In vivo imaging of the human thyroid with a positron camera using 124I

Abstract

A high-density avalanche chamber (HIDAC) positron camera was used for tomographic imaging of the human thyroid in vivo. Images were made 7 and 24 h after the oral administration of the positron-emitting radionuclide, sodium iodide 124I (with activities varying between 0.3 and 1 mCi), to patients scheduled for either partial thyroidectomy or radioiodine treatment. The results of thyroid imaging performed on 38 patients and their clinical relevance are discussed; as an illustration, three typical cases are presented. In Graves' disease, it was found that, whereas standard 131I and 124I scintigrams showed a diffuse goitre, positron images indicated a marked heterogeneity of the activity distribution, with "cold" areas in 8 out of the 11 cases studied. In conventional scintigrams, multinodular goitre showed a non-uniform radioiodine distribution, while positron images revealed considerable regional differences of activity uptake, with hot and cold areas in all of the 13 cases studied. As a consequence of the high spatial resolution of the camera [2.5 mm full width at half maximum (FWHM)], the functional volume of the thyroid may be estimated from 2 mm-thick transverse tomographic sections to within about 13%. This estimate may be compared with the measured volume after partial thyroidectomy, and in a follow-up scan, a further estimate can be made of the residual thyroid tissue remaining within the patient's body. In the case of radioiodine treatment in Graves' disease and multinodular goitre, the appropriate therapeutic dose of 131I can calculated according to the functional volume of the thyroid estimated from 124I tomographic images.

Combined PET/CT with iodine-124 in diagnosis of spread metastatic thyroid carcinoma: a case report

“…Furthermore, the additional morphologic information showed iodine-negative and FDG-positive metastasis in the thoracic vertebrae; hence, systematic evaluation of iodine-124 PET/CT in staging of DTC in clinical studies appears to be mandatory. Moreover, a further advantage of iodine-124 PET in the management of DTC lies in exact dosimetry for iodine-131 therapy [12,13,14,15,16,17,18,19]. By combining anatomical information and activity concentration of iodine-124 PET/CT has the potential to further improve dosimetry.…”

“…Because of a complex decay scheme including several high-energy gamma rays [12,13,14,15,16,17,18,19], iodine-124 is not appropriate for imaging with a gamma camera and PET scanners have only recently become more widely available. Although PET is a superior imaging system with physical advantages compared with planar cameras and single photon emission computed tomography (SPECT), it has not been established for imaging thyroid cancer with iodine.…”

Value of 124I-PET/CT in staging of patients with differentiated thyroid cancer

“…Iodine-124, an isotope with a half-life of 4.2 days, is suitable for PET imaging and has already been used for dosimetry [7][8][9][10][11][12][13]. Although PET is a superior imaging system with physical advantages compared to planar gamma cameras and SPECT, it has not been established for routine imaging of thyroid cancer with iodine for several reasons: first, because of the complex decay scheme of 124 I that includes several high-energy gamma rays and makes 124 I imaging a challenge for a gamma camera.…”

Tomographic Imaging of the Human Thyroid with a Positron Camera before and after Partial Thyroidectomy

“…Irrespective of the clinical application, the tomographic images clearly show the varia tions in iodine uptake within the thyroid, even though, at present, this uptake cannot be measured in absolute terms [1], Detailed differences were observed between the tomo graphic images and the conventional scinti gram that may affect both the conclusions concerning diseases such as Graves' disease and multinodular goiter, and the procedure for thyroidectomy.…”