Reversed laminar appearance of articular cartilage by T1‐weighting in 3D fat‐suppressed spoiled gradient recalled echo (SPGR) imaging

Abstract

To investigate the reversed intensity pattern in the laminar appearance of articular cartilage by 3D fat-suppressed spoiled gradient recalled echo (FS-SPGR) imaging in magnetic resonance imaging (MRI). The 3D SPGR experiments were carried out on canine articular cartilage with an echo time (TE) of 2.12 msec, a repetition time (TR) of 60 msec, and various flip angles (5 degrees to 80 degrees ). In addition, T1, T2, and T2* in cartilage were imaged and used to explain the laminar appearance in SPGR imaging. The profiles of T2 and T2* in cartilage were similar in shape. However, the T2 values from the multigradient-echo imaging sequence were about 1/3 of those from single spin-echo sequences at a pixel resolution of 26 mum. While the laminar appearance of cartilage in spin-echo imaging is caused mostly by T2-weighting, the laminar appearance of cartilage in fast imaging (ie, short TR) at the magic angle can have a reversed intensity pattern, which is caused mostly by T1-weighting. The laminar appearance of articular cartilage can have opposite intensity patterns in the deep part of the tissue, depending on whether the image is T1-weighted or T2-weighted. The underlying molecular structure and experimental protocols should both be considered when one examines cartilage images in MRI.