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Diffusion-weighted imaging of the spinal cord: interleaved echo-planar imaging is superior to fast spin-echo
Roland Bammer1, Michael Augustin, Rupert W Prokesch
1Lucas MRS/I Center, Radiological Science Laboratory, Stanford University, Stanford, California 94305-5488, USA. roland@s-word.stanford.edu
Purpose:
To compare and evaluate two novel diffusion-weighted sequences, based either on fast spin-echo (FSE) or interleaved echo-planar imaging (EPI) methods, as potential tools for investing spinal cord abnormalities.
Materials And Methods:
Following recent improvements, both interleaved EPI (IEPI) and FSE techniques could be alternative approaches for rapid diffusion-weighted imaging (DWI). Therefore, a navigated diffusion-weighted multishot FSE sequence and a fat-suppressed navigated diffusion-weighted IEPI sequence with local shimming capabilities were tested. Both methods were compared in a consecutive series of five healthy volunteers and five patients with suspected intramedullary lesions. The sequences were graded qualitatively as either superior, inferior, or equal in quality, and also quantitatively by measuring the amount of ghosting artifacts in the background. Quantitative measurements of the diffusion coefficients within the spine were included.
Results:
The overall image quality of IEPI was superior to FSE. Two out of five FSE scans were rated with poor image quality, whereas all IEPI scans were of sufficient quality. The ghosting levels ranged from approximately 3.3% to 6.2% for IEPI and from approximately 7.5% to 18.9% for FSE. Diffusion coefficients measured in healthy volunteers were similar for both IEPI and FSE, but showed higher fluctuations with the FSE technique.
Conclusion:
Despite potential advantages of FSE, the IEPI technique is preferable for DWI applications in the spinal cord.