Canadian researchers have proposed a new optical tool for angioplasty balloon manufacturers that could ultimately lead to better treatment of clogged arteries and better devices to treat cardiovascular problems.
Writing in a recent article for the SPIE Newsroom, Guy Lamouche, Sébastien Vergnole, and Hamed Azarnoush of the Industrial Materials Institute at the National Research Council say that intravascular optical coherence tomography (IVOCT) technology could provide powerful development information for manufacturers of angioplasty balloons.
Their NRC lab in Québec is involved in developing materials for the next generation of these and similar biomedical devices.
Balloons for angioplasty
The balloons used in an angioplasty procedure, where a balloon-tipped catheter is inserted into an artery and inflated, must be well designed and vigorously tested. A balloon rupture during the procedure could be fatal.
Manufacturers test the balloons through inflation under predetermined conditions, and this is traditionally done with an external laser scanner that provides measurements of the balloon's outer diameter at a given location. However, the NRC researchers note, these measurements are only obtained from a side view and from a particular orientation.
IVOCT allows a better testing method, they say, because it provides for full, 3D characterization of balloon diameter and wall thickness during the test inflation process and detailed cross-sectional imaging of the artery wall with a resolution of approximately 10 micrometers.
Images may be acquired during a 'pullback' (backward translation of the imaging probe, usually at a predetermined speed), so that pictures are obtained at different positions along the inside of the artery. IVOCT also allows realistic 3D reconstructions.
Based on OCT technology
The researchers' IVOCT probe is composed of a single-mode fiber laser, a gradient index lens, and a small prism to redirect light in a direction perpendicular to the probe axis. The whole assembly rotates and translates in a liquid within a polymer sheath.
The semi-compliant balloon is then connected at both ends to a tube. The OCT probe is introduced into the balloon through a T-connector that also connects the balloon to the high pressure line of the deployment tester. The scientists obtained the compliance and elastic modulus by measuring the average diameter of the balloon as a function of the pressure. They also compared the complete data to a 3D simulation of the balloon deformation to infer mechanical properties at all locations.
To monitor balloon inflation under more realistic conditions, they used the same setup and inserted the balloon inside an excised artery or an artery phantom (a silicone-based structure composed of three layers that provide the same optical signatures as the three artery layers).
The research group is investigating applications of the IVOCT technology in other percutaneous (through-the-skin) coronary intervention (PCI) devices as well, perhaps for new stent designs or new atherectomy devices that remove accumulated plaque on artery walls.
Read more in the SPIE Newsroom and see a real-time imaging of a balloon deployment inside an artery phantom: spie.org/ivoct.
The authors also presented a paper on this technique at SPIE Medical Imaging in February. See: Proceedings of SPIE 7964, 79641V (2011).
OCT probe monitoring balloon inflation.
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