University of Heidelberg
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Optimized Protocol for High Resolution Functional Magnetic Resonance Imaging at 3T using Single-Shot Echo Planar Imaging

S. Domsch, J. Zapp, L. Schad, F. Nees, H. Hill, D. Hermann, K. Mann and S. Vollstädt-Klein

J Neurosci Meth, 239, pp.170-182

Background: To translate highly accelerated EPI-fMRI protocols as commonly used at ultra-high field strengths to clinical 3 T settings. New method: EPI protocols with increasing matrix sizes and parallel imaging (PI) factors were tested in two separate fMRI studies, a simple motor-task and a complex motivation-task experiment with focus on the sensorimotor cortex (SMC) and the nucleus accumbens (NAcc), respectively. Results: By increasing the matrix size and the PI-factor simultaneously, BOLD-sensitivity in terms of maximal t-values and numbers of activated clusters was uncompromised in single individuals in both fMRI experiments. In the SMC, the multi-subject analysis revealed an increase of 66% of the maximal t-value whereby the number of activated clusters was increased by a factor of 3.3 when the matrix size (PI-factor) was increased from 96 x 96 (R = 2) to 192 x 192 (R = 4). In the NAcc, the number of activated clusters increased from 5 to 7 whereby the maximal t-value remained unaffected when the matrix size (PI-factor) was increased from 96 x 96 (R = 2) to 160 x 160 (R = 3). Comparison with existing method: Using the proposed high-resolution EPI protocol, spatial blurring was clearly reduced. Further, BOLD sensitivity was clearly improved in multi-subject analyses and remained unaffected in single individuals compared to using the standard protocols. Conclusions: Conventionally used matrix sizes (PI-factors) might be non-optimal for some applications sacrificing BOLD spatial specificity. We recommend using the proposed high-resolution protocols applicable in detecting robust BOLD activation in fMRI.

Contact: Dr. Frank Zöllner last modified: 21.09.2020
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