CXT file format

The cxt file format is an ASCII format that mirrors the DICOM-RT structure set format. The command “plastimatch convert” converts from CXT to DICOM-RT structure set.

The cxt file format contains the following sections

Header section	Various flexible ascii fields
ROI section	List of ROI’s in the structure set, along with a fixed set of information on each
Contour section	List of contours, with a fixed set of information about each

The header section contains mostly information about the associated volume:

SERIES_CT_UID uid	The uid field specifies the UID for the associated CT volume
OFFSET x y z	The x y z fields specify the position of the first (upper left) voxel in the image
DIMENSION x y z	The x y z fields specify the size of the volume
SPACING x y z	The x y z fields specify the inter-voxel spacing

Each line of the ROI section contains three fields, separated by the ASCII space “ ”.

Field	Value	Example
Structure number	A positive integer	1
Color	RGB tuple, separated by backslashes	02550
Structure name	ASCII string	gtv_primary

Each line of the contour section has 6 fields, separated by the pipe symbol “|”.

Field	Description	Example
ROI Number	A postitive integer, referring to the structure	1
Contour thickness	This is included by GE dicom export. Not sure how useful it is	2.5
Number of points	How many points in the contour?	3
Slice index	Which slice does this contour belong to within the CT series of interest? The numbering start with 0 for the first slice sorted by Z.	20
Associated slice UID	Which slice does this contour belong to within the CT series of interest?	2.16.840.1.114362.1.90609.1196125535718.935
Points	Sequence of xyz tuples, separated by backslashes. Units are mm. z value should be the same for all of the points.	5.4-63.2108.4-66.2101.8-49.010