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

Abstract

BackgroundNeedle‐based procedures, such as fine needle aspiration 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.PurposeThe 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 radiofrequency ablation.MethodsWe have developed a single‐use 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 magnetic resonance imaging scans utilizing the relaxometry changes of coagulated egg albumen, and the temperature distribution was monitored using an array of fiber Bragg grating sensors.ResultsThe physical properties of the phantom were verified both on ultrasound as well as in terms of the phantom response to thermal ablation. The final temperature achieved (92°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.ConclusionAn 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.

Super phantoms: advanced models for testing medical imaging technologies

“…While our Perspective has centered on super phantoms for imaging applications, these tools can play a roles in planning therapeutic interventions such as radiation therapy 41 , thermal ablations 42 , and surgery 43 . The principles and insights discussed in our work can serve as a foundation for application of super phantoms in these areas.…”

Assessment of thermochromic phantoms for characterizing microwave ablation devices

“…The estimated spatial power absorption profile is sensitive to temperature sensor positioning due to the steep radial gradient of power absorption and temperature [23], [24]. The development of fiber-optic thermometry based on fiber bragg grating (FBG) technology has provided a means for considerably improved spatial sampling of temperature profiles, due to the ability to record temperatures at multiple points along a fiber [25]. Non-invasive, volumetric thermometry techniques such as magnetic resonance imaging (MRI) thermometry [26], can also be used, but integrating ablation instrumentation within the MRI environment is a considerable barrier.…”