Experimental Evaluation of an Ultrasound-Guided High-Intensity-Focused Ultrasound Probe for Sonication of Artery

Objectives

This study aimed to develop an ultrasound-guided high-intensity-focused ultrasound (USgHIFU) probe for arterial sonication and to evaluate vascular contraction.

Methods

The USgHIFU probe comprised two confocal spherical transducers for sonication and a US color Doppler flow imaging probe for guidance. A vessel-mimicking phantom was sonicated in two directions. In the vascular radial direction, an isolated rabbit aorta embedded in ex vivo pork liver was sonicated at different acoustic powers (245 and 519 W), flow rates (25, 30, and 50 mL/minute), and sonication energies (519, 980, and 1038 J). Changes in the postsonication vessels were evaluated using US imaging, microscopic observation, and histopathological analysis.

Results

Beam focusing along the vascular radial direction caused significant deformation of both tube walls (n = 4), whereas focusing along the axial direction only affected the contraction of the anterior wall (n = 4). The contraction index (D_c) of the vessel sonicated at 245 W and 980 J was 56.2 ± 9.7% (n = 12) with 25 mL/minute. The D_c of the vessel sonicated at 519 W and 1038 J was 56.5 ± 7.8% (n = 17). The D_c of the vessel sonicated at 519 J total energy was 18.3 ± 5.1% (n = 12).

Conclusion

The developed USgHIFU probe induced greater vascular contractions by covering a larger area of the vessel wall in the radial direction. Sonication energy affects vascular contraction through temperature elevation of the vessel wall. When the acoustic power was high, an increase in acoustic power, even with comparable sonication energy, did not result in greater vessel contraction.