How long does a scan appointment take? MRI, CT, ultrasound, X-ray and PET compared

The time you spend on the scanner is usually shorter than the time you are in the building. The figures below come from NHS pages for each type of scan, and they describe the scan itself rather than the whole visit. They are typical, and your own appointment letter is the best guide because it reflects the way your hospital runs that particular test.

As a rough order, a plain X-ray is quickest, followed by CT, then ultrasound and MRI, with PET and some nuclear medicine tests taking longest because they need time for a tracer to circulate before pictures are taken.

The NHS describes an MRI scan as taking usually between 15 minutes and 1 hour, but it can take longer. You lie flat, wear ear plugs or headphones because the scanner makes loud bangs and clicks, and need to stay still so the images are clear. Some people are given an injection of contrast medium to show more detail. If so, the NHS says you may be asked to wait for up to 30 minutes afterwards to make sure you do not react.

A CT scan is usually quicker. The NHS says it usually takes between 10 and 20 minutes. The scanner is a large ring that moves around part of your body as you lie on a flat bed, and you may be asked to breathe in, out or hold your breath at times. Depending on the reason for the scan, you may have contrast medium in a drink, an injection or via your bottom, and again may wait up to 30 minutes afterwards if it was injected.

Both pages stress that preparation varies. For a CT scan the NHS says you may be asked to follow a special diet, take certain medicines or not eat or drink for several hours beforehand, which does not change the scanner time but may change when you need to arrive.

The NHS says an ultrasound scan can take around 10 to 45 minutes, but it might take longer. A healthcare professional moves a probe, covered in gel, across the skin, or in some cases uses an internal probe. They may stop to make notes or take measurements. For some scans you are asked to drink a few glasses of water without going to the toilet so that you have a full bladder, and you may need to undress behind a screen or in a changing room.

An X-ray is the quickest test in this group. The NHS says that having the X-ray itself should only take a few minutes. You may be asked to keep very still for a few seconds while one or more images are taken, and to move into different positions. The time you may add is for changing, for any contrast medium or barium, and for waiting. The NHS says that if you were given barium or contrast medium you may be asked to wait for up to 30 minutes.

PET scans take more time overall. The NHS says the scan usually takes around 30 to 60 minutes. About an hour before the scan you are given an injection of a small amount of a radioactive liquid, called a tracer, and you lie down and rest while it works. The NHS also says you will usually be asked to stop eating 6 hours before and to avoid strenuous exercise for up to 24 hours before.

Other nuclear medicine tests can be longer again, and the leaflets from individual hospitals show how varied they are. For a DOTATATE or similar PET-CT, the Christie NHS Foundation Trust tells patients to expect to be in the department for 3 to 4 hours altogether. A MUGA heart scan takes up to 45 minutes for the pictures at one trust, and one to two hours for the whole study at another. An MIBG scan is a two-day test, and Cambridge University Hospitals says to allow at least six hours on day 1 and about two hours on day 2.

Some tests involve a needle or a short procedure before the scan, so the whole visit is much longer than the scanning time. A CT myelogram is an example. The Royal Berkshire NHS Foundation Trust describes being admitted to a day bed in the X-ray department for the morning, having contrast injected into the spinal canal, returning to the bed for about an hour, and then having a scan that it describes as painless and taking only a few seconds. Newcastle Hospitals says the whole procedure for a myelogram is likely to take about one hour, followed by a few hours on the ward.

The lesson is that the length of the scan and the length of the appointment are different questions. If your letter mentions a day bed, a cannula, a blood test or a waiting period, plan for the longer visit.

Results are a separate wait. The NHS says it usually takes between 1 and 2 weeks to get MRI results, and that a CT scan usually takes 1 to 2 weeks but can take up to 4 weeks depending on how urgent the scan is and where you live. For PET scans the NHS says it usually takes 1 or 2 weeks. An ultrasound result may be given at the end of the appointment or take a few weeks, depending on the reason for the scan. For X-rays, results may be given on the same day or a few weeks later.

In each case the images are looked at by a specialist called a radiologist, who writes to the doctor who referred you. If you have not heard anything after a few weeks, the NHS advises contacting the doctor who referred you.