sodium-pertechnetate-tc-99m and Cat-Diseases

Topics: Animals; Cat Diseases; Cats; Female; Hyperthyroidism; Iodine Radioisotopes; Male; Neck; Radionuclide Imaging; Retrospective Studies; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Thyroid Gland

The aim of this study was to assess inter- and intraobserver variability of commonly used semi-quantitative and quantitative parameters in feline thyroid scintigraphy: thyroid to salivary gland ratio (T/S), thyroid to background ratio (T/B) and the percentage technetium pertechnetate uptake for the thyroid glands (%TcUT). These parameters are being used to diagnose thyroid disease and to assess its severity, but may be influenced by operator related factors when processing the images. Additionally, inter- and intraobserver variability of the percentage technetium pertechnetate uptake for the salivary glands was determined (%TcUSG). The study included technetium pertechnetate scans of 100 hyperthyroid cats. Variability within and between three observers was determined using a random effects model and variance components were estimated by the restricted maximum likelihood procedure. The %TcU for the thyroid and salivary glands, as well as the T/S ratio, showed little to no difference in inter- and intraobserver variability, whereas this was clearly present for the T/B ratio. Overall, the T/S ratio and %TcUSG showed a good repeatability and reproducibility with low inter- and intraobserver variabilities. Inter- and intraobserver variability was higher for the %TcUT, however variations were still considered to be acceptable. On the contrary, inter- and intraobserver variability was clearly larger for the T/B ratio. These findings suggest the preferential use of the T/S ratio or %TcU, especially in facilities with a less experienced staff.

Topics: Animals; Cat Diseases; Cats; Hyperthyroidism; Observer Variation; Radionuclide Imaging; Reproducibility of Results; Salivary Glands; Sodium Pertechnetate Tc 99m; Thyroid Gland

Thyroid scintigraphy is commonly used for evaluation of cats with hyperthyroidism, with the thyroid-to-salivary ratio (T/S) being the most common method to quantify the degree of thyroid activity and disease. Calculation of thyroid-to-background ratios (T/B) or percent thyroidal uptake of (99m) TcO(-) 4 (TcTU) has only been reported in a few studies. The purpose of this prospective, cross-sectional study was to evaluate a number of quantitative scintigraphic indices as diagnostic tests for hyperthyroidism, including the T/S, three different T/B, TcTU, and estimated thyroid volume. Of 524 cats referred to our clinic for evaluation of suspected hyperthyroidism, the diagnosis was confirmed (n = 504) or excluded (n = 20) based on results of a serum thyroid panel consisting of thyroxine (T4 ), triiodothyronine (T3 ), free T4 (fT4 ), and thyroid-stimulating hormone (TSH) concentrations. In the hyperthyroid cats, median values for TcTU, T/S, and three T/B ratios were all significantly higher (P < 0.001) than values in euthyroid suspect cats or clinically normal cats. All scintigraphic parameters were relatively sensitive and specific as diagnostic tests for hyperthyroidism, but the T/S ratio had the highest test accuracy. The T/S ratio correlated strongly with the TcTU (r = 0.85). However, the TcTU had a higher and more significant correlation (P < 0.01) with serum T4 (r = 0.76 vs. 0.64), T3 (r = 0.77 vs. 0.64), and estimated thyroid volume (r = 0.62 vs. 0.38). Overall, calculation of TcTU is an accurate diagnostic test, but also appears to be the best parameter to predict the functional volume and metabolic activity of the feline adenomatous thyroid gland.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Hyperthyroidism; Male; Methimazole; Radionuclide Imaging; Saliva; Sodium Pertechnetate Tc 99m; Thyroid Gland

Portosystemic shunts (PSS), congenital or acquired, occur uncommonly in the feline population. The diagnostic approach is similar to one in dogs suspected of a PSS based on the clinical signs and haematological and biochemical changes. Diagnostic imaging, however, is key for the confirmation of a PSS. Although abdominal ultrasound is the first-choice diagnostic imaging modality, the results are not always unequivocal. Transsplenic portal scintigraphy (TSPS) using (99m)Tc-pertechnetate is a well-established technique in canine medicine, providing relatively fast and easy confirmation of the presence or absence of a PSS. As the prevalence of PSS is much lower in the feline population, this technique has not been widely used in cats. This retrospective study of 12 cases gives an overview of the potential of TSPS in the diagnostic work-up of PSS in cats (2005-2012).

Topics: Animals; Cat Diseases; Cats; Female; Gated Blood-Pool Imaging; Male; Portal System; Retrospective Studies; Sodium Pertechnetate Tc 99m

This study investigated the recombinant human thyrotropin (rhTSH) stimulation test in healthy cats (group 1), cats with non-thyroidal illness (group 2) and cats with low serum total T(4) (TT(4)) and azotaemia after (131)I treatment (group 3). Serum TT(4) responses and thyroidal pertechnetate uptake after administration of 25 microg rhTSH IV were assessed. Baseline serum TT(4) was significantly lower in group 3 compared with group 1, but not between other group pairs. Serum TT(4) increased significantly in groups 1 and 2 but not in group 3 after rhTSH administration. Post-rhTSH serum TT(4) concentrations differed significantly between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. Thyroid/salivary gland uptake ratio (T/S uptake ratio) differed only significantly between groups 1 and 3. Stimulation with rhTSH is valuable to differentiate euthyroidism from iatrogenic hypothyroidism in cats.

Topics: Animals; Azotemia; Case-Control Studies; Cat Diseases; Cats; Diagnosis, Differential; Female; Hyperthyroidism; Hypothyroidism; Iodine Radioisotopes; Radionuclide Imaging; Recombinant Proteins; Sodium Pertechnetate Tc 99m; Thyroid Gland; Thyrotropin; Thyroxine

This study investigated the thyroidal response to administration of recombinant human thyroid stimulating hormone (rhTSH) by means of serum total thyroxine (TT(4)) concentration and pertechnetate uptake by the thyroid gland in six healthy euthyroid spayed female cats. A pertechnetate scan was performed on day 1 to calculate thyroid/salivary gland (T/S) uptake ratio. On day 3, 25 microg rhTSH was injected intravenously. Six hours later the thyroid scan was repeated as on day 1. Blood was drawn for serum TT(4) measurement prior to injection of rhTSH and performance of the pertechnetate scan. Statistically significant differences in mean serum TT(4) concentration, T/S uptake ratio before and 6h after rhTSH administration and T/S uptake ratio between left and right lobes were noted. We can conclude that 25 microg rhTSH increases pertechnetate uptake in the thyroid glands of cats, this should be taken into account when thyroid scintigraphy after rhTSH administration is interpreted.

Topics: Animals; Cat Diseases; Cats; Female; Hypothyroidism; Radionuclide Imaging; Recombinant Proteins; Sodium Pertechnetate Tc 99m; Thyroid Gland; Thyrotropin; Thyroxine; Time Factors

To assess whether the risk of development of hypothyroidism after treatment with iodine 131 (131I) was associated with the pattern of sodium pertechnetate Tc 99m activity in the thyroid gland detected via scintigraphy before treatment in cats with hyperthyroidism.. Retrospective study.. 165 cats.. Medical records of cats with hyperthyroidism that had been treated with 131I (from 1990 to 2002) and had undergone scintigraphy of the thyroid gland before treatment were reviewed; data regarding signalment, scintigraphic findings (classified as unilateral, bilateral-asymmetric, bilateral-symmetric, or multifocal patterns), serum total thyroxine (T4) concentrations before treatment and prior to hospital discharge, and 131I treatment were collected. A questionnaire was sent to each referring veterinarian to obtain additional data including whether the cats subsequently developed hypothyroidism (defined as serum total T4 concentration less than the lower reference limit > or = 3 months after treatment).. 50 of 165 (30.3%) 131I-treated cats developed hypothyroidism. Hypothyroidism developed in 39 of 109 cats with bilateral, 10 of 50 cats with unilateral, and 1 of 6 cats with multifocal scintigraphic patterns of their thyroid glands. Cats with a bilateral scintigraphic pattern were approximately 2 times as likely to develop hypothyroidism after 131I treatment than were cats with a unilateral scintigraphic pattern (hazard ratio, 2.1; 95% confidence interval, 1.04 to 4.2).. Cats with hyperthyroidism that have a bilateral scintigraphic pattern in the thyroid gland before 131I treatment appear to have a significantly higher risk of subsequently developing hypothyroidism, compared with cats with a unilateral scintigraphic pattern.

Topics: Animals; Cat Diseases; Cats; Female; Hyperthyroidism; Hypothyroidism; Iodine Radioisotopes; Male; Radionuclide Imaging; Retrospective Studies; Risk Factors; Sodium Pertechnetate Tc 99m; Thyroid Gland; Thyroid Hormones

Medical records of 176 animals that underwent transcolonic sodium pertechnetate Tc 99m scintigraphy between September 1988 and June 1992 were reviewed. The study included 162 dogs, 10 cats, and 4 potbellied pigs. Whenever possible, scan results were confirmed during exploratory surgery or necropsy. For animals that did not undergo surgery or necropsy, additional medical information, (ie, results of histologic examination of hepatic biopsy specimens, clinicopathologic testing, abdominal ultrasonography, and clinical outcome) was evaluated to estimate the likelihood that the scan interpretation was correct. Interpretations were classified as confirmed true, probable true, possible false, or unconfirmed results. Of the 97 scans interpreted as positive for portosystemic shunting, 85 were classified as confirmed true-positive results, 5 were classified as probable true-positive results, and 7 were classified as unconfirmed results. None were classified as confirmed or possible false-positive results. Of the 79 scans interpreted as negative for portosystemic shunting, 3 were classified as confirmed true-negative results, 54 were classified as probable true-negative results, 1 was classified as a possible false-negative result, and 21 were classified as unconfirmed results. Our results suggest that transcolonic pertechnetate scintigraphy has satisfactory performance as a diagnostic test for macrovascular portosystemic shunting.

Topics: Animals; Breeding; Cat Diseases; Cats; Cattle; Dog Diseases; Dogs; Evaluation Studies as Topic; Portal System; Predictive Value of Tests; Radionuclide Imaging; Retrospective Studies; Sodium Pertechnetate Tc 99m; Swine; Swine Diseases; Swine, Miniature