Dimensions

MINC associates the dimensions of a medical image with standard textual names, such as ``xspace'' or ``time''. This association serves both to clarify the interpretation of each dimension and to specify the relationships among variables which share the same coordinate space. The length of a dimension is defined when the file is created.

NetCDF's model of a dimension is very simple, associated just a name, a numeric identifier, and a length with each dimension. To extend this model to represent the full set of attributes associated with a MINC dimension object, MINC relies on the concept of a ``dimension variable'', which is a variable with the same name as the corresponding dimension object.

While specialized applications can and occasionally do define additional dimensions, MINC defines the following standard dimension names:

• xspace - Spatial axis, defined to increase from patient left to patient right.
• yspace - Spatial axis, defined to increase from patient posterior to patient anterior.
• zspace - Spatial axis, defined to increase from patient inferior to patient superior.
• time - Time axis.
• xfrequency - Spatial frequency axis.
• yfrequency - Spatial frequency axis.
• zfrequency - Spatial frequency axis.
• tfrequency - Temporal frequency axis.
• vector_dimension - Axis used for components of a vector field. If present, this dimension should be the fastest-varying dimension of the image variable. Unlike the rest of the dimensions, this dimension is not associated with a dimension variable.