A novel Rib-sparing transcostal high-intensity focused ultrasound system based on resonant sound-blocking principle
Date Issued
2015
Date
2015
Author(s)
Chao, Yu-Tin
Abstract
The main challenge in transcostal high-intensity focused ultrasound therapy is minimizing heat deposition on the ribs while ensuring that a sufficient dose is delivered to the target region. Current approaches rely on expensive multichannel phased-array systems to turn individual transducer on and off according to either geometrical arrangements or complicated wave calculations. Notice that to protect the ribs from heating one must prevent the ultrasound energy not only from reaching the ribs but also from accumulating in front of the ribs. This research proposes a different approach to attach a sound-blocking structure with similar effects to those of the exhaust muffler of an engine in front of the rib cage and establish an ablation treatment system. The sound-blocking structure is designed based on the muffler principle to prevent the ultrasound energy from reaching the ribs while not causing too much energy to reflect back to the applicator. Finite-element simulations with 0.5 MHz transducer of the overall sound fields and temperature distribution showed that the ultrasound pressure and energy level decreases behind the novel sound-blocking structures, thereby achieving lower temperature on the ribs than on the tumor. Without the protecting structure the rib temperature reaches 104.19℃ while reaching only 37.86℃ with the structure. An experimental setup using porcine ribs with phantom was also developed to validate the proposed concept. The results showed that the rib temperature reached 72.80℃ without protection within only 1 minute of ablation time while maintained at 36.39℃ with the proposed device. The tumor region in the tests reached 51.39℃ and 49.33℃ respectively.
Subjects
Muffler
HIFU therapy
Pennes equation
Transfer matrix method
Helmholtz resonator
Electro-mechanical-acoustical analogy
Type
thesis