Table C.8-100b specifies the Attributes of the MR Arterial Spin Labeling Macro.
Table C.8-100b. MR Arterial Spin Labeling Macro Attributes
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A Sequence that provides the position of Arterial Spin Labeling regions deposited as part of the pulse sequence. |
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The purpose of the Arterial Spin Labeling. Required if Frame Type (0008,9007) is ORIGINAL. May be present otherwise. See Section C.8.13.5.14.1 for further explanation. |
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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. |
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Consecutive number identifying the different slabs used for labeling, starting with 1. |
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>>Include Table 10-7 “General Anatomy Optional Macro Attributes” |
The anatomical region where the slab is positioned. Anatomic Region Sequence (0008,2218) DCID 4030 “CT, MR and PET Anatomy Imaged”. Anatomic Region Modifier Sequence (0008,2220) and Primary Anatomic Structure Modifier Sequence (0008,2230) DCID 2 “Anatomic Modifier”. |
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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. |
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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. |
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Duration (in milliseconds) of the Label or Control pulse. See Section C.8.13.5.14.3 for further explanation. |
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Indicates if an ASL Crusher Method has been used. See Section C.8.13.5.14.2 for further explanation. |
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Description of the ASL Crusher Method. Required if ASL Crusher Flag (0018,9259) is YES. |
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Sequence that specifies the timing of the Bolus Cut-off technique and possibly its (scientific) description. |
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Bolus Cut-off pulse delay time (in ms). See Section C.8.13.5.14.3 for further explanation. |
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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.
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.
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.
