"Purpose: To acquire ultra high resolution MRI images of the human brain at 8 Tesla within a clinically acceptable time frame.
Method: Gradient echo images were acquired from the human head of normal subjects using a TEM resonator operating in quadrature and tuned to 340 MHz. In each study, a group of 6 images was obtained containing a total of 208 Mbytes of unprocessed information. Typical acquisition parameters were as follows: matrix = 2000x2000, FOV = 20 cm, slice thickness = 2 mm, NEX= 1, flip angle = 45°, TR = 750 ms, TE = 17ms, receiver bandwidth = 69.4 kHz. This resulted in a total scan time of 23 min, an in-plane resolution of 100 m m and a pixel volume of 0.02 mm3.
Results: The ultra high resolution images acquired in this study represent more than a 50 fold increase in in-plane resolution relative to conventional 256 x 256 images obtained with a 20 cm field of view and a 5 mm slice thickness. Nonetheless, the ultra high resolution images could be acquired both with adequate image quality and signal to noise. They revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter.
Discussion: The elevated signal to noise ratio observed in UHFMRI, can be utilized to acquire images with a level of resolution approaching the histological level under in-vivo conditions. However, brain motion is likely to degrade the useful resolution. This situation may be remedied in part with cardiac gating. Nonetheless, these images represent a significant advance in our ability to examine small anatomical features with non-invasive imaging methods."