Effects of cardiac gating on fMRI of the human auditory system

摘要: Guimaraes et al. (1998) showed that sound-evoked fMRI activation in the auditory midbrain was significantly improved by a method which reduces image signal variability associated with cardiac-related brainstem motion. The method, cardiac gating, synchronizes acquisition to constant phase of cycle. Since study, several improvements have been made, and it is unclear whether gating still yields worthwhile benefits. present study re-evaluated effects for detecting current standards. In 11 experiments, we directly compared images acquired fixed repetition time (ungated) vs. those triggering (gated) oxygen saturation at fingertip (SpO2), an indirect measure activity. Three these experiments Sp 0 2 R-wave electrocardiogram (ECG). routinely detected all levels pathway from cochlear nucleus cortex. Compared ungated acquisitions, SpO2 reduced centers system increased magnitude inferior colliculus (p < 0.01) medial geniculate body 0.1). Simultaneous measurements ECG indicated peak followed approximately 400 ms, placing early motion-stable cycle during Sp02-gated experiments. This may account fact acquisitions always lower than ECG-gated acquisitions. That could be regularly without indicates not worth minimal experimental complexity entails. However, attempting responses sounds evoke small changes signal, especially or thalamus, when one interested individual rather group averages, prove extremely beneficial. Thesis Supervisor: Jennifer R. Melcher Associate Professor Otolaryngology, Harvard Medical School Louis D. Braida Henry Ellis Warren Electrical Engineering, MIT