A CT Pulmonary Angiogram, often referred to as a CTPA, is a specialized medical imaging test. It employs computed tomography (CT) to generate detailed images of the pulmonary arteries within the lungs, visualizing the blood vessels that transport blood from the heart to the lungs.
What a CT Pulmonary Angiogram Is
A CT Pulmonary Angiogram is a type of computed tomography (CT) scan. It uses a specialized iodine-containing contrast material, injected into a vein, typically in the arm, to highlight the blood vessels in the lungs. This contrast agent travels through the bloodstream, making the pulmonary arteries appear bright white on the scan images.
As the contrast material fills the pulmonary arteries, multiple X-ray images are taken from various angles. These images are then processed by a computer to create detailed cross-sectional and three-dimensional views of the pulmonary arteries and veins. This allows medical professionals to identify any blockages or abnormalities, which appear as darker areas where the contrast material is absent or diminished.
When This Scan is Performed
A CTPA is commonly performed when a medical professional suspects a pulmonary embolism (PE). A pulmonary embolism occurs when a blood clot lodges in an artery in the lung, which can be a serious and potentially life-threatening condition. The CTPA is considered a highly sensitive and specific test for diagnosing this condition.
Medical professionals may also order a CTPA to evaluate other conditions affecting the pulmonary arteries. These can include pulmonary artery malformations, such as aneurysms, or chronic thromboembolic pulmonary hypertension, a type of high blood pressure affecting the lung arteries.
The decision to perform a CTPA is typically based on a clinical suspicion of PE, often following an initial assessment that may include a chest X-ray. If the probability of PE is considered low, a blood test called a D-dimer may be performed first. A negative D-dimer result, combined with a low risk, often means a CTPA is not necessary.
Preparing for and Undergoing the Scan
Preparation for a CTPA involves specific instructions. You may be asked to fast for a period, usually about six hours, before the procedure, and to avoid clear fluids for two hours prior. It is important to discuss all medications with your doctor, especially those for diabetes or blood thinning, as adjustments may be needed.
You will also need to inform the medical staff about any allergies, particularly to contrast dye or shellfish, as well as any kidney problems or pregnancy. Upon arrival at the radiology department, you will likely be asked to change into a hospital gown and remove any metal objects, such as jewelry, which can interfere with the scan images.
During the scan, a nurse or radiographer will insert a thin tube, called a cannula, into a vein in your arm for the contrast injection. You will then lie on your back on the CT table, usually with your arms positioned above your head. The CT scanner, which is a large, donut-shaped machine, will move around you as it takes images.
You will hear buzzing or whirring sounds during the scan, and the table will move in and out of the machine. The radiographer will provide breathing instructions, such as holding your breath for a few seconds at a time, to ensure clear images and minimize motion blur. The entire scanning process is relatively quick, often taking around 10 minutes.
After the Scan: Results and Considerations
After the CTPA scan, the cannula inserted for the contrast injection will be removed, and pressure may be applied to the site to prevent bleeding. You may be asked to wait briefly while the medical staff checks the scan images for quality.
A radiologist, a doctor specializing in interpreting medical images, will review the CTPA images to determine the presence or absence of a pulmonary embolism or other findings. The results are then typically communicated to you by the ordering doctor, who will discuss any next steps or follow-up appointments.
Some minor side effects associated with the contrast dye can occur, such as a brief warm sensation, a metallic taste in your mouth, or a mild headache. These usually subside quickly. Rare but more serious risks include allergic reactions to the dye, which can range from mild to severe, and potential kidney issues, especially in individuals with pre-existing kidney problems.
Radiation exposure is another consideration with CT scans, and while the benefits often outweigh the risks, it is a factor to discuss with your healthcare provider. To help flush the contrast dye from your body after the procedure, it is generally recommended to drink plenty of water.