OBJECTIVE. The aim of this study was to compare the clinical usefulness of MRI and radioiodine (¹³¹I) whole-body scintigraphy for the detection of lymph node metastases in differentiated thyroid carcinoma (DTC). MATERIALS AND METHODS. After surgery and ¹³¹I therapy, 40 patients with DTC underwent ¹³¹I whole-body scintigraphy and MRI. Each patient was clinically suspected of having or already had evidence of nodal recurrences (confirmed by laboratory studies, cytologic analysis, or whole-body scintigraphy). Planar whole-body scintigraphy was done after administration of 111 MBq of ¹³¹I, and MRI was done using spin-echo T1- and T2-weighted imaging, T1-weighted spin-echo imaging with fat suppression, and STIR sequences. RESULTS. MRI detected nodal metastases as partly or entirely cystic and as heterogeneously enhanced on contrast-enhanced T1-weighted images. Hyperintense cystic areas appeared on T1- and T2-weighted images and STIR sequences in 57% of cases. Nodal metastases showed extracapsular spread in 24% of patients. MRI results were true-positive in 76%, true-negative in 90%, false-negative in 24%, and false-positive in 11% of cases, whereas ¹³¹I whole-body scintigraphy results were true-positive in 71%, true-negative in 91%, and falsenegative in 29% of cases. There were no false-positive results of ¹³¹I whole-body scintigraphy. False-negative whole-body scintigraphy was induced by tumor dedifferentiation. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of MRI were 76.2%, 89.5%, 82.5%, 88.9%, and 77.3%, respectively, and the corresponding values for ¹³¹I whole-body scintigraphy were 71.4%, 100%, 85%, 100%, and 76%, respectively. CONCLUSION. Whole-body scintigraphy is more specific than MRI in the detection of nodal metastases in patients with DTC. The principal value of MRI is in non-iodine-avid recurrences and in evaluation of mediastinal foci.

Purpose Differentiated thyroid microcarcinoma (DTM) has a good prognosis and survival, but recurrent disease may appear during follow-up. The aim of this study was to evaluate the influence of initial treatment including surgery and radioactive iodine (¹³¹I) on the survival and recurrence in patients with DTM. Methods Between January 1979 and December 2006, 130 patients with DTM were retrospectively evaluated, with a median follow-up of 10 years. Total/near-total thyroidectomy was performed in 121 (93.1%) of 130 patients, followed with ¹³¹I ablation in 71 (54.6%) of 130 patients. Results The probability of disease-specific survival was 97.7% ± 1.3% after 5 and 10 years; the probability of disease-specific survival was 95.9% ± 2.2% after 15, 20, 25, and 28 years after the initial treatment and was significantly influenced by recurrence, clinical stage, and patients’ age (P = 0.0001, P = 0.0005, and P = 0.02, respectively). Sex, histopathological type of the tumor, metastases at presentation, initial treatment, performance of radioactive therapy, and risk categories had no influence on survival (P = 0.8, P = 0.6, P = 0.1, P = 0.4, P = 0.5, and P = 0.1, respectively). The overall recurrence rate was 10.8%, (6.9% in lymph nodes, 1.5% in thyroid bed, and 2.3% at distant sites), with a median appearance time of 30 months. Recurrences were significantly influenced by regional metastases at presentation, radioiodine ablation, and initial treatment (P = 0.0002, P = 0.005, and P = 0.003, respectively); there was no relationship based on age, sex, histological type of the tumor, and tumor multifocality. Conclusions To perform more accurate surveillance for recurrence, total/near-total thyroidectomy followed by radioiodine ablation may be the optimal initial treatment for patients with DTM.

PET/CT imaging is a dual-modality diagnostic technology that merges metabolic and structural imaging. There are several currently available radiotracers, but ¹⁸F-FDG is the most commonly utilized due to its widespread availability. ¹⁸F-FDG PET/CT is a cornerstone of head and neck squamous cell carcinoma imaging. ⁶⁸Ga-DOTA-TOC is another widely used radiotracer. It allows for whole-body imaging of cellular somatostatin receptors, commonly expressed by neuroendocrine tumors and is the standard of reference for the characterization and staging of neuroendocrine tumors. The normal biodistribution of these PET radiotracers as well as the technical aspects of image acquisition and inadequate patient preparation affect the quality of PET/CT imaging. In addition, normal variants, artifacts and incidental findings may impede accurate image interpretation and can potentially lead to misdiagnosis. In order to correctly interpret PET/CT imaging, it is necessary to have a comprehensive knowledge of the normal anatomy of the head and neck and to be cognizant of potential imaging pitfalls. The interpreter must be familiar with benign conditions which may accumulate radiotracer potentially mimicking neoplastic processes and also be aware of malignancies which can demonstrate low radiotracer uptake. Appropriate use of structural imaging with either CT, MR or ultrasound can serve a complimentary role in several head and neck pathologies including local tumor staging, detection of bone marrow involvement or perineural spread, and classification of thyroid nodules. It is important to be aware of the role of these complementary modalities to maximize diagnostic accuracy and patient outcomes. The purpose of this article is to outline the basic principles of PET/CT imaging, with a focus on ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA PET/CT. Basic physiology, variant imaging appearances and potential pitfalls of image interpretation are presented within the context of common use cases of PET technology in patients with head and neck cancers and other pathologies, benign and malignant.

Radioiodine imaging in initial perioperative settings, after the total thyroidectomy, includes pre-treatment and post-treatment radioiodine imaging. While the benefit of post-treatment whole-body imaging (PT-WBI) is well established, the role of diagnostic whole-body imaging (dx WBI), prior to radioiodine (I-131) ablative or therapeutic doses, is controversial. Dx WBI has been abandoned in most nuclear medicine centers long ago. Planar low-dose dxWBI provides the volume of postoperative thyroid remnants, but it cannot detect occult metastatic foci in the neck. The modern integrated multimodality, i.e., SPECT/CT imaging, provides three dimensional images and accurate anatomic/metabolic data. This hybrid technology offers better spatial resolution but not better sensitivity. Dx WBI has low theranostic power because of the radioiodine indifference and low detection sensitivity for small-volume nodal disease in the neck. Since dx WBI cannot clarify the paratracheal cervical uptake, thyroid remnants may be easily misinterpreted as nodal disease, leading to a false N upstaging (from N0 stage to N1 stage) in DTC patients. Post-ablation I-131 imaging has a significant role in the initial staging of radioiodine-avid DTC and in the identification of non-radioiodine avid tumors. Additionally, SPECT/CT in the post-treatment setting provides more accurate initial TNM staging and better risk stratification of DTC patients. Post-treatment I-131 imaging is obligatory and must be performed in all DTC patients who receive radioiodine treatment.

Therapy with radioactive iodine (I-131) following a total thyroidectomy has been a gold standard in the treatment of differentiated thyroid cancer (DTC) for over 80 years. Over the years, its role has shifted from routine use to a more selective, risk-adapted approach, informed by tumor biology, patient risk stratification and evolving clinical guidelines. This review examines the changing landscape of I-131 therapy, tracing its historical foundations, current indications, and future directions shaped by molecular medicine. We discuss the transition from a standardized, one-size-fits-all treatment approach to an individualized, dynamic stratification model that allows for ongoing risk reassessment and tailored treatment strategies. Key updates in clinical practice, such as the 2015 ATA Guidelines, the 2022 ETA Consensus Statement, and joint SNMMI and EANM nuclear medicine recommendations, are critically examined. We also address ongoing controversies in the management of low- and intermediate-risk patients, including the roles of I-131 whole-body scanning, activity selection, and overall treatment approach. Molecular theranostics is ushering in a new era in DTC management, enabling improved patient selection and more precise treatment. Advances in molecular profiling, imaging, and targeted therapies support a personalized treatment approach that aims to optimize therapeutic decisions while minimizing side effects and enhancing long-term safety.

Radioiodine in various forms (as sodium iodide and as the iodinated compounds MIBG, LIPIODOL, et al.) has been used as a therapeutic agent in oncology. Differentiated thyroid carcinoma (DTC) has been successfully treated by 131I therapy. Neuroendocrine tumors can be treated by palliative therapy, including Meta 131Iodobenzylguanidine therapy (131I-MIBG). Diagnostic 131I or 123I-MIBG scintigraphy is usually performed to image neuroblastoma and malignant pheochromocytoma. Following the establishment of the diagnosis, 131I-MIBG may be applied as a therapeutic agent but with limited success. Hepatocellular carcinoma (HCC) is treated by surgery only in 10% of patients. In others, palliative therapy should be administered. Radionuclide therapy for this disease is a therapeutic option with a major advantage compared to systemic chemotherapy, estrogen and progesterone therapy, and immunotherapy. 131I-lipiodol can be used to treat HCC without side effects. Compared to untreated patients, those who received 131Ilipiodol, showed significantly better survival and a decreased recurrence rate. The modern aspect of the neoplasm treatment involves radioimmunotherapy with radioiodine and some other radionuclides. Monoclonal antibody therapy with radioiodine has been extensively succeeded in the therapy of B-cell non-Hodgkin?s lymphoma, prostate cancer. Radioimmunotherapy is also efficiently performed in some other malignancies such as: medullary thyroid carcinoma, breast cancer, colorectal cancer and malignant brain tumors. Radioimmunotherapy will play a key role in the treatment of malignant diseases, especially hematopoietic neoplasms during this millennium.