svkEPSIPhaseCorrect Class Reference

#include <svkEPSIPhaseCorrect.h>

Inheritance diagram for svkEPSIPhaseCorrect:

Public Member Functions
	vtkTypeMacro (svkEPSIPhaseCorrect, svkImageInPlaceFilter)
void	SetNumEPSIkRead (int numKspaceSamples)
void	SetEPSIAxis (int epsiAxis)
void	SetEPSIOrigin (float epsiOrigin)
float	GetEPSIOrigin ()
Public Member Functions inherited from svkImageInPlaceFilter
	vtkTypeMacro (svkImageInPlaceFilter, vtkImageInPlaceFilter)
svkImageData *	GetOutput ()
svkImageData *	GetOutput (int port)
svkImageData *	GetImageDataInput (int port)

Static Public Member Functions
static svkEPSIPhaseCorrect *	New ()

Protected Member Functions
	svkEPSIPhaseCorrect ()
	~svkEPSIPhaseCorrect ()
virtual int	FillInputPortInformation (int port, vtkInformation *info)
virtual int	RequestData (vtkInformation *request, vtkInformationVector **inputVector, vtkInformationVector *outputVector)
Protected Member Functions inherited from svkImageInPlaceFilter
	svkImageInPlaceFilter ()
	~svkImageInPlaceFilter ()
virtual int	FillOutputPortInformation (int vtkNotUsed(port), vtkInformation *info)
virtual int	FillInputPortInformation (int vtkNotUsed(port), vtkInformation *info)

Detailed Description

This class corrects for the time shift of spectra in the EPSI direction that results from the EPSI sampling trajectory. For each TR, the spectra from neighboring K space values along the EPSI k-space axis are displaced in time relative to one another by Dt (time between EPSI samples). This time-domain shift is corrected here via the Fourier shift theorem, by applying a linear phase shift to the spectra in the frequency domain, where the magnitude of the phase shift is a linear functino of the distance of the spectrum from the origin of k-space (in EPSI direction). Spectra are then inverse FT'd back to the time domain resulting in a rectilinear spectral/spatial data set (see Figure 3 and equation 3 in the following reference).

References: Charles H. Cunningham, Daniel B. Vigneron, Albert P. Chen, Duan Xu, Sarah J. Nelson, Ralph E. Hurd, Douglas A. Kelley, John M. Pauly: "Design of Flyback Echo-Planar Readout Gradients for Magnetic Resonance Spectroscopic Imaging", Magnetic Resonance in Medicine 54:1286-1289 (2005).

Constructor & Destructor Documentation

svkEPSIPhaseCorrect ( )

protected

Constructor. Initialize any member variables.

~svkEPSIPhaseCorrect ( )

protected

Clean up any allocated member variables.

Member Function Documentation

int FillInputPortInformation ( int  port, vtkInformation *  info  )

protectedvirtual

Set the input data type, e.g. svkMrsImageData for an MRS algorithm.

float GetEPSIOrigin

(

)

Get the origin index along the EPSI encoding axis default = (numEPSIkRead-1)/2. This is the c-lang index, thus the -1, e.g.: if numEPSIkRead is 8, and data index varies from 0-7, the default origin index is 3.5. However, should depend on whether k=0 was sampled or not. If not, (default, then origin is .5 higher.

static svkEPSIPhaseCorrect* New ( )

static

int RequestData ( vtkInformation *  request, vtkInformationVector **  inputVector, vtkInformationVector *  outputVector  )

protectedvirtual

This method is called during pipeline execution. Calculates the 2D array of linear phase correction factors, which are a function of the epsi k-space index, as well as the spectral index. Applies these to all spectra in data set to generate a rectilinear spectral/spatial (k-space, time-domain) data set.

References svkDcmHeader::COL_INDEX, svkMrsImageFFT::FORWARD, svkImageData::GetDcmHeader(), svkDcmHeader::GetDimensionIndexVector(), svkDcmHeader::GetDimensionVectorIndexFromCellID(), svkDcmHeader::GetDimensionVectorValue(), svkImageInPlaceFilter::GetImageDataInput(), svkDcmHeader::GetIntValue(), svkDcmHeader::GetNumberOfCells(), svkMrsImageData::GetSpectrum(), svkMrsImageFFT::REVERSE, svkDcmHeader::ROW_INDEX, and svkDcmHeader::SLICE_INDEX.

void SetEPSIAxis

(

int

epsiAxis

)

Set the axis index corresponding to the EPSI encoding (0,1 or 2).

void SetEPSIOrigin

(

float

epsiOrigin

)

Set the origin index along the EPSI encoding axis default = (numEPSIkRead-1)/2. See notes for GetEPSIOrigin.

void SetNumEPSIkRead

(

int

numKspacePoints

)

Set the number of k-space samples along the EPSI encoding direction (number of samples per lobe). This is the number of samples per echo in the EPSI acquisition trajetory (not necessarily the final k-space dimensionality).

vtkTypeMacro	(	svkEPSIPhaseCorrect	,
		svkImageInPlaceFilter
	)

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The documentation for this class was generated from the following files:

• svkEPSIPhaseCorrect.h
• svkEPSIPhaseCorrect.cc