CT angiography

Definition:
CT angiography is an angiography through a CT scanner to produce detailed images of both blood vessels and tissues in various parts of the body. An iodine-rich contrast material (dye) is usually injected through a small catheter placed in a vein of the arm. A CT scan is then performed while the contrast flows through the blood vessels to the various organs of the body. After scanning, the images will be processed using a special computer and software and reviewed in different planes and projections.

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Common uses of CT Angiography (CTA):  

CT angiography is used to examine blood vessels and the organs supplied by them in various body parts, including:

*brain
*neck
*heart
*chest
*abdomen (such as the kidneys and liver)
*pelvis
*legs and feet
*arms and hands

Physicians use this test to diagnose and evaluate many diseases of blood vessels and related conditions such as:

*injury
*aneurysms
*blockages (including those from blood clots or plaques)
*disorganized blood vessels and blood supply to tumors
*congenital (birth related) abnormalities of the heart, blood vessels or various parts of the body which might be supplied by abnormal blood vessels

Also, physicians use this exam to check blood vessels following surgery, such as:

*identify abnormalities, such as aneurysms, in the aorta, both in the chest and abdomen, or in other arteries.
*detect atherosclerotic (plaque) disease in the carotid artery of the neck, which may limit blood flow to the brain and cause a stroke.
*identify a small aneurysm or arteriovenous malformation (abnormal communications between blood vessels) inside the brain or other parts of the body.
*detect atherosclerotic disease that has narrowed the arteries to the legs and help prepare for endovascular intervention or surgery.
*detect disease in the arteries to the kidneys or visualize blood flow to help prepare for a kidney transplant or stent placement.
*guide interventional radiologists and surgeons making repairs to diseased blood vessels, such as implanting stents or evaluating a stent after implantation.
*detect injury to one or more arteries in the neck, chest, abdomen, pelvis or extremities in patients after trauma.
*evaluate arteries feeding a tumor prior to surgery or other procedures such as chemoembolization or selective internal radiation therapy.
*identify dissection or splitting in the aorta in the chest or abdomen or its major branches.
*show the extent and severity of the effects of coronary artery disease and plan for a surgical operation, such as a coronary bypass and stenting.
*examine pulmonary arteries in the lungs to detect pulmonary embolism (blood clots, such as those traveling from leg veins) or pulmonary arteriovenous malformations.
*look at congenital abnormalities in blood vessels, especially arteries in children (e.g., malformations in the heart or other blood vessels due to congenital heart disease).
*evaluate obstructions of vessels.

Preparations to be done:
The patient should wear comfortable, loose-fitting clothing for the exam. He or she may be given a gown to wear during the procedure.

Metal objects, including jewelry, eyeglasses, dentures and hairpins, may affect the CT images and should be left at home or removed prior to the exam. The patient may also be asked to remove hearing aids and removable dental work. Women will be asked to remove bras containing metal underwire. He or she may be asked to remove any piercings, if possible.

The patient will be asked not to eat or drink anything for a few hours beforehand, if contrast material will be used in the exam. He or she should inform the physician of all medications that are taking and if he or she has any allergies. If known allergy to contrast material, or “dye,” the doctor may prescribe medications (usually a steroid) to reduce the risk of an allergic reaction. These medications generally need to be taken 12 hours prior to administration of contrast material.

Also the doctor should be informed of any recent illnesses or other medical conditions and whether history of heart disease if any, asthma, diabetes, kidney disease or thyroid problems. Any of these conditions may increase the risk of an unusual adverse effect.

Women should always inform their physician and the CT technologist if there is any possibility that they may be pregnant.

If one is breastfeeding at the time of the exam, one should ask the doctor how to proceed. It may help to pump breast milk ahead of time and keep it on hand for use after contrast material has cleared from the body, about 24 hours after the test.

The experience during and after the procedure one will have.:
CT exams are generally painless, fast and easy. With multidetector CT, the amount of time that the patient needs to lie still is reduced.

Though the scanning itself causes no pain, there may be some discomfort from having to remain still for several minutes and with placement of an IV. If you have a hard time staying still, are very nervous or anxious or have chronic pain, you may find a CT exam to be stressful. The technologist or nurse, under the direction of a physician, may offer you some medication to help you tolerate the CT scanning procedure.

For exams (excluding head and neck) your head will remain outside the hole in the center of the scanner. The scanner is approximately 24 inches wide, therefore, your entire body will be “inside” the scanner at one time such as with MRI.

If an intravenous contrast material is used, you will feel a pin prick when the needle is inserted into your vein. You will likely have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for at most a minute or two. You may experience a sensation like you have to urinate; however, this is actually a contrast effect and subsides quickly.

When one enter the CT scanner, special light lines may be seen projected onto one’s body, and are used to ensure that he or she is properly positioned. With modern CT scanners, one will hear only slight buzzing, clicking and whirring sounds as the CT scanner’s internal parts, not usually visible, revolve around the patient during the imaging process.

The patient will be alone in the exam room during the CT scan, unless there are special circumstances. For example, sometimes a parent wearing a lead shield may stay in the room with their child. However, the technologist will always be able to see, hear and speak with you through a built-in intercom system.

After a CT exam, the intravenous line used to inject the contrast material will be removed by the technologist, and the tiny hole made by the needle will be covered with a small dressing. The patient can returned to normal activities just after the test.

Benefits:
*Angiography may eliminate the need for surgery. If surgery remains necessary, it can be performed more accurately.
*CT angiography is able to detect narrowing or obstruction of blood vessels allowing for potentially corrective therapy to be done.

CLICK TO  READ : CT coronary angiogram
*CT angiography may give more precise anatomical detail than magnetic resonance imaging (MRI), particularly in small blood vessels.
*Many patients can undergo CT angiography instead of a conventional catheter angiography (catheterization) to diagnose blood vessel problems.
*Compared to catheter angiography which involves placing a catheter (plastic tube), usually at the groin, into your major blood vessels and injecting contrast material, and may require sedation or general anesthesia, CT angiography is faster, non-invasive and has less complications.
*CT angiography is a useful way of detecting arterial (such as narrowing of blood vessels in the heart) and venous disease as well as structural abnormalities of the heart before there are symptoms or when symptoms are not clearly related to blood vessel disease, such as a heart attack.
*CT angiography is a lower cost examination compared to catheter angiography.
*There is also potentially less discomfort because contrast material is injected into an arm vein rather than into a catheter inserted into a large artery or vein.
*No radiation remains in a patient’s body after a CT examination.
X-rays used in CT scans should have no immediate side effects.

Risks Factors:
Most patients complete CT angiography with no adverse events.

*There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.
*If the patient has a history of allergy to x-ray contrast material, the doctor may advise him or her to take special precautionary medication, such as a steroid, for a few hours or the day before CT angiography to lessen the chances of allergic reaction. Another option is to undergo a different exam that does not require iodinated contrast material.
*In patients who are at risk for kidney failure and who already have borderline kidney function, administering iodinated contrast material could potentially further damage kidney function. Check with your referring doctor and radiologist to obtain more information regarding this risk.
*If a large amount of x-ray contrast material leaks out from the vein being injected and spreads under the skin where the IV is placed, it may damage the skin, blood vessels and nerves. If you feel any pain or tingling sensation in this area during or immediately after the contrast material injection, you should immediately inform the nurse/technologist.
*Women should always inform their physician and x-ray or CT technologist if there is any possibility that they are pregnant. See the Safety page for more information about pregnancy and x-rays.
*Manufacturers of intravenous contrast indicate mothers should not breastfeed their babies for 24-48 hours after contrast medium is given. However, both the American College of Radiology (ACR) and the European Society of Urogenital Radiology note that the available data suggest that it is safe to continue breastfeeding after receiving intravenous contrast. For further information please consult the ACR Manual on Contrast Media and its references.
*The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare, and hospitals are well-equipped to deal with them.

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Resources:
https://www.radiologyinfo.org/en/info.cfm?pg=angioct#overview

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