Stent deployment using an integrated semi-compliant balloon ultrasound catheter

A new integrated balloon ultrasound catheter prototype was designed to image from inside the balloon for real-time guidance of stent deployment. It was fabricated using a semi-compliant balloon material (polyethylene) and a 20 MHz 64-element circumferential ultrasound array. The array position was fixed for imaging the balloon mid-plane. A commercial stent, nominally 4.4 mm in diameter and 12 mm in length, was used for a phantom study and placed along the length of the integrated balloon ultrasound catheter. A rubber phantom was created with an elastic modulus of 175 kPa. The phantom height was 10 cm with cross-sectional dimensions of 5.4 cm × 5.4 cm. The phantom lumen was 4.36 mm in diameter. Real-time balloon pressure measurements were recorded using a digital pressure sensor, and real-time rf (radio-frequency) data were captured as the balloon was inflated. During the experiment, the integrated balloon ultrasound catheter was pressurized up to 12 atm in 12 sec. The balloon cross-sectional area was computed for each frame using a Fourier based least-squares fit model. The slope of the area pressure ratio (balloon cross-sectional area divided by balloon pressure) versus pressure curve was generated for the stent experiment in the rubber phantom and compared to the corresponding curve for stent in water. Using the minimum slope for the balloon and stent in water as the measure for optimal stent deployment, the plots clearly indicate stent deployment at 11.1 atm. This measure could serve as a valuable tool for guiding stent deployment to reduce arterial injury and subsequent restenosis. After the experiment, rf data also were captured as the balloon catheter was moved along the length of the stent in pullback mode to confirm successful stent deployment. Ultimately, an integrated balloon catheter device could aid clinicians by monitoring cardiovascular interventions during procedures to minimize intimal injury, aid in pre- and post-procedure evaluation, and reduce the number of catheters used.