Table C.8-100 specifies the attributes of the MR Velocity Encoding Functional Group macro. This Functional Group contains the velocity encoding values as valid for the reconstructed Images, rather than for their acquisition. The velocity encoding directions for acquisition are described in the Velocity Encoding Acquisition Sequence (0018,9092) defined in the MR Pulse Sequence Module Section C.8.13.4.
Table C.8-100MR VELOCITY ENCODING MACRO ATTRIBUTES
|Attribute Name||Tag||Type||Attribute Description|
|MR Velocity Encoding Sequence||(0018,9197)||1||Identifies the velocity encoding of this frame. One or more Items shall be included in this sequence.|
|>Velocity Encoding Direction||(0018,9090)||1C||The direction cosines of the velocity encoding vector with respect to the patient. See C.220.127.116.11.1 and C.18.104.22.168.1 for further explanation. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.|
|>Velocity Encoding Minimum Value||(0018,9091)||1C||Minimum velocity in cm/s. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.|
|>Velocity Encoding Maximum Value||(0018,9217)||1C||Maximum velocity in cm/s. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.|
The direction of the flow in a flow image is defined by the direction of the relevant flow vector in the MR Velocity Encoding Sequence (0018, 9197).
The actual flow value (as specified in the Real World Value Mapping Sequence (0040,9096)) has a positive sign when the flow direction coincides with the Velocity Encoding Direction (0018,9090) vector.