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Biomedical subjects

T M Gimlette

Publications and source records attributed to T M Gimlette.

At least 19 recordsLinked to original sources
PubMed1989

Comparison of techniques for thallium-201-technetium-99m parathyroid imaging.

It is impracticable to compare the variety of techniques advocated for thallium-technetium (Tl-Tc) subtraction parathyroid imaging by repeated studies in patients. We therefore carried out studies using a phantom assembly to simulate thyroid and parathyroid in the neck, containing activities of 99Tcm and 201Tl similar to those likely to be present in patient imaging. An initial study of imaging protocol confirmed that correction for scatter from 99Tcm in the 201Tl window usefully improved the image. After making a preliminary selection of gamma cameras and collimators it was found that the GE Maxicamera 400T just visualized the 0.3 g "parathyroid" in a 5 min image with the pinhole collimator and 6 mm insert (A). It performed slightly less well with the HR converging collimator (B) and only marginally better with the 4 mm insert (C), but this is unduly slow unless it is placed close enough to limit the field of view unacceptably. The Siemens Orbiter 75 ZLC with special thyroid collimator (D) gave results similar to (A), is convenient for positioning the patient and is very suitable for parathyroid imaging.

Models, Structural↗
PubMed1989

Pertechnetate uptake in the prediction of early outcome after radioiodine therapy.

99mTc-pertechnetate uptake was estimated 8-13 weeks after radioiodine therapy for hyperthyroidism in 132 patients in order to evaluate the usefulness of the uptake test in predicting both persisting hyperthyroidism and the early onset of hypothyroidism during the first year after therapy. The estimation was simple, the result immediately available, and its sensitivities, positive predictive value and its overall accuracy (83%) compared favourably with that of in-vitro tests, FT4I (75%) and FT3I (80%), carried out on the same occasions during the early follow-up period. Pertechnetate uptake can be a useful guide to management by promptly identifying patients likely to need further radioiodine therapy and those with transient or permanent hypothyroidism. The study confirmed some previous findings that hypothyroidism was more frequent in patients with thyroid antibodies and less frequent in patients with nodular thyroids, and it also indicated that hypothyroidism was more frequent in those treated with carbimazole before and after radioiodine, and that hyperthyroidism was more likely to persist in those treated with carbimazole before or after radioiodine.

Follow-Up Studies↗
PubMed1988

Factors predicting hypothyroidism in long-term follow-up after 131I therapy.

187 patients, euthyroid for more than a year after radioiodine treatment for hyperthyroidism, were studied for 10 years; 81 (43%) became hypothyroid. The incidence of hypothyroidism was lower in patients initially presenting with large thyroids (28%) or with nodular thyroids (22%) and in those without thyroid autoantibodies (31%). During follow-up, an elevated serum TSH was present in all 81 patients when they became hypothyroid (sensitivity and negative predictive value 100%), and was present for at least a year in 98% of these. However, an elevated serum TSH was also present in 48% of 106 patients remaining euthyroid (positive predictive value 61%). FT4I was low in 94% of patients who became hypothyroid and normal in 80% of patients who remained euthyroid (positive predictive value 78%, negative predictive value 93%). Serum TSH and FT4I were the best biochemical predictors. FT3I and serum cholesterol were less satisfactory. A palpable thyroid becoming impalpable, though readily assessed, was limited in usefulness. Clinical appraisal remains important and a progressive, though perhaps less rapid, later increase in the incidence of hypothyroidism appears likely.

Aged↗
PubMed1987

Assessment of an enhanced chemiluminescent immunometric assay for TSH in 1127 patients.

An enhanced immunochemiluminometric assay for serum TSH ('Amerlite', Amersham, Bucks, UK) was studied in 1127 patients in routine clinical practice to assess its value as a first-line test of thyroid status. Good correlation with clinical thyroid status was found in the untreated euthyroid patients, in the untreated hyperthyroid and hypothyroid patients, in pregnancy and in the sick euthyroid. However, a large proportion of clinically euthyroid patients with nodular goitre, as well as those treated by thyroidectomy, radioiodine or antithyroid drugs and those on replacement l-thyroxine showed TSH values outside the reference range. Therefore, additional tests are likely to be needed frequently in these categories.

Female↗
PubMed1986

Limits to parathyroid imaging with thallium-201 confirmed by tissue uptake and phantom studies.

Correct location by 201TI imaging of 48 parathyroids in 35 patients was related to size; 25 out of 26 parathyroids of mass greater than 1.0 g were correctly located, none of ten parathyroids less than 0.3 g was correctly located. In seven patients previously imaged, 108 microCi (4.0 MBq) of 201TI was injected when the thyroid was first exposed surgically. Subsequently weighed and histologically confirmed samples of parathyroid, thyroid, and skeletal muscle were counted against a standard in a well counter. Thallium-201 uptake, as %/g, did not differ between hyperplastic and adenomatous parathyroids. Mean parathyroid uptake was 0.018%/g, thyroid 0.01%/g, muscle 0.0026%/g of administered dose. Lower limits for correct location lay between 0.006-0.0149% of administered dose and between 0.25-0.8 g. Studies using a 201TI phantom containing small aliquots of 201TI at higher concentrations suggested approximately 0.0075% of the usual patient imaging dose as a lower limit for correct location.

Adenoma↗
PubMed1985

Localization of enlarged parathyroid glands by thallium-201 and technetium-99m subtraction imaging. Gland mass and parathormone levels in primary hyperparathyroidism.

Twenty-two patients, all with surgically proven primary hyperparathyroidism, were studied by TI-201 thallous chloride and Tc-99m pertechnetate subtraction imaging. Fifteen parathyroid adenomata and one hyperplastic gland between 0.33 and 14.8 g were correctly localized in 16 patients. Two adenomata and seven hyperplastic or histologically normal parathyroids between 0.1 g and 1.4 g in seven patients were not localized. One patient had a correctly localized 13.0-g adenoma with a nonlocalized 0.3 g hyperplastic parathyroid gland and there were two false positive localizations. Sensitivity was 64% (glands), and 73% (patients). There was only fair correlation with parathormone (PTH) levels, but these were elevated in all but four of the patients with correctly localized parathyroids. The authors conclude that the imaging procedure is useful but its sensitivity is limited by difficulty in localizing correctly small glands, particularly those of less than 0.5 g, which comprised 29% of those excised.

Adenoma↗
PubMed1982

Assessment of optimal L-thyroxine replacement dose by the TRH test.

Two hundred patients taking varying L-thyroxine replacement doses were studied using a normal TRH test as the index of optimal replacement dose. The mean optimal dose was 141 microgram/day. Normal serum T3 and FT3I were found in most patients, whatever the TRH response, and they are probably too unspecific. Serum T4 and FT4I were elevated in many patients with a normal TRH response. A higher range for FT4I of 102-166, although only 66.5% accurate, gave the best index of optimal L-thyroxine replacement of the single in-vitro tests.

Antibody Specificity↗
PubMed1981

Serum thyroglobulin in thyroid cancer.

Serum thyroglobulin (Tg) was measured in 274 patients with differentiated thyroid cancer; 266 had previous thyroidectomy, which had been followed by ablative iodine-131 in 183 cases. Neither the presence nor the titre of anti-Tg antibodies appeared to affect Tg assays. Serum Tg reflected the presence or absence of cancer in 83% of 164 patients not receiving thyroxine (T4). This concordance improved to 97.5% in 158 patients tested while receiving T4. 34 patients in remission were tested both on and off T4 therapy; in all these patients the Tg level when receiving T4 was less than 5 micrograms/l. In 19 of 21 patients with cancer T4 treatment did not suppress Tg. Serum Tg thus provides an excellent marker for the presence or absence of thyroid cancer in patients taking T4, even if anti-Tg antibodies are present. It is proposed that monitoring of patients by assay of serum Tg should supplant routine assessment by radioactive-iodine scans of the neck or whole body.

Autoantibodies↗
PubMed1981

The effect of carbimazole following radioiodine therapy on radiation dose to the thyroid.

Radioiodine in the thyroid gland after a therapy dose of 131I was measured serially in 7 patients without Carbimazole, and in 11 patients starting Carbimazole 60 mg daily fourteen days after the therapy dose. Effective half-life for radioiodine in the gland initially 5.53 plus or minus 1.08 days fell to 4.26 plus or minus 1.12 days (p less than 0.01) during Carbimazole, and returned to 5.83 plus or minus 1.21 days (NS) after stopping the drug. The radiation dose to the thyroid from a given therapy dose of 131I followed by Carbimazole was calculated to be 97% of that without Carbimazole when he drug was started after 14 days, and 90% and 75% when the drug was started after 7 days and 1 day respectively.

Antithyroid Agents↗
PubMed1979

Change in shape and position of the pancreas with posture of the patient.

A comparison of images obtained using 75Se-methionine revealed changes in the shape and position of the pancreas when the patient was in the supine and right lateral decubitus positions. These changes, which were appreciable and often marked in 93% of 168 patients with a probable normal pancreas, sometimes helped in the interpretation of an image. Similar changes were noted in 12 (63%) of 19 patients with chronic pancreatitis where an adequate image could be obtained.

Chronic Disease↗
PubMed1977

Comparison of thyroid stimulating hormone and triiodothyronine response to thyrotrophin releasing hormone in the assessment of thyroid status.

The response to an intravenous dose of 200 microng of thyrotrophin releasing hormone (TRH) has been studied by estimating, by radioimmunoassay, baseline levels followed by further estimations of thyroid stimulating hormone (TSH) 20 minutes after the injection and triiodothyronine (T3) three hours after the injection in 112 patients referred for routine thyroid assessment. Comparison of diagnostic accuracy of the response to TRH gave similar results with both procedures but slightly better overall accuracy for the response measured by TSH assay. However, estimation of baseline T3 is a valuable test for hyperthyroidism, in contrast to baseline TSH, and combined with the estimation of T3 three hours after TRH injection provides an accurate additional test in borderline cases.

Humans↗
PubMed1975

The use of discriminatory values for thyroid uptake and free thyroxine index.

The distributions of 4 hour 132I neck uptake and 20 minute 99mTcO4 thyroid uptake in euthyroid patients were found to conform closely to a log normal distribution, from which a statistical normal range may be obtained. More accurate discriminatory values for determining thyroid status may be established by plotting intersecting distribution curves for hypo-, hyper- and euthyroid groups. Subdivision by age and by the presence or absence of a palpable thyroid reveals considerable variations from which a series of more accurate discriminatory values may be established for these subgroups. For Free Thyroxine Index (T4RT3 index) more accurate discriminatory values were also obtained by similar methods; while no significant variations related to age or palpable thyroid were observed, subdivision of the patients into two groups referred as suspected hypothyroidism and suspected hyperthyroidism yielded a further small improvement in accuracy.

Adult↗
PubMed1975

Mechanism of Rh prophylaxis: an experimental study on specificity of immunosuppression.

The mechanism by which Rh immunization is prevented by IgG anti-D was investigated by studying the specificity of immunosuppression. 62 D-negative Kell(K)-negative male volunteers were given two successive stimuli of 1 ml D-positive K-positive red cells. Thirty-one of the volunteers were also given 13-14 mug of IgG anti-K immediately after each stimulus, the others acting as controls. Anti-D developed in 11 of the 31 controls and in one of the 31 volunteers who had received anti-K. This marked suppression of the anti-D response by IgG anti-K was accompanied by the rapid clearance of the injected red cells to the spleen. This shows that the predominant mechanism that must be operating when IgG anti-D prevents Rh immunization is not antigen specific but is one that must involve the whole red cell, probably through destruction within splenic macrophages.

Antibody Formation↗
PubMed1975

Relation between thyroid function and serum levels of long-acting thyroid stimulator.

Bioassays of long-acting thyroid stimulator (LATS) were performed in three groups of subjects: in normal controls, in thyrotoxic patients before and serially after 131-I treatment, and in patients with hypopituitarism. Of the untreated thyrotoxic patients, 27.7% had raised serum LATS levels initially. There was no correlation between the relapse rate after 131-I therapy and the initial or subsequent LATS titres: in particular, thyrotoxicosis sometimes recurred after an initially high LATS titre had fallen into the normal range. The distribution of the results of LATS assays in the hypopituitary patients was significantly different from that in the normal subjects; 4 out of 27 hypopituitary patients had LATS levels above the normal range, although they had no thyrotoxicosis. On the other hand, the majority of the patients with hypopituitarism, 19 out of 27, had LATS titres below the mean normal level, possibly due to deficiency of a substance we have termed pseudo LATS. These results raise doubts about a direct causative role for LATS in most cases of thyrotoxicosis.

Biological Assay↗