Hyperecho in ultrasound images of HIFU therapy: involvement of cavitation.
High-intensity focused ultrasound (US), or HIFU, treatment of soft tissues has been shown to result in a hyperechoic region in B-mode US images. We report on detecting cavitation in vivo in correlation with the appearance of a hyperechoic region. The US system consisted of a HIFU transducer (3.3 MHz), a broadband A-mode transducer for active and passive cavitation detection and an US-imaging probe that were all confocal and synchronized. HIFU, at in situ intensities of 220 to 1710 W/cm(2), was applied for 10 s to pig muscles in vivo. Active and passive cavitation detection results showed a strong correlation between the onset of cavitation and the appearance of a hyperechoic region. Passive cavitation detection results showed that inertial cavitation typically occurred prior (within 0.5 s) to the appearance of a hyperechoic region. The observed cavitation activity confirms that bubbles are present during the formation of a hyperechoic region at the HIFU focus.
Department of Bioengineering, University of Washington, Seattle, WA 98105, USA.
Brian A
BA
Rabkin
Vesna
V
Zderic
Shahram
S
Vaezy
D000162:Acoustics; D000818:Animals; D007091:Image Processing, Computer-Assisted / Q000379:methods; D045423:Microbubbles; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D013552:Swine; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*; D014463:Ultrasonography