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C.8.13.5.14 MR Arterial Spin Labeling Macro (Current)
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##### C.8.13.5.14 MR Arterial Spin Labeling Macro

Table C.8-100b specifies the Attributes of the MR Arterial Spin Labeling Functional Group Macro.

Table C.8-100b. MR Arterial Spin Labeling Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
MR Arterial Spin Labeling Sequence | (0018,9251) | 1 | A Sequence that provides the position of Arterial Spin Labeling regions deposited as part of the pulse sequence. One or more Items shall be included in this Sequence.
>ASL Technique Description | (0018,9252) | 2 | Text describing the used labeling technique in more detail.
>ASL Context | (0018,9257) | 1C | The purpose of the Arterial Spin Labeling. Enumerated Values: LABEL CONTROL M_ZERO_SCAN Required if Frame Type (0008,9007) is ORIGINAL. May be present otherwise. See Section C.8.13.5.14.1 for further explanation.
>ASL Slab Sequence | (0018,9260) | 1C | Sequence describing the ASL Slab geometry and anatomical region. One or more Items shall be included in this Sequence. Required if ASL Context (0018,9257) is CONTROL or LABEL. May be present otherwise.
>>ASL Slab Number | (0018,9253) | 1 | Consecutive number identifying the different slabs used for labeling, starting with 1.
>>Include Table 10-7 “General Anatomy Optional Macro Attributes” | The anatomical region where the slab is positioned. Defined CID for the Anatomic Region Sequence (0008,2218) is CID 4030 “CT, MR and PET Anatomy Imaged”. Defined CID for Anatomic Region Modifier Sequence (0008,2220) and Primary Anatomic Structure Modifier Sequence (0008,2230) is CID 2 “Anatomic Modifier”.
>>ASL Slab Thickness | (0018,9254) | 1 | Thickness of slab in mm.
>>ASL Slab Orientation | (0018,9255) | 1 | The direction cosines of a normal vector perpendicular to the ASL slab with respect to the patient. See Section C.7.6.2.1.1 for further explanation.
>>ASL Mid Slab Position | (0018,9256) | 1 | The x, y, and z coordinates of the midpoint of the slab in mm with respect to the patient. See Section C.7.6.2.1.1 for further explanation.
>>ASL Pulse Train Duration | (0018,9258) | 1 | Duration (in milliseconds) of the Label or Control pulse. See Section C.8.13.5.14.3 for further explanation.
>ASL Crusher Flag | (0018,9259) | 1 | Indicates if an ASL Crusher Method has been used. Enumerated Values: YES NO See Section C.8.13.5.14.2 for further explanation.
>ASL Crusher Flow Limit | (0018,925A) | 1C | Maximum Flow Limit (in cm/s). Required if ASL Crusher Flag (0018,9259) is YES.
>ASL Crusher Description | (0018,925B) | 1C | Description of the ASL Crusher Method. Required if ASL Crusher Flag (0018,9259) is YES.
>ASL Bolus Cut-off Flag | (0018,925C) | 1 | Indicates if a Bolus Cut-off technique is used. Enumerated Values: YES NO
>ASL Bolus Cut-off Timing Sequence | (0018,925D) | 1C | Sequence that specifies the timing of the Bolus Cut-off technique and possibly its (scientific) description. Only a single Item shall be included in this Sequence. Required if ASL Bolus Cut-off Flag (0018,925C) is YES.
>>ASL Bolus Cut-off Delay Time | (0018,925F) | 1 | Bolus Cut-off pulse delay time (in ms). See Section C.8.13.5.14.3 for further explanation.
>>ASL Bolus Cut-off Technique | (0018,925E) | 2 | Text describing the cut-off technique.

###### C.8.13.5.14.1 ASL Context

The Attribute ASL Context (0018,9257) categorize the Original ASL images according to three contexts. This categorization allows post processing applications to select the correct type of image.

LABEL: Images are acquired with magnetically labeled arterial blood supply.

CONTROL: Images are acquired with a 'control' pulse in the proximal vessels.

M_ZERO_SCAN: Images are acquired with no label or control pulse in the proximal vessels.

###### C.8.13.5.14.2 ASL Crusher Flag

In order to quantify the perfusion accurately, it may be necessary to suppress signals within the macroscopic blood vessels (crushing). This can be used to separate the arterial input function from the brain parenchymal signal. The ASL Crusher Flag (0018,9259) indicates the application of an ASL crushing technique.

### Note

Frames with and without crushing may be present in one SOP Instance.

###### C.8.13.5.14.3 Relationship of ASL Timing Attributes

The general description of the ASL Acquisition technique requires a number of time related Attributes that are depicted in Figure C.8.13.5.14-1.

Figure C.8.13.5.14-1. Attributes for Quantitative ASL

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