Implementation And Applications Of SPIRAL Imaging On 4.7T MRI Scanner

A SPIRAL fast imaging method was implemented on a 4.7 T MRI scanner. The PC based software package was developed for the SPIRAL image construction, off-resonance correction and analysis. The method had been used to take the images of moving object, rat brain.1. Theoretical and technical aspects of the fast SPIRAL MRI method were reviewed. The factors, such as the off-resonance effect and gradient shape, which affect the quality of the SPIRAL imaging were discussed.2. SPIRAL magnetic resonance imaging (MRI) technique was implemented on a Bruker Biospec47/30 scanner. The technique includes the pulse sequence for generation and detection of the k-space MRI signal (FID, free induction decay), and PC based programs for the data gridding, and off-resonance correction.3. Single shot SPIRAL was used to obtain the image of a lemon with acquisition as short as 11 ms and the total scan time of only 1/64 of usual methods (FOV=8cm, matrix_size=64×64). The quality of the image is similar to that obtained using conventional MRI method. The T2 value measured using the spin-echo SPIRAL approach was exactly the same of that measured by usual method.4. The temporal resolution of 70 ms (14 images per second) was achieved using the SPIRAL method. This makes it possible to take real time images of moving object. The technique is demonstrated using a pendulum (tube) filled with water. The motional artifacts were discussed experimentally and theoretically. The motion caused the phase shift affects only the high frequency signal and reduces spatial resolution.5. An interleaved SPIRAL imaging method was achieved and tested using a lemon, phantom and the rat brain. The number of leaves from 2 to 32 is applicable according to the required spatial resolution. The effect of off-resonance was discussed. The diffusion weighting was implemented into the SPIRAL method and used to obtain D-MRI of rat brain in the early ischemia at temporal resolution of 100 s.