DICOM PS3.3 2021e - Information Object Definitions

C.36.12.2 Well-known Frame of Reference For Equipment

The following sections contain specifications of Well-known Frames of Reference used as the Equipment Frame of Reference.

C. IEC 61217 Fixed Reference System Frame of Reference

The Well-known Value of 1.2.840.10008. for Equipment Frame of Reference UID (300A,0675) defines the IEC 61217 Fixed Coordinate System Frame of Reference as follows:

  • The Equipment Coordinate System is the [IEC 61217] FIXED coordinate system.

  • The Base Beam Modifier Coordinate System for all beam modifiers is the [IEC 61217] GANTRY coordinate system. However, RT Radiation SOP Classes allow each Beam Modifier Coordinate System to rotate independently from the Base Beam Modifier Coordinate System.


  1. [IEC 61217] refers to the X-axis, Y-axis and Z-axis of the various coordinate systems. When referenced in this Standard the capital X/Y/Z is preserved which is not otherwise a DICOM convention.

  2. For the C-arm Photon-Electron Radiation IOD and the Tomotherapeutic Radiation IOD, the RT Beam Modifier Definition Distance (300A,0688) is the same as the Radiation Source-Axis Distance (300A,0640).

DICOM PS3.3 2021e - Information Object Definitions