Simultaneous assessment of thyroid structure and function with the gamma camera using pertechnetate: a comparison with radioiodine and biochemical diagnosis.

Abstract

Summary: Thyroid structure and function have been simultaneously assessed using 99mTc‐pertechnetate and a gamma camera in an initial ‘pilot’ study using 83 patients and a subsequent study of 512 patients.The morphology of the gland shown by this technique has been compared with rectilinear scans using both 99mTc and 131I. The results show that gamma camera scintiphotos with 99mTc provide superior delineation of thyroid structure compared with the rectilinear scanner using either 99mTc or 131I.Thyroid function assessed by 99mTc uptake at 40 minutes and measured with the gamma camera has been compared with 3 hr and 24 hr 131I uptakes and also with biochemical estimations of total thyroxine, thyro‐binding index and free thyroxine index. The 99mTc uptake was shown to be unreliable in the diagnosis of hypothyroidism, but it is as reliable as 131I uptakes in the diagnosis of hyperthyroidism. Visualisation of gland structure is always necessary, for the 99mTc uptake is less reliable in nodular goitres than in diffuse goitres. The currently available measurements of circulating thyroid hormone are more accurate than uptake measurements in the assessment of thyroid function.