Introduction: In general the Thyroid Scan and Uptake involves administering either 99mTc-pertechnetate or Iodine-123, followed by a series of images and measurements acquired after a delay time. Most nuclear medicine departments in Australia have set a general delay time of 15-20minute for all patients however this delay has not been validated. The aim of this project was to determine an optimal delay time for 99m Tc Pertechnetate thyroid uptakes.

Method: Adjustments were made to the current protocol in our department extending the scan time from one acquisition at 20 minutes to one minute acquisitions for 20 minutes. Thyroid uptake values over the 20 minutes plus thyroid function tests (TFT) results were recorded for 13 patients.

Results: The range of peak uptake values was 0.51-38.0% for hyperthyroid patients, 0.22-0.93% for hypothyroid patients and 1.23-3.40% for MNG patients.

Discussion: This study identified three categories of thyroid disease based on TFT results. It appears that the hyperthyroid uptake values peaked earlier than 20 minutes while the values for the hypothyroid group peaked at 20 minutes. As a pilot study with only 13 patients there was insufficient data to determine the optimal delay time for thyroid uptake measurements. However the study indicated a relationship between peak uptake time and the disease state of the patient. It also raised questions about the validity of using a 20 minute delay for hyperthyroid patients. These preliminary results indicate further study with a larger group of patients would provide more definitive results about optimal delay times.