DICOM PS3.17 2019a - Explanatory Information
TTT.2.7.3.2 X-Ray 3D Angiographic Image IOD
TTT.2.7.3.2.1 Frame of Reference Module Recommendations

This module encodes the identifier for the spatial relationship, which will be the same for the volume and the projection image. The reconstruction application will assign the Frame of Reference UID to the reconstruction equal to the Frame of Reference UID of the Enhanced XA projection image.

TTT.2.7.3.2.2 Patient Orientation Module

This module encodes the patient position and orientation with respect to the table. It is supposed to contain the same values in the 3D volume and in the 2D static image.

TTT.2.7.3.2.3 Image - Equipment Coordinate Relationship Module

This module encodes the coordinate transformation matrix to allow the spatial registration of the volume with the Isocenter reference system of the angiographic equipment.

The reconstruction application defines the patient origin as an arbitrary point on the equipment. The 3D slices of the volume are all related to the patient coordinate system by the Attributes Image Position (Patient) (0020,0032) and Image Orientation (Patient) (0020,0037).

Image Position of the slice related to an application-defined patient coordinates

Figure TTT.2.7-4. Image Position of the slice related to an application-defined patient coordinates


The patient is related to the Isocenter by the Attribute Image to Equipment Mapping Matrix (0028,9520) which indicates the spatial transformation from the patient coordinates to the Isocenter coordinates. A point in the Patient Coordinate System (Bx, By, Bz) can be expressed in the Isocenter Coordinate System (Ax, Ay, Az) by applying the Image to Equipment Mapping Matrix as follows.

Transformation from patient coordinates to Isocenter coordinates

Figure TTT.2.7-5. Transformation from patient coordinates to Isocenter coordinates


The terms (Tx,Ty,Tz) of this matrix indicate the position of the patient origin (i.e., a fixed point on the table) in the Isocenter coordinate system.

Transformation of the patient coordinates relative to the Isocenter coordinates

Figure TTT.2.7-6. Transformation of the patient coordinates relative to the Isocenter coordinates


Table TTT.2.7-1. Image-Equipment Coordinate Relationship Module Recommendations

Attribute Name

Tag

Recommendation

Equipment Coordinate System Identification

(0028,9537)

The value will be ISOCENTER.


TTT.2.7.3.2.4 X-Ray 3D Angiographic Acquisition Module Recommendations

This module encodes the table position and angles used during the rotational acquisition to allow the spatial transformation of the volume points from the Isocenter coordinates to the table coordinates. See Section C.8.19.6.13.1 “Isocenter Reference System Attribute Description” in PS3.3 for further explanation about the spatial transformation from the Isocenter reference system to the table reference system.

As soon as the volume points are related to the table coordinate system, and assuming that the patient does not move on the table between the 2D acquisitions, the volume points can be projected on the image plane of any further projection acquisition even if the table has moved between the acquisitions. See Section C.8.19.6.13.1 “Isocenter Reference System Attribute Description” in PS3.3 for further explanation about the projection on the image plane of a point defined in the table coordinate system.

DICOM PS3.17 2019a - Explanatory Information