Gustav Andreisek MD, Presenter: Nothing to Disclose

Lawrence M. White MD, Abstract Co-Author: Nothing to Disclose

Andrea Kassner PhD, Abstract Co-Author: Nothing to Disclose

George Tomlinson, Abstract Co-Author: Nothing to Disclose

Marshall Stephen Sussman PhD, Abstract Co-Author: Nothing to Disclose

To systematically assess the optimal b-value for DTI and fiber tractography of the median nerve at 1.5T.

Prospective study which was carried out with institutional review board approval and written informed patient consent. Fifteen healthy volunteers (male, 7; female, 8; mean age, 31.2 years) underwent diffusion tensor imaging (DTI) of the wrist. A single-shot spin-echo-based echo-planar imaging sequence (TR/TE, 7000/103 ms) was performed in each subject at 8 different b-values ranging from 325 to 1550 s/mm2. Number and length of reconstructed fiber tracts, fiber density index (FDi), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were calculated for the median nerve. Signal-to-noise ratio (SNR) was also calculated for each acquisition. The overall image quality was assessed by two readers in consensus by ranking representative fiber tract images for each subject using a scale range from 1-8 (1=best to 8=worst image quality).

Longest fibers were observed for b-values between 500 and 1200 s/mm2. Maximum FDi was found at b-values of 1025 s/mm2. FA was between 0.5 and 0.6 for all b-values. ADC gradually decreased from 1.44 x 10–3 mm2/s to 0.92 x 10–3 mm2/s with increasing b-values. Maximum SNR (175.4 ± 72.6 (±SD)) was observed at the lowest b-value and decreased with increasing b-values. SNR at b-values of 1025 s/mm2 was 48.5% of the maximum SNR. Optimal fiber tract image quality was found for b-values of 1025 s/mm2.

The optimal b-value for DTI and fiber tractography of the median nerve at 1.5T was 1025 s/mm2.

Our results can help to optimize protocols for diffusion tensor imaging and fiber tractography of peripheral nerves at 1.5T.

Andreisek, G, White, L, Kassner, A, Tomlinson, G, Sussman, M, Diffusion Tensor Imaging and Fiber Tractography of the Median Nerve at 1.5 T: Optimization of b-Value.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6010897.html