by photon-absorptiometry), the present study provides further evidence as to the efficacy of this compound in suppressing skeletal metabolism.

Alkaline Phosphatase↗
PubMed1981

A comparison of skeletal uptakes of three diphosphonates by whole-body retention: concise communication.

Twenty normal volunteers had measurements of 24-hr whole-body retention (WBR) of three structurally related Tc-99m-labeled phosphonate skeletal imaging agents: (1-hydroxyethylidene) diphosphonate (HEDP), methylene diphosphonate (MDP), and hydroxymethylene diphosphonate (HMDP). The average WBR values, reflecting skeletal uptake, were 18.4, 30.3, and 36.6%, respectively. These results clearly illustrate that slight alterations in diphosphonate molecular structure have a significant effect upon specificity for osseous tissue, and thus may affect skeletal image quality and the usefulness of the WBR technique in diagnosing metabolic bone disease.

Adult↗
PubMed1981

Measurement of 24-hour whole-body retention of Tc-99m HEDP by a gamma camera.

Measurement of 24-hr whole-body retention of Tc-99m HEDP, using a shadow-shield, whole-body monitor, has been shown to be a sensitive measure of skeletal metabolism and of value in the diagnosis of metabolic bone disease. A new method of measuring the retention using a gamma camera, with a scanning (fishtail) collimator and patient placed at 2.,3 m distance, has been evaluated in 18 patients undergoing routine bone scans. The patients also had whole-body monitor (WBM), and the two methods correlated well, yielding a regression line GC% = -0.82 + 0.98 WBM%, r = 0.975, p less than 0.001. The limitations to, and repeatability of, the gamma-camera measurements are discussed. This work shows that measurements of whole-body retention can be obtained in any nuclear medicine department possessing a gamma camera with a suitable collimator.

Body Burden↗
PubMed1980

Skeletal uptake of diphosphonate. Method for prediction of post-menopausal osteoporosis.

24-h whole-body retention (WBR) of diphosphonate (a sensitive indicator of skeletal metabolism) was measured in 37 oophorectomised women. 14 women had been prescribed oestrogen supplements and 3 of these had defaulted from therapy. For the study group there was a significant correlation between WBR and both the rate of bone loss as measured by photonabsorptiometry (r = 0.7, p ¿ 0.001) and urinary hydroxyproline (r = 0.53, p < 0.001). The oestrogen-treated group had significantly lower values for WBR and rate of bone loss than the untreated group (p < 0.01, p < 0.01 respectively) indicating suppressed skeletal metabolism. However, the highest values were found in those who had defaulted from oestrogen therapy suggesting a rebound period of accelerated skeletal metabolism and bone loss. There was a significant negative correlation between WBR and oestrogen dosage (r = 0.75, p < 0.02) suggesting that it may be possible to adjust the dosage for optimal skeletal metabolic activity. WBR of diphosphonate provides a simple and sensitive measure of skeletal metabolism which correlates well with conventional measurements of bone loss. WBR may be useful in the screening and identification of women who have increased bone turnover just after the menopause and who may subsequently be at risk of osteoporosis developing.

Aged↗
PubMed1980

Application of the occupancy principle in studies of the metabolism of vitamin B12 in man.

1. The long-term clearance of radioactive vitamin B12 from serum and from whole body was measured in control subjects and patients with treated pernicious anaemia and the data were analysed by the occupancy principle to provide estimates of dietary intake, daily requirements and whole-body mass of vitamin B12. 2. In six cases the daily requirement for vitamin B12 ranged from 0.15 to 1.9 microgram with an average of 1.0 microgram. The whole-body vitamin B12 in four cases ranged from 780 to 1350 microgram with an average of 1060 microgram. 3. Estimates of the whole-body vitamin B12 on the assumption of single-pool equilibrium gave constantly changing results, which, together with discrepant half-lives for serum radioactivity and whole-body radioactivity, constitute evidence against the concept of single-pool equilibrium.

Anemia, Pernicious↗
PubMed1980

A comparison of visual and semiquantitative analysis of stress thallium-201 myocardial images in patients with suspected ischemic heart disease.

Three methods of analyzing stress thallium-201 myocardial images were performed on 79 patients with suspected coronary artery disease. The results of visual analysis of unprocessed Polaroid images, background subtracted and contrast enhanced computer generated color television images, and a semiquantitative regions-of-interest method were each compared to the coronary arteriographic findings in all patients. Analysis by the semiquantitative method achieved the highest accuracy for the classification of patients as either having or not having coronary artery disease. This method of interpreting myocardial images appears worthy of further study.

Coronary Disease↗
PubMed1980

Semi-quantitative analysis of the bone scan in acromegaly: correlation with human growth hormone values.

99Tcm-HEDP bone scans were obtained in 20 acromegalic patients. Twelve patients had active disease with elevated basal serum human growth hormone (HGH) levels. Eight patients were in clinical and biochemical remission. The bone scans, assessed independently by three observers, showed features characteristic of metabolic bone disease in patients with active acromegaly. The metabolic index derived from the scan correlated well with serum HGH levels (R = 0.71, p < 0.002). The bone scan may accurately reflect oversecretion of HGH and is of potential value in the assessment of patients with acromegaly.

Acromegaly↗
PubMed1979

Semi-quantitative interpretation of the bone scan in metabolic bone disease: definition and validation of the metabolic index.

Certain easily recognisable features are commonly seen in the bone scans of patients with metabolic bone disorders. Seven such features have been numerically graded by three independent observers in the scans of 100 patients with metabolic bone disease and of 50 control subjects. The total score for each patient is defined as the metabolic index. The mean metabolic index for each group of patients with metabolic bone disease is significantly greater than that for the control group (P less than 0.001).

Bone Diseases↗
PubMed1979

The significance of the abnormal rest thallium-201 myocardial image in coronary artery disease.

Rest Thallium-201 myocardial images were abnormal in 20 out of 40 patients with arteriographically proven coronary artery disease. The myocardial image appearances did not accurately reflect the extent of coronary artery disease present. However, in 35 of the 40 patients (88%) the presence or absence of abnormalities on the rest myocardial image correleted respectively with the presence or absence of abnormal wall motion at left ventriculography. Most rest image abnormalities could be attributed to previous myocardial infarction, but in six patients myocardial ischaemia was possibly the cause. These results suggest that though myocardial fibrosis is usually the cause of rest myocardial image abnormalities in coronary artery disease, this is not invariably so. The possible therapeutic implications are discussed.

Adult↗
PubMed1979

A clinical comparison of Tc-99m HEDP and Tc-99m MDP in the detection of bone metastases: concise communication.

We have compared bone scintigrams made with Tc-99m-tagged HEDP (1-hydroxyethylidene diphosphonate)and MDP (methylene diphosphonate), the former at 4 hr after injection, the latter at both 2 and 4 hr. In 17 patients with skeletal metastases, there was no significant difference in lesion count or scan quality between the 4-hr images. The tumor-to-bone ratio (T/B) was significantly higher with Tc-HEDP (p less than 0.02). Lesion detection rate and T/B ratios were both lower with Tc-MDP at 2 hr when compared with the 4-hr values for both Tc-HEDP (p less than 0.02, p less than 0.005) and Tc-MDP (p less than 0.02, p less than 0.01). The 4-hr Tc-MDP scan was of significantly higher quality than the 2 hr Tc-MDP scan (p less than 0.01). Although Tc-HEDP produces a higher T/B ratio at 4 hr, the present study does not suggest that either agent is superior in clinical practice.

Adult↗