Cerebrovascular reactivity measurements using 3T BOLD MRI and a fixed inhaled CO2 gas challenge: Repeatability and impact of processing strategy oleh Emilie Sleight, Emilie Sleight, Michael S. Stringer, Michael S. Stringer, Isla Mitchell, Madeleine Murphy, Ian Marshall, Ian Marshall, Joanna M. Wardlaw, Joanna M. Wardlaw, Joanna M. Wardlaw, Michael J. Thrippleton, Michael J. Thrippleton, Michael J. Thrippleton