MRI characteristics of cervical radioiodine-avid lymph nodes detected on post-therapeutic ¹³¹I whole-body scintigraphy in differentiated thyroid carcinoma.

OBJECTIVE

This study aimed to characterize the magnetic resonance imaging (MRI) features of cervical metastatic lymph nodes in differentiated thyroid carcinoma (DTC) and provide imaging-based evidence for identifying metastatic cervical lymph nodes prior to administration of radioactive iodine (¹³¹I) therapy.

METHODS

Clinical and imaging data from 32 patients with histologically confirmed DTC who underwent ¹³¹I therapy at Haikou People's Hospital between June 2019 and May 2024 were retrospectively analyzed. All patients demonstrated cervical radioiodine-avid lymph nodes on post-therapeutic ¹³¹I whole-body scintigraphy (¹³¹I-Rx-WBS). Cervical ultrasonography (US) and MRI examinations were conducted prior to 131I therapy. The MRI characteristics of the lymph nodes identified as radioiodine-avid on ¹³¹I-Rx-WBS were assessed, including anatomical location, number, shape, margin definition, presence of hilum, proximity to vascular structures, and relative size within the nodal population.

RESULTS

All participants were diagnosed with papillary thyroid carcinoma. The median age was 45.5 years (range, 28-66 years). Cervical US detected lymph node metastasis in 15.6% (5/32) of cases. A total of 58 radioiodine-avid lymph nodes were identified across cervical levels II-VI and the supraclavicular region. MRI analysis demonstrated that most radioiodine-avid lymph nodes exhibited hyperintensity on T1- and T2-weighted sequences. Morphologically 65.5% were round to ovoid and 32.8% were irregular in shape. Ill-defined margins were observed in 69.0% of nodes, absence of the lymphatic hilum in 91.4%, and vascular adjacency in 77.6%. In 96.9% (31/32) of patients, at least 4 lymph nodes were visualized on MRI, however, imaging features of radioiodine-negative lymph nodes often overlapped with those of radioiodine-avid nodes.

CONCLUSION

Cervical lymph nodes demonstrating radioiodine uptake on ¹³¹I-Rx-WBS frequently present with round to ovoid or irregular morphology and indistinct margins on MRI. However, given the high density of cervical lymph nodes and overlapping imaging characteristics between radioiodine-avid and radioiodine-negative nodes, a comprehensive assessment integrating multimodal imaging and clinical correlation is essential for accurate assessment before ¹³¹I therapy.