Studies on developments of imaging and analytical methods and evaluations of properties mainly on image quality in MRI (in Japanese)

Abstract

The aims of this thesis were to develop imaging and analytical methods in magnetic resonance imaging (MRI) to obtain morphological and functional information of the human body and to evaluate image quality of an MRI system. Various new methods are illustrated. A fast imaging method for obtaining a T1‐weighted image by using the rapid acquisition relaxation enhanced sequence combined with the variable flip angle excitation is described. Next, the thesis describes a method for performing a dynamic contrast‐enhanced T1‐weighted and study simultaneously to evaluate regional hemodynamics in brain tumors. This method can increase the amount of vascular information and reveals the hemodynamics of the brain tumor and surrounding regions in greater detail. The thesis describes a frequency analysis of cerebrospinal fluid (CSF) flow measured with an ECG gated phase contrast cine‐MRI to clarify the flow dynamics of intracranial CSF in normal pressure hydrocephalus (NPH). This frequency analysis can noninvasively provide a picture of the pathophysiology of NPH and of intracranial changes. Developments of the above imaging and analytical methods in MRI make it possible to obtain more detailed information on the human body. In addition, the thesis describes a new method to accurately measure the modulation transfer function and the signal‐to‐noise ratio in the positive and negative frequencies in MRI with a specially designed phantom. This evaluation method makes it possible to obtain more detail on the image quality of MRI, and is useful in various performance assessments such as the evaluation of pulse sequences.