C.8.14.4 MR Spectroscopy Data Module

Table C.8-106 specifies the attributes that describe the Spectroscopy Data.

Table C.8-106MR SPECTROSCOPY DATA MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Rows (0028,0010) 1 Number of voxels in the vertical direction in the frame.
Columns (0028,0011) 1 Number of voxels in the horizontal direction in the frame.
Data Point Rows (0028,9001) 1 Number of rows of data points in spectroscopic data.
Data Point Columns (0028,9002) 1 Number of columns of data points in spectroscopic data.
Data Representation (0028,9108) 1 Data representation of the data points. Each data point shall have the same representation. Enumerated Values: COMPLEX = Data is complex pair REAL = Data contains only real component IMAGINARY = Data contains only imaginary component MAGNITUDE = Magnitude data
Signal Domain Columns (0028,9003) 1 Domain of represented signal in column direction. Enumerated Values: FREQUENCY TIME
Signal Domain Rows (0028,9235) 1C Domain of represented signal in row direction. Enumerated Values: FREQUENCY TIME Required if Data Point Rows (0028,9001) has a value of more than 1.
First Order Phase Correction Angle (5600,0010) 1C First Order Phase Correction Angle. Number of values is determined by Row ( Column ( Number of Frames. Required if First Order Phase Correction (0018,9198) equals YES
Spectroscopy Data (5600,0020) 1 A data stream of the signal intensities that comprise the spectroscopic data. See C.8.14.4.1 for further explanation.

C.8.14.4.1 Spectroscopy Data

The Spectroscopy Data attribute (5600,0020) contains the Signal intensities for the spectra. The order of voxels sent for each spectral plane is left to right, top to bottom, i.e., the upper left voxel (labeled 1,1) is sent first followed by the remainder of row 1, followed by the first voxel of row 2 (labeled 2,1) then the remainder of row 2 and so on. Each "voxel" represents an entire spectrum. The complete spectral data from each voxel is sent, followed by the spectral data from the next voxel position.

The number of voxels on each frame are described by Rows (0028,0010) and Columns (0028,0011). The number of frames is described by Number of Frames (0028,0008). The frames may represent different locations in a 3D acquisition, or the same position at a different point of time, or a difference of some other combination of attributes.

Note: Either Rows or Columns or both may have a value of 1 (e.g., for single voxel spectroscopy). A value of zero for the corresponding value of Pixel Spacing in the Pixel Measures Macro is permitted under these circumstances. See 10.7.1.3.

The spectral data points are ordered from high frequencies to low frequencies for a fixed static magnetic field strength, in the case that the Signal Domain Columns (0028,9003) or Signal Domain Rows (0028,9235) attributes contain the value FREQUENCY.

The spectral data points are ordered in sequence of increasing time in the case that the Signal Domain Columns (0028,9003) or Signal Domain Rows (0028,9235) attributes contain the value TIME.

The apparent rotation of magnetization in a quadrature representation shall be counterclockwise (from the (positive) real part to the (positive) imaginary part) for positive relative frequencies.

Note: When Complex time data points are transformed by a straightforward Fourier transformation to complex spectral data points, these are ordered from low frequency to high frequency.

For two-dimensional spectral acquisitions, the ordering is such that all data points from a row (corresponding to all data points acquired in an individual sampling period), are followed by all data points from the successive sampling period. Following all data of the rows from a given voxel position, the data from the subsequent voxel position are sent. The axis parallel to the row direction corresponds to the sampling time axis. The axis parallel to the column direction corresponds to the evolution time axis.

The dimensions of each spectrum that make up a voxel are described by Data Point Rows (0028,9001) and Data Point Columns (0028,9002). In the case of 1D spectra, the number of Data Point Rows shall be 1.

For a Data Representation (0028,9108) value of COMPLEX, the order of data points is real channel followed by imaginary channel for each spectral data point. For the other Data Representation values (REAL, IMAGINARY and MAGNITUDE), each spectral data point contains only a single value.

The Figure C.8-18 depicts 6 frames each made up of 4 rows and 4 columns of voxels. Specific values for Data Point Rows (0028,9001) and Data Point Columns (0028,9002) of these voxels are not depicted.

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Figure C.8-18Dimensions of spectroscopy data.