At Newcastle University, we are investigating the long-term health risks of low dose medical radiation exposure. Currently we are focusing on computed tomography (CT) scans and cardiac catheterizations (x-ray guided procedures used to diagnose and treat heart disease).

‎We have assembled two cohorts of patients exposed to medical radiation in order to improve knowledge of the cancer risks at low doses.

• A cohort of around 410,000 individuals who received a CT scan while aged under 22 years, and:
• A smaller cohort of around 14,000 individuals who underwent a cardiac catheterization while aged under 22 years.

Both cohorts were assembled from records of each examination type recorded at participating hospitals. Radiation doses for each examination were estimated using a type of computer modelling called Monte Carlo simulation. Cohort members were matched to the NHS England cancer registry to determine who has developed cancer, the cancer site and the date of diagnosis.

What have we found, so far?

We have found evidence of an increased risk of brain tumours and leukaemia from CT scans, but not Hodgkin’s lymphoma. Our findings suggest the cancer risks from medical x-ray exposures are reasonably small, and compatible with previous risk estimates. We have also found that the radiation doses from medical x-ray procedures have fallen markedly over the last decade. Typical doses for chest and abdomen CT scans are now comparable with the yearly dose from natural background sources (radon gas, cosmic rays etc.).

What are we doing now?

We are combining our CT cohort with others from Europe to produce a single pooled cohort of around 1 million individuals. The advantage of this is that the increased study size will improve statistical power, meaning we have a better ability to detect the risks at low doses. The combined CT cohort is called EPI-CT and is part of the MEDIRAD project. The combined cardiac catherization cohort is part of the HARMONIC project. In addition to studying the risks for brain tumours, leukaemia and lymphoma, we will also investigate other cancer sites, such as thyroid or breast cancer. In parallel, we are working to improve estimates of radiation doses, using the latest Monte Carlo computer modelling techniques.