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MR imaging of joints: Analytic optimization of GRE techniques at 1.5 T

  • Author(s): Yao, L
  • Sinha, S
  • Seeger, LL
  • et al.
Abstract

To clarify the choice of imaging parameters for optimal gradient-recalled echo MR scanning of joints, we analyzed the behavior of contrast-to-noise and signal-to-noise ratios for spoiled (i.e., fast low-angle shot [FLASH] or spoiled GRASS) and steady-state (i.e., gradient-recalled acquisition in the steady state [GRASS] or fast imaging with steady precession) techniques at 1.5 T. The analysis is based on tissue characteristics derived from spin-echo measurements of hyaline cartilage and synovial fluid signal in the patellofemoral joints of 11 volunteers. Separate analysis of contrast-to- noise and signal-to-noise ratios for multiplanar (long TR) acquisitions shows that these parameters are each improved compared with single-slice methods. At TRs greater than 250 msec, there is no significant difference in the contrast behavior of FLASH and GRASS. For optimal contrast-to-noise ratio (synovial fluid-cartilage), the best multiplanar sequence (for TE <23 msec) is with a short TE and a large flip angle (e.g., 400/9/73° [TR/TE/flip angle]). If a single-scan or three-dimensional technique is desired, then a GRASS sequence at minimal TR and TE and intermediate flip angle (18/9/32°) is best. For optimal signal-to-noise ratio (for both synovial fluid and hyaline cartilage), the best multiplanar sequence uses a short TE and an intermediate flip angle (e.g., 400/9/30°). If a short TR, high signal-to- noise technique is desired, then GRASS (18/9/13°) is superior to FLASH.

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