Observation of acoustic cavitation in excised canine urinary bladders

Abstract

A high‐intensity ultrasonic field has been used to generate bubbles within urinary bladders excised from dogs. Following the exposure, bubbles were easily visualized using an ATL UltraMark 9 diagnostic scanner with a 5‐MHz mechanical sector scanhead. Scattering of the high‐intensity ultrasound by the bubbles was also observed as uniformly high amplitude scan lines during the irradiation. The bladders were removed surgically after tying off the ureters and urethra to prevent urine loss and exposure to external contaminants. Each bladder was sealed in a plastic bag filled with a degassed aqueous solution of sodium chloride (0.9% by weight) and sodium azide (1 g/liter). A bag containing a bladder was centered in a sealed degassed water path at the common focal point of a 7‐cm‐diam, 500‐kHz transducer, and a 10‐cm‐diam brass reflector. The transducer and reflector were both focused at 10 cm and were aligned coaxially. Exposures were 10 s in duration but intensity or pressure values were not available as of the writing of this abstract. No significant discoloration of the exterior bladder wall was observed within the beam path. Results of this study suggest that bubbles might be externally generated in vivo for use as echo contrast agents and for studying the bioeffects of acoustic cavitation.