To scan or not to scan?

As a doctor, there's only so much I can do with my eyes, my ears and a stethoscope. I can hear your heart, listen to your lungs and look at your rash or your joints. But if I really want to know what's going on inside you, sometimes only a scan will do.

Ultrasound can't pass through bone, so can't be used, for instance, to look at your brain inside your skull. It can give a good picture of non-bony organs like your womb, that can't be seen with normal X-rays. CT scans and MRIs can give accurate pictures of a whole cross-section of your body, including blood vessels, bones and internal organs. There's almost no part of the body they can't reach!


Great for bones, joints and lungs, X-rays aren't good at showing what's going on with your internal organs. For that, your doctor would need to send you for an ultrasound, CT or MRI scan.


In ultrasound tests, high-frequency sound waves are used to build up a picture of your internal organs, because the waves pass through some organs and 'bounce' off others. This gives a light and shade picture that allows doctors to find out what's happening in organs like your ovaries and womb, your heart valves or your kidney, liver or gall bladder. Sometimes the probe is put on your skin. Sometimes - for instance, to get a good picture of your ovaries (or in men the prostate gland) - it will be need to be put into your vagina or bottom. Ultrasounds can also be used to look at your stomach and gullet by getting you to swallow a small tube with an ultrasound probe attached. There's no radiation involved, so it's safe even in pregnancy. Ultrasound scans have been used for years to give women their first glorious glimpse of their baby's beating heart - now that's a sight worth waiting for!

MRI scans

MRI, or magnetic resonance imaging, uses magnets and radio waves to build up its picture. There's no radiation involved, but because of the strength of the magnets you can't have an MRI scan if you have any metal implants. This includes a heart pacemaker. The magnets are inside a tube, and you need to lie in this tube for a quarter of an hour to one and a half hours, depending on the areas being scanned.

CT scans

A CT or CAT (computerised axial tomography) scan use X-ray pictures to build up a 3-D image of what's going on inside the part of your body it's looking at.

You'll usually be asked to lie on your back while an X-ray tube rotates round your body, and the images are picked up on the opposite side of your body. It takes 10-30 minutes and, apart from having to lie very still, isn't at all uncomfortable. It does expose you to X-rays but for a single scan done for a medical reason, the benefits are likely to outweigh the risks by a long way.

CT scan and stroke - a whole new world

The treatment of stroke has been revolutionised by 'clot-busting' drugs which can melt away clots in the brain after strokes. However, they need to be given quickly if they're going to work and they can make matters worse if your stroke has been caused by a bleed rather than a clot. An urgent CT scan tells clots from bleeds and means you can get this remarkable treatment if you need it.

If you suspect someone you know has had a stroke, think FAST:

  • Is their Face weak?
  • Can they raise their Arms above their head?
  • Is their Speech affected?
  • If so, Time to call an ambulance FAST!

Headaches & scans

Lots of my patients push very hard for scans, assuming that they'll give them answers and don't carry any risks. Never is this more true than with headaches. It's not surprising - headaches are incredibly common and can be very severe and debilitating. If you had pain that bad in your chest, for instance, there's a fair chance you'd be whisked off to A&E for heart tracing and blood tests. Everyone seems to be terrified of brain tumours, and we know brain scans show them up.

In 2012, the National Institute for Health and Care Excellence came out with clear guidance that people shouldn't be offered brain scans for headaches, to give them reassurance that there was no serious underlying cause. (1) Firstly, the severity of your headache doesn't bear any relationship to how likely you are to have an abnormality on scanning. For instance, cluster headaches are so severe that they're sometimes called 'suicide headaches', but they're diagnosed based on the symptoms you have and a brain scan would be normal. Secondly, if the condition doesn't go away (and some forms of headache, like migraine usually don't), any reassurance from a normal scan has usually worn off within a year. Thirdly, scans involve being exposed to significantly more radiation than X-rays and NICE highlights that we shouldn't be doing them without good cause.

How will I find out the results?

GPs regularly order ultrasounds and X-rays, and some can get direct access to CT and MRI scans. If you have a test that's been ordered by your GP, the result should be ready in 10 days or so. If a hospital doctor has ordered a scan, you'll usually be given a follow-up outpatient appointment where the hospital doctor can discuss the result with you. Your GP won't find out the result until after you do.



With thanks to 'My Weekly' where this article was originally published.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.