Computerised Tomography (CT) scan
CT stands for Computerised Tomography – it used to be commonly called a CAT scan. A CT scan uses X-rays to take incredibly detailed pictures of the inside of your body. It helps us find the cause of your problem and guide us to find the best treatment options for you. A standard X-ray does not give the same level of detail as a CT scan. We can scan just about any part of the body, from head to toe. The scanner is so advanced, we can even scan your heart in between beats.
The CT scanner is the ‘doughnut’ shaped scanner. In our experience, patients do not feel claustrophobic while having a CT scan because their head is outside of the scanner for most of the examination.
There are lots of different types of scan and you should be aware of what you are having scanned before you arrive at the scanner. The Radiographer will explain more about your scan if you ask them.
A head CT may be done to detect effects of trauma, abscesses, tumours, birth defects, sinus problems, blood vessels or to find the cause of headaches, weakness or a change in mental status. A neck CT checks the soft tissues of the neck and is frequently used to study a lump or mass in the neck or to look for enlarged lymph nodes or glands. A CT of the chest is frequently used to further study an abnormality seen on a plain chest X-ray. It is also often used to look for enlarged lymph nodes. We might be looking at the veins and arteries in your chest to rule out a blood clot or an aneurysm. An abdominal CT scan offers images of the internal organs, bones, soft tissue and blood vessels of the belly area. This procedure is typically used to help diagnose the cause of abdominal or pelvic pain and diseases of the internal organs, small bowels and colon. It is also performed to guide biopsies and drain abscesses, plan for and assess the results of surgery and stage, plan and properly administer radiation treatments for tumours. CT Colonography, also known as virtual colonoscopy, uses low-dose radiation scanning to obtain an interior view of the colon (large bowel) that is otherwise only seen with a more invasive procedure where a small camera is inserted to the rectum and passed through the entire colon (Endoscopy). The major reason for performing this examination is to screen for polyps or cancers in the large bowels. The goal is to find these growths in their early stages so that they can be removed.
You should continue to take any prescribed medication. If you are taking medicines for diabetes (for example metformin), these may need to be altered around the time of your scan. It is important that there is no metal on your clothing, as it may obscure details of your organs, so if possible please try and come to your appointment wearing leisure clothes, for example a tracksuit, leggings, etc. If this is not possible, changing facilities and hospitals gowns are available. Contact your GP or please feel free to telephone us on 02476 865017 if you have any questions about your medications that haven’t been answered in your appointment letter/leaflet.
The bowel-cleansing regimen for CT Colonography is similar to that for a colonoscopy. Your diet will be restricted to clear liquids the day before the examination. It is very important that your colon is cleaned out the night before your examination so that the Radiologist can clearly see any polyps that might be present. You will be asked to take laxatives as well.
CT scans use X-rays and are associated with radiation, however the dose we use is small and the modern machines we use are very efficient at reducing the dose even more. The benefits of the scan are always considered to outweigh any risks of not having the scan.
Sometimes we need to give you an injection of contrast dye before the scan in order to see your internal organs better. This contains iodine, which some people are allergic to. Before your scan, we will check whether you’ve had any previous allergies or have had any problems with your thyroid gland.
Any time an injection is done into a vein, there is a risk of the contrast leaking outside the vein under the skin. Sometimes this is a minor inconvenience but if a large amount of contrast leaks under the skin you might require some additional support. If this happens, we have very clear guidelines on how we can help you.
What to expect
The room where the machine is will be cold. This is so that the scanner doesn’t overheat. We perform approximately 58 CT examinations daily, and the machines work really hard, so we need to keep them as cool as possible so they don’t breakdown.
It is very important that you remain still throughout the scan. If you find it difficult or uncomfortable lying still, please tell the Radiographer. The Radiographer will be able to see you at all times and you will be able to communicate via a microphone and speaker. If you feel short of breath or like you might have to vomit, please let a Radiographer know.
Your appointment may take about 10-20 minutes. The scan itself is very short. If you need an injection of contrast dye, one of the CT staff will insert a small needle into a vein in the back of your hand or the inside of your elbow. When the dye is injected, you might feel warm, dizzy, have a hot flush and/or get a metallic taste in your mouth. This is all perfectly normal and is nothing to worry about. Sometimes people also have a sensation that they are passing urine, but don’t worry, you won’t. These sensations all pass within a few seconds to a minute.
Sometimes we will ask you to hold your breath for up to 20 seconds during the scan so that the images are in focus.
You might sometimes be given some water to drink or a drink called Gastrografin during the hour before your scan to give a clear outline of your stomach and intestine on the CT scan. This extra time is allowed for in your appointment time. If you are coming for virtual colonoscopy a very small, flexible tube will be inserted into your rectum to allow air to be gently pumped into the colon. This is done so that the bowels are expanded to reduce any folds or wrinkles that might hide smaller polyps.
In most cases, once the scan is completed, you will be able to go home or back to the ward if you are an inpatient. You can eat, drink and go back to your normal activities straight away.
You may need to wait 15-20 minutes before we take out your cannula (the small tube in your vein) to ensure you don’t have a delayed reaction to the contrast. If you have had a cardiac scan and have been given medication in department you will have to have your heart rate checked before you leave the department.
You might have a sense of fullness when the colon is inflated with air, and you might feel the need to pass wind. If you have received a contrast dye injection, you may need to wait 10 minutes before you can go so we can check you are ok after the injection. The results of your scan are unlikely to be available the same day, but a copy of them will be sent to your GP and also the person who asked for the scan.
Can I still breastfeed after getting IV contrast?
After your CT scan with IV contrast, you can continue to breastfeed normally. Only a tiny amount of the contrast (less than 0.01%) passes from your breast milk to your baby.
There have been no reports of harm to the baby from breastfeeding individuals who received IV contrast.
If you are still worried about any harm to the baby/infant, you can:
1. express (pump) and throw away your breast milk for 24 hours,
2. feed your baby with stored breast milk or formula during this time and
3. start breastfeeding again after 24 hours.
GEH 637 21-24 July 2021