What are the criteria to start Magnetic Resonance Angiography (MRA)?

From the Guidelines

Magnetic Resonance Angiography (MRA) should be initiated when non-invasive vascular imaging is needed to evaluate blood vessel abnormalities, particularly in patients with suspected vascular disorders, those requiring follow-up evaluation of known vascular disease, or those undergoing pre-surgical planning for vascular procedures. The primary criteria for starting MRA include:

• Suspected vascular disorders such as aneurysms, arteriovenous malformations, stenosis, or occlusions
• Follow-up evaluation of known vascular disease
• Pre-surgical planning for vascular procedures
• Screening in high-risk patients with family history of vascular conditions MRA is preferred when radiation exposure should be avoided, as it uses magnetic fields rather than ionizing radiation 1. Patients must be able to remain still during the procedure and should not have contraindications such as certain metallic implants, pacemakers, or severe claustrophobia. Prior to the procedure, patients should remove all metal objects, and those with impaired renal function may need assessment before receiving gadolinium contrast agents due to the risk of nephrogenic systemic fibrosis 1. The choice between contrast-enhanced and non-contrast MRA depends on the specific clinical question, with contrast generally providing better vessel visualization but carrying additional risks 1. MRA offers excellent soft tissue contrast and can provide detailed information about vessel walls and surrounding structures without the risks associated with catheter angiography. In patients with renal insufficiency, noncontrast MRA techniques may be used to evaluate suspected aortoiliac and femoropopliteal lesions 1. Overall, MRA is a valuable diagnostic tool for evaluating vascular disease, and its use should be guided by the specific clinical question and patient characteristics.

From the Research

Criteria to Start Magnetic Resonance Angiography (MRA)

The criteria to start MRA are not explicitly stated in the provided studies, but we can infer some guidelines based on the information given:

• MRA is used most often in the evaluation of renal arteries of patients with abdominal aortic aneurysms or allergies to iodinated contrast media, or when other noninvasive screening examinations have been inconclusive 2.
• MRA is helpful in patients who have accelerating hypertension and accelerating renal insufficiency, especially when conventional angiography is risky due to possible contrast nephropathy 2.
• The technique is widely accepted for the diagnosis of vascular disease, including arterial and venous diseases 3.
• MRA has a high level of accuracy in grading carotid artery stenosis and is routinely used in cerebral arterial occlusive diseases 3.
• Gadolinium-enhanced MRA has been shown to have high sensitivity and specificity for detecting renal artery stenosis, and may replace arteriography in most patients with suspected renal artery stenosis 4.

Indications for MRA

Some indications for MRA include:

• Detection of main renal artery stenosis
• Evaluation of renal arteries in patients with abdominal aortic aneurysms or allergies to iodinated contrast media
• Diagnosis of cerebral arterial occlusive diseases
• Detection of venous thrombosis of the cervical/mediastinal veins
• Assessment of collateral vessels in case of complete cervical/mediastinal venous thrombosis
• Detection of aneurysms, occlusions, and stenoses in various vascular territories 2, 3, 5.

Limitations of MRA

Some limitations of MRA include:

• Generally poorer resolution compared to conventional angiography
• Restrictions on the use of MRA in certain patients, such as those with claustrophobia or certain metal implants
• The need for corollary studies with standard MRI or CA methods in some cases
• The potential for overestimation of the degree of renal stenosis, which can be compensated for by performing phase contrast MRA 5, 6.