Monitoring the Wall Mechanics During Stent Deployment in a Vessel

This experiment uses non-contact strain measuring equipment to monitor and capture the stent induced non-uniform strain on a mock artery. First, prepare a mock vessel for the stent expansion environments. After calibrating the aramis software system, expand the stent and capture the deformation of the mock vessel.

Results from analyses of the stent induced strain along one axial path of mock vessel. Show that the stent induced strain distribution on mock vessel is non-uniform. The primary advantage of the Aramis camera system versus other methods of strain measurements such as strain gauges, are that the ARAMIS camera system allows for non-contact strain measurement.

This protocol will demonstrate how to calibrate the aramis system along with analysis of the sample Here. This method offers insights into a stream distribution due to stand expansion. It can also be applied to other systems like a string on a head during the shock wave or on a string on steel bar on tension.

First, fix both ends of the latex vessel to barbed hose connections that have fastened on a sturdy workbench. For a stent test center the area of interest between the barbed hose connectors and include approximately one inch on each side of the stent. In order to observe the strains outside the stented area, measure the area of interest on the latex vessel to determine the field of view.

Next, record the distance from the outside edge of one barbed hose connector to the center location between the connectors. Translate the distance onto the catheter by measuring from the center of the stent up the catheter. Then mark the catheter with a marker.

Now remove the latex vessel from the barbed hose connectors. Prepare the latex vessel by spraying the area of interest with a stochastic pattern of white and black spray paint or marking the area of interest with random dots. Using a permanent marker, select a calibration panel that is slightly larger than the area of interest.

Then place the calibration panel between the barbed hose connectors at the area of interest. Ensure that the area of interest is well lit. Now, adjust the distance between the two cameras, the distance from the sample and the camera height to open a new project in Aramis select file and then new project.

Next, click on the sensor tab and select calibration. Then full calibration for the RMS software to step through calibration of the cameras with, with the lens aperture fully open, focus the camera on the calibration panel by loosening the set screw on the camera and rotating the lens. Once focused, re-tighten the set screw and close the aperture.

Take the first image of the calibration process. Displace the calibration panel according to the demonstration on the computer until the image is focused on the computer screen. Then take the second image.

Repeat this process for the remainder of the calibration images. Once all of the calibration images are taken, the RM S imaging analysis software will calculate the calibration settings. If the calibration deviation is less than 0.04, remove the calibration panel and place the painted latex vessel back onto the barb hose.

Connectors, given that increased frames per second will produce more uniform strain results. Determine the number of frames per second for the test. Also adjust the shutter speed to less than one frame per second.

To minimize red on the image, take five images, then add start points on the image series and compute the test while holding control. Click on the center of the sample to observe the background noise. If the pretest noise is above 75 micros drain.

Repeat the calibration process. Prepare for stent deployment by selecting the number of images desired to take during the test. 200 images will suffice for the stent expansion.

Proceed to gradually insert the catheter into the latex vessel. Use the marker indicator on the catheter to guide the stent insertion until it reaches the central location. Begin taking images with AAMI for the balloon expandable stent.

Gradually increase the balloon pressure to expand the stent until the balloon is fully expanded. Then gradually decrease the pressure of the balloon to zero, to deflate the balloon to withdraw along with the catheter for the self-expanding stent. Gradually remove the sheath until the stent is fully expanded.

Then gradually retract the catheter to calculate strain history of a specific point on the vessel. First, create a stage point by holding the control key and clicking on the area of interest. Then select strain type to plot the strain at the point selected over the duration of the test for spatial strain along a specific path of the vessel.

Create a multi-stage point line by clicking on the sections tab and then create section. Select a line on the image parallel to the X axis at y equals zero. This will create a number of stage points in a line and display a series of lines on one plot.

Each line represents the strain at one instance in time along the length of the section. To analyze expansion rate and radius of the vessel, create a best fit cylinder in the upper toolbar, select primitives, then best fit cylinder. Using the select through surface tool, identify a small section of the image for the A is software to generate a three dimensional best fit cylinder cycle through these fit cylinder images to observe variation of the diameter of the latex vessel.

To evaluate the distance between two points under the analysis tab, click on point to point distance. Then select two points to indicate the length on the image that is desired for analysis. Proceed to cycle through the images to observe the change in distance between the two points over time.

This experiment demonstrates strain mapping during the recoil process of a balloon expandable stent, as well as major strain history. At one specific point, while the stent struts expand the vessel wall outwards, the high speed cameras captured and tracked displacement of the black reference points on the conduit. Based on the recorded movement of reference points, the software calculated the strains of the conduit or any other targeted object.

Clearly, the implanted stent led to non-uniform strain distribution on the vessel surface. Furthermore, the major strain history curve of a specific point 10 demonstrated distinguishable stages of stent implantation. The balloon expansion occurs from approximately 10 to 12 seconds, and stent recoil following the deflation of the balloon occurs between 12 and 14 seconds.

Last mastered. This technique can be performed in two hours. Remember to complete the calibration process correctly.