Radiology, Vol 175, 775-778, Copyright © 1990 by Radiological Society of North America
MR imaging of the knee with a 0.064-T permanent magnet
PA Rothschild, JM Domesek, L Kaufman, DM Kramer, SF Dye, LJ Anderson, JL Lewis and MK Gon
Radiologic Imaging Laboratory, University of California, San Francisco 94080.
Magnetic resonance (MR) imaging has proved beneficial in the evaluation of
internal derangements of the knee. A limitation to general acceptance of MR
imaging of the knee has been availability and cost. The recent introduction
of low-field-strength MR imaging has shown promise in decreasing the cost
and increasing the availability of this modality. High-resolution (pixel
size, 0.7 mm2), three-dimensional Fourier transform (3DFT), thin-section
(3.5 mm) imaging performed on a 0.064-T permanent magnet was used to
evaluate 117 knees in 114 consecutive patients. The appearance of normal
anatomy and internal derangements of the knee at low-field-strength imaging
is described. Arthroscopic correlation was available for 28 knees. Findings
from low- field-strength MR imaging and arthroscopy agreed in 79% of cases
in the determination of meniscal tears. Partial-flip-angle techniques with
3DFT produced thin-section images of the knee of diagnostic quality. The
authors conclude that in patients with internal derangements of the knee,
low-field-strength (0.064-T) MR imaging may provide useful information.
