Cerebral and carotid MRA describes magnetic resonance imaging studies that demonstrate the cervical and cranial vasculature (arterial and/or venous systems).
There are several magnetic resonance imaging angiographic (MRA) techniques. They can broadly be divided into techniques where protons in blood are made to appear low signal- known as ‘dark blood’ techniques- or techniques resulting in blood appearing high signal – known as ‘bright blood’ techniques. This latter ‘bright blood’ group is the most commonly used in cerebral MRA, and include non-contrast techniques (most commonly time-of flight [TOF]) or contrast-enhanced techniques, which use Gadolinium-based contrast administered intravenously.
Administration of IV contrast affords the best resolution of the deep cerebral venous system and carotid/vertebrobasilar arterial systems with less flow artefacts, accounting for this technique most commonly being used for these indications. Non-contrast TOF cerebral MRA offers very good spatial resolution of the intracranial arterial tree, with IV contrast less commonly required to improve diagnostic specificity in selected cases.
Intracranially, thin-section images are acquired in the axial plane and MIP reformatting summates the images to allow panoramic 3D multiplanar vessel visualization. Multiplanar reformatting is also possible in imaging of the carotid/vertebrobasilar arterial tree.
A suggested stroke workup protocol1 includes a non-contrast MRI brain, TOF cerebral MRA and a contrast-enhanced carotid MRA.
Northcoast MRI provides cerebral and carotid angiography including cerebral venography using a state-of-the-art 1.5T machine. Angiographic studies are performed in 15-20 minutes and when included with standard brain imaging may usually take a total of about 35 minutes.
|1. Aneurysms||1. Diagnosing abnormalities of vertebrobasilar system|
|2. Vascular malformations e.g. arteriovenous malformations (AVMs), dural arterial venous fistula (dAVF)||2. Abnormal carotid Doppler ultrasound, bruit on examination|
|3. Symptoms of occlusion/stenosis e.g. TIAs, CVA||3. Suspected cervicocranial dissection|
|4. Suspected vasculitis||4. Suspected vasculitis (e.g. giant cell arteritis)|
LIMITATIONS OF PROCEDURE
- Ability to breath-hold, remain relatively still during examination
- Morbid obesity, claustrophobia, MRI unsafe devices
- Contrast safety issues: allergic reaction (very rare; 0.004 – 0.7%), risk of nephrogenic systemic fibrosis in patients with renal failure or impairment (GFR <60ml/min).
At 1.5T, MRA is suitable and performs as well as or better than many other non-invasive imaging modalities:
- For all indications related to cervicocranial vascular pathology
- Without radiation
- Oftentimes without IV contrast
REFERENCES 1. Expert Panel on Neurologic Imaging:, Salmela MB, Mortazavi S, Jagadeesan BD, Broderick DF, Burns J, Deshmukh TK, Harvey HB, Hoang J, Hunt CH, Kennedy TA, Khalessi AA, Mack W, Patel ND, Perlmutter JS, Policeni B, Schroeder JW, Setzen G, Whitehead MT, Cornelius RS, Corey AS. ACR Appropriateness Criteria (®) Cerebrovascular Disease. J Am Coll Radiol. 2017 May;14(5S):S34-S61. Last accessed April 18, 2018. 2. van Zwam WH, Hofman PAM, Kessels AG, Oei TK, Heijboer RJ, Wilmink JT. Diagnostic performance of contrast enhanced magnetic resonance angiography in detecting intracranial aneurysms in patients presenting with subarachnoid haemorrhage. EJMINT. October 4, 2012. 3. Sailer AM, Wagemans BA, Nelemans PJ, de Graaf R, van Zwam WH. Diagnosing intracranial aneurysms with MR angiography: systematic review and meta-analysis. Stroke. 2014 Jan;45(1):119-26 4. Gamal et al: Diagnostic accuracy of contrast enhancement MRI versus CTA in diagnosis of intracranial aneurysm in patients with non-traumatic subarachnoid hemorrhage. The Egyptian Journal of Radiology and Nuclear Medicine. Volume 46, Issue 1, March 2015, Pages 125-130. Last accessed: April 18, 2018. 5. Fig 6++ Source: http://4.bp.blogspot.com/-XnhCTLX4MuA/UIQv_H_l2kI/AAAAAAAACxY/LbL_EM-xLUE/s1600/MRA%20dissection%20combo%201.jpg