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Q‐space truncation and sampling in diffusion spectrum imaging
Author(s) -
Tian Qiyuan,
Rokem Ariel,
Folkerth Rebecca D.,
Nummenmaa Aapo,
Fan Qiuyun,
Edlow Brian L.,
McNab Jennifer A.
Publication year - 2016
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26071
Subject(s) - truncation (statistics) , ringing , sampling (signal processing) , displacement (psychology) , orientation (vector space) , probability density function , artifact (error) , mathematics , physics , nuclear magnetic resonance , computer science , statistics , geometry , artificial intelligence , optics , detector , enhanced data rates for gsm evolution , psychology , psychotherapist
Purpose To characterize the q‐space truncation and sampling on the spin‐displacement probability density function (PDF) in diffusion spectrum imaging (DSI). Methods DSI data were acquired using the MGH‐USC connectome scanner ( G max = 300 mT/m) with b max = 30,000 s/mm 2 , 17 × 17 × 17, 15 × 15 × 15 and 11 × 11 × 11 grids in ex vivo human brains and b max = 10,000 s/mm 2 , 11 × 11 × 11 grid in vivo. An additional in vivo scan using b max =7,000 s/mm 2 , 11 × 11 × 11 grid was performed with a derated gradient strength of 40 mT/m. PDFs and orientation distribution functions (ODFs) were reconstructed with different q‐space filtering and PDF integration lengths, and from down‐sampled data by factors of two and three. Results Both ex vivo and in vivo data showed Gibbs ringing in PDFs, which becomes the main source of artifact in the subsequently reconstructed ODFs. For down‐sampled data, PDFs interfere with the first replicas or their ringing, leading to obscured orientations in ODFs. Conclusion The minimum required q‐space sampling density corresponds to a field‐of‐view approximately equal to twice the mean displacement distance (MDD) of the tissue. The 11 × 11 × 11 grid is suitable for both ex vivo and in vivo DSI experiments. To minimize the effects of Gibbs ringing, ODFs should be reconstructed from unfiltered q‐space data with the integration length over the PDF constrained to around the MDD. Magn Reson Med 76:1750–1763, 2016. © 2016 International Society for Magnetic Resonance in Medicine