Computed tomography angiography
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|Computed tomography angiography|
Sagittal thin slice of a computed tomography angiography abdominal aortic aneurysm (AAA) (arrows)
Computed tomography angiography (also called CT angiography or CTA) is a computed tomography technique used to visualize arterial and venous vessels throughout the body. This ranges from arteries serving the brain and heart to those bringing blood to the lungs, kidneys, pelvis, arms and legs.
- 1 Medical uses
- 2 Technique
- 3 Risks
- 4 History
- 5 See also
- 6 References
CTA can be used to examine blood vessels in many key areas of the body, including the brain, kidneys, pelvis, and the lungs.
Coronary CT angiography
Coronary CT angiography (CTA) is the use of CT angiography to assess the coronary arteries of the heart. The subject receives an intravenous injection of radiocontrast and then the heart is scanned using a high speed CT scanner, allowing radiologists to assess the extent of occlusion in the coronary arteries, usually in order to diagnose coronary artery disease. CTA has not replaced invasive catheter coronary angiography. The procedure is able to detect narrowing of blood vessels in time for corrective therapy to be done. This method displays the anatomical detail of blood vessels more precisely than magnetic resonance imaging (MRI) or ultrasound. Today, many patients can undergo CTA in place of a conventional catheter angiogram. CTA is a useful way of screening for arterial disease because it is safer and much less time-consuming than catheter angiography and is also a cost-effective procedure. CTA also has less discomfort because contrast material is injected into an arm vein rather than into a large artery in the groin.
Thoracic aorta and great arteries
CTA is used in the chest to:
- Identify aneurysms in the aorta or in other major blood vessels. Aneurysms are diseased areas of a weakened blood vessel wall that bulge out. Aneurysms can life-threatening if they rupture.
- Identify dissection in the aorta or its major branches. Dissection is when the layers of the artery wall peel away from each other. Dissection can cause pain and can be life-threatening.
CT pulmonary angiogram (CTPA) is used to examine the pulmonary arteries in the lungs, most commonly to rule out pulmonary embolism, a serious but treatable condition. It has become the technique of choice for detection of pulmonary embolism due to its wide availability, short exam time, low level of patient monitoring during the study and a high degree of confidence in the validity of the test.
Abdominal aorta and abdominal veins
Imaging for abdominal aortic aneurysms and acute mesenteric ischemia is performed with CTA. When aneurysm assessment is being carried out before and after endovascular stenting, CTA is the test of choice due to the ability to detect calcium within the wall.
Visualization of blood flow in the renal arteries (those supplying the kidneys) in patients with high blood pressure and those suspected of having kidney disorders can be performed using CTA. Stenosis (narrowing) of a renal artery is a cause of hypertension (high blood pressure) in some patients and can be corrected. A special computerized method of viewing the images makes renal CT angiography a very accurate examination. CTA is also used in the assessment of native and transplant renal arteries.
Carotid, vertebral and intracranial vessels
Identify a small aneurysm or arteriovenous malformation inside the brain that can be life-threatening. While CTA can produce high quality images of the carotid arteries for grading the level of stenosis (narrowing of the vessel), calcium deposits (calcified plaques) in the area where the vessels split can lead to interference with accurate stenosis grading. Because of this, magnetic resonance angiography is used more often for this purpose.
CTA can be used to detect atherosclerotic disease that has narrowed the iliac arteries (arteries to the legs).
CT angiography should not be used to evaluate for pulmonary embolism when other tests indicate that there is a low probability of a person having this condition. A D-dimer assay might be a preferred alternative to test for pulmonary embolism, and that test and a low clinical prediction score on the Wells test or Geneva score can exclude pulmonary embolism as a possibility.
Harms of overuse of CT angiography include radiation exposure and the possibility of finding then seeking treatment for a clinically insignificant pulmonary embolism which ought not be treated.
Adverse reactions may occur whenever iodine contrast is injected. These reactions range in severity and it is difficult to predict if they will occur. The severity of the reaction can be broken down into three groups:
- Mild - no treatment required: nausea, vomiting, and/or hives.
- Moderate - requires treatment: severe hives, lightheadedness or brief loss of consciousness, mild bronchospasm, and/or increased heart rate.
- Severe - requires immediate treatment: severe bronchospasm, throat swelling, seizure, severe low blood pressure, and/or cardiac arrest.
A patient with a history of allergy to x-ray dye may be advised to take special medication for 24 hours before CTA to lessen the risk of allergic reaction or to undergo a different exam that does not call for contrast material injection.
The use of CTA in patients with renal failure, kidney disease or long-standing severe diabetes should be considered carefully, as the use of IV iodine contrast material can further harm kidney function. The contrast material can lead to contrast-induced nephropathy (also called CIN). While CIN can occur in any patient receiving IV iodine contrast, patients with pre-existing kidney disease are at an increased risk.
If a large amount of x-ray contrast material leaks out under the skin where the IV is placed, skin damage can result.
Compared with other imaging modalities, CTA is associated with a significant dose of ionizing radiation. Depending on patient age and exam protocol, CTA may cause a considerable increase in lifetime cancer risk. However, there are many clinical situations for which the benefits of performing the procedure outweigh this risk.
By 1994 CT angiography began to replace conventional angiography in diagnosing and characterizing most cardiovascular abnormalities. Prior to this, conventional angiography had been in use for 70 years.
- Andy., Goh, Vicky. Adam, (2016). Grainger & Allison's diagnostic radiology. Elsevier. ISBN 9780702069352. OCLC 922460588.
- American College of Chest Physicians; American Thoracic Society (September 2013), "Five Things Physicians and Patients Should Question", Choosing Wisely: an initiative of the ABIM Foundation, American College of Chest Physicians and American Thoracic Society, retrieved 6 January 2013, which cites
- Fesmire, FM; Brown, MD; Espinosa, JA; Shih, RD; Silvers, SM; Wolf, SJ; Decker, WW; American College of Emergency, Physicians (Jun 2011). "Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected pulmonary embolism". Annals of Emergency Medicine. 57 (6): 628–652.e75. doi:10.1016/j.annemergmed.2011.01.020. PMID 21621092.
- Qaseem, A; Snow, V; Barry, P; Hornbake, ER; Rodnick, JE; Tobolic, T; Ireland, B; Segal, J; Bass, E; Weiss, KB; Green, L; Owens, DK; Joint American Academy of Family Physicians/American College of Physicians Panel on Deep Venous Thrombosis/Pulmonary, Embolism (Jan–Feb 2007). "Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians". Annals of Family Medicine. 5 (1): 57–62. doi:10.1370/afm.667. PMC 1783928. PMID 17261865.
- Torbicki, A; Perrier, A; Konstantinides, S; Agnelli, G; Galiè, N; Pruszczyk, P; Bengel, F; Brady, AJ; Ferreira, D; Janssens, U; Klepetko, W; Mayer, E; Remy-Jardin, M; Bassand, JP; ESC Committee for Practice Guidelines, (CPG) (Sep 2008). "Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC)". European Heart Journal. 29 (18): 2276–315. doi:10.1093/eurheartj/ehn310. PMID 18757870.
- Basic radiology. Chen, Michael Y. M., Pope, Thomas Lee, Jr., Ott, David J. (David James), 1946- (2nd ed.). New York: McGraw Hill Medical. 2011. ISBN 9780071766647. OCLC 681348027.
- Einstein, A. J.; Henzlova, M. J.; Rajagopalan, S (2007). "Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography". JAMA. 298 (3): 317–23. doi:10.1001/jama.298.3.317. PMID 17635892.
- Rubin, Geoffrey D.; Leipsic, Jonathon; Schoepf, U. Joseph; Fleischmann, Dominik; Napel, Sandy. "CT Angiography after 20 Years: A Transformation in Cardiovascular Disease Characterization Continues to Advance". Radiology. 271 (3): 633–652. doi:10.1148/radiol.14132232. PMC 4669887. PMID 24848958.