In recent months I have had three CT scans — one of my abdomen and two of my chest. I am 83 years old, and I was curious if it is dangerous to have so many scans.

Doreen Roberts, via email.

Radiation from Xrays or scans can be risky if there are multiple investigations. However most people get more radiation from natural sources that medical checks.

You may have heard that Marie Curie (radium, the radioactive substance used in Xrays) died from anemia in 1934 at the age 66. She had been exposed to it for a long time.

But to put this in perspective, in an average year, we are exposed to about 3 millisieverts (mSv, the unit of measurement) of radiation from ‘background’ sources such as radon (a gas that leaks from rocky ground, especially where there is lots of granite, limestone or sandstone) or even cosmic rays from outer space.

Radiation from X-rays and scans is, in theory, risky if you have multiple investigations, but most people get more from natural sources than medical checks

Radiation from Xrays and scans can be dangerous if you have multiple investigations. However, most people get more benefit from natural sources than medical checkups.

Modern X-ray imaging uses much lower doses of radiation than the old methods.

This applies to CT scans, also known as computerised tomography (CT), which were created at the end of 1970s. While CT scans require a higher dose than plain X-rays for radiation, most exposures are still very low. For example, a standard chest X-ray might require just 0.1mSv, while a low dosage CT lung scan may require around 1.5mSv.

According to Cancer Research UK, a CT scan of the abdomen or pelvis can involve higher exposure — up to around 10 mSv.

But the point to remember here is that the medical information your doctors have gained from those three CT scans outweighs significantly the risk of any future health damage from the ionising radiation — so please don’t worry.

While CT scans require higher radiation doses than plain X-rays for some purposes, most people are still exposed to a relatively low level of radiation. 

I have white patches at the back my mouth. Oral thrush was diagnosed by my GP. He has prescribed fluconazole several times, but it returns after a few weeks. Could it be my daily steroid-inhaler to control my asthma and my tablets for osteoporosis that I took?

Emily Harris, Cambridgeshire.

This is indeed oral thrush – an infection of the mouth and throat caused by a yeast called Candida albicans.

If the white flecks are removed with a microbiology cotton wool bud or microbiology swab, they leave a red, often inflamed, mark that quickly heals.

Fluconazole, an antifungal medication and common treatment for thrush is very effective in clearing it up. A single (150mg), dose usually banishes symptoms in 48 hours.

However, your condition is almost certain relapsing if you are using a corticosteroid to manage your asthma.

Steroids can suppress the immune system, and this is what’s allowing the infection to keep coming back.

This is why GPs instruct asthma steroid-inhaler patients to rinse their mouth with water immediately following use to remove any residue. If not, the steroid residues can suppress the immune response in the mouth, throat, and cause Candida albicans proliferation.

Proper inhaler technique is also essential to minimise steroid deposits in the throat and ensure as much of the drug as possible ends up where it needs to be — in the lungs.

When using the inhaler, take as much air as you can and coordinate activation with your inhalation.

While you can probably avoid more episodes of thrush, it might be worth having a spare dose of fluconazole.

Write to Dr. Scurr

Write to Dr Scurr at Good Health, Daily Mail, 2 Derry Street, London W8 5TT or email — include your contact details. Dr Scurr can not enter into personal correspondence.

Replies should be taken in context. Always consult your doctor if you have questions.

In my view…Don’t delay your booster shot

There is strong evidence to support the administration of a Covid-19 booster vaccination or a third injection to people over 50 and those with chronic diseases that could put them at high risk for infection.

We know, for example, two doses of the Pfizer vaccine are 90 per cent effective at preventing hospital admission if you catch the virus after being vaccinated — even with new variants. As vaccine-induced immunity wears off, that number drops to 47% after five months. However, a third shot at that point boosts it to 95 percent.

Also, research on the over-60s shows a third jab means they’re 11 times less likely to catch Covid-19 and 19 times less likely to fall seriously ill if they do.

But there is a problem. Just as they deal with a huge backlog, GPs have been responsible for the rollout. As a consequence, progress has been slow.

And the adverse publicity over side-effects may misguidedly deter some elderly or vulnerable people from coming forward — even though research shows no safety concerns from a third jab.

I’d urge all those in need of a booster to do everything they possibly can to make sure they get one. Without it, it could be a difficult winter ahead.