Gary H. Glover1, Catherine E. Chang1
The susceptibility difference between air and tissue induces intravoxel dephasing that causes signal dropout in BOLD fMRI. Thin slices can mitigate some of this loss but at a severe SNR efficiency penalty that is only partially offset by summing adjacent slices together. We propose a method that uses Hadamard encoding of two thin subslices per slice subsequently combined incoherently with UNFOLD to recover signal at no loss of SNR in uniform regions. Results using 2 2mm subslices and a hypercapnic challenge demonstrate a 10% increase in activation volume in frontal-orbital regions when compared with conventional 4 mm slice acquisitions.