Computed tomographic angiography (CTA) is a less invasive technique than standard angiography for imaging blood vessels. This technology uses 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. The radiographic computerized techniques used to manipulate the captured images vary from simple assessment of images in a single or two planes, to complex computer reconstruction in three dimensions. The medical literature assessing these techniques often fails to describe the type of image processing used. In addition, there is no consistency in the use of the term CTA from one study to another.

Magnetic resonance angiography (MRA) uses magnetic resonance imaging (MRI) technology to detect, diagnose, and aid in the treatment of disorders affecting blood vessels. As with CTA, this field is also rapidly evolving.

This document addresses the use of both CT and MR studies with contrast with or without specific computerized reconstruction of the images for the evaluation and imaging of vessels in the chest excluding the coronary arteries, abdomen, and upper and lower extremities.

Note: CTA of the Coronary Arteries is addressed in RAD.00035 Contrast-Enhanced Cardiac Computed Tomography Angiography (CTA) and Cardiac Magnetic Resonance Angiography (MRA).

Note: Please see the following documents for further information regarding imaging topics addressed in this clinical UM guideline:

• CG-RAD-08 CTA/MRA Brain and Neck
• CG-RAD-15 CT/MRI of the Thoracic Cavity
• RAD.00035 Contrast-Enhanced Cardiac Computed Tomography Angiography (CTA) and Cardiac Magnetic Resonance Angiography (MRA)
• RAD.00055 MR Angiography (MRA) of the Spinal Canal

Note: Radiation exposure should be taken into account when considering the use of this technology.  Follow-up scanning should be limited to organ or area of interest.

Medically Necessary:

I.  Pulmonary CT Angiography:

Pulmonary CTA studies are considered medically necessary for the following:

• For the primary diagnosis of pulmonary embolism (PE) in patients with suggestive clinical and/or radiographic findings, when this study is done with contrast enhanced chest CT using conventional axial and two dimensional images.
• For the evaluation of candidates for pulmonary thromboendarterectomy.
• For patients requiring pulmonary angiography but who have contraindications to conventional catheter-based pulmonary arteriography.
• Pulmonary sequestration.
• Pulmonary venous and left atrial evaluation, pre- and post radiofrequency ablation for atrial fibrillation (See MED.00064, Transcatheter Radiofrequency Ablation of Arrhythmogenic Foci in the Pulmonary Veins as a Treatment of Atrial Fibrillation (Radiofrequency and Cryoablation)).

II. Renal CT Angiography/Renal MR Angiography:

CTA or MRA is considered medically necessary as part of the diagnostic evaluation for renal artery stenosis for any of the following patient groups:

• Patients with documented hypertension associated with any of the following clinical scenarios:
  • Abrupt onset.
  • Accelerated progression.
  • Onset of hypertension before age 20.
  • Refractory to at least 2 conventional medications.
• Patients with renal insufficiency that is either unexplained or induced by angiotensin-converting enzyme inhibitors.
• Patients with unilateral small kidney.
• Patients with renal artery bruits.
• Patients with negative ultrasound but suspected accessory renal artery.

CTA or MRA is considered medically necessary for the following indications:

• Planning for renal tumor resection.
• Surgical planning for kidney donor.

III.  Thoracic CT Angiography:

CTA is considered medically necessary for any of the following thoracic indications:

• As a screening tool for aortic aneurysms when ultrasound images are suboptimal or non-diagnostic.
• As a diagnostic test for disease of the thoracic aorta including aortic dissection, intramural hematoma, aneurysm, atheromatous disease such as penetrating ulcer and aortitis.
• Post-traumatic vascular injury.
• Stent graft evaluation.
• Post-operative or post interventional vascular procedure for luminal patency versus re-stenosis (due to atherosclerosis, thromboembolism, intimal hyperplasia and other causes) as well as complications such as pseudoaneurysms, leaks, infection related to:
  • Surgical bypass grafts.
  • Vascular stents and stent-grafts.
• As a diagnostic test for developmental anomalies, congenital heart disease, and congenital abnormalities of the great vessels and thoracic vasculature, including aortic coarctation.
• Suspected venous thrombosis or occlusion including superior vena cava syndrome.
• Subclavian steal syndrome.
• Vascular involvement from neoplasm.
• Cardiac masses and tumors.
• Pericardial disease not adequately characterized by echocardiography.
• Vasculitis.
• Identification of the source for embolism or occlusion (when the suspected source is the thoracic aorta and/or proximal arch arteries).

IV. Thoracic MR Angiography:

MRA is considered medically necessary for any of the following thoracic indications:

• As a diagnostic test for disease of the thoracic aorta including aortic dissection, intramural hematoma, aneurysm, atheromatous disease including penetrating ulcer and aortitis.
• As a diagnostic test for developmental anomalies of the thoracic vasculature including aortic coarctation.
• For the identification of the source of systemic venous thrombosis or occlusion (when the suspected source is the thoracic aorta and/or proximal arch arteries).
• For the evaluation of the extension of a lung tumor into the great vessels or pericardium.
• For patients suspected of having pulmonary emboli that are unable to undergo CTA or pulmonary arteriography because of contraindications the presence of a medical condition that would reduce the likelihood of a diagnostic ventilation/perfusion (V/Q) study.
• Post-operative or post interventional vascular procedure for luminal patency versus re-stenosis (due to atherosclerosis, thromboembolism, intimal hyperplasia and other causes) as well as complications such as pseudoaneurysms, leaks or infections related to:
  • Surgical bypass grafts.
  • Vascular stents and stent-grafts.
• Systemic thrombosis including superior vena cava syndrome.
• Subclavian steal syndrome.
• Thoracic outlet syndrome.
• Congenital anomalies of the heart, thoracic aorta and great vessels.
• Pulmonary venous and left atrial evaluation, pre and post radiofrequency ablation for atrial fibrillation (See MED.00064 Transcatheter Ablation of Arrhythmogenic Foci in the Pulmonary Veins as a Treatment of Atrial Fibrillation (Radiofrequency and Cryoablation)).

V. Abdominal and Pelvic CT Angiography/MR Angiography:

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

• Suspected aortic disease or disease of the major branches of the aorta including aneurysm, intramural hematoma, or dissection.
• Pre-operative imaging for abdominal aortic aneurysm (AAA) repair via surgery or stent placement;
• As a pre-operative test prior to liver resection or liver transplantation.
• As a pre-operative test prior to the insertion of a portal-system shunt.
• For evaluation of suspected mesenteric ischemia.
• Vasculitis. 
• Traumatic vascular injury.
• Assessment of unexplained blood loss.
• Pelvic vein thrombosis or thrombophlebitis.
• Prior to the placement of endovascular stents and after their placement.  Post procedure studies assess for placement, leakage.  Baseline studies generally performed soon after placement.  Follow up studies at longer intervals with time, unless symptoms dictate earlier.       
• Venous thrombosis or occlusion of the following:
  • Portal and mesenteric venous system.
  • Systemic venous system, including IVC thrombosis and hepatic vein thrombosis (Budd-Chiari syndrome).
  • Renal vein thrombosis.
  • Other major abdominal vessels.

VI.  Upper Extremity CTA or MRA

NOTE: CTA or MRA studies are often used rather than conventional angiography in the extremities.   

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

• Evaluation of a dialysis graft.
• Pre/Post-operative or interventional vascular procedure for luminal patency versus re-stenosis (due to atherosclerosis, thromboembolism, intimal hyperplasia and other causes) as well as complications such as pseudoaneurysms related to:
  • Surgical bypass grafts.
  • Vascular stents and stent-grafts.
• Suspected vascular disease aneurysm, arteriovenous malformation (AVM), fistula, vasculitis, or intramural hematoma.
• Raynaud's syndrome.
• Arterial entrapment syndrome.
• Vascular invasion or displacement by tumor. 

VII.  Pelvic/Lower Extremity CT Angiography or MR Angiography:

NOTE: These studies are often used rather than conventional angiography in the extremities.    

MRA or CTA is considered medically necessary for any of the following indications of the pelvis or lower extremities:

• For the pre-operative evaluation of aortoiliac occlusion or peripheral vascular disease of the leg, especially when there are contraindications to conventional arteriography and ultrasound has indicated significant disease, but was inconclusive regarding the pathology, in terms of whether it would be amenable to surgery.
• Assessment of significant ischemia in the presence of ulcers or gangrene or symptoms of significant claudication.
• Assessment of disease of large vessels:  aneurysm, dissection, AV malformations and fistulas, intramural hematoma, vasculitis.
• Arterial entrapment syndrome.
• Venous thrombosis, if diagnosis is not clear from other studies.
• Vascular invasion or displacement by tumor.   
• Pre/Post-operative or interventional vascular procedure for luminal patency versus re-stenosis (due to atherosclerosis, thromboembolism, intimal hyperplasia and other causes) as well as complications such as pseudoaneurysms related to:
  • Surgical bypass grafts.
  • Vascular stents and stent-grafts.

Not Medically Necessary:

CTA or MRA of extra-cranial vessels is considered not medically necessary when the criteria outlined above are not met.

Clinical Considerations:

• Clinical situations may influence whether an MRA is suitable for pregnant women and children.
• Immunosuppressed individuals require a higher level of suspicion.
• Contraindications for scans requiring intravascular administration of contrast material may include individuals: 
  • Who have a documented allergy from prior contrast administration or a history of atopy.
  • Who have impaired renal function, when considering an enhanced CT with intravascular iodinated contrast agents.
• Contraindications for MRA imaging may include:
  • Those with 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).
  • Those who have intracranial surgical clips, that are not compatible with the use of MRI, placed for an aneurysm.
  • Those with conditions requiring external devices for care (e.g., portable O2 tank).
  • Those who are claustrophobic (in such cases an open MRA may be appropriate).
• CTA or MRA is not appropriate as a screening tool, (i.e., for asymptomatic patients without a previous diagnosis).

Place of Service:  Inpatient or outpatient, in a hospital or special procedures imaging center. 

The following codes for treatments and procedures applicable to this guideline 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.

Coding Note: For CT imaging of thoracic blood vessels (e.g., for pulmonary embolism) the appropriate code for CT imaging with contrast or CT angiography (CTA) should be used based on the actual study performed. Coding rules indicate that for a study to be coded as a CT angiography, three-dimensional reconstruction post-processing of angiographic images and specialized interpretation of the images is required. If this is not done, the CT with contrast imaging codes should be utilized; from a coding perspective, these codes include two-dimensional reconstruction of images after contrast (for example, reformatting an axial scan into the coronal plane).

Computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) combine the use of CT and MRI radiographic imaging technology in conjunction with intravenously administered radio-opaque contrast material in order to visualize the blood flow in arterial vessels throughout the body. This technique has been found to be useful in identifying aberrant vascular structures and compromised blood flow that may be difficult to detect by other means. 

CTA and MRA are useful in a select group of patients who are likely to have proximal renal artery stenosis associated with hypertension.  If clinical findings strongly suggest the possibility of renovascular disease in these patients, MRA or CTA should be performed.  Both these techniques are very accurate in diagnosing proximal renal artery lesions.

CTA with contrast injection is indicated in the diagnosis of aortic dissection and allows for the exclusion of other causes of mediastinal widening, detection of intraluminal and periaortic thrombus, and diagnosis of pericardial and pleural effusions. Newer gadolinium-enhanced 3-dimensional MRA techniques permit rapid acquisition of MR angiograms of the thoracic and abdominal aorta and their branch vessels.

Contrast enhanced CT of the chest, often referred to as CTA in the medical literature, is indicated in the evaluation of patients suspected of pulmonary embolism (PE).  A variety of algorithms incorporating clinical factors, laboratory testing (D Dimers) and imaging are currently in clinical use.  All existing data indicates that imaging studies are most useful when used with assessment of the underlying probability of a positive test based on clinical factors in conjunction with laboratory tests.  In addition, risks such as radiation exposure or adverse reactions to contrast materials should be considered.  Studies have shown CTA to be highly sensitive and specific and a medically necessary adjunct in clinical settings when there is sufficient suspicion of pulmonary embolus and a need for more definitive data exists.  In the Annals of Internal Medicine December 2004 a meta-analysis evaluated the use of CT of the pulmonary artery.  This study involved 4657 patients in 23 studies found to have negative CTA exams.  In these patients with negative CTA exams, the 3 month rates of subsequent venous thromboembolic events was 1.4% and the 3 month fatality rate of pulmonary embolus was .51%.  The authors noted that this compared favorably with conventional angiography.  The radiographic techniques varied both across and within these studies, however, all studies used early generation CT technology and none of the studies used reconstruction algorithms for interpretation.  Thus, while this may not be directly applicable to patients with more sophisticated data acquisition methods, and there is an assumption that newer technologies could improve overall outcomes. 

Another more recent blinded, randomized controlled trial by Anderson and colleagues (2007) involved the comparison of V/Q scanning vs. computed tomography pulmonary angiography (CTPA) in patients suspected of pulmonary embolus.  In this study 1417 patients were evaluated for PE. Those found to have a high probability of PE (n=234) received further testing with either CTPA (n=133) or V/Q scanning (n=101). As with other studies, the term CTPA was described as radiographic procedure with axial images, rather than 3 dimensional imaging.       The results found no significant difference between groups in the primary outcome of thromboembolism within 3 months of evaluation.  However, the study did find that CTPA identified a greater number of thromboembolism diagnoses compared to V/Q scanning.  The significance of this finding requires further evaluation, as it is unclear whether this is a result of better accuracy in finding true cases of PE, or that CTPA identifies a high number of false positives.  Overall the authors report that "a strategy to rule out pulmonary embolism that used clinical probability assessment, D-dimer, and lower extremity ultrasound in conjunction with either CTPA or V /Q scanning resulted in low and similar rates of venous thromboembolic events in 3 months follow-up in the 2 groups."

It is important to note that, at this time,  there is no data to support this assumption that three dimensional post-processing imaging improves health-related outcomes for those with pulmonary embolus.

Although MRA is not widely utilized for detecting pulmonary emboli, it has proven valuable where contrast administration is contraindicated.

Diagnostic alternatives to CTA/MRA imaging would include ultrasound and conventional angiography.

Peer Reviewed Publications:

1. Anderson ER, Kahn SR, Rodger MA, et al. Computed Tomographic Pulmonary Angiography vs Ventilation-Perfusion Lung Scanning in Patients with Suspected Pulmonary Embolism. JAMA. 2007;  298(23):2743- 2753.
2. Brenner DJ, Hall EJ. Computed tomography--an increasing source of radiation exposure. N Engl J Med. 2007; 357(22):2277-2284.
3. Carman TL, Olin JW, Czum J.  Noninvasive imaging of the renal arteries. Urol Clin North Am. 2001 28(4): 815-826.
4. Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA. 2007; 298(3):317-323.
5. Garg K, Macey L. Helical CT scanning in the diagnosis of pulmonary embolism. Respiration. 2003; 70(3):231-237.
6. Horton KM, Fishman EK. CT angiography of the GI tract. Gastrointest Endosc. 2002; 55(7 Suppl):S37-41.
7. Koelemay MJ, Lijmer JG, Stoker J, et al. Magnetic Resonance Angiography for the evaluation of lower extremity arterial disease: a meta-analysis. JAMA. 2001; 285(10);1338-1345.
8. Kouskouras C, Charitanti A, Giavroglou C, et al.  Intracranial aneurysms: evaluation using CTA and MRA. Correlation with DSA and intraoperative findings. Neuroradiology. 2004; 46(10):842-850.
9. Moores, LK Jackson, WL, et al.  Meta-Analysis:  Outcomes in Patients with Suspected Pulmonary Embolism Managed with Computed Topographic Pulmonary Angiography.  Ann Intern Med.  2004; 141:866-874. 
10. Remy-Jardin M, Mastora I, Remy J.  Pulmonary embolus imaging with multislice CT. Radiol Clin North Am. 2003; 41(3):507-519.
11. Stein PD, Fowler SE, Goodman LR, et al.; PIOPED II Investigators. Multidetector computed tomography for acute pulmonary embolism. N Engl J Med. 2006; 354(22):2317-2327.
12. Tatli S, Yucel EK, Lipton MJ. CT and MR imaging of the thoracic aorta: current techniques and clinical applications. Radiol Clin North Am. 2004; 42(3):565-585.

Government Agency, Medical Society, and Other Authoritative Publications:

1. American College of Radiology. "Radiologic Investigation of Patients with Renovascular Hypertension," ACT Appropriateness Criteria^™, 2003. Available at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria.aspx. Accessed on December 6, 2007.
2. American College of Radiology. ACT Appropriateness Criteria ^™, Acute chest pain-suspected pulmonary embolism. 2005. Available at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria.aspx. Accessed on December 6, 2007.
3. American College of Radiology. ACT Appropriateness Criteria ^™, Acute chest pain-suspected aortic dissection, 2005. Available at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/app_criteria.aspx. Accessed on December 6, 2007.
4. Centers for Medicare and Medicaid Services. National Coverage Determination for Magnetic Resonance Angiography (MRA). NCD #220.3. Effective July 1, 2003.  Available at: http://www.cms.hhs.gov/mcd/index_list.asp?list_type=ncd. Accessed on December 6, 2007.
5. Centers for Medicare and Medicaid Services. National Coverage Determination for Magnetic Resonance Imaging (MRI). NCD #220.2. Effective March 22, 1994. Available at: http://www.cms.hhs.gov/mcd/index_list.asp?list_type=ncd.  Accessed December 6, 2007.
6. Hayes Medical technology Directory. Cardiac Magnetic Resonance Angiography. Lansdale, PA: Hayes, Inc. August 18, 2005. Search updated September 3, 2007.
7. Nickoloff EL, Alderson PO. Radiation Exposures to Patients from CT: reality, public perception, and policy. AJR. 2001; 177:285–287.

Angiography, Computed Tomographic
Angiography, Magnetic Resonance
Computed Tomographic Angiography
CTA/MRA, Extra-Cranial Vessels
Magnetic Resonance Angiography