APPLICATION OF KEYHOLE IMAGING TO INTERVENTIONAL MRI - A SIMULATION STUDY TO PREDICT SEQUENCE REQUIREMENTS

A wide variety of techniques have been proposed recently to improve th e temporal resolution of MRI. These include echo-planar imaging method s, wavelet encoding, singular value decomposition encoding, and k-spac e sharing methods known as ''keyhole'' imaging, In this work, we use a simulation study to investigate the phase-encoding ordering and data- sharing methods required for the application of keyhole imaging to int erventional MRI (I-MRI), The advantages of keyhole imaging over other methods are its simplicity and the use of conventional phase encoding and Fourier transform reconstruction found on virtually all modern MR imagers. Our analysis has predicted that conventional keyhole methods that repeatedly acquire only the center portion of k space, and those that sequentially progress from the center of k space outward, will no t meet the combination of temporal and spatial resolution required for tip localization during I-MRI needle insertion, Instead, acquisitions that acquire both high and low k-space data, in ranked order, should provide acceptable tip position and needle width accuracy in both temp oral and spatial domains for use in I-MRI.