고강도 집속 초음파를 이용한 CTO 조직 괴사에 관한 연구

Abstract

When substances made ​​up of fat and cholesterol are deposed in internal of the arteries, the lumen of the blood vessels and blood flow are reduced by the materials of deposition. Those symptoms make the artery completely be occluded. The coronary artery bypass graft(CABG) or percutaneous coronary intervention(PCI) as the treatment of cardiovascular disease are performed to remove CTO. However, these treatments take a long time to heal, and the recurrence rate is high. HIFU system used to overcome these advantages is a non-invasive and needs the shorter operating time and this will strengthen the immune system. In this study, using HIFU system, CTO tissue was necrotized by the focused high-intensity ultrasound energy. In general, the ultrasound for medical devices is used in the frequency range of 0.5 ~ 5.5MHz. Ultrasound of 1.1MHz is mainly used for the destruction of tumor tissue and 3.0MHz is used in the recovery of soft tissue damage. The pressure and deformation on the CTO tissue were simulated for several frequencies using COMSOL software. As the frequency of ultrasound actuator is lower, the depth of tissue necrosis of CTO are bigger. As a result, necrotic depth of CTO tissue is higher at 1.1MHz than 5.4MHz. Next, the optimal conditions were measured to necrotize the CTO tissue. Experiments show that intensity of necrosis was greatest for 62.5mm focal distance and 8Vpp voltage. Basic study was performed in a non-invasive treatment. Ultrasound was transmitted in the polyethylene tube and tissue necrosis is examined without the damage of tube. The ultrasonic energy was transmitted well at the low-frequencies and higher voltages. Because water is low viscid and requires a large installation space, treatment of contact movement is not suitable. Thus, the agar gel was used as a couplant instead of water. The result shows that the ultrasound is transmitted well at 1% agar gel.