| Summary: | 碩士 === 國立交通大學 === 生醫工程研究所 === 107 === In recent year, the increasing number of patients with essential tremor and the patients are also easily to suffer from Parkinson's disease at the same time. Besides, treatment options for patients with drug-resistant essential tremor(ET) are limited. The most recent advance in this area is magnetic resonance-guided focused ultrasound ( MRgFUS ), which is non-invasive, deep penetration, real-time monitoring and immediately benefits after the surgery. The currently ultrasonic therapy technology is a 1024-element hemispherical phased array high-intensity focused ultrasound. However, in this study, a 256-element ring-shaped phased array high-intensity focused ultrasound is investigated to test the feasibility of essential tremor surgery. In addition, urging to reduce the cost and complexity by reducing elements and channels.
In this study, not only Rayleigh integral and secondary source model but also the CT pictures of skull were used to improve the simulations. With the Matlab 2015a, the pressure field inside the brain are calculated. The frequency of 500 kHz, 600 kHz, 700 kHz, 750 kHz, 875 kHz, 1000 kHz and the height of the ring-shaped ultrasonic transducer 3 ~ 6 cm are simulated individually. In order to focus approximately the size of 4×10×6 mm3 on the ventral intermediate nucleus of the thalamus. The results show that at the frequency of 750 kHz and the height of 5 cm and 6 cm would perform achievable. Nonetheless, the focus range would be slightly larger than 10 mm but the intensity is sufficient.
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