Magic angle effect on adiabatic T1ρ imaging of the Achilles tendon using 3D ultrashort echo time cones trajectory

作者：Wu, Mei; Ma, Yajun; Wan, Lidi; Jerban, Saeed; Jang, Hyungseok; Chang, Eric Y.; Du, Jiang^*

来源：NMR in Biomedicine, 2020, 33(8): e4322.

DOI：10.1002/nbm.4322

• Achilles tendon
• AdiabT(1 rho)
• CW-T-1 rho
• magic angle
• MSK
• quantitative evaluation
• T-2*
• ultrashort echo time

The protons in collagen-rich musculoskeletal (MSK) tissues such as the Achilles tendon are subject to strong dipolar interactions which are modulated by the term (3cos(2)theta-1) where theta is the angle between the fiber orientation and the static magnetic field B-0. The purpose of this study was to investigate the magic angle effect in three-dimensional ultrashort echo time Cones Adiabatic T-1 rho (3D UTE Cones-AdiabT(1 rho)) imaging of the Achilles tendon using a clinical 3 T scanner. The magic angle effect was investigated by Cones-AdiabT(1 rho) imaging of five cadaveric human Achilles tendon samples at five angular orientations ranging from 0 degrees to 90 degrees relative to the B-0 field. Conventional Cones continuous wave T-1 rho (Cones-CW-T-1 rho) and Cones T-2* (Cones-T-2*) sequences were also applied for comparison. On average, Cones-AdiabT(1 rho) increased 3.6-fold from 13.6 +/- 1.5 ms at 0 degrees to 48.4 +/- 5.4 ms at 55 degrees, Cones-CW-T-1 rho increased 6.1-fold from 7.0 +/- 1.1 ms at 0 degrees to 42.6 +/- 5.2 ms at 55 degrees, and Cones-T2* increased 12.3-fold from 2.9 +/- 0.5 ms at 0 degrees to 35.8 +/- 6.4 ms at 55 degrees. Although Cones-AdiabT(1 rho) is still subject to significant angular dependence, it shows a much-reduced magic angle effect compared to Cones-CW-T-1 rho and Cones-T-2*, and may be used as a novel and potentially more effective approach for quantitative evaluation of the Achilles tendon and other MSK tissues.

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