MR imaging of articular cartilage using driven equilibrium

The high incidence of osteoarthritis and the recent advent of several new s urgical and non-surgical treatment approaches have motivated the developmen t of quantitative techniques to assess cartilage loss. Although magnetic re sonance (MR) imaging is the most accurate non-invasive diagnostic modality for evaluating articular cartilage, improvements in spatial resolution, sig nal-to-noise ratio (SNR), end contrast-to-noise ratio (CNR) would be valuab le. Cartilage presents an imaging challenge due to its short T-2 relaxation time and its low water content compared with surrounding materials. Curren t methods sacrifice cartilage signal brightness for contrast between cartil age and surrounding tissue such as bone, bone marrow, and joint fluid. A ne w technique for imaging articular cartilage uses driven equilibrium Fourier transform (DEFT), a method of enhancing signal strength without waiting fo r full T-1 recovery. Compared with other methods, DEFT imaging provides a g ood combination of bright cartilage and high contrast between cartilage and surrounding tissue. Both theoretical predictions and images show that DEFT is a valuable method for imaging articular cartilage when compared with sp oiled gradient-recalled acquisition in the steady state (SPGR) or fast spin echo (FSE). The cartilage SNR for DEFT is as high as that of either FSE or SPGR, while the cartilage-synovial fluid CNR of DEFT is as much as four ti mes greater than that of FSE or SPGR. Implemented as a three-dimensional se quence, DEFT can achieve coverage comparable to that of other sequences in a similar scan time. Magn Reson Med 42:695-703, 1999. (C) 1999 Wiley-Liss, Inc.