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Read metadata from NRRD file



info = nrrdinfo(filename) reads the metadata from the nearly raw raster data (NRRD) image file filename and returns the metadata structure info.


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Read the metadata from an NRRD format file. The file is part of a data set containing the 3-D CT and MRI scans from The Retrospective Image Registration Evaluation (RIRE) Dataset, converted to the NRRD file format. The original data set was provided by Dr. Michael Fitzpatrick. For more information, see the RIRE Project homepage. The size of the entire data set is approximately 35 MB. Download the data set from the MathWorks® website, then unzip the folder.

zipFile = matlab.internal.examples.downloadSupportFile("medical","");
filepath = fileparts(zipFile);

Specify the name of the NRRD file to read.

filename = fullfile(filepath,"supportfilesNRRD","Patient007CT.nrrd");

Read the metadata from filename.

info = nrrdinfo(filename);

The ImageSize metadata field contains the image volume size, in pixels.

ans = 1×3

   512   512    28

The PixelDimensions metadata field contains the voxel size in each dimension, in real world units such as millimeters.

ans = 1×3

    0.6536    0.6536    4.0000

The SpatialMapping metadata field contains an affinetform3d object that defines the transformation between the intrinsic and patient coordinate systems for the volume.

ans = 
  affinetform3d with properties:

    Dimensionality: 3
                 A: [4×4 double]

The RawAttributes metadata field contains the raw metadata extracted from the NRRD header information.

ans = struct with fields:
          dimension: '3'
              sizes: '512 512 28 '
               type: 'float'
           encoding: 'raw'
             endian: 'little'
     spacedimension: '3'
        spaceorigin: '(1.653595, 1.653595, 5.000000)'
    spacedirections: '(0.653595,0.000000,0.000000) (0.000000,0.653595,0.000000) (0.000000,0.000000,4.000000)'

Input Arguments

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Name of the NRRD file, specified as a string scalar or a character vector. The file must contain a valid NRRD file header. The nrrdinfo function supports NRRD files containing header and image data (.nrrd) as well as detached header files (.nhdr). Specify filenameas the absolute path to the file, a relative path from the current directory, or a relative path from a directory on the MATLAB® path.

Data Types: char | string

Output Arguments

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NRRD metadata, returned as a structure.

Version History

Introduced in R2022b

See Also