Generation of ultrasound contrast microbubbles for diagnosis of urinary reflux.

A high intensity ultrasound system has been proposed and is being developed to generate microbubbles in vivo for use as ultrasound contrast in the urinary system for diagnosing urinary reflux (or vesicoureteral reflux, VUR). VUR occurs due to a dysfunctional valve (the vesicoureteral junction, UVJ) that allows retrograde and high pressure flow of urine towards the kidney. Current diagnosis of VUR requires X-ray contrast agent and urethral catheterization. This transcutaneous bubble generation system has demonstrated that the cavitation threshold in the rabbit and canine urinary bladder can be reached, and that numerous bubbles can be produced to serve as seed bubbles for contrast in the urinary tract. Furthermore, in vitro studies were performed that point to the importance of increasing the gas content of the urine, in order to produce bubbles that can be seen with a diagnostic scanner. Administration of sodium bicarbonate is indicated as a method for increasing the gas content, and thus increasing the likelihood of generating more long lived bubbles that will aid in the reflux diagnosis. The overall goal of this thesis is to develop a safe and effective alternative to the current procedure used to diagnose urinary reflux. Such a system, based on transcutaneous ultrasound contrast production in the urinary bladder, may eliminate the need for ionizing radiation and more importantly the requirement for urinary catheterization which is particularly traumatic in pediatric cases.