Lawrence Yao MD, Presenter: Nothing to Disclose

John T. Pitts, Abstract Co-Author: Nothing to Disclose

David Thomasson PhD, Abstract Co-Author: Nothing to Disclose

Proton density weighted (PD) spin echo sequences are a mainstay of musculoskeletal MRI evaluation. Multi-channel receiver coils and parallel acquisition technology now make isotropic 3D turbo spin echo (TSE) imaging clinically feasible. We apply this strategy to ankle imaging at 3.0 Tesla and compare it to 2D TSE imaging.

We implemented a 3D TSE sequence with DRIVE, spatially non-selective refocusing RF pulses, and half-Fourier phase sampling. Other scan parameters include: voxel size= 0.55 x 0.55 x 0.5 mm, SENSE factors = 2 (slice) and 2 (phase), TE/TR= 31/717 msec, ETL = 11, scan time = 7:25. Scan parameters for 2D TSE imaging were: TE/TR = 35/3500 msec, ETL = 6, voxel size=0.43x0.55x30mm, scan time = 6:16. 8 ankles in 4 normal volunteers underwent MRI on a 3.0 Tesla (Philips Intera) scanner, with a 6 channel receiver coil (Invivo). Signal values were measured in representative tissues. The visibility of 5 anatomic structures were scored on 2D and reformatted 3D images in the axial plane, using a workstation (Kodak System 5.2).

Muscle/fat signal ratios were lower (mean -114%, p<.001), while fluid/cartilage signal ratios were higher (mean +37%, p<.05) on 3D TSE as compared to 2D TSE. Nerve/vein and tendon/ligament signal ratios did not significantly differ between the two techniques. The perimalleolar segment of the peroneus brevis tendon was better visualized on axial 2D TSE (p<.05) than on axial reformatted 3D TSE, but there was no difference for four other key anatomic structures. The benefits of 3D TSE acquisition were realized during interactive compound oblique image reformation tailored to specific anatomy.

Tissue contrast can differ between 3D and 2D PD TSE and is influenced by a complex interaction of scan parameters. Isotropic 3D TSE facilitates a more robust and detailed evaluation of small parts than 2D TSE when coupled with real time multiplanar image reformation. In this viewing mode, volumetric TSE acquisition is "comprehensive," circumventing patient positioning and scan plane prescription requirements required for conventional, multiplanar 2D MRI evaluation.

J.T.P.: Employed by Invivo Diagnostic Imaging, a division of Intermagnetics General Corporation, Latham, NY.

Yao, L, Pitts, J, Thomasson, D, Comprehensive MRI of the Ankle at 3.0 Tesla: Isotropic 3D Proton Density-weighted Fast Spin Echo.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4406041.html