C.8.13.5.2 MR Timing and Related Parameters Macro
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##### C.8.13.5.2 MR Timing and Related Parameters Macro

Table C.8-89 specifies the attributes of the MR Timing and Related Parameters Functional Group Macro.

Table C.8-89. MR Timing and Related Parameters Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
MR Timing and Related Parameters Sequence | (0018,9112) | 1 | Identifies the timing and safety information of this frame. Only a single Item shall be included in this Sequence.
>Repetition Time | (0018,0080) | 1C | The time in ms between two successive excitations of the same volume. Shall be 0 (zero) if there is a single excitation per volume. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>Flip Angle | (0018,1314) | 1C | Steady state angle in degrees to which the magnetic vector is flipped from the magnetic vector of the primary field. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>Echo Train Length | (0018,0091) | 1C | Number of lines in k-space acquired per excitation of the same volume regardless of the type of echo or the number of frames derived from them. See Section C.8.13.5.2.1. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>RF Echo Train Length | (0018,9240) | 1C | Number of RF echoes collected per RF shot (or excitation) per frame. A value of zero shall correspond to a pure gradient echo frame. Note that this value corresponds to the current frame. Several frames may be derived from the same shot. See Section C.8.13.5.2.1. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>Gradient Echo Train Length | (0018,9241) | 1C | Number of gradient echoes collected per RF echo per shot (or excitation) per frame. A value of zero shall correspond to a pure RF echo frame. If RF Echo Train Length (0018,9240) is non zero and Gradient Echo Train Length is as well then only the central echo will be an RF Spin Echo, all others will be gradient echoes. See Section C.8.13.5.2.1. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>Specific Absorption Rate Sequence | (0018,9239) | 1C | Sequence containing the methods of SAR calculation and the corresponding values. One or more Items shall be included in this Sequence. Required if the system is capable of calculating Specific Absorption Rate (0018,9181).
>>Specific Absorption Rate Definition | (0018,9179) | 1 | Specification of the method of SAR calculation as defined in Applicable Safety Standard Description (0018,9174). Defined Terms: IEC_WHOLE_BODY IEC_PARTIAL_BODY IEC_HEAD IEC_LOCAL
>>Specific Absorption Rate Value | (0018,9181) | 1 | Specific Absorption Rate in W/kg.
>Gradient Output Type | (0018,9180) | 1C | Definition of gradient output unit, for which the value is stored in Gradient Output (0018,9182). Defined Terms: DB_DT in T/s ELECTRIC_FIELD in V/m PER_NERVE_STIM percentage of peripheral nerve stimulation Required if the system is capable of calculating Gradient Output (0018,9182).
>Gradient Output | (0018,9182) | 1C | Unit is defined by Gradient Output Type (0018,9180). Required if the system is capable of calculating Gradient Output (0018,9182).
>Operating Mode Sequence | (0018,9176) | 1C | Sequence of operating mode information relating to the frame/SOP instance as required to adhere to the Applicable Safety Standard Agency (0018,9174) regulations. One or more Items shall be included in this Sequence. Required if required by law or regulations. May be present otherwise.
>>Operating Mode Type | (0018,9177) | 1 | Defined Terms: STATIC FIELD RF GRADIENT
>>Operating Mode | (0018,9178) | 1 | Operating mode applicable for the defined by the applicable standard. Defined Terms: IEC_NORMAL IEC_FIRST_LEVEL IEC_SECOND_LEVEL

###### C.8.13.5.2.1 RF Echo Train Length and Gradient Echo Train Length Attributes Usage

The three Echo Train Length attributes all specify information related to the pulse sequence, one or more frames, and the echo type. The following examples illustrate their usage.

For a sequence with each excitation/shot producing 2 spin echoes that produce a line of k-Space for 2 different frames, the following values would be used for each frame:

Echo Train Length | 2
Gradient Echo Train Length | 0
RF Echo Train Length | 1

For a sequence with each excitation/shot producing 2 gradient echoes that produce a line of k-Space for 2 different frames, the following values would be used:

Echo Train Length | 2
Gradient Echo Train Length | 1
RF Echo Train Length | 0

For a sequence with each excitation/shot producing 8 spin echoes that produce 8 lines of k-Space for 1 frame, the following values would be used:

Echo Train Length | 8
Gradient Echo Train Length | 0
RF Echo Train Length | 8

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