Magnetic resonance imaging modeling and applications to fast imaging and guidance of ultrasound surgery.

Abstract

Magnetic Resonance Imaging (MRI) is the only known radiological modality that provides a diagnostic cross sectional images non-invasively in virtually any orientation without patient repositioning. The principles of MRI are based on Bloch's equations, which describe the behavior of proton molecules in the presence of a magnetic field. There are many interesting areas where MRI has contributed, such as perfusion and diffusion studies, MR angiography, cardiac studies as weIl as therapeutic applications in cancer treatment. In this dissertation two MRI related topics were investigated. First, a computer program was developed to simulate virtually any MRI pulse sequence. The phase encoding gradient pulses are also included which has proved to be very useful in predicting image artifacts and contrast behavior. The second is the application of MRI in guiding ultrasound surgery. A detailed study was performed on the sensitivity of MRI parameters to temperature changes. In-vivo studies were also performed on seven Greyhound dogs and twenty five rabbits. Temperature elevations were successfully depicted using MRI. Computer simulations were also used to study the effects of changing temperature during image acquisition.