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Using the Excimer Laser in Angioplasty
Our group is developing a new procedure to treat atherosclerosis. Atherosclerosis is the main cause of cardiovascular diseases which leed to thickening and hardening of the arterial wall and therefore to reduced blood flow in the diseased region. This results in most cases in heart attacks and strokes. Because of a high rate of restenosis (the reblockage of an artery after treatment) of state of the art methods there is a big need to improve the treatment of atherosclerosis.
State of the art methods today are mainly balloon angioplasty and stenting. The main disadvantage of these methods are the injury of the inner layer of the arterial wall the so called intima. This injury can lead to new stenosis and thrombosis.
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Fig.1: Principle of the ELAN procedure, tissue removal leads to dilatation. |
The idea of our method is to treat the vessel from the outer side of the arterial wall and thereby leave the intima intact. Because the elasticity of the vessel wall is directly related to its thickness it is possible to recover wall elasticity by removing tissue from the wall. After removal of tissue the blood pressure leads to an expansion of the artery, e.g. an increased artery diameter resulting in an increased blood flow (see fig.1).
Dr. Ajoy Singh the inventor of the procedure named it Extraluminal Laser Angioplasty (ELAN)
Because of costs and due to a possible and simple integration in a clinical system we use an excimer laser emitting at 193 nm for the tissue removal. Tissue ablation with this wavelength is well understood and allows cutting and removal of tissue with µm-precision and neglible or no thermal damages.(see fig. 2)
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Fig.2: Histological cut through the arterial wall after Excimer treatment. |
The main aims of our experiments are to find optimal parameters, pattern and depth of ablation, to obtain therapeutical effects without generating aneurysms (bulges in the vessel) or cutting through the arterial wall. Therefore we perfom FEM-Simulations of the bio-mechanical properties and the biomechanical answer of human arteries after its treatment. These are compared to experimental findings in-vitro and in vivo.
During the procedure it is very important to monitor the residual wall thickness. We use Optical Coherence Tomography, a technique for imaging biological tissue with µm resolution.
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