An anthropomorphic thyroid phantom for ultrasound-guided radiofrequency ablation of nodules

TL;DR

This study presents a realistic anthropomorphic thyroid phantom designed for ultrasound-guided radiofrequency ablation, enabling improved development, testing, and training for thyroid nodule treatments with well-characterized physical and thermal properties.

Contribution

The paper introduces a novel, anatomically accurate phantom that mimics thyroid tissue and surrounding structures, validated for ultrasound and thermal ablation, aiding procedural development and training.

Findings

Phantom accurately mimics ultrasound and thermal properties of thyroid tissue.

Achieved median ablation of 82.1% of the nodule volume.

Median temperature during ablation reached 92°C, with minimal impact on critical structures.

Abstract

Background: Needle-based procedures such as fine needle aspiration (FNA) and thermal ablation, are often applied for thyroid nodule diagnosis and therapeutic purposes, respectively. With blood vessels and nerves nearby, these procedures can pose risks in damaging surrounding critical structures. Purpose: The development and validation of innovative strategies to manage these risks require a test object with well-characterized physical properties. For this work, we focus on the application of ultrasound-guided thermal radio-frequency ablation (RFA). Methods: We have developed an anthropomorphic phantom mimicking the thyroid and surrounding anatomical and physiological structures that are relevant to ultrasound-guided thermal ablation. The phantom was composed of a mixture of polyacrylamide, water, and egg white extract and was cast using molds in multiple steps. The thermal, acoustical, and electrical characteristics were experimentally validated. The ablation zones were analyzed via non-destructive T2-weighted MRI scans utilizing the relaxometry changes of coagulated egg albumen, and the temperature distribution was monitored using an array of fiber Bragg sensors. Results: The physical properties of the phantom were verified both on ultrasound as well as its response to thermal ablation. The final temperature achieved (92{\deg}C), the median percentage of the nodule ablated (82.1%), the median volume ablated outside the nodule (0.8 mL), and the median number of critical structures affected (0) were quantified. Conclusion: An anthropomorphic phantom that can provide a realistic model for development and training in ultrasound-guided needle-based thermal interventions for thyroid nodules has been presented. In the future, this model can also be extended to novel needle-based diagnostic procedures.