Simple, rapid thyroid function testing with 99mTc-pertechnetate thyroid uptake ratio and neck/thigh ratio

Standardizing Normal Reference Value for Thyroid Uptake of Technetium-99m Pertechnetate in Nepalese Population

Objective  Changes in normal reference values of thyroid uptake for iodine have been reported due to geographical and chronological fluctuations in dietary iodine intake in different populations. Nepal is a country with mixed ethnicity, with access to dietary iodine in the form of successful universal salt iodination program by the government of Nepal since 1973. The aim of this study was to establish the normal reference values for thyroid uptake of technetium-99m (Tc-99m) pertechnetate in the Nepalese population in iodine sufficiency era. Methods  We prospectively evaluated 52 clinically and biochemically euthyroid participants (46 females and 6 males) with age range from 20 to 71 years who underwent a thyroid Tc-99m pertechnetate scan and uptake between December 2019 to November 2023 in the Department of Nuclear Medicine, Chitwan Medical College fulfilling inclusion/exclusion criteria. Biochemical thyroid function tests were reviewed and Tc-99m pertechnetate thyroid uptake values were determined for each patient. Blood was withdrawn for thyroid hormone assessment. Euthyroid participants were then administered 3.5 to 4.5 mCi of Tc-99m pertechnetate intravenously and their percentage thyroid uptake was calculated after 20 minutes. Results  The mean and median uptake of Tc-99m pertechnetate in euthyroid patients were 1.26 and 0.85%, respectively, and the interquartile range was 0.7 to 1.7%. The normal reference uptake value for Tc-99m pertechnetate in the studied population ranged between 0.3 and 3.6%. The fifth and 95th percentiles for pertechnetate uptake were 0.5 and 2.9%, respectively. Conclusion  The normal reference range for Tc-99m pertechnetate thyroid uptake in Nepalese population was 0.5 to 2.9% that is lower than the currently accepted international standard of 0.75 to 4.5%. Uptake also increased with increasing age. This study highlights the importance of periodically redefining the geographic location specific normal thyroid uptake reference values.

Quantitative analysis of 99mTc-pertechnetate thyroid uptake with a large-field CZT gamma camera: feasibility and comparison between SPECT/CT and planar acquisitions

PURPOSE

The main objective of this study was to evaluate the ability of a large field Cadmium Zinc Telluride (CZT) camera to estimate thyroid uptake (TU) on single photon emission computed tomography (SPECT) images with and without attenuation correction (Tomo-AC and Tomo-NoAC) compared with Planar acquisition in a series of 23 consecutive patients. The secondary objective was to determine radiation doses for the tracer administration and for the additional Computed Tomography (CT) scan.

METHODS

Cross-calibration factors were determined using a thyroid phantom, for Planar, Tomo-AC and Tomo-NoAC images. Then Planar and SPECT/CT acquisitions centered on the thyroid were performed on 5 anthropomorphic phantoms with activity ranging from 0.4 to 10 MBq, and 23 patients after administration of 79.2 ± 3.7 MBq of [^99mTc]-pertechnetate. We estimated the absolute thyroid activity (AThA) for the anthropomorphic phantoms and the TU for the patients. Radiation dose was also determined using International Commission on Radiological Protection (ICRP) reports and VirtualDose^TMCT software.

RESULTS

Cross-calibration factors were 66.2 ± 4.9, 60.7 ± 0.7 and 26.5 ± 0.3 counts/(MBq s), respectively, for Planar, Tomo-AC and Tomo-NoAC images. Theoretical and estimated AThA for Planar, Tomo-AC and Tomo-NoAC images were statistically highly correlated (r < 0.99; P < 10^-4) and the average of the relative percentage difference between theoretical and estimated AThA were (8.6 ± 17.8), (- 1.3 ± 5.2) and (12.8 ± 5.7) %, respectively. Comparisons between TU based on different pairs of images (Planar vs Tomo-AC, Planar vs Tomo-NoAC and Tomo-AC vs Tomo-NoAC) showed statistically significant correlation (r = 0.972, 0.961 and 0.935, respectively; P < 10^-3). Effective and thyroid absorbed doses were, respectively (0.34_CT + 0.95_NM) mSv, and (3.88_CT + 1.74_NM) mGy.

CONCLUSION

AThA estimation using Planar and SPECT/CT acquisitions on a new generation of CZT large-field cameras is feasible. In addition, TU on SPECT/CT was as accurate as conventional planar acquisition, but the CT induced additional thyroid exposure. Trial registration Name of the registry: Thyroid Uptake Quantification on a New Generation of Gamma Camera (QUANTHYC).

TRIAL NUMBER

NCT05049551. Registered September 20, 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT05049551?cntry=MC&draw=2&rank=4 .

Utility of 99m Technetium Pertechnetate Thyroid Scan and Uptake in Thyrotoxic Patients: Jordanian Experience

Objective  The objective of this study was to assess our local experience with ^99m Technitium thyroid uptake (TcTU) in thyrotoxicosis by examining mean and range of TcTU in both euthyroid patients and thyrotoxic patients. We also wanted to see how well TcTU performed as a substitute for radioiodine thyroid uptake in thyrotoxicosis. Methods  The medical records of thyrotoxic patients were reviewed retrospectively. Inclusion criteria were: (1) thyrotoxicosis was proven biochemically, (2) the patient underwent TcTU at the time of thyrotoxicosis diagnosis, (3) at least 6 months of follow-up, and (4) the final diagnosis was documented. All TcTU of euthyroid patients were also reviewed to determine local normal TcTU mean and range. Patients were divided into three groups: Graves' disease, toxic nodular goiter, and subacute thyroiditis. Each patient group's TcTU mean and range were assessed separately. Results  There were 209 patients in total (54 euthyroid, 112 Graves' disease, 26 toxic nodules, and 17 patients with subacute thyroiditis). TcTU mean±standard deviation and range for euthyroid patients were 1.5±1.1% and 0.17 to 4.8%, 10.6±10% and 0.43 to 40% for Graves' disease, 4.5±4% and 0.6 to 15% for toxic nodules, and 0.5±0.4% and 0.18 to 1% for subacute thyroiditis. Although one-third of thyrotoxic patients' TcTU values overlapped with the normal TcTU range, the diagnosis was made using qualitative image analysis. Subacute thyroiditis was characterized by poor thyroid visualization, whereas Graves'/toxic nodular goiter was well visualized. Conclusion  The mean and range of our local normal TcTU were similar to those previously published. TcTU was a useful alternative to radioiodine in the evaluation of thyrotoxicosis. About two-thirds of the patients had accurate test results. The diagnosis was reached in the remaining one-third of patients by combining quantitative and qualitative image features. This method allowed us to stop giving radioiodine to our patients, resulting in a significant reduction in patient radiation exposure.

The utility of technetium-99m pertechnetate thyroid scintigraphy assessing thyroid/salivary ratio as an alternative to thyroid uptake percentage in evaluation of thyroid function, with establishing normal reference values of both parameters: single Egyptian center study

BACKGROUND/OBJECTIVE

Management of thyroid disorders depends on accurate clinical assessment, appropriate investigations and radionuclide imaging, which plays an established important role either qualitatively or quantitatively. The aim of this study was to assess the utility of the thyroid/salivary ratio (TSR) as an alternative to technetium-99m (Tc99m) pertechnetate thyroid uptake (TcU) percentage in the evaluation of thyroid function and in the same time to establish reference range for the thyroid uptake of Tc99m-pertechnetate and TSR among Egyptian populations.

PATIENTS AND METHODS

This retrospective study enrolled 270 patients, out of which 250 with different thyroid disorders and 20 without thyroid diseases, as a control group who all underwent full clinical examination, thyroid function tests and Tc99m pertechnetate thyroid scintigraphy. The TcU percentage and TSR were calculated and then correlated to the thyroid hormonal profile.

RESULTS

The normal reference ranges of TcU and TSR were 0.75-3.5% and 1.25-4.8%, respectively. The sensitivity and specificity of TSR to diagnose hyperthyroidism were slightly lower compared with TcU (84.5 and 92.3% vs. 86.2 and 98.3%, respectively) at TSR cutoff value of more than 4.8 and TcU cutoff value of more than 3.5. Meanwhile, they had comparable sensitivity and specificity to diagnose hypothyroidism (86.0 and 93.3% vs. 86.5 and 94.5%) at cutoff values <0.75 and <1.25, respectively.

CONCLUSION

The current study established a reference range for TcU and TSR in our institution. TSR is comparable to TcU in the evaluation of thyroid function among hyper-and hypothyroid patients and TSR can be used in doubtful cases of mal-thyroid function for confirmation of the diagnosis.

Fixed 30 mCi (1110 MBq) 131I-iodine therapy in autonomously functioning nodules: Single toxic nodule as a predictive factor of success

Aims:

The aim of this study is to evaluate the efficacy of a fixed 30 mCi (1110 MBq) ¹³¹I-iodine dose for the treatment of hyperthyroidism due to uninodular or multinodular toxic goiter and identify predictors of success.

Materials and Methods:

Fifty-nine patients diagnosed with nonautoimmune toxic goiter were treated with a fixed 30 mCi dose of ¹³¹I-iodine and were followed at a tertiary service between 2000 and 2016. The therapy was considered successful if the patient reached euthyroidism or hypothyroidism without needing an extra ¹³¹I-iodine dose or antithyroid drugs for at least 1 year after the radioiodine therapy (RIT).

Results:

Patients with a single toxic nodule were younger at diagnosis (52 vs. 63 years; P = 0.007), presented a shorter disease duration until RIT (2 vs. 3.5 years; P = 0.007), smaller total thyroid volume (20 vs. 82 cm³; P = 0.044), and lower pre-RIT thyroid uptake (P = 0.043) than patients with multinodular goiter. No significant difference was seen with antithyroid drug use, thyroid-stimulating hormone and free thyroxine level, and follow-up after RIT. After RIT, 47 patients (79.66%) met the success criteria, and 12 (20.33%) remained hyperthyroid. Among the success group, 32 (68.08%) reached euthyroidism, while 31.92% developed hypothyroidism after 1 year. Patients with single toxic nodules who achieved success after RIT presented smaller nodules (2.8 vs. 5.75 cm; P = 0.043), while the pre-RIT thyroid uptake was higher among patients with multinodular toxic goiter who achieved success after RIT (5.5% vs. 1.5%; P = 0.007). A higher success rate was observed among patients with a single toxic nodule than those with a toxic multinodular goiter (92.3% vs. 55%; P = 0.001), and a single toxic nodule presentation was found to be an independent predictor of success (P = 0.009).

Conclusions:

The fixed 30 mCi ¹³¹I-iodine dose was particularly effective in the group of patients with single autonomously functioning nodule rather than the group with multiple nodules. A single toxic nodule was an independent predictor of treatment success.

Fixed 30 mCi 131I-iodine therapy without recombinant human thyroid-stimulating hormone stimulation as an attractive therapeutic alternative in nontoxic nodular goiter

OBJECTIVE

To analyze outcomes of patients with compressive nontoxic multinodular goiter after 131I-iodine 30 mCi treatment without previous use of recombinant human thyroid-stimulating hormone or methimazole.

METHODS

We evaluated fixed-dose radioiodine therapy outcomes in patients with nontoxic multinodular goiter who did not accept thyroidectomy as a therapeutic option. Laboratory thyroid function and thyroid volume estimated by ultrasound were assessed before and one year after radioiodine therapy.

RESULTS

Twenty euthyroid female patients received 30 mCi of 131I-iodine without recombinant human thyroid-stimulating hormone or methimazole pretreatment. Median thyroid volume and Tc-99m sodium pertechnetate thyroid uptake before radioiodine therapy were 68.05 cm (31.3-295.3) and 0.5% (0.1%-1.2%), respectively. One year after radioiodine therapy, thyroid volume decreased to 55.4 cm (19.8-149.9), and merely 4 patients (20%) developed hypothyroidism. Thyroid volume decreased significantly after radioiodine therapy, presenting a variation of -21.1 cm (-161.3 to -0.8) and -30.61% (-73.88 to -1.02), both with P < 0.0001. Thyroid volume variation was positively correlated with thyroid uptake in Spearman's correlation (r = 0.4730; P = 0.0352). The group satisfied with radioiodine therapy (85%, n = 17) showed a significant reduction in thyroid volume, -25.8 cm (-161.3 to -6.2) and -36.74% (-73.88 to -9.95). The dissatisfied group (15%, n = 3) showed -1.0 cm (-2.0 to -0.8) and -1.67% (-3.38 to -1.02) in thyroid volume, P = 0.0081. Patients that complained about dysphagia presented a lower percentage of thyroid volume decrease after radioiodine therapy, -21.97% (-70.12 to -1.02, P = 0.0430).

CONCLUSIONS

A substantial reduction in thyroid volume associated with a low incidence of hypothyroidism and a high satisfaction rate support the use of conventional radioiodine therapy with a fixed dose of 30 mCi. This therapy is an attractive and cheaper therapeutic alternative in selected patients with nontoxic multinodular goiter.

Assessment of normal reference values for thyroid uptake of technetium-99m pertechnetate in a single centre UK population

OBJECTIVE

This study aims to explore the normal reference values for thyroid uptake of technetium-99m (Tc) pertechnetate in a UK population.

PATIENTS AND METHODS

A retrospective review of 60 euthyroid patients who underwent thyroid imaging with Tc pertechnetate between January 2012 to April 2014 as part of dual-tracer subtraction parathyroid scintigraphy. Tc pertechnetate thyroid uptake values were determined for each patient. Medical records and biochemical thyroid function tests were reviewed to ensure that all patients were not on medication that could affect thyroid function and they were both clinically and biochemically euthyroid 6 months before and following the scan.

RESULTS

Median and interquartile uptake range of Tc pertechnetate in euthyroid patients were 0.9 and 0.5-1.4%, respectively. The normal reference range in the study population was 0.2-2.0%. Thyroid uptake inversely correlated with age in females (r=-0.40, P=0.04), males (r=-0.50, P=0.04), and whole group (r=-0.40, P=0.002).

CONCLUSION

The calculated normal reference range in this study was found to be less than that used in our own and many other UK institutions. The results demonstrate the importance of periodic evaluation of normal uptake values and provide support for prospective studies defining the normal reference range to be performed.

PREDICTION OF RELAPSE FROM HYPERTHYROIDISM FOLLOWING ANTITHYROID MEDICATION WITHDRAWAL USING TECHNETIUM THYROID UPTAKE SCANNING

OBJECTIVE

Technetium thyroid uptake (TTU) is not inhibited by antithyroid drugs (ATD) and reflects the degree of thyroid stimulation. We intended to predict the relapse rate from hyperthyroidism based on TTU measurement.

METHODS

Out of 44 initially enrolled subjects, 38 patients aged 41.6 ± 14.6 with Graves disease (duration: 84 ± 78 months) completed the study. TTU was performed with 40-second imaging of the neck and mediastinum 20 minutes after injection of 1 mCi technetium-99m pertechnetate. TTU was measured as the percentage of the count of activity accumulated in the thyroidal region minus the mediastinal background uptake to the count of 1 mCi technetium-99m under the same acquisition conditions. Then methimazole was stopped and patients were followed. The optimal TTU cutoff value for Graves relapse prediction was calculated using Youden's J statistic.

RESULTS

Hyperthyroidism relapsed in 11 (28.9%) patients 122 ± 96 (range: 15-290) days post-ATD withdrawal. The subjects in remission were followed for 209 ± 81 days (range: 88-390). TTU was significantly higher in patients with forthcoming relapse (12.0 ± 8.0 vs. 3.9 ± 2.0, P = .007). The difference was significant after adjustment for age, sex, history of previous relapse, disease duration, and thyroid-stimulating hormone (TSH) levels before withdrawal. The area under the receiver operative characteristic (ROC) curve was 0.87. The optimal TTU cutoff value for classification of subjects with relapse and remission was 8.7 with sensitivity, specificity, and positive and negative predictive value of 73%, 100%, 100%, and 90%, respectively (odds ratio [OR] = 10.0; 95% confidence interval [CI]: 3.4-29.3).

CONCLUSION

TTU evaluation in hyperthyroid patients receiving antithyroid medication is an accurate and practical method for predicting relapse after ATD withdrawal.

ABBREVIATIONS

ATD = antithyroid drugs RIU = radio-iodine uptake TSH = thyroid-stimulating hormone TSI = thyroid-stimulating immunoglobulin TTU = technetium thyroid uptake.

Use of radiopharmaceuticals in diagnostic nuclear medicine in the United States: 1960-2010

To reconstruct reliable nuclear medicine-related occupational radiation doses or doses received as patients from radiopharmaceuticals over the last five decades, the authors assessed which radiopharmaceuticals were used in different time periods, their relative frequency of use, and typical values of the administered activity. This paper presents data on the changing patterns of clinical use of radiopharmaceuticals and documents the range of activity administered to adult patients undergoing diagnostic nuclear medicine procedures in the U.S. between 1960 and 2010. Data are presented for 15 diagnostic imaging procedures that include thyroid scan and thyroid uptake; brain scan; brain blood flow; lung perfusion and ventilation; bone, liver, hepatobiliary, bone marrow, pancreas, and kidney scans; cardiac imaging procedures; tumor localization studies; localization of gastrointestinal bleeding; and non-imaging studies of blood volume and iron metabolism. Data on the relative use of radiopharmaceuticals were collected using key informant interviews and comprehensive literature reviews of typical administered activities of these diagnostic nuclear medicine studies. Responses of key informants on relative use of radiopharmaceuticals are in agreement with published literature. Results of this study will be used for retrospective reconstruction of occupational and personal medical radiation doses from diagnostic radiopharmaceuticals to members of the U.S. radiologic technologists' cohort and in reconstructing radiation doses from occupational or patient radiation exposures to other U.S. workers or patient populations.

Analysis of the factors associated with Tc-99m pertechnetate uptake in thyrotoxicosis and graves' disease

To determine the factors associated with 20 minute Tc-99m pertechnetate thyroid uptake, we examined all patients in whom thyrotoxicosis was diagnosed at Chiba-Hokusoh Hospital, Nippon Medical School from 2001 April through 2003 March. Patients with thyrotoxicosis diagnosed during this period were 57 with Graves' disease (76%), 11 with transient hyperthyroxinemia (TH)(14.7%), and 7 with subacute thyroiditis (SAT)(9.3%). The uptake of Tc-99m ranged from 0.97% to 40.1% in Graves' disease and from 0.15% to 0.8% in TH. Although TH may include spontaneous resolution of Graves' disease as well as painless thyroiditis, no treatment was necessary for these patients. Uptake in all patients with SAT was less than 0.5%. There were significant correlations between the level of Tc-99m uptake and the levels of free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH)-binding inhibitory immunoglobulin (TBII), and thyroid stimulating antibody (TSAb) in patients with Graves' disease. Older patients with Graves' disease showed lower uptake than did younger patients. Both Tc-99m pertechnetate uptake and TBII levels, but not fT3, fT4 or TSAb levels, at the beginning of antithyroid drug treatment correlated significantly with the duration of treatment until the daily dose of methimazole reached 5 mg. These data suggest that Tc-99m pertechnetate uptake reflects the severity of Graves' disease and its response to the medical treatment and that antithyroid drug therapy is not necessary when the uptake is less than 0.9%.

High pre-therapy [99mTc]pertechnetate thyroid uptake, thyroid size and thyrostatic drugs: predictive factors of failure in [131I]iodide therapy in Graves' disease

BACKGROUND AND OBJECTIVE

Several factors may interfere with the success rate of radioiodine therapy (RIT) in Graves' disease. Our aim was to evaluate, retrospectively, some of these factors in the outcome of RIT.

METHODS

Patient gender, age at diagnosis, ophthalmopathy, disease duration, thyroid size, drug used as clinical treatment, thionamide withdrawal period during RIT preparation, FT4, TSH and [99mTc]pertechnetate thyroid uptake prior to RIT were studied as potential interference factors for RIT success. Eighty-two Graves' disease patients were submitted to RIT after thionamide treatment failure. Prior to RIT, 67 patients were receiving methimazole and 15 propylthiouracil. Thirty-three patients received thionamides during RIT; in 49 patients the medication was withdrawn for 2-30 days. [99mTc]pertechnetate thyroid uptake was determined before RIT. Fixed doses of 370 MBq of [131I]iodide were administered to all patients.

RESULTS

Eleven patients became euthyroid; 40 became hypothyroid and 31 remained hyperthyroid. There was no association between outcome and age at diagnosis, gender, ophthalmopathy, pre-RIT FT4, TSH, antithyroid antibodies or thyrostatic drug. Multiple logistic regression showed higher probability of treatment success in patients with thyroid mass <53 g (odds ratio (OR)=8.9), with pre-RIT thyroid uptake <12.5% (OR=4.1) and in patients who withdrew thionamide before RIT (OR=4.9).

CONCLUSIONS

Fixed doses of 370 MBq of radioiodine seem to be practical and effective for treating Graves' disease patients with [99mTc]pertechnetate uptake <12.5% and thyroid mass <53 g. This treatment is clearly not recommended for patients with large goitre. In contrast to what could be expected, patients with a high pre-RIT thyroid uptake presented a higher rate of RIT failure.

Thyroid uptake and scintigraphy using 99mTc pertechnetate: standardization in normal individuals

CONTEXT

Thyroid uptake and scintigraphy using 99mTc-pertechnetate has proven to be more advantageous than with 131I-iodide, since the images have better quality, the procedure is faster and the patient is submitted to a lower radiation dose.

OBJECTIVE

The purpose of this study was to standardize a simple and fast methodology for performing thyroid uptake and scintigraphy and to determine the normal values for 99mTc- pertechnetate uptake.

TYPE OF STUDY

Prospective, non-randomized.

SETTING

Division of Nuclear Medicine, Department of Radiology, School of Medical Sciences, Campinas State University.

PARTICIPANTS

The study consisted of 47 normal individuals, 30 women and 17 men, with ages ranging from 19 to 61 years (mean of 33 years).

PROCEDURES

The laboratory assessment of thyroid function consisted of serum dosages of ultra-sensitive thyroxin and thyrotrophin. Twenty minutes after an intravenous injection of 10 mCi (370 MBq) of 99mTc-pertechnetate, the images were obtained on a computerized scintillation camera equipped with a low-energy high-resolution parallel hole collimator.

RESULTS

All the individuals were euthyroid both on clinical and laboratory evaluation. The baseline thyroid 99mTc-pertechnetate uptake ranged from 0.4 to 1.7%. The uptake values obtained in these normal individuals showed that 95% presented a thyroid uptake that ranged from 0.4 to 1.5% of the injected dose.

CONCLUSION

The assessment of thyroid structure and function using 99mTc-pertechnetate is a simple, fast and efficient method, which could easily become a part of the routine studies in nuclear medicine laboratories.

Technetium thyroid uptake ratios in pediatric Graves disease

Patients with Graves disease were prospectively followed by means of three 99mtechnetium thyroid uptake ratios. These three ratios were greater than 90% sensitive and specific for the detection of hyperthyroidism in the patient with untreated Graves disease. Twelve of 15 patients experienced prolonged remission after normalization of the ratios. These ratios exhibit significant linear correlation with serum thyroxine and triiodothyronine concentrations (r = 0.4-0.6, P less than 0.01) and are a very sensitive index of medical oversuppression of thyroid function.