Nuclear Medicine in Thyroid Diseases in Pediatric and Adolescent Patients

Abstract

Both benign and malignant diseases of the thyroid are rare in the pediatric and adolescent population, except congenital hypothyroidism. Nuclear medicine plays a major role, both in the diagnosis and therapy of thyroid pathologies. Use of radioactivity in pediatric population is strictly controlled due to possible side effects such as secondary cancers; therefore, management of pediatric patients requires detailed literature knowledge. This article aims to overview current algorithms in the management of thyroid diseases and use of radionuclide therapy in pediatric and adolescent population.

Nuclear Medicine in the Assessment of Thyrotoxicosis Associated with Increased Thyroid Function and Radioiodine 131 Ablative Therapies

“…There are certain echographic characteristics such as echogenic behavior of the thyroid nodule (as purely cystic or hyperechoic nodules), good demarcation and external vascularization suggesting signs of benign course (e.g., a thyroid adenoma). On the contrary, solid hypoechogenic nodules, irregular borders, internal vascularization, presence of microcalcifications or recent increase in size on follow-up are associated with malignancy [10].…”

“…Ultrasound is, therefore, an image modality from which morphological information of the thyroid gland is obtained. On the other hand, thyroid scintigraphy is a functional imaging test that visualizes the distribution of active thyroid tissue and is used as a complementary test for definite diagnosis [6,10].…”

“…Regarding the evaluation of thyroid nodules by thyroid scintigraphy, it plays an important role in the identification of the functional state of the nodule. Non-functioning thyroid nodules do not present radiotracer uptake ("cold nodules") and present a higher risk of malignancy, while functioning thyroid nodules have tracer uptake ("hot nodules") and are usually benign nodules [10].…”

“…The biodistribution of 99m Tc-O4 in the body is taken up by the thyroid, but this is also taken up by other structures such as salivary glands. Its secretion by saliva, sweat or urine may give false positive image [10].…”

18F-Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography for Other Thyroid Cancers: Medullary, Anaplastic, Lymphoma and So Forth

“…A recent study by Archier et al ( 25 ) has also revealed that 18 F-DOPA PET/CT was reliable for a compartment based approach in lymph node involvement. Gallium-68 labeled peptides are also under scope for this use, especially to identify patients with tumors positive for somatostatin receptors, and thus candidates for radionuclide therapy ( 26 , 27 ). 18 F-FDG PET/CT should not be considered as the first step in the diagnostic algorithm and must be spared for the cases with elevated levels of tumor markers but negative conventional imaging examinations.…”