Development of transverse relaxation and susceptibility methods for high field MRI

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Magnetic Resonance Imaging (MRI) systems using very strong magnetic fields that are greater than eighty thousand times the Earth's field are becoming increasingly available. These MRI systems are much stronger than standard clinical MRI systems that are at a field strength of 3.0 Tesla or lower. However, these higher field MRI systems still lack an adequate array of imaging methods for human imaging. New methods are needed to overcome the specific challenges of high field MRI. We will introduce new MRI methods for human brain imaging. Our work will provide insight into technical MRI and release new means to exploit inherent MRI contrast at both standard and high magnetic fields. Our methods are largely related to two features of high field MRI. First, the power used by higher fields increases with the square of the magnetic field, which can limit use of powerful MRI methods such as "T2 transverse relaxation" measurement. Second, high fields can provide a greater sensitivity to iron, a very important element in the human body. We will design methods that enable effective T2 measurement, and methods that increase the sensitivity to iron changes. The methods are designed by using computer simulations as well as experimental imaging of objects and human brain. The design process involves probing the means of performing MRI, which includes many more variables than x-ray imaging, and probing the response of tissue to these methods. The response is studied theoretically through Bloch equation and quantum mechanical simulations. Simulations are then verified with actual experiments on test tubes and on healthy human subjects. This work will lead to new MRI methods for human brain imaging.