Demonstration of urinary reflux diagnosis with in situ ultrasound generated contrast bubbles in a refluxing canine model

摘要

A surgical urinary reflux model has been developed in canines, to test a less invasive method for diagnosing urinary reflux (VUR) using ultrasound contrast microbubbles generated by transcutaneous application of high intensity focused ultrasound (HIFU) in the urinary bladder. This surgical reflux procedure was performed on two canines. After approximately six weeks of recovery, examinations performed tested for reflux over the next seven weeks. The canines were positioned prone (slightly head down) on a tilted table with a hole exposing the depilated abdomen, where a 1.18 MHz high intensity focused ultrasound transducer could be coupled. Before each examination, the resulting reflux due to the surgery was confirmed by standard fluoroscopy. When high grade reflux was detected with x-ray, a dilute solution of Optison was infused into the urinary bladder via a transurethral catheter. The Optison was identified in the refluxing kidney with a diagnostic scanner (Toshiba PowerVison 8000) in color Doppler mode; this reconfirmation of reflux served as a targeting mechanism for position the scanhead (3.75 MHz curvilinear) to obtain an optimal image of the renal pelvis and/or collecting system of the kidney. Then aqueous solutions with elevated CO{sub}2 were placed in the bladder, and copious microbubbles were generated using a 10 sec application of 1.18 MHz ultrasound (25 cycle bursts with 0.5% duty factor, and peak rarefactional amplitude of 8.5 MPa). Reflux of the generated bubbles into the kidney resulted in about as strong color Doppler signal as with the dilute Optison in both canines. Methods can naturally produce elevated CO{sub}2, and contrast bubbles should be producible transcutaneously for reflux diagnosis without ionizing radiation and catheterization.