Multi-channel flow phantom for MRI-guided focused ultrasound

Although numerous studies have explored agar-silica phantoms in Magnetic Resonance guided Focused Ultrasound (MRgFUS) research, flow dynamics have not been considered. This study introduces a simple agar-silica flow phantom model specifically designed for MRgFUS preclinical applications.

The phantom design incorporated multiple 0.8-mm channels for degassed water circulation using a peristaltic pump, while remaining compact, lightweight, and MR-compatible. A series of sonications were performed targeting the modelled vessel network at varying power levels, with near real-time MR thermometry monitoring in a 3 T scanner, using a homogeneous (no vessel) phantom as a reference.

The flow phantom system was successfully integrated into the MR imaging (MRI) setting, demonstrating reliable performance under MR thermometry-guided sonications. It exhibited a consistent temperature rise in response to increasing ultrasonic energy. Under no-flow conditions (channels filled with static liquid), the thermal response resembled that of the homogeneous phantom, with well-confined heating. Under flow, however, the focal point shifted proximally toward the transducer, accompanied by pronounced near-field heat accumulation, indicating a flow-related alteration in heating.

Preliminary evaluation of the proposed agar-silica flow phantom indicates its potential for MRgFUS preclinical research, though further investigation is required to fully assess its role in simulating the dynamics of small-caliber vessel networks under FUS exposure.