Olivier K. Colliou
E. Carr Everbach
Dept. of Eng., Swarthmore College, Swarthmore, PA 19081-1397
Current medical technologies for removing the arterial plaque of patients with cardiac disease include balloon angioplasty and laser ablation. In the first, balloons are introduced via catheter into the blocked artery and expanded to allow increased blood flow, but macroscopic plaque pieces can leave arterial walls and enter the circulatory system, causing brain embolism. In laser ablation, an optical fiber is passed into the artery and intense laser light is used to heat the plaque until micron-sized particles are removed. Unfortunately, the ablation is not limited to the plaque, and punctures can occur in the healthy arterial walls once the plaque layer has thinned. A new technology, intra-arterial ultrasonic angioplasty, is being developed in which a wire, acting as an acoustic waveguide, is inserted into the artery and intense ultrasonic waves are used to ablate the plaque at the wire tip. Alternatively, tiny transducers can be inserted into the artery and excited to produce intense ultrasonic waves. Violent cavitation occurring at the plaque surface is believed to be responsible for the ablation, which occurs preferentially in the harder, stiffer plaque rather than in the softer, healthy vessel walls. A series of measurements on several of these acoustic devices and an analysis of the parameters that could be used to optimize their efficacy and safety are presented here.