Computed tomographic angiography (CTA) uses a computerized analysis of x-ray images (enhanced by contrast material injected into a peripheral vein) to visualize the blood flow in arterial and venous structures throughout the body. Magnetic resonance angiography (MRA) uses magnetic resonance imaging (MRI) technology to detect, diagnose, and aid in the treatment of disorders affecting blood vessels. This document addresses the use of CTA and MRA for the evaluation and imaging of vessels in the head and neck.

Note: Please see the following documents for additional information:

• CG-RAD-09 CTA/MRA of the Thoracic Cavity, Abdomen and Extremities
• CG-RAD-14 CT/MRI of the Spine (Cervical, Thoracic, Lumbar)
• RAD.00035 Coronary Artery Imaging: Contrast-Enhanced Coronary Computed Tomography Angiography (CCTA) and Coronary Magnetic Resonance Angiography (MRA)
• RAD.00055 MR Angiography (MRA) of the Spinal Canal

CTA or MRA Neck 

Medically Necessary:

CTA or MRA neck is considered medically necessary for any of the following:

I.  Aneurysm and Arteriovenous Malformation

II. Suspected Stenosis or Occlusion of either of the following:

• Extracranial cerebral arteries causing transient ischemic attack (TIA) and cerebral vascular accident (CVA) when other imaging does not provide adequate information and the results may alter patient management; or
• Vertebrobasilar arteries in patients with symptoms highly suggestive of vertebrobasilar syndrome (binocular vision loss, [positional] vertigo, dysarthria, diplopia) when the results may alter patient management. 

III. Other Vascular Conditions

• Dissection; or
• Intramural hematoma; or
• Suspected thrombosis (venous or arterial) of the major vessels; or
• Vasculopathy, including fibromuscular dysplasia; or
• Postoperative evaluation of carotid endarterectomy associated with new signs or symptoms. 

IV. Evaluation of Tumors

• Preoperative evaluation of blood supply to tumors, such as carotid artery (e.g., glomus tumor)

Not Medically Necessary:

CTA or MRA neck is considered not medically necessary for any of the following:

• Routine screening for aneurysms when there is a family history or associated hereditary disorder (e. g., polycystic kidney disease, Ehlers-Danlos syndrome type IV or neurofibromatosis); or
• Routine screening for other conditions; or
• When the above criteria are not met.

CTA or MRA Head 

Medically Necessary:

CTA or MRA head is considered medically necessary for any of the following:

I. Aneurysm and Arteriovenous Malformation

• Subarachnoid, subdural, intracerebral hemorrhage secondary to trauma or cerebral aneurysm, or arteriovenous malformation (AVM) (symptoms include recent onset of severe unexplained headache, alteration in cognitive status, or other focal neurological defect [e.g., loss of vision]), to determine the site of bleeding; or
• Preoperative surgical planning of the resection of AVMs or aneurysms when the results may alter patient management; or
• Pre-procedure planning prior to percutaneous vascular intervention for aneurysms or AVMs; or
• Follow-up for:
  • Known AVM; or
  • Known non-ruptured intracranial aneurysm. 

II. Suspected Stenosis or Occlusion ofeither of the following:

• Carotid cerebral arteries; or
• Vertebrobasilar arteries in patients with symptoms highly suggestive of vertebrobasilar syndrome (binocular vision loss, [positional] vertigo, dysarthria, diplopia) when the results may alter patient management. 

III. Evaluation of Tumors

• Evaluation of cerebral arteriovenous neoplasm, hemangioma; or
• Preoperative planning to define the vascular supply of intracranial or glomus tumors; or
• Evaluation of suspected dural sinus obstruction or invasion.

IV. Evaluation of Signs or Symptoms

• Evaluation of sudden onset of headaches associated with exertion or positional changes; or
• Evaluation of pulsatile tinnitus in patients with signs or symptoms suggestive of a vascular lesion.

V. Other Vascular Conditions

• Dissection; or
• Dural arteriovenous fistula; or
• Intramural hematoma; or
• Traumatic vascular injury; or
• Congenital anomalies; or
• Vascular abnormalities associated with sickle cell disease in children; or
• Vasculitis.

Not Medically Necessary:

CTA or MRA head is considered not medically necessary for any of the following:

• Routine screening for aneurysms when there is a family history or associated hereditary disorder (e. g., polycystic kidney disease, Ehlers-Danlos syndrome type IV or neurofibromatosis); or
• Routine screening for other conditions; or
• When the above criteria are not met. 

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy.  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

Magnetic resonance angiography (MRA) of the head is a noninvasive technique for imaging vascular anatomy and pathology without utilizing ionizing radiation and generally without the use of contrast agents. It is based on magnetic resonance imaging (MRI). MRA employs special imaging pulse sequences that emphasize the motion of blood relative to surrounding stationary tissue, with the goal of minimizing the signal from tissue and enhancing the signal from moving blood. The technique used in MRA allows for short repetition times, resulting in rapid image acquisition and reduced signal from background tissue. MRA may be used as an adjunct to Doppler ultrasonography or as an alternative to invasive catheter-based conventional angiography. In surgical planning, the MRA provides a three-dimensional rendering of vascular anatomy. MRA data can be acquired on standard MRI scanners.

Computed tomography angiography (CTA) is an examination that uses x-rays to visualize blood flow in arterial structures supplying the brain. CTA combines the use of x-rays with computerized analysis of the images. Beams of x-rays are passed from a rotating device through the area of interest from several different angles creating cross-sectional images, which then are assembled by computer into a three-dimensional picture of the area being studied. Compared to catheter angiography, which involves injecting contrast material into an artery, CTA is much less invasive because the contrast material is injected intravenously. CTA can be done on conventional CT scanning equipment. Spiral (helical) CT scanners, with continuous gantry rotation and patient table movement, allow for image acquisition during the period of optimal intravascular contrast enhancement.

The ability of either CTA or MRA to image vascular structures has been well established, and the indications listed above summarize the most common vascular conditions involving the head or neck. In general, signs, symptoms, and results of initial imaging with CT, MRI or Doppler ultrasound will prompt consideration of either CTA or MRA. A more controversial indication is screening of asymptomatic patients at increased risk of harboring an intracranial aneurysm, including patients with a family history of aneurysm, or those with predisposing hereditary disorders, such as polycystic kidney disease, Ehlers-Danlos syndrome or neurofibromatosis. Screening indications always require consideration of final patient outcomes. For example, the risk of rupture of aneurysms, based on size and location, is not well understood, so it is likely that many patients with screen-detected aneurysms would undergo unnecessary neuroendovascular or surgical interventions, which are associated with their own risks. In the discussion of their appropriateness criteria, the American College of Radiology (2006) notes,

Because of the cumulative long-term risk of morbidity and mortality from subarachnoid hemorrhage, especially with larger aneurysms and the relatively low risks of clipping or coiling unruptured aneurysm, there may be a clinical role for prophylactic screening.

To date, individuals with a history of aneurysm or subarachnoid hemorrhage in a first-degree relative have been considered candidates for screening. Nevertheless, significant gaps in knowledge of the natural history (and thus the risk of rupture) of intracranial aneurysm remain. Hence, while screening with MRA or CTA may be appropriate in patients with a positive family history, its impact on patient management is questionable.

The indications for MRA and CTA are identical. Imaging modality may depend on availability or specific patient circumstances. CTA or MRA are rarely performed as the initial imaging study, both are typically performed as the result of abnormalities found on initial imaging with CT or MRI studies that require additional clarification, or when other imaging techniques such as Duplex ultrasonography studies do not provide adequate information and the results will be used in treatment planning. The following are examples of specific patient characteristics that may dictate one imaging modality over another:

• Clinical situations may influence whether a CTA or MRA is suitable for pregnant women and children

• Absolute and relative contraindications for scans requiring administration of intravascular contrast material may include:
  • Documented allergy from prior contrast administration or a history of atopy
  • Impaired renal function, when considering an enhanced CT with intravascular iodinated contrast agents
  • Multiple myeloma

• Contraindications for MRA imaging may include situations where individuals:
  • Had placement of metal devices within the body. However, for those who have small amounts of implanted metal not located in the imaging area, an open MRA may be appropriate
  • Have intracranial surgical clips placed for an aneurysm that are not compatible with the use of MRI
  • Have conditions requiring external devices for care (e.g., portable oxygen tank)
  • Are claustrophobic; an open MRA may be appropriate

Peer-Reviewed Publications:

1. Brenner DJ, Hall EJ. Computed tomography--an increasing source of radiation exposure. N Engl J Med. 2007; 357(22):2277-2284.
2. Brown R, Piepgras D. Screening for intracranial aneurysms after subarachnoid hemorrhage: Do our patients benefit? Neurology. 2004; 62(3):354–356.
3. Koelemay MJ, Nederkoorn PJ, Reitsma JB, Majoie CB. Systematic review of computed tomographic angiography for assessment of carotid artery disease. Stroke. 2004; 35(10):2306-2312.
4. Marks MP, Lane B, Steinberg GK, Chang PJ. Magnetic resonance angiography in relatives of patients with subarachnoid hemorrhage study group. Risk and benefits of screening for intracranial aneurysms in first-degree relatives of patients with sporadic subarachnoid hemorrhage. N Engl J Med. 1999; 341(18):1344-1350.
5. Ruigrok Y, Rinkel G, Algra A, et al. Characteristics of intracranial aneurysms in patients with familial subarachnoid hemorrhage. Neurology. 2004; 62(6):891–894.
6. Wermer M, van der Schaaf I, Bossuyt P, et al. Yield of screening for new aneurysms after treatment for subarachnoid hemorrhage. Neurology. 2004; 62(3):369–375.

Government Agency, Medical Society, and Other Authoritative Publications:

1. American College of Radiology. ACR Appropriateness Criteria^® Cerebrovascular Disease. (2006) Available at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria/pdf/ExpertPanelonNeurologicImaging/CerebrovascularDiseaseDoc2.aspx. Accessed on June 19, 2009.
2. American College of Radiology. Practice Guideline for the performance of pediatric and adult cerebrovascular magnetic resonance angiography (MRA). 2006. Available at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/guidelines/dx/head-neck/cerebrovascular_mra.aspx. Accessed on June 19, 2009.
3. Centers for Medicare and Medicaid Services. National Coverage Determination: Magnetic Resonance Angiography (MRA). NCD #220.3. Effective July 1, 2003. Available at: http://www.cms.hhs.gov/mcd/viewncd.asp?ncd_id=220.3&ncd_version=2&basket=ncd%3A220%2E3%3A2%3AMagnetic+Resonance+Angiography+%28MRA%29. Accessed on June 19, 2009.
4. Hayes Inc. Medical Technology Directory. Computed Tomography Angiography for Acute Ischemic Stroke. Hayes, Inc. Lansdale, PA. February 9, 2005. Search updated March 8, 2008.
5. Hayes Inc. Medical Technology Directory. Computed Tomography Angiography for Intracerebral Aneurysm and Subarachnoid Hemorrhage. Hayes, Inc. Lansdale, PA. February 11 2005. Search updated March 9, 2008.

Aneurysms
Arteriovenous Malformation (AVM)
Cerebral Arteries
Computed Tomographic Angiography (CTA)
Magnetic Resonance Angiography (MRA)
Magnetic Resonance Venography (MRV)