Return to Source Localization - SAM
The sam_hfo program is an experimental program which may aid in the localization of epileptiform activity. This program first bandpass filters the data to visualize high frequency activity only (typically above 150Hz). For each voxel in the image, a time-series is computed and a Hilbert envelope is applied to the source. Excess kurtosis of the Hilbert envelope is used to localize potential events, such as short bursts of high frequency oscillations (HFOs). Before running sam_hfom epoched data must be saved in a continuous format.
sam_hfo -r <dataset_name> -m <parameter_file_name> [options]
The -r flag designates the dataset name (with or without the .ds suffix), and -m designates the parameter file name.
-v Verbose mode, without this flag sam_wts works silently except for error messages
CovBand: Bandwidth used for covariance matrix calculation ImageBand: Bandwidth used for covariance matrix calculation SmoothBand: designates the lowpass filter for smoothing the Hilbert envelope CovType: Must be GLOBAL ImageMetric: Must be KURTOSIS
FilterType: choose the applied filter, IIR vs. FFT ImageDirectory: Directory where the output images are written, default is the SAM directory PrefixLength: Number of characters in the MEG dataset name used for naming MRI files
sam_hfo Creates a single 3D NIFTI format image of kurtosis (g2) of the Hilbert envelope of high frequency activity. The output file will be named using the PrefixLength parameter, and will be appended with "HFO."