CT scans use X-rays to create detailed cross-sectional images. They can provide important diagnostic information, but unlike MRI and ultrasound, they involve ionising radiation. The decision to perform a CT should consider the clinical benefit, the potential risk and whether the scan is likely to answer the question being investigated.
At PrivateScans, our pre-scan GP consultation helps review your symptoms and whether a CT scan is appropriate before you proceed. Appointments can usually be arranged within 1–3 days, with results provided within 3 days of your scan.
Why does a CT scan use radiation?
A CT scanner takes X-ray measurements from different angles and combines them into detailed images. The radiation helps create information about structures inside the body that may not be visible on a standard X-ray. The amount of radiation varies according to the body area, the equipment and the scan protocol.
CT may be useful for investigating certain injuries, abdominal or chest problems, blood vessels and other conditions where detailed images are needed. It is not automatically the best test for every symptom.
What are the potential risks?
Ionising radiation can damage cells, and exposure carries a small potential long-term cancer risk. The level of risk depends on factors including the dose, age and body area examined. The risk from an individual scan is generally considered alongside the medical benefit of obtaining the information.
A CT should be performed when there is a clear clinical reason. Imaging professionals tailor the examination to the question and use techniques intended to keep exposure as low as reasonably achievable while still producing diagnostic images.
CT compared with MRI and ultrasound
MRI uses a magnetic field and radio waves rather than ionising radiation. Ultrasound uses sound waves. These tests have different strengths and limitations: MRI can provide detailed soft-tissue images, ultrasound is useful for selected structures and real-time assessment, and CT can be especially helpful when speed or detailed cross-sectional views are needed.
The absence of radiation does not automatically make another test better. The correct choice depends on what your doctor needs to investigate and the risks and limitations of each option.
What if you have had several scans?
Tell our doctor about recent imaging, especially repeated examinations of the same area. Previous images may sometimes answer the question without repeating the test. Keep copies of reports when possible and share them with the team.
Do not decline or delay a recommended scan solely because you are concerned about radiation. Ask your doctor to explain why it is being recommended, whether alternatives are suitable and how the result could affect care.
Pregnancy and other safety considerations
Tell the imaging provider if you are pregnant or might be pregnant before the examination. The team will assess whether CT is appropriate and whether another test could answer the question. This is particularly important for scans involving the abdomen or pelvis.
If contrast is planned, also tell the team about kidney problems, diabetes, allergies or previous reactions to contrast, and relevant medicines. These details relate to contrast safety as well as scan planning.
Questions to ask before booking
You can ask what clinical question the CT is intended to answer, whether another type of imaging may be appropriate, whether contrast is needed and what preparation is required. If the scan was suggested by a doctor, confirm the body area and protocol rather than selecting a different examination yourself.
How CT radiation is managed
CT uses ionising radiation to create cross-sectional images. The amount of radiation depends on the body area, the scan protocol, the equipment and the number of image acquisitions needed. There is no single dose that applies to every CT examination. Imaging teams use protocols designed to obtain images of adequate diagnostic quality while keeping exposure as low as reasonably achievable for the clinical purpose.
The potential risk from radiation is generally small for an individual medically justified examination, but it is not zero. The balance depends on the clinical situation, the person’s age and the scan being considered. The reason for the examination and whether the result is likely to influence care are important parts of deciding whether CT is appropriate.
Pregnancy, previous scans and personal circumstances
Tell the referring doctor and radiographer if you are pregnant or could be pregnant, and mention previous imaging if it is relevant. A necessary scan should not be delayed without advice, but the team may consider whether ultrasound, MRI or another approach could answer the same question. The best alternative depends on the body area and the condition being investigated.
Having had previous CT scans does not automatically mean another scan is unsafe or should be refused. doctors consider the information needed now, previous examinations where available, and whether repeating imaging is likely to change management. If you have questions about why CT has been recommended, ask what the scan is intended to find and whether an alternative would be suitable.
What to ask before a CT scan
- What clinical question is the CT intended to answer?
- Will the result affect treatment or the next step in my care?
- Is contrast required, and are there preparation instructions for me?
- Should I tell the team about pregnancy, kidney disease, diabetes, allergies or previous contrast reactions?
- Who will explain the report and arrange any follow-up?
Do not cancel a clinically recommended examination solely because of general information about radiation. Discuss your individual circumstances with the doctor looking after your care so the benefits, risks and alternatives can be considered properly.
Sources and further reading
These NHS resources provide further information. They do not replace individual clinical advice.
This article is for general information only and does not replace an individual assessment or advice from a qualified healthcare professional. Scan suitability and preparation depend on your circumstances and the specific examination. If you are worried about symptoms, speak to a healthcare professional. Seek urgent help for emergency symptoms.
Frequently asked questions
Answers to common questions about your scan, how to prepare and what happens next.
Does a CT scan expose me to radiation?
Yes. CT uses ionising radiation. your doctor and imaging team consider the expected diagnostic benefit and use an appropriate protocol.
Is MRI safer than CT?
MRI does not use ionising radiation, but it has different limitations and safety checks, including those relating to metal and implants. The most appropriate scan depends on the clinical question.
Should I avoid CT if I have had one before?
Not necessarily. Tell your doctor about previous imaging so they can consider whether repeat imaging is needed. Do not delay an important examination without discussing it with a healthcare professional.
Can I have a CT scan if I might be pregnant?
Tell the provider before the scan. They will assess the circumstances and decide whether CT or an alternative examination is most appropriate.
Ready to arrange your scan?
At PrivateScans, we make arranging your scan straightforward. Appointments can usually be arranged within 1–3 days, and your results are provided within 3 days of your scan. When you’re ready, book online. If you have questions before booking, our team is here to help.