A CT (Computed Tomography) scan is a kind of x-ray scan which we can use to get very detailed pictures of the heart. Generally, it takes a still picture of the heart (like a photograph), so it is very useful for seeing where all of the heart structures are. To get a picture of the heart, we need to give a special dye into the veins which shows up on x-ray just before taking the picture.
What is needed for a CT scan?
In order to give the dye (called “contrast”) into the veins, you will need to have a small plastic tube (an intravenous cannula) put into one of your veins. For children, this is usually done on our ward where we have creams and sprays to numb the skin so this does not hurt too much.
Although the scan is very quick, you will need to stay still when the picture is being taking otherwise it will come out blurry – just like taking a picture with a camera.
For younger children (under 5 years old) we often give some medication to make them feel sleepy so that they don’t move when the scan picture is being taken. This medication works best if the child has not had a sleep between waking up in the morning and coming in for the scan (for example, try not to let them sleep in the car on the drive to the hospital).
Most children 5 years and over can manage without medication; but for those that still may not cope we will perform the scan with the help of an anaesthetist, who can give some stronger medication to make the child sleepy (the kind of medications used for younger patients are not usually effective for older children).
To avoid interfering with the scan, we ask that all metal objects around the chest are removed. This includes necklaces, clothing with metal poppers, underwired bras, or clothing with sequins. You will be provided with a gown if you need to remove clothing for the scan.
For certain specific scans, we may need to give some medication to slow the heart down. If this is required, the doctors performing the scan will discuss this with you when you come in.
It is the hospital policy that all girls aged 10 years old or more need to have a negative pregnancy test (performed with a urine dipstick) before undergoing any scan involving X-rays.
What happens in the scanner?
We will put the patient on the scanner bed, and attach some ECG cables with stickers on the skin
We will check that the cannula that has been put in is working by giving an test injection of saline
We will decide if one of the doctors will stay in the scanner and give the dye with a syringe (for younger or more anxious patients), or if we will use an automatic machine to give the dye
We will take some pictures to start with, so that we can set up the scanner – older patients may be asked to hold their breath for a few seconds a few times
We will let the patient know when we are giving the dye – this can make you feel hot, give you a funny taste in your mouth or make you feel like you need to pass urine. This is completely normal and will pass
It is very important to stay still when the dye in being given, as the scan will happen shortly afterward. The actual scan usually takes less than a second, and you may be asked to hold your breath again just before.
That’s it! Once the scan is done, we can take you off the table.
Children who have been given medication to make them sleepy will have to go to the ward until the medication has worn off.
Patients who have not required this medication will be asked to sit in the waiting area for a few minutes. After this, the cannula can be removed and you can go home
What are the risks of a CT scan?
CT scans use X-rays to make the picture. X-rays are a type of radiation, so exposure to them carries a risk. X-rays can damage the DNA in cells, which can raise the risk of developing cancer in later life. Modern CT scanners use much lower doses of X-rays than were used previously, and we take all possible measures to reduce this to the lowest amount possible. We also only ever perform CT scans on children if we feel that it is absolutely necessary in order to treat their heart condition. With the small doses of X-rays which we use, the risks of developing cancer in later life are very small – it is important to balance the risk of this against not having all of the information available which we can get from a CT scan.
Very rarely, some patients can have an allergic reaction to the dye we use for CT scans. We have all of the medicines and equipment available to manage this in the CT department. It is important to let us know if you have ever had an allergic reaction to the dye which we used (the same dye is also used for cardiac catheter procedures).
It is important to know if you have any previous kidney problems. The dye is removed from the blood by the kidneys, and if they are not working well then the dye can make the kidney function worse. If there are pre-existing kidney problems, then we can give treatment before and after giving the dye to reduce the risk of this happening. It is therefore important to let us know if you have any kidney problems before you come for the scan
We always check the that the cannula is working before injecting the dye, but if the dye leaks out of the vein into the tissues (called “extravasation”) then it can cause some irritation. This is usually mild, and can be treated with a cold compress to reduce swelling and pain. If extravasation happens, then you will be informed and given advice. If you experience any of the following a CT scan, please seek medical attention:
Increase in pain or swelling over time
Blistering, ulceration or other changes to the skin where the dye was injected
Changes in how the skin feels (e.g. numbness or tingling) where the dye was injected
Can parents / carers stay in the CT room when the scan is being performed?
We usually ask parents or carers to leave the room when the scan is being performed. This is because when the scan is being performed, anyone in the room will receive a dose of X-rays. For certain patients who are very anxious and may not cope without a parent or carer in the room, we will allow one person to stay so long as they confirm that they are not pregnant, and that they wear a lead apron and neck guard to reduce their X-ray exposure.
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