Stent Deployment using Intravascular Ultrasound





B-scan frame from human stent deployment procedure

Background

Stenting has become a significant coronary intervention to manage arterial disease. A stylized illustration of a fully extended stent is presented in Figure 1 below. To deploy this device in a coronary artery, a relaxed stent is placed over a catheter balloon and positioned within the artery lumen at the site of stenosis. As the balloon is pressurized, the stent expands. If properly deployed, a stent can provide long term structure integrity to an artery opened with conventional balloon dilation. Unfortunately, there is no established procedure to ensure full stent deployment.

Using the tracking methods established for elasticity imaging, we have investigated a new procedure to monitor stent deployment. As the pressure within the balloon increases, the cross sectional area of the ballloon should increase rapidly until the stent begins to contact the artery wall. Once in contact with the wall, the balloon area should increase much more slowly as a function of pressure until the area-pressure curve saturates when the stent is fully deployed. By precisely monitoring balloon area as a function of balloon pressure, stent deployment can be monitored.

To test this hypothesis, an ex vivo artery model was used. A stent was delivered to an excised segment of pig femoral artery using the integrated deformation-imaging catheter used for elasticity imaging. Real-time ultrasound data were acquired as the balloon was pressureized. A single frame near the end of the real-time sequence of images recorded during stent placement is shown in Figure 2. Several of the stent struts are clearly visible in this image.

Using speckle tracking procedures developed as a part of the PIST algorithm (for elasticity imaging), the balloon cross sectional area was measured as a function of balloon pressure. The results of this processing are presented in Figure 3. As expected, the area-pressure curve saturates when the stent is fully deployed. These results strongly suggest that stenting can be monitored using an imaging transducer integrated into the balloon delivery system.

These results were presented at the 1997 IEEE UFFC Ultrasonics Symposium in an invited talk by Matt O'Donnell.






Figure 1: Stylized diagram of arterial stent




Figure 2: B-scan frame from ex vivo arterial stent model




Figure 3: Ultrasonically measured area-pressure relation during stent deployment


Publications




Correspondence:

Link to: http://bul.eecs.umich.edu/research/ivus/ivus_stent/
Last modified by: cdchoi@umich.edu