# Dual-Polarity GRAPPA (DPG) demo

This collection of Matlab code and data presents one implementation of the method described in
"Dual-Polarity GRAPPA for simultaneous reconstruction and ghost correction of EPI data."
_Magn Reson Med_. 76(1):32-44, Jul 2016.
http://dx.doi.org/10.1002/mrm.25839


## Data source

EPI gradient-echo BOLD data

- 3T Siemens Trio
- 32 Channel Head coil
- TR 3sec
- TE 30msec
- Echo Spacing 770usec
- 2.0mm isotropic resolution

- 96x60   matrix size
- 192x120 (mm) FOV
- 32 slices, 2mm thick


collected on 2015-05-18, data file MID902

## Demo Filelist:

    data/dpg_acs1.nd     ACS data, with the first readout acquired using RO+
    data/dpg_acs2.nd     ACS data, with the first readout acquired using RO-
    data/dpg_C.nd        The PLACE ACS image, formed from a combination of dpg_acs1 and dpg_acs2
    
    data/dpg_k.nd        one frame of R=2 EPI data
    data/dpg_k_pcref.nd  navigator data for dpg_k, to perform traditional Nyquist ghost correction
    data/y.nd            NGC coefficients, derived from dpg_k_pcref and used with phzapply.m
    data/y_acs2.nd       NGC coefficients, derived from A and B and used with phzapply.m
    
    dpg_cal.m       the DPG calibration code
    dpg_recon.m     the DPG reconstruction code
    phzshift.m	    calculates the coordinate shift between two k-space data sets using SIEPCM
    phzapply.m      a script to apply standard Nyquist ghost correction coefficients
    fif.m           a 2D FFT macro script
    ifi.m           a 2D FFT macro script
    readnd.m        script to read the .nd data files
    
    runthis.m       the main demo script
    runthis2.m      an alternate demo script (w/o GESTE/PLACE acs data)