DICOM PS3.3 2019a - Information Object Definitions

C.8.4.12 NM Tomo Acquisition Module

This Module applies to a TOMO Multi-frame Image. This Module is present when Image Type (0008,0008) Value 3, is equal to TOMO, GATED TOMO, RECON TOMO, or RECON GATED TOMO. The elements found in this Module describe the acquisition of the Image.

Table C.8-12. NM Tomo Acquisition Module Attributes

Attribute Name



Attribute Description

Rotation Information Sequence



Sequence of Items that describe TOMO rotational groups. A new rotation is defined whenever the direction of the detector motion changes, or Table Traverse (0018,1131) changes.

Zero or more Items shall be included in this Sequence.

The number of Items shall be equal to Number of Rotations (0054,0051). If Rotation Vector (0054,0050) is present, the first Item corresponds to frames with value of 1 in Rotation Vector (0054,0050), the second Item with value 2, etc.

>Start Angle



Position of the detector about the patient for the start of this rotation, in degrees. Zero degrees is referenced to the origin at the patient's back. Viewing from the patient's feet, angle increases in a counter-clockwise direction (detector normal rotating from the patient's back towards the patient's left side).

>Angular Step



The angular scan arc step between views of the TOMO acquisition, in degrees. See Section C. for further explanation.

>Rotation Direction



Direction of rotation of the detector about the patient. See Start Angle (0054,0200) for further explanation of direction.

Enumerated Values:


clockwise (decreasing angle)


counter-clockwise (increasing angle).

>Scan Arc



The effective angular range of the scan data in degrees. The value shall be positive.

>Actual Frame Duration



Nominal acquisition time per angular position, in msec.

>Radial Position



Radial distance of the detector from the center of rotation, in mm. It shall have a single value that is an average value for this rotation, or it shall have one value per angular view.

>Distance Source to Detector



Distance in mm from transmission source to the detector face. Required if Image Type (0008,0008) Value 4 is TRANSMISSION.

>Number of Frames in Rotation



Number of angular views in this rotation.

>Table Traverse



Location of the patient table (or gantry relative to the table) in mm. The range and values of this element are determined by the manufacturer.

>Table Height



The distance in mm of the top of the patient table to the center of rotation. Table height below the center of rotation has a positive value.

Type of Detector Motion



Describes the detector motion during acquisition.

Enumerated Values:


Interrupted motion, acquire only while stationary


Gantry motion and acquisition are simultaneous and continuous


Interrupted motion, acquisition is continuous

C. NM Tomo Acquisition Attribute Descriptions
C. Angular Step

Angular Step (0018,1144) is the nominal frame-to-frame incremental angle for TOMO and GATED TOMO acquisition images, defined in degrees. Angular Step (0018,1144) shall be a positive number. Summation of Angular Step values is not defined to give accurate Angular Position or Scan Arc values. The Angular Step is the effective angular spacing between resultant frames of the Multi-framed planar image data.

DICOM PS3.3 2019a - Information Object Definitions