Compensation of Non-T1-Related Artifacts in Variable TR FMRI at 1.5T

¹School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA; ²Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA; ³National Institute of Mental Health, Bethesda, MD, USA

The objective of this study is to assess signal fluctuations induced by non-T1-related confounds in variable repetition time fMRI and to develop a compensation procedure. Dummy acquisitions (gradient readout sequences with radio-frequency excitation disabled) were effected at variable offsets between actual acquisitions, allowing the study of non-T1-related confounds such as eddy currents and gradient coil heating that may arise in variable TR experiments. Three imaging sessions utilizing a phantom were conducted to assess the signal fluctuations, which were modeled as a second order system. A modified projection procedure was successfully implemented to correct for signal fluctuations arising from non-T1-related confounds.