Sonographic measurement of thyroid nodule changes after microwave ablation: relationship between multiple parameters

Area of Science:

• Endocrinology
• Minimally Invasive Surgery
• Medical Imaging

Background:

• Microwave ablation (MWA) is a recognized treatment for benign thyroid nodules.
• Assessing treatment effectiveness typically relies on volume reduction.
• The need to evaluate other parameters beyond size reduction requires investigation.

Purpose of the Study:

• To determine if variables other than volume reduction are necessary for follow-up after MWA for benign thyroid nodules.
• To introduce and evaluate Index R (surface area to volume ratio) for assessing nodule shape changes.

Main Methods:

• A retrospective analysis of 236 benign thyroid nodules in 230 patients treated with MWA.
• Parameters including maximum diameter (Dmax), volume (V), volume reduction ratio (VRR), and Index R were measured pre-treatment and at multiple follow-up intervals (1, 3, 6, >12 months).
• Statistical comparisons were made between baseline and follow-up measurements for the entire cohort and subgroups.

Main Results:

• MWA resulted in significant thyroid nodule volume reduction (mean decrease from 17.40 mL to 1.31 mL).
• Index R increased significantly over time (from 2.55 to 8.10), indicating shape changes after three months, irrespective of initial nodule size.
• Index R, V, and VRR showed similar evaluation capabilities for nodules with baseline Dmax ≤ 3.4 cm before six months.

Conclusions:

• Long-term follow-up of MWA-treated benign thyroid nodules highlights the importance of shape and spatial structure changes over mere size reduction.
• Index R (surface area to volume ratio) effectively reflects these shape alterations during follow-up.
• Shape parameterization, particularly using Index R, provides valuable insights into nodule evolution post-MWA.