Influences of Microbubble Diameter and Ultrasonic Parameters on In Vitro Sonothrombolysis Efficacy

• Published in: Journal of vascular and interventional radiology Vol. 23; no. 12; pp. 1677 - 1684.e1
• Main Authors: Borrelli, Michael J., PhD, O’Brien, William D., PhD, Hamilton, Eric, MS, Oelze, Michael L., PhD, Wu, Jonah, BS, Bernock, Laura J., MS, Tung, Stephen, PhD, Rokadia, Husein, PhD, Culp, William C., MD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2012
• Subjects: Animals; Blood; Blood Coagulation - physiology; Blood Coagulation - radiation effects; High-Intensity Focused Ultrasound Ablation - methods; Mechanical Thrombolysis - methods; Microbubbles - therapeutic use; Particle Size; Rabbits; Radiation Dosage; Radiology; Treatment Outcome; PBS; PD; tPA; tissue plasminogen activator; MB; PRF; AFM; microbubble; phosphate-buffered saline; pulse repeat frequency; atomic force microscopy; pulse duration
• ISSN: 1051-0443; 1535-7732
• DOI: 10.1016/j.jvir.2012.08.019

Abstract Purpose To quantify the effects of microbubble (MB) size, elasticity, and pulsed ultrasonic parameters on in vitro sonothrombolysis (ultrasound [US]-mediated thrombolysis) efficacy. Materials and Methods Monodispersive MBs with diameters of 1 μm or 3 μm were exposed to pulsed US (1 MHz or 3 MHz) to lyse rabbit blood clots. Sonothrombolysis efficacy (clot mass loss) was measured as functions of MB size and concentration, ultrasonic frequency and intensity, pulse duration (PD), pulse repeat frequency (PRF), and duty factor. Results Sonothrombolysis at 1 MHz was more effective using 3-μm MBs and at 3 MHz using 1-μm MBs. Sonothrombolysis was more effective at 1 MHz when≥75% of MBs remained intact, especially for 3-μm MBs; improving sonothrombolysis by increasing PRF from 100 Hz to 400 Hz at 3 MHz was associated with increasing 3-μm MB survival. However, 60% of 1-μm MBs were destroyed during maximal sonothrombolysis at 3 MHz, indicating that considerable MB collapse may be required for sonothrombolysis under these conditions. Conclusions The ability to control MB size and elasticity permits using a wide range of US parameters (eg, frequency, intensity) to produce desired levels of sonothrombolysis. Comparable, maximal sonothrombolysis efficacy was achieved at 20-fold lower intensity with 3-μm MBs (0.1 W/cm2 ) than with 1-μm MBs (2.0 W/cm2 ), a potential safety issue for in vivo sonothrombolysis. US parameters that maximized MB survival yielded maximal sonothrombolysis efficacy except with 1-μm MBs at 3 MHz where most MBs were destroyed.