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Wrist: Improved MR Imaging with Optimized Transmit-Receive Coil Design¹

¹ From the Magnetic Resonance Imaging Research Laboratory, Mayo Clinic, 200 First St SW, Rochester, MN 55905. From the 2000 RSNA scientific assembly. Received April 20, 2001; revision requested June 14; final revision received December 20; accepted January 4, 2002. Supported by a grant from the Whitaker Foundation. Address correspondence to A.K. (e-mail: kocharian.armen@mayo.edu).

View larger version (125K): [in a new window]   Figure 1. Optimized birdcage transmit-receive coil for wrist MR imaging.

View larger version (104K): [in a new window]   Figure 2. Axial T1-weighted MR image (400/20, 10-cm field of view, 256 x 192 acquisition matrix, 3-mm section thickness) depicts the phantom (water solution of CuSO4 surrounded by canola oil). Dashed circles indicate the regions of interest for signal intensity measurements.

View larger version (166K): [in a new window]   Figure 3a. Transverse in vivo T1-weighted MR images (500/14, 200-cm field of view, 512 x 512 matrix, 3-mm section thickness) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) cylindric PAC. Arrows indicate the areas of the carpal tunnel, which appear sharper and with higher SNR in a.

View larger version (163K): [in a new window]   Figure 3b. Transverse in vivo T1-weighted MR images (500/14, 200-cm field of view, 512 x 512 matrix, 3-mm section thickness) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) cylindric PAC. Arrows indicate the areas of the carpal tunnel, which appear sharper and with higher SNR in a.

View larger version (137K): [in a new window]   Figure 4a. Transverse in vivo T2-weighted MR images (3,000/48, 10-cm field of view, 256 x 256 matrix, 3-mm section thickness, echo train length of eight) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) cylindric PAC. Arrow indicates the nonuniform fat saturation that can occur with the cylindric PAC.

View larger version (133K): [in a new window]   Figure 4b. Transverse in vivo T2-weighted MR images (3,000/48, 10-cm field of view, 256 x 256 matrix, 3-mm section thickness, echo train length of eight) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) cylindric PAC. Arrow indicates the nonuniform fat saturation that can occur with the cylindric PAC.

View larger version (174K): [in a new window]   Figure 5a. Coronal in vivo T2-weighted gradient-echo MR images (33/15, 256 x 192 matrix, 10-cm field of view, 1-mm section thickness, 0° flip angle) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) hand and wrist two-coil array. Arrows indicate the regions of signal intensity falloff and decreased z-axis coverage associated with the smaller coil.

View larger version (171K): [in a new window]   Figure 5b. Coronal in vivo T2-weighted gradient-echo MR images (33/15, 256 x 192 matrix, 10-cm field of view, 1-mm section thickness, 0° flip angle) of a normal wrist in a male volunteer were obtained with the (a) optimized birdcage wrist coil and (b) hand and wrist two-coil array. Arrows indicate the regions of signal intensity falloff and decreased z-axis coverage associated with the smaller coil.

View larger version (27K): [in a new window]   Figure 6a. SNR profiles of phantom images correspond to coronal plane. In a and b, BC10 = optimized birdcage wrist coil, MRID = hand and wrist two-coil array coil, PACC = cylindric PAC, and PACF = flat PAC. Uniform distribution is seen along (a) the z axis and (b) the x axis. In a and b, the optimized birdcage coil data demonstrate improved SNR and uniformity compared with data for the other coils.

View larger version (24K): [in a new window]   Figure 6b. SNR profiles of phantom images correspond to coronal plane. In a and b, BC10 = optimized birdcage wrist coil, MRID = hand and wrist two-coil array coil, PACC = cylindric PAC, and PACF = flat PAC. Uniform distribution is seen along (a) the z axis and (b) the x axis. In a and b, the optimized birdcage coil data demonstrate improved SNR and uniformity compared with data for the other coils.

View larger version (26K): [in a new window]   Figure 7a. SNR profiles of phantom images correspond to axial plane. In a and b, BC10 = optimized birdcage wrist coil, MRID = hand and wrist two-coil array coil, PACC = cylindric PAC, and PACF = flat PAC. Uniform distribution is seen along (a) the x axis and (b) the y axis. In a and b, the optimized birdcage coil data demonstrate improved SNR and uniformity compared with data for the other coils.

View larger version (26K): [in a new window]   Figure 7b. SNR profiles of phantom images correspond to axial plane. In a and b, BC10 = optimized birdcage wrist coil, MRID = hand and wrist two-coil array coil, PACC = cylindric PAC, and PACF = flat PAC. Uniform distribution is seen along (a) the x axis and (b) the y axis. In a and b, the optimized birdcage coil data demonstrate improved SNR and uniformity compared with data for the other coils.