Effects of Attenuation and Thrombus Age on the Success of Ultrasound and Microbubble Mediated Thrombus Dissolution

摘要

The purpose of this study was to examine the effects of applied mechanical index, incident angle, attenuation, and thrombus age on the ability of 2D versus 3D diagnostic ultrasound and microbubbles to dissolve thrombi. A total of 180 occlusive porcine arterial thrombi of varying age (3 or 6 hours) were examined in a flow system. A tissue-mimicking phantom of varying thickness (5–10 cm) was placed over the thrombosed vessel and the 2D or 3D diagnostic transducer aligned with the thrombosed vessel using a positioning system. Diluted lipid encapsulated microbubbles were infused during ultrasound application. Percent thrombus dissolution (%TD) was calculated by comparison of clot mass before and after treatment. Both 2D and 3D guided ultrasound increased % TD compared to microbubbles alone, but % TD achieved with six hour old thrombi was significantly less than three hour old thrombi. Thrombus dissolution was achieved at 10 cm tissue mimicking depths, even without inertial cavitation. In conclusion, diagnostic 2D or 3D ultrasound can dissolve thrombi with intravenous non-targeted MB even at tissue attenuation distances of up to 10 centimeters. This treatment modality is less effective, however, for older aged thrombi.