What is a CT angiogram / CT angiography (CTA)?
CT angiography (CTA) is an imaging technique which produces pictures of vertical slices of the body. It is used to look at the blood vessels and to detect any problems related to blood flow around the body.
Angiography and arteriography are slightly different imaging techniques which may be used interchangeably by one’s doctor. Arteriography is used to refer to techniques which produce images of the arteries, specifically. Angiography is an umbrella term used to describe the process of imaging all kinds of blood vessels. This can involve visualising blood vessels (arteries and veins) throughout the body, including the head and blood vessels in various organs. Usually, this is facilitated with the help of specific contrast materials.
CTA is performed by a specialist doctor/physician called a radiologist using a computerised tomography scanner. This is a large ring-shaped piece of hospital equipment which creates detailed virtual cross-sectional or multidimensional images of the blood vessels while the body passes through it, lying on a motorized bed.
The images produced are called CT angiograms. The person undergoing CTA will usually be injected, usually in a vein in their arm, with a special dye called contrast material which makes particular blood vessels show up in the images taken by the CT scanner.
The radiologist will analyse the images and produce a radiology report to give to the doctor who ordered the scan. Doctors can use radiology reports from CTA to diagnose accurately and/or rule out a wide range of conditions, such as cardiovascular diseases (diseases which affect the heart or blood vessels), often much earlier on in their course than would be possible by many other means.
CTA is typically used by doctors for:
- Confirming suspected conditions: for example, a pulmonary embolism in the lung can be diagnosed with the aid of CT pulmonary angiography (CTPA).
- Identifying the cause of unexplained symptoms: headaches or seizures, which are unexplained, may indicate the presence of a range of possible underlying conditions and are typical reasons why a doctor may suggest CTA.
- Assessing internal damage: CTA can be useful in identifying problems, such as internal bleeding related to an area that has been injured — or that may have been injured — in an accident.
Types of CTA include scans of a particular blood vessels, such as a CT aortogram (of the aorta, the body’s biggest blood vessel), or scans of an area of the body containing several blood vessels, such as a CT coronary angiogram (an overall scan of the blood vessels in the heart) or a CT pulmonary angiogram (an overall scan of the blood vessels in the lungs).
Common types of CTA include:
- CT aortogram (of the aorta, the body’s biggest, main artery)
- CT carotid angiogram (of the head and neck)
- CT cerebral angiogram (of the brain)
- CT coronary angiogram (of the heart)
- CT pelvic angiogram (of the stomach, including its lower part, ending at the legs)
- CT peripheral angiogram (of the arms and legs)
- CT pulmonary angiogram (of the lungs)
People who are scheduled for a CT angiogram can generally undergo the procedure as an outpatient and can leave the hospital the same day.
What conditions does CTA screen for?
CTA is used to look for, identify and confirm a variety of conditions. With the insights gained from the angiograms, doctors can begin to treat the affected person much earlier on in the course of the disease than would otherwise be possible.
Aneurysms can occur anywhere in the body, but are most common in the aorta (the body’s main artery), brain, intestines, legs (especially the arteries behind the knees) and spleen. Aneurysms are the result of a weakened blood vessel wall, which can occur due to high blood pressure weakening the arteries caused by external factors like major accidents , but is also often hereditary. When the weakened area bulges, it becomes filled with blood and is more likely to rupture. This can cause internal bleeding, serious complications and even, in case of a rupture, death. It is possible to have an aneurysm without knowing about it or perceiving any signs or symptoms.
A CT angiogram for aneurysms is usually performed as a way of ruling out an aneurysm, when unspecific symptoms or certain signs are in the foreground upon examination. For example, in a case of severe recurring headaches or when the doctor finds a pulsating aortic mass on a physical examination of the abdomen.
CTA can detect the formation of blood clots or the build-up of plaque (a substance primarily composed of fat, cholesterol and calcium) in the blood vessels around the body. CTA has been found to be often more reliable than other methods of testing for blockages.
Birth defects, such as malformations of the heart or other blood vessels, can be detected with CTA.
Coronary artery disease (CAD)
This is a group of diseases including myocardial infarction (heart attack), stable and unstable angina (problems with blood flow to the heart due to obstruction or spasm of the arteries) and sudden cardiac death (where the heart stops functioning unexpectedly). There may be no symptoms present for CAD, but many people experience chest pain which travels to the neck, back, arm, jaw or shoulder.
High blood cholesterol, smoking, poor diet and excessive alcohol consumption are all risk factors for CAD, as they make the arteries less effective at transporting oxygenated blood to the heart.CAD is the most common cause of death globally. 
CT coronary angiograms are one of the most common type of CT angiogram and are prescribed as a matter of course to detect coronary heart disease — the leading cause of death in both men and women in the United States.
Factors which render a person at high risk of developing coronary heart disease include:
- High blood pressure
- High LDL (low density lipoprotein) cholesterol, or bad cholesterol
- Low HDL (high density lipoprotein) cholesterol, or good cholesterol
- A family history of coronary heart disease
- Smoking tobacco
- Being post-menopausal (in women)
- Being older than 45 (in men)
- Having diabetes
- Being obese
Diseases of the vessels of the kidneys
Problems which affect the blood vessels going to and from the kidneys can be diagnosed with the aid of a renal angiogram. The procedure may also be carried out to visualise the blood vessels in and around the kidneys before a kidney transplant or before the insertion of a stent (a thin, flexible tube which helps stabilize structures of the urinary system like the ureter, running from kidney to bladder after, for example, kidney stone removal.
Disordered blood vessels
CTA can identify areas where blood vessels have been modified in their structure through various conditions and/or the body’s reactions to these conditions, so that they no longer transport the blood around the body effectively. Conditions which involve these changes of the blood vessels include:
- Peripheral vascular disease (PVD), a condition in which blood circulation disorder causes the blood vessels outside of the heart to block, narrow, spasm or become dilated. This can affect arteries or veins and typically causes pain and fatigue, often in the legs and especially during exercise. In case of the arteries being affected, this would then be called Peripheral artery disease (PAD). Pain related to PAD usually improves with rest. In the case of the veins being affected, this most often shows as dilated or varicose veins of the legs.
- Arteritis/vasculitis (inflammation of the arteries)
When the body sustains an injury, the blood vessels can be affected. This is not always easily detected by examining the outside of the body, and a CT angiogram may be prescribed to survey the extent of any internal damage.
This condition involves a blockage (such as a blood clot) obstructing the pulmonary artery, which carries blood to the lungs or one of its many branches. This can be life-threatening, as oxygen-rich blood will be prevented from reaching the lungs. Blood clots, which obstruct the lungs, usually form in the legs as a result of a condition called deep vein thrombosis (DVT) and travel up the body towards the pulmonary artery. Leading an active lifestyle to improve one’s blood circulation, avoiding smoking tobacco and drinking alcohol, and refraining from staying still for long periods (for example, on long-haul flights) can help prevent DVT.
Before beginning treatment following the discovery of tumours, a doctor will often use CTA to investigate the arteries which are carrying blood to the tumour. It is important for the doctor to be able to visualise the blood vessels in the affected area when they are planning the treatment programme or deciding on a treatment.
Who is CTA suitable for?
In general, adults, children and even babies can undergo a CT angiogram without any adverse effects or complications. However, CTA is more commonly prescribed for adults, and is used to scan for a wider range of conditions in adults than in children or babies. CTA may not be suitable for people who are known to be allergic to contrast material.
Doctors may consider using alternative methods to CTA when they are examining people with one or more of the following characteristics:
- A history of allergic reactions to contrast material
- Unstable pulse or blood pressure
- Impaired kidney function
For people who are pregnant and/or who are undergoing radiation therapy to treat other conditions, the decision to prescribe a CT angiogram will be taken by the doctor, in discussion with the affected person, on a case-by-case basis.
Factors which will be taken into consideration include:
- The type of angiogram
- The condition(s) to be screened for
- The cumulative (total) amount of radiation that the individual would be exposed to over the course of the total number of procedures that they are scheduled to undergo which involve radiation
- Whether the area of the body to be screened includes the womb and/or the unborn child
- The timeline of the pregnancy: after 15 weeks, the foetus is considered to be sufficiently developed that the risks from the exposure to radiation, that a single scan involves, are thought to be negligible. (See FAQs.)
A person who is scheduled for a CT angiogram may often be advised to avoid eating or drinking for a number of hours before the procedure. The exact length of this period depends on the body parts being examined and how extensive the angiogram will be. Talk to a doctor about the details of any forthcoming scan and follow their advice about how to prepare.
Please talk to the doctor beforehand about how to take prescribed or OTC medication before the scan and on the day of the scan. Usually, there is no need to change one’s medication regimen before the scan.
On the day of the procedure, the person undergoing a CT angiogram will be asked to remove their clothing, jewelry and any other metal objects (such as a removable mouth-brace). A loose gown will be provided by the hospital. If they feel anxious about the scan, a sedative (medication which relaxes and calms individuals) may be provided. A sedative may also be prescribed if the person being scanned is a young child, or for anybody who experiences difficulties remaining still.
Almost all CT angiograms require the use of a contrast material. This is a dye which can be seen by X-ray equipment. For an angiogram, contrast material is injected into the body through a vein, making the blood vessels stand out from the rest of the image. Contrast material is normally harmless and passes out of the body during urination following the scan.
However, before administering contrast material, the doctor will check the clinical history of the individual to ascertain whether it is suitable. Contrast material may cause kidney damage in people who have previously experienced kidney problems. If a person has a history of asthma, or previous allergic reactions to contrast material, the chances of experiencing an adverse allergic reaction are heightened. Often, counter measures can be taken to ensure that these people are able to undergo an CT examination if needed.
During the CTA
The CT scanner is made up of the scanning device (a large ring containing X-ray equipment) and a motorized bed. During a CT angiogram, the person lies down on the motorized bed of the scanner and remains as still as possible. The radiologist will operate the CT scanner from a separate room. The person undergoing CTA will be able to communicate with the radiologist throughout the procedure using an intercom. During the procedure, the person may be asked to breathe out or hold their breath at certain points to ensure the clarity of the images.
After the CTA
Following a CT angiogram, the images collected are processed by a computer. They will depict cross-sections (slices) of the body, in which the blood vessels under examination are differentiated from the rest of the image by the contrast material. The radiologist will analyse the images, taking into account the person’s medical history and any suspected diagnoses, and produce a radiology report. The report will usually be passed to the doctor who ordered the scan. It is normal to wait days, or in rare cases, even weeks to receive the results of a CT angiogram.
Almost all CT angiograms require the use of contrast material. Therefore a person who was injected with contrast material for a CT angiogram is usually asked to wait in the hospital for up to an hour so that they can be monitored for signs of an allergic reaction. It is important to drink plenty of fluids after the scan and over the following day to flush the contrast material out of one’s system. If a sedative was used, a family member or friend should accompany the affected person home, and they should avoid driving or operating machinery for the rest of the day.
CT angiography in comparison to regular and MRI angiography
For someone who has been prescribed an angiogram, there are several factors to consider in order to decide whether a CT angiogram is the most suitable option for their needs. The doctor will decide whether CT, MRI or regular angiography is suitable on a case-by-case basis.
Invasive or non invasive
One of the most important aspects of the experience to consider is whether the recommended scan will be an invasive or a non-invasive procedure.
Traditional angiography is an invasive procedure in which an incision is made in the skin so that the contrast material can be administered using a catheter, whilst X-rays are used to create the images. A local anaesthetic will be used to numb the area before the catheter is inserted. Catheters are thin, flexible tubes which are tailor-made for a range of different functions, like in this case administering the contrast material.
The other types of angiography — computed tomography (CT) angiograms and magnetic resonance imaging (MRI) angiograms — are non-invasive procedures. This means that they can be performed by injecting the contrast material into the relevant part of the body through a vein, without the need to use an anaesthetic. CT and MRI angiography are generally preferred by patients for these reasons in comparison to invasive, regular angiography.
Level of detail
An important advantage of CTA over regular angiography is that it is possible for the radiologist to view and evaluate bones, soft tissues and blood vessels all at the same time. This increases the possibility that a single angiography session will be enough to reveal everything that the doctor needs to know in order to accurately diagnose and therefore later on properly treat the affected person.
In the case of coronary artery disease (CAD) using CT angiography was shown to be more sensitive and also more specific than an MRI angiography. This means that that the coronary artery disease will be more likely properly diagnosed with CT angiography. Furthermore when CT angiography is used to screen for CAD, this allows the radiologist to perform a scan using less contrast material than an MRI angiography would require.
However, in general, the suitability of CT or MRI angiography depends on the body part being scanned and the condition(s) to be screened for.
What can be accomplished during each scanning procedure?
A CT angiogram can be used for diagnosis or investigation. A separate treatment plan must be devised based on the findings.
For this reason, somebody who is undergoing a coronary angiogram because of a possible problem with their heart may, in some cases, be recommended a regular angiogram rather than a CT coronary angiogram. CTA is generally preferred by patients as the quicker and less painful option for a scan.
However, use of a catheter in regular angiography makes it possible to sometimes combine diagnosis and treatment in a single procedure. It is for example possible to identify and treat an aneurysm or restore blood flow to a part of the body by removing a blood clot or blockage via the catheter during the scan itself with a regular coronary angiography – avoiding the need for further treatment.
Q: Is CTA safe?
A: The radiation-related risks associated with CTA are far outweighed by the benefits. CTA gives doctors the ability to make rapid and accurate diagnoses and prescribe appropriate treatments for otherwise harder-to-identify conditions. However, care must still be taken to minimize the exposure to radiation from the X-ray equipment. Being exposed to X-rays is often associated with an increased risk of developing cancer later on.
It is advisable to limit the number of X-rays performed on a single person — including those associated with CTA — to those which are absolutely necessary. However, CT scanners have sophisticated radiation dose controls to minimize the risk of developing cancer as much as possible. Furthermore, it is possible to opt for a low-dose radiation X-ray in all cases where a lesser quality CT angiogram will be sufficient to make a diagnosis.
Q: Is CTA suitable for someone who is pregnant?
A: In the early stages of pregnancy, the foetus is most at risk of experiencing adverse effects from being exposed to the ionizing radiation involved in CTA. For this reason, it is recommended that pregnant women do not undergo CTA during the first fifteen weeks of their pregnancy, if the purpose of the scan is to produce an angiogram showing a section of the body which includes the gravid uterus (the area containing the foetus).
From fifteen weeks post-conception, the foetus is considered to have developed sufficiently for there to be a negligible risk of damage from exposure to the ionizing radiation involved in a single scan. At this point, it is generally considered that the risk of damage to the unborn child is outweighed by the benefits of performing a CT angiogram in order to diagnose and treat any conditions which may affect the mother and unborn child if left untreated. There is no reason for a pregnant woman to avoid contrast material at any point in the pregnancy, so intravenous contrast material can be administered as needed.
Q: Is CTA suitable for children
A: Due to technological advances, contemporary CTA can be performed even on newborn children. The range of reasons that CTA is usually performed on children is narrower than for adults. In children, CTA is most often used to assess congenital diseases (birth defects), postoperative vascular diseases (abnormal conditions that can develop in the blood vessels and veins as a result of surgery) and cardiac diseases. One advantage of performing CTA on children is that it can be possible to avoid long periods of sedation, which are associated with MRI angiography and reduce high-intensity radiation exposure, which is associated with regular angiography.
“Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015: a systematic analysis for the Global Burden of Disease Study 2015.” The Lancet. 08 October 2016. ↩
“Adverse Reactions to Contrast Material: Recognition, Prevention, Treatment].” American Family Physician. October 2002. ↩
“CT More Accurate Than MRI for Ruling out Coronary Artery Disease.” Medscape: News and Perspective. 02 February 2010. ↩