Optimal echo time for functional MRI of the infant brain identified in response to noxious stimulation

Authors


Abstract

Purpose

Blood oxygen level dependent (BOLD) brain activity, measured using functional MRI (fMRI), is dependent on the echo time (TE) and the reversible spin–spin relaxation time constant ( math formula) that describes the decay of transverse magnetization. Use of the optimal TE during fMRI experiments allows maximal sensitivity to BOLD to be achieved. Reports that math formula values are longer in infants (due to higher water concentrations and lower lipid content) have led to the use of longer TEs during infant fMRI experiments; however, the optimal TE has not been established.

Methods

In this study, acute experimental mildly noxious stimuli were applied to the heel in 12 term infants (mean gestational age = 40 weeks, mean postnatal age = 3 days); and the percentage change in BOLD activity was calculated across a range of TEs, from 30 to 70 ms, at 3 Tesla. In addition, math formula maps of the whole brain were collected in seven infants.

Results

The maximal change in BOLD occurred at a TE of 52 ms, and the average math formula across the whole brain was 99 ms.

Conclusion

A TE of approximately 50 ms is recommended for use in 3T fMRI investigations in term infants. Magn Reson Med, 2016. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

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