DESCRIPTION:

Most eccet renderers expect at least a grey/norm field to be
present in the dataset. To add segmentation information to the
field a classfield needs to be allocated. To speed up rendering,
many renderers require a depth field.

However, there is more to a volume than just the datafields.
Volumes also carry associated metadata that can e.g. be used
to determine the physical sizes of the volume, determine the
meaning of grey values (e.g. HU mapping) or carry other information
related to the dataset (like the patient's name).