Title :
An IVUS transducer for microbubble therapies
Author :
Kilroy, Joseph ; Patil, Abhijit ; Rychak, Joshua ; Hossack, John
Author_Institution :
Dept. of Biomed. Eng., Univ. of Virginia, Charlottesville, VA, USA
Abstract :
There is interest in examining the potential of modified intravascular ultrasound (IVUS) catheters to facilitate dual diagnostic and therapeutic roles using ultrasound plus microbubbles for localized drug delivery to the vessel wall. The goal of this study was to design, prototype, and validate an IVUS transducer for microbubble-based drug delivery. A 1-D acoustic radiation force model and finite element analysis guided the design of a 1.5-MHz IVUS transducer. Using the IVUS transducer, biotinylated microbubbles were displaced in water and bovine whole blood to the streptavidin-coated wall of a flow phantom by a 1.5-MHz center frequency, peak negative pressure = 70 kPa pulse with varying pulse repetition frequency (PRF) while monitoring microbubble adhesion with ultrasound. A fit was applied to the RF data to extract a time constant (π). As PRF was increased in water, the time constant decreased (π = 32.6 s, 1 kHz vs. π = 8.2 s, 6 kHz), whereas in bovine whole blood an adhesion-no adhesion transition was found for PRFs ≥ 8 kHz. Finally, a fluorophore was delivered to an ex vivo swine artery using microbubbles and the IVUS transducer, resulting in a 6.6-fold increase in fluorescence. These results indicate the importance of PRF (or duty factor) for IVUS acoustic radiation force microbubble displacement and the potential for IVUS and microbubbles to provide localized drug delivery.
Keywords :
adhesion; biomedical transducers; blood; blood vessels; bubbles; catheters; drug delivery systems; drugs; finite element analysis; fluorescence; haemodynamics; patient diagnosis; phantoms; radiation therapy; ultrasonic therapy; ultrasonic transducers; 1D acoustic radiation force model; IVUS acoustic radiation force microbubble displacement; IVUS transducer; adhesion-no adhesion transition; biotinylated microbubbles; bovine whole blood; dual diagnostic roles; duty factor; ex vivo swine artery; finite element analysis; flow phantom; fluorescence; fluorophore; frequency 1 kHz; frequency 1.5 MHz; frequency 6 kHz; localized drug delivery; microbubble adhesion monitoring; microbubble therapies; microbubble-based drug delivery; modified intravascular ultrasound catheters; peak negative pressure; pulse repetition frequency; streptavidin-coated wall; therapeutic roles; time 32.6 s; time 8.2 s; vessel wall; water; Acoustics; Arteries; Blood; Ceramics; Finite element analysis; Imaging; Transducers;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
DOI :
10.1109/TUFFC.2014.2929