Search PubMed⌕ Search

Biomedical subjects

G M Blake

Publications and source records attributed to G M Blake.

118 records · Page 7Linked to original sources
PubMed1985

Adrenal scintigraphy with 75Se selenonorcholestenol: a review.

We have reviewed 58 patients on whom adrenal scintigraphy has been performed using 75Se selenonorcholestenol. For 15 patients whose adrenal function was biochemically normal, the upper limit of normal of the 7 day adrenal uptake test was 0.45%, considerably higher than the generally accepted value of 0.3%. There is evidence from this group of patients that stress and obesity might account for uptakes in the range 0.3-0.45%. The sensitivity of the uptake test is poor, with 7 out of 23 patients with Cushing's syndrome having uptakes within the normal range. Scintigraphy of such patients may still be useful in differentiating between unilateral and bilateral adrenal involvement.

Adrenal Cortex↗
PubMed1985

Thallium-technetium subtraction scintigraphy as an aid to parathyroid surgery.

We describe the application of thallium-technetium subtraction scintigraphy in nine patients with failed previous parathyroid surgery or with tertiary hyperparathyroidism due to chronic renal failure. The technique successfully located all adenomas, but only 45% of hyperplastic glands. The series included three abnormal glands located retrosternally. The technique appeared to be more useful in patients with primary hyperparathyroidism than in tertiary hyperparathyroidism, possibly related to differences in gland mass. We conclude that this method of scintigraphy is a valuable adjunct to the management of patients with parathyroid disorders, particularly those requiring revision surgery.

Adenoma↗
PubMed1985

Assessment of thallium-pertechnetate subtraction scintigraphy in hyperparathyroidism.

Reliable techniques for detecting and localising abnormal parathyroid tissue have been a persistent problem. We have evaluated thallium-pertechnetate subtraction scintigraphy in a prospective study of 40 patients with clinical and biochemical evidence of hyperparathyroidism prior to parathyroid surgery. Four patients were excluded as they were shown to have goitre, making subtraction scanning non-diagnostic. 89% of parathyroid adenomas (totalling 27 glands in 26 patients) and 41% of hyperplastic glands (17 glands in 6 patients) were accurately localised prior to surgery. These included three retrosternal glands, four patients with renal failure and tertiary hyperparathyroidism and five patients who had previously undergone neck exploration. The apparent discrepancy between detecting hyperplastic and adenomatous glands was associated with the smaller size of the former. For both types of gland, scintigraphy successfully located parathyroids 0.6 g or more in weight. These results suggest that this simple and non-invasive method is a useful technique for locating parathyroid tissue before parathyroid surgery.

Adenoma↗
PubMed1984

Diagnosis of deep-vein thrombosis: comparison of clinical evaluation, ultrasound, plethysmography, and venoscan with X-ray venogram.

In 50 patients with suspected deep-vein thrombosis the diagnostic accuracy of standardised clinical examination, doppler ultrasound, impedance plethysmography, and technetium-99m-labelled-fibrinogen scintigraphy (venoscan) was compared with that of X-ray venography. Physical examination was the least accurate method. Impedance plethysmography, venoscan, and ultrasound had accuracies of 65%, 80%, and 82%, respectively. The initial X-ray venogram report had an accuracy of 90% compared with the interpretation of two experienced radiologists. The venoscan was equivocal in 32% of patients, and in the remaining patients the accuracy was 97%. Objective methods of investigation are essential for diagnosing deep-vein thrombosis. Of those tested, the X-ray venogram was the only investigation suitable for definitive diagnosis. The venoscan may have a role as a screening procedure, to be followed by X-ray venography in patients with equivocal venoscan results.

Adolescent↗
PubMed1984

Potassium supplements and total body potassium in elderly patients.

Total body potassium (TBK) and serum potassium measurements have been obtained in nine elderly patients in controlled heart failure on differing diuretic regimens. The patients were randomly maintained on a potassium-sparing diuretic, on frusemide, and on frusemide with potassium supplements (48 mmol/day) for a minimum of one month. TBK levels increased by a mean of 128 mmol on frusemide with potassium supplements compared with no supplements (P less than 0.001), a 7% increase in TBK. Serum potassium levels increased, similarly, from 4.1 mmol/l to 4.8 mmol/l (P less than 0.01). The potassium-sparing diuretic had the same effect as frusemide with supplements in increasing TBK in six patients. However, in three cases there was no increase in TBK compared with frusemide alone. The results demonstrate that potassium supplements are effective in raising TBK levels and serum potassium levels in elderly patients with heart failure.

Aged↗
PubMed1983

A new method giving a two criteria diagnosis of venous occlusion using isotope imaging of 99mTc-labelled fibrinogen.

A new method for the diagnosis of venous occlusion involves three stages: first, injection of 99mTc-labelled fibrinogen into a distal vein in the suspected limb with a dynamic gamma scan of venous flow; second, a static pool scan of both limbs to show the anatomy of the veins seen in the dynamic scan and third, a later static scan showing 99mTc-fibrinogen associated with thrombus. In occlusion, absence of flow in the dynamic scan corresponds to the presence of isotope in thrombus in the second static scan. The test uses a low-volume, low-radioactivity injection and may be repeated many times.

Adult↗
PubMed1979

Inheritance of isozyme variation and heterozygosity in Pinus ponderosa.

Techniques are presented to detect 23 isozyme loci in the long-lived perennial plant, ponderosa pine. Meiotically derived megagametophyte from seeds is used to examine directly the segregation of allelic variants. Approximately seven seeds were initially examined for 12 enzymes from each of 47 trees from ten stands throughout the northern Rocky Mountain region. Additional seeds were also examined from selected families to confirm the inheritance of observed electrophoretic variants at 13 polymorphic loci and to estimate linkage relationship. Significant norandom segregation was consistently detected for three pairs of loci: ADH-1:AAT-2, ADH-1:PGI-1, and LAP-2:6PG-1. Preliminary estimates of population parameters reveal a relatively high average heterozygosity (H = 0.123). This is partitioned into a high amont of genetic variation within local stands, with only approximately 12% of the total heterozygosity resulting from genic difference between stands.

Gene Frequency↗
PubMedDate not supplied

Dual energy x-ray absorptiometry: the effects of beam hardening on bone density measurements.

X-ray tubes have superseded radionuclide sources for dual photon absorptiometry of the spine and hip. However, the use of a polyenergetic spectrum is a potential source of error for x-ray absorptiometers since beam hardening may result in a nonlinear measurement scale for bone mineral density (BMD). A quantitative study of the effects of beam hardening on measurements made with a commercial dual energy x-ray scanner has been performed. Bone was represented by layers of aluminum of linearly increasing thickness which were scanned under water thicknesses ranging from 0 to 25 cm to represent different body thicknesses of soft tissue. Beam hardening had two effects on measured BMD: (i) at a constant true BMD, measured BMD varied with water thickness; (ii) at a constant water thickness, the BMD scale was not precisely linear. For conditions appropriate to spine and hip studies (BMD) values in the range 0.7 to 1.4 g/cm2 and body thickness between 15 and 25 cm) the maximum deviation of measured BMD from a linear scale was 0.023 g/cm2, while the root-mean-square deviation (0.01 g/cm2) was comparable to the measurement precision for a spine or femoral neck scan (about 1%). The largest departures from linearity were found to occur at the thinnest water thicknesses for BMD values in the range 0.2 to 0.6 g/cm2. The effect of scale nonlinearity on the results of longitudinal studies was examined: for a spine scan at 20-cm body thickness, measured changes in BMD slightly overestimated the true change and implied an error of 0.15%/year for a measurement of a true rate of loss of 3% year in a postmenopausal woman.

Absorptiometry, Photon↗