Application of analyzer based X-ray imaging technique for detection of ultrasound induced cavitation bubbles from a physical therapy unit.
BACKGROUND
The observation of ultrasound generated cavitation bubbles deep in tissue is very difficult. The development of an imaging method capable of investigating cavitation bubbles in tissue would improve the efficiency and application of ultrasound in the clinic. Among the previous imaging modalities capable of detecting cavitation bubbles in vivo, the acoustic detection technique has the positive aspect of in vivo application. However the size of the initial cavitation bubble and the amplitude of the ultrasound that produced the cavitation bubbles, affect the timing and amplitude of the cavitation bubbles' emissions.


METHODS
The spatial distribution of cavitation bubbles, driven by 0.8835 MHz therapeutic ultrasound system at output power of 14 Watt, was studied in water using a synchrotron X-ray imaging technique, Analyzer Based Imaging (ABI). The cavitation bubble distribution was investigated by repeated application of the ultrasound and imaging the water tank. The spatial frequency of the cavitation bubble pattern was evaluated by Fourier analysis. Acoustic cavitation was imaged at four different locations through the acoustic beam in water at a fixed power level. The pattern of cavitation bubbles in water was detected by synchrotron X-ray ABI.


RESULTS
The spatial distribution of cavitation bubbles driven by the therapeutic ultrasound system was observed using ABI X-ray imaging technique. It was observed that the cavitation bubbles appeared in a periodic pattern. The calculated distance between intervals revealed that the distance of frequent cavitation lines (intervals) is one-half of the acoustic wave length consistent with standing waves.


CONCLUSIONS
This set of experiments demonstrates the utility of synchrotron ABI for visualizing cavitation bubbles formed in water by clinical ultrasound systems working at high frequency and output powers as low as a therapeutic system.
Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9, Canada. zai206@mail.usask.ca.
Zahra
Z
Izadifar
Biomedical Imaging and Therapy Beamlines, Canadian Light Source Inc., University of Saskatchewan, 44 Innovation, Boulevard, Saskatoon, SK, S7N 2V3, Canada. George.Belev@lightsource.ca.
George
G
Belev
Department of Medical Imaging, Royal University Hospital, University of Saskatchewan and Saskatoon Health Region, 103 Hospital Drive, Saskatoon, SK, S7N0W8, Canada. Paul.Babyn@saskatoonhealthregion.ca.
Paul
P
Babyn
Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9, Canada. dean.chapman@usask.ca.|Anatomy and Cell Biology, University of Saskatchewan, 3B34 Health Sciences Building, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada. dean.chapman@usask.ca.
Dean
D
Chapman
D061848:Optical Imaging / Q000295:instrumentation / Q000379:methods*; D017356:Synchrotrons; D014464:Ultrasonic Therapy; D014965:X-Rays