Michael M. Poplawski MD, PhD, Presenter: Nothing to Disclose

Richard Joseph Thomas Gorniak MD, Abstract Co-Author: Speaker, Koninklijke Philips NV

M. Alex Dresner PhD, Abstract Co-Author: Employee, Koninklijke Philips NV

Adam Eugene Flanders MD, Abstract Co-Author: Nothing to Disclose

ZOOM-EPI technique has been shown to provide subjectively superior MR diffusion image quality compared to full-field ssEPI (fEPI) in the cervical cord. However, it has not been shown if the diffusion tensor imaging (DTI) metrics are comparable for the two techniques. The study aim was to determine consistency of DTI values in normal human cervical spinal cord using ZOOM DTI.

Regions-of-interest were drawn at seven levels on axial DTI images from C1/2 to C7/T1 in 9 normal cervical cords acquired with fEPI and ZOOM on a Philips Achieva 1.5 T, with parameters (TR/TE/NSA/FOV/Matrix/slice#/slice(mm)/in plane(mm)): fEPI 6176/82/8/220x130mm/144x84/36/4mm/1.53x1.53mm, ZOOM 4950/95/4/110mm/96x96/32/4mm/1.15x1.15mm. Both sequences used 6 directions at b=800, and acquisition time of under 5 minutes. Mean fractional anisotropy (FA), apparent diffusion coefficient (ADC), and signal-to-noise (SNR) values were compared. These metrics were also compared in age-matched normal cords that were imaged with one DTI technique (fEPI, n=22), or the other (ZOOM, n=23) using two-way ANOVA, followed by Sidak’s test.

Measured cord ROI volumes were equivalent at all levels, despite disparate voxel size. In a paired comparison within same cords, FA was higher (p<0.01) in ZOOM v. fEPI at all cord levels, except C1/2, with the average FA difference of 0.1 (range of 0.09-0.11). The ZOOM FA was more consistent with published data. ADC was lower (p<0.01) using ZOOM at all cord levels, with the average difference of 0.23 x 10-³mm²/s (range of 0.16-0.32). The coefficient of variation was less for FA (p<0.01) and ADC (p=0.04) with ZOOM. SNR was similar (21.62±6.9 vs. 21.67±6.9, p=0.98) for both techniques. Group-wise comparisons of FA and ADC in cords imaged with either ZOOM or fEPI, showed equivalent results.

Within similar acquisition times, ZOOM provides more consistent estimates of FA and ADC in the cervical cord. This is attributed to a gain in resolution, less volume averaging from CSF, and diminished artifact. With superior image quality and more reliable DTI metrics, ZOOM is recommended over conventional ssEPI DTI for clinical applications in cervical spinal cord imaging.

Introduction of spinal cord DTI into clinical practice will depend on availability of a reliable and practical DTI sequence. In that respect, ZOOM-EPI DTI provides a clear advantage over ssEPI DTI.

Poplawski, M, Gorniak, R, Dresner, M, Flanders, A, Improved Reliability of Diffusion Tensor Imaging Utilizing Reduced Field-of-View ZOOM-EPI in Normal Human Cervical Spinal Cord.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003499.html