Magnetic Resonance Imaging Characteristics of Multiple Sclerosis Plaques Imaged with Two‐dimensional and Three‐dimensional Fourier Transform Techniques at Low and Mid Field Strengths

Abstract

A total of 58 multiple sclerosis lesions from 16 patients were used to characterize the performance of a low field system for the detection of edematous (e.g., water-elevating) brain lesions. Contrast, signal-to-noise, and their product (signal difference to noise) were measured for two-dimensional and three-dimensional Fourier transform techniques at low field strength (640 G) and compared to two-dimensional sequences at mid field strength (3,500 G). The results showed numerically that low-field strength magnetic resonance imaging can reliably detect multiple sclerosis lesions, and, by extension, other water-elevating lesions, although with lower confidence levels.

Two‐Gradient‐Echo, TwoDimensional, Fourier Transform Multisection Imaging: Comparison with Spin‐Echo Imaging

“…Taking into account spatial resolution, imaging time, and number of sections, the lowfield-strength sequence has approximately 64% of the S/N of a conventionallong-TR, double SE sequence at 0.35 T using a quadrature detection coil. This assertion results A B c D from a synthesis of previously published data for the SE sequence [4], and the current results.…”

“…Increasing the number of sections requires either repeating the sequence or lengthening the TR. In both cases this is equivalent to changing imaging (4) This function peaks at a TR of 1.26 T1 and has a broad peak of 90% of the maximum for TR between 0_6 and 2.6 T1 [17]. From the point of view of obtaining the contrast desired for these sequences (the long-TR contrast), it is necessary to operate with TR values on the order of at least 2 T1 [12]_ At high field strength, for a typical T1 of about 1 second, TR of approximately 2 seconds begins to satisfy this contrast condition.…”