What is a CT scan?
A CT (Computed Tomography) scan is an X-ray imaging technique used to produce detailed images of your organs and blood vessels (See figure 1). A CT angiogram is an enhanced CT scan technique used to visualise blood vessels through the injection of a radiocontrast agent (a liquid that shows up on X-rays) into an arm vein immediately prior to the CT scan commencing. This scan produces a series of images that can be reconstructed into cross-sectional views aiding your surgeon's accurate diagnosis and treatment for your condition.
What happens during a CT scan?
During a CT angiogram, the patient is asked to lie still on a table that passes through a ‘polo mint’ shaped opening in the scanner (See figure 2). Unlike a magnetic resonance imaging (MRI) scan, the CT scanner does not surround your whole body and thus is better suited for patients who suffer with claustrophobia. A radiographer will operate the scanner and be in a separate room whilst the CT scan occurs. They will communicate during the scan through a two-way intercom system and you may be asked to hold your breath several times during the scan. For those having a CT angiogram, an intravenous cannula (Venflon) will be sited in one of your arms and a contrast agent injected during your scan.
How long does a CT scan take?
A CT angiogram typically takes between 10 and 30 minutes to complete, however, this may vary depending on an individual’s co-morbidities and concurrent drug therapies.
Is a CT scan painful?
CT angiography is generally painless, but there may be some discomfort associated with the insertion of an intravenous cannula and from lying still for several minutes. During the injection of the contrast agent you may feel a warm flushed effect and/or a metallic taste in the mouth; both pass within minutes.
Are there any risks associated with CT scans?
The benefits of getting an accurate diagnosis and treatment plan generally outweigh the few risks associated with undergoing a CT angiogram. The main risks associated with CT angiogram: Radiation Exposure: The radiation from the X-rays during a CT scan is equivalent to receiving up to five years of natural background radiation and is thus considered minimal. However, there is always a slight risk for cancer from repeated exposure to radiation and thus we try to minimise the number of scans people undergo, particularly if another non-X-ray based imaging modality will provide similar information. Kidney injury: The contrast media used to visualise the artery on the CT scan is excreted through your kidneys. Patients with underlying kidney disease may suffer a further deterioration in their kidney function as a result of the contrast injuring the kidney filtration system. This is temporary in the vast majority of cases, but can occasionally cause permanent damage to the kidneys leading to the requirement for dialysis. Prior to your CT angiogram your kidney function will be assessed to guide your requirement for prophylactic therapy to help prevent this complication. Allergic reaction: Some people may have an allergy to the contrast media or other materials used during these procedures which has not been previously identified. The majority of these reactions are self-limiting and mild, causing hives or a rash. On rare occasions (1:100,000) an anaphylactic reaction can occur requiring emergency treatment.
What happens after a CT scan?
You should not feel any ill effects following completion of your CT scan and will be able to go home immediately. If you have been given contrast as part of a CT angiogram you may be requested to wait a period of time to ensure you have not had a reaction to the contrast media.
When do the results of a CT scan come through?
The scans are individually reported by our radiology team and reviewed with each patient’s lead surgeon. You will then be reviewed in clinic to discuss the scan findings and how we may be able to help.
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What should I do next?
If you think you have one of these conditions or any of the described symptoms we recommend you seek medical advice.
For further information or to arrange an appointment at Circulation Clinic
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Figure 1: CT angiogram reconstruction showing an aneurysm affecting the right popliteal artery (white arrow)