The progression of thrombus in an ex-vivo shunt model evaluated by intravascular ultrasound radiofrequency analysis

We tested the ability of ultrasound radiofrequency (RF) signal analysis to characterize thrombus accumulation in a Dacron graft incorporated into the exteriorized arteriovenous shunt in 3 baboons with constant blood how for 6 0 min. Thrombus formation was quantified by sequential measurements df (111 )Indium-labeled platelet deposition. RF signals were acquired every 15 min at 2 sites in the graft, using a 2.9 Fr intravascular ultrasound catheter-b ased transducer (30 MHz) and digitized at 250 MHz in 8-bit resolution, Regi ons of interest were placed within a 0.5-mm perimeter adjacent to the graft wall. Integrated backscatter increased significantly (p < 0.001) with incr easing platelet deposition, However, mean-to-standard deviation ratio of th e RF envelope showed no significant change and the distribution pattern of the RF probability function remained constant and consistent with a Rayleig h scattering process. These results provide a basis for using RF analysis t o monitor the time-course of thrombus formation. (C) 1999 World Federation for Ultrasound in Medicine & Biology.