MRI Brain Angiography (MRA Brain) - Planning & Protocol

What is MRA Brain?

MRA (Magnetic Resonance Angiography) of the brain is used to assess abnormalities in the arterial blood supply of the brain. The most commonly used method is 3D Time-of-Flight (TOF) MRA, which does NOT require contrast injection and provides excellent visualization of the Circle of Willis.

Indications

Intracranial aneurysm (detection/follow-up)
Arteriovenous malformations (AVM)
Ischemic stroke / TIA
Arterial stenosis or occlusion
Moyamoya disease
Thunderclap headache (vascular cause suspected)
Dural sinus thrombosis (MRV)

Sequences in MRA Brain Protocol

1. Three-Plane Localizer (Scout)

Run first - takes < 25 seconds
T1-weighted, low-resolution
Used to localize anatomy and plan all subsequent sequences

2. T2 TSE Axial (Morphological Brain Sequence)

Planning:

Plan on the sagittal plane
Angle the block parallel to the genu and splenium of the corpus callosum
Check in coronal plane: perpendicular to the 3rd ventricle and brainstem
Coverage: vertex to foramen magnum (entire brain)

3. 3D TOF (Time-of-Flight) - The KEY MRA Sequence

Principle:

T1-weighted gradient echo sequence
Uses flow-related enhancement: flowing blood entering the slab gives bright signal; stationary tissue is saturated and suppressed
Short TR deliberately saturates background tissue while incoming "fresh" blood remains bright
No contrast needed

Planning Steps:

Step	Action
Plane	Plan the axial 3D block on the sagittal localizer
Angulation	Angle the block parallel to the genu and splenium of the corpus callosum
Coverage	From 1 cm above the corpus callosum down to the foramen magnum - must cover the entire Circle of Willis
Coronal check	Ensure block is perpendicular to the 3rd ventricle and brainstem
Saturation band	Place a superior saturation band on top of the axial block to suppress venous inflow (preventing contamination from draining veins)
Multi-slab	Can use multi-slab acquisition to cover a larger volume while maintaining SNR

4. Typical Scan Parameters (3D TOF)

Parameter	Value
TR	30-40 ms
TE	5-9 ms
Flip angle	25°
NEX	1
Slice thickness	0.7 mm
Matrix	256 x 256
FOV	250 mm
Phase direction	R > L
Gap	33%
MTC (Magnetization Transfer Contrast)	Yes

5. Post-Processing: Maximum Intensity Projection (MIP)

After acquiring the 3D TOF volume, MIP reconstructions are generated
MIP projects the brightest voxels along any viewing direction
Creates angiogram-like images of the Circle of Willis
Rotate in multiple planes (axial, coronal, oblique) for complete vascular assessment

Sequence Order Summary

Localizer 3-plane (scout)
T2 TSE Axial (brain morphology)
TOF 3D Axial Multi-Slab (MRA - Circle of Willis)

Important Tips

No contrast needed for standard TOF MRA (non-contrast technique)
Contrast-enhanced MRA (CE-MRA) uses a fast 3D gradient echo (FLASH/SPGR) with gadolinium - used for follow-up after aneurysm coiling or when TOF is suboptimal
Saturation bands are essential to suppress venous signal - place SUPERIOR to the slab
On Siemens scanners: avoid excessive angulation of the slab to prevent signal loss or flow artifacts - keep the slab as straight (no tilt) as possible
MRA brain is combined with MRA neck for full vascular workup in stroke patients
MRV (MR Venography) uses 2D TOF in oblique sagittal + phase contrast sequences

Circle of Willis Coverage (Key Anatomy)

The planning must include all major intracranial arteries:

Internal carotid arteries (ICA) and their branches
Middle cerebral arteries (MCA) - M1, M2
Anterior cerebral arteries (ACA) - A1, A2
Posterior communicating arteries (PComm)
Basilar artery
Posterior cerebral arteries (PCA)
Vertebral arteries (intracranial)

Sources: MRIMaster - MRA Brain Protocol | Radiopaedia - TOF Angiography | Bradley and Daroff's Neurology in Clinical Practice

Image

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Analyze MRI/MRA brain scans
Identify planning landmarks (corpus callosum, Circle of Willis, etc.)
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Create a reference poster of MRA brain planning landmarks

Generating Image

A professional medical reference poster titled "MRA Brain Planning Landmarks" for MRI technologists. The poster shows two main diagrams side by side: LEFT SIDE - Sagittal brain MRI diagram (clean anatomical illustration) with labeled arrows pointing to: - Genu of corpus callosum (front) - Splenium of corpus callosum (back) - A horizontal planning line drawn parallel to the genu-splenium axis - 3D TOF slab block shown as a shaded rectangle covering from "1 cm above corpus callosum" down to "Foramen magnum" - Superior saturation band shown as a striped band above the slab - Label: "Coverage: Circle of Willis" RIGHT SIDE - Axial brain diagram (top-down view) showing the Circle of Willis with labeled vessels: - Internal Carotid Artery (ICA) - bilateral - Middle Cerebral Artery (MCA) - bilateral - Anterior Cerebral Artery (ACA) - bilateral - Anterior Communicating Artery (AComm) - Posterior Communicating Artery (PComm) - bilateral - Posterior Cerebral Artery (PCA) - bilateral - Basilar Artery - Vertebral Arteries - bilateral BOTTOM SECTION - A clean parameter table: "3D TOF Key Parameters: TR 30-40ms | TE 5-9ms | Flip Angle 25° | Slice 0.7mm | FOV 250mm | Matrix 256x256" BOTTOM RIGHT - Small inset box: "Saturation Band: Place SUPERIOR to slab (suppresses venous signal)" Color scheme: Dark navy blue background, white and cyan text, bright yellow annotation arrows, light blue anatomical structures. Clean, professional radiology department style. Medical poster layout.

Here is your MRA Brain Planning Landmarks reference poster. It includes:

Sagittal planning diagram - showing the 3D TOF slab positioned parallel to the genu-splenium of the corpus callosum, with the superior saturation band
Circle of Willis axial diagram - all major vessels labeled (ICA, MCA, ACA, AComm, PComm, PCA, Basilar, Vertebrals)
Key scan parameters - TR, TE, Flip angle, Slice thickness, FOV, Matrix
Saturation band reminder - placement tip to suppress venous contamination

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