Using only imaging data from an fMRI time series carotid cardiac cycle information may be automatically extracted. By merging data across slices "faster than TR" sampling is achieved. The resulting time series agree with pulse oximetry (PO) data. The distribution of relative peak times between PO and fMRI has standard deviation of around 40ms. The fMRI data was quite reliable with cardiac signal observed for all but two of approximately 3000 seconds; PO data was much less reliable.