Rethinking intraoperative MRI
Michael Schulder, Kevin Sheth, Prashin Unadkat
Introduction: A new portable, mobile, ultra-low-field MRI unit has been developed. It has a 0.064 Tesla (T) magnet, is self-shielded, and can be adapted for intraoperative use.
Objective: To assess the image quality of a novel, ultra-low-field and self-shielded MRI.
Methods: Five healthy volunteers had brain imaging with MR imagers having magnet strengths of 1.5 T, 0.15 T (an established intraoperative MRI [iMRI], and 0.064 T. Images were acquired using various sequences. We used a 1 to 5 scale comparing 6 parameters for the 0.15 and 0.064 scans (it was understood that the images from the 1.5T MRI constituted a benchmark for the purpose of this study). These assessments were done by three experienced observers. An MRI phantom was imaged to measure signal to noise ratio (SNR) in each scanner.
Results: Overall, images at 0.064 T were rated as higher than at 0.15 T (mean score 3.1, SD 1.7 vs. 2.3, SD 2.7, P + 0.007). Differences were most pronounced with T2 weighted (3.4 +/- 0.2 vs. 2.0 +/- 0.4, p =0.01) and FLAIR (3.5 +/- 0.2 vs. 2.0 +/- 0.3, p = 0.0001) images. The field of view encompassed the whole head using the 0.06 T images, and gave only partial coverage at 0.15 T. SNR was not significantly different between the two low-field scanners.
Conclusions: Imaging at 0.064 T with a self-shielding scanner provided images that were better than those with an established 0.15 T iMRI. Unique features of this new device make it ideally suited for use in the operating room.