DICOM PS3.3 2019a - Information Object Definitions

C.7.6.21 Image - Equipment Coordinate Relationship Module

This section describes the Image - Equipment Coordinate Relationship Module. Table C.7.6.21-1 contains the Attributes that specify how the equipment (e.g., gantry) and patient oriented coordinate system (in conjunction with Image Position (Patient) (0020,0032) and Image Orientation (Patient) (0020,0037) Attributes) are related.

Table C.7.6.21-1. Image - Equipment Coordinate Relationship Module Attributes

Attribute Name



Attribute Description

Image to Equipment Mapping Matrix



A 4x4 rigid transformation matrix that maps patient coordinate space of the reconstructed image to the equipment defined original coordinate space. Matrix elements shall be listed in row-major order. See Section C.

Equipment Coordinate System Identification



Identification of the type of equipment coordinate system in which the projection images were acquired. See Section C.

Defined Terms:


C. Image to Equipment Mapping Matrix

The Image to Equipment Mapping Matrix (0028,9520) is used to describe the relationship between the patient oriented coordinate system and a modality specific equipment coordinate system. This mapping can only be used with systems that have a well-defined equipment coordinate system (such as XA, etc.).

The Image to Equipment Mapping Matrix AMB describes how to transform a point (Bx,By,Bz) with respect to the Patient-Based Coordinate System into (Ax,Ay,Az) with respect to the equipment coordinate system according to the equation below.

Equation C. 

The Image to Equipment Mapping Matrix is a rigid transformation that involves only translations and rotations. Mathematically, the matrix shall be orthonormal and can describe six degrees of freedom: three translations, and three rotations.


Both the Patient-Based Coordinate System and the Equipment-Based Coordinate System are expressed in millimeters.

DICOM PS3.3 2019a - Information Object Definitions