Post-therapy I-131 whole-body scan with SPECT/computed tomography-based mapping of residual metastatic lymph nodes in...

Differentiated thyroid carcinoma (DTC) frequently metastasizes to lymph nodes, significantly influencing patient prognosis. Posttherapy I-131 whole-body scan with SPECT/computed tomography (CT) (Rx-WBS) is crucial in detecting residual metastatic lymph nodes (reLNs). This study aimed to construct spatial heatmaps of reLNs based on the Rx-WBS to visualize anatomical distribution and to provide references for optimizing lymph node dissection (LND) strategies.

This retrospective study included 110 intermediate- to high-risk DTC patients who underwent thyroidectomy and LND, followed by I-131 therapy within 3 months postoperatively. reLNs were manually identified and segmented on Rx-WBS using ITK-SNAP. All reLNs were registered onto a reference patient's CT image based on anatomical landmarks. Representative axial and sagittal heatmaps were generated to illustrate the reLNs' spatial patterns. Univariate analysis and multivariable negative binomial regression were used to identify the factors associated with reLNs.

A total of 276 reLNs from 110 patients were mapped to the reference CT. Heatmaps demonstrated that reLNs were most concentrated in level Ⅵ (39.5%), followed by levels Ⅳ (19.2%) and Ⅲ (17.0%), clustering around the internal carotid artery and jugular vein. Levels I, Ⅴ, and the retropharyngeal space showed lower involvement. Univariate analysis revealed that age and the extent of LND were potential influencing factors.

This study constructed anatomical heatmaps of reLNs, revealing spatial 'hotspots' of residual metastases. These visualizations illustrate the anatomical distribution of reLNs and may assist in refining LND strategies.