Orientational analysis of the Achilles tendon and enthesis using an ultrashort echo time spectroscopic imaging sequence

Du, Jiang; Chiang, Alan Jing-Tzyh; Chung, Christine B.; Statum, Sheronda; Znamirowski, Richard; Takahashi, Atsushi; Bydder, Graeme M.

doi:10.1016/j.mri.2009.06.002

« Previous Next »Magnetic Resonance Imaging
Volume 28, Issue 2 , Pages 178-184, February 2010

Orientational analysis of the Achilles tendon and enthesis using an ultrashort echo time spectroscopic imaging sequence

Jiang Du
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA
- Corresponding author. Tel.: +1 619 471 0519; fax: +1 619 471 0503.
Alan Jing-Tzyh Chiang
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA
Christine B. Chung
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA
Sheronda Statum
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA
Richard Znamirowski
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA
Atsushi Takahashi
- Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA 94025, USA
Graeme M. Bydder
- Department of Radiology, University of California, San Diego, CA 92103-8756, USA

Received 2 April 2009; received in revised form 10 June 2009; accepted 25 June 2009. published online 20 August 2009.

Abstract

Tendons and entheses are magnetic resonance (MR) “invisible” when imaged with conventional clinical pulse sequences. When the highly ordered, collagen-rich fibers in tendons and entheses are placed at the magic angle, dipolar interactions are decreased and their T2s are often considerably increased. The bulk magnetic susceptibility of tendons and entheses also varies with orientation to B₀, leading to a direction-dependent resonance frequency shift. Ultrashort echo time (UTE) sequences with a minimum TE of 8 μs provide high signal from both tendons and entheses. The combination of a UTE sequence with an interleaved undersampled variable TE acquisition scheme provides a new approach for fast spectroscopic imaging of short T2 tissues. This UTE spectroscopic imaging (UTESI) technique provides quantitative information including T2⁎, chemical shift and resonance frequency shift due to bulk susceptibility effect. In this article, the orientational effects on tendons and entheses were investigated using a UTESI sequence on a clinical 3-T scanner. T2⁎ was found to increase fivefold for tendons and twofold for entheses due to the magic angle effect. A resonance frequency shift up to 1.2 ppm was observed for both tendons and entheses due to the bulk susceptibility effect when their orientation was changed from 0° to 90° relative to B₀.

Keywords: Ultrashort TE, Spectroscopic imaging, Short-T2, Tendon, Enthesis, Magic angle, Bulk susceptibility