New technology could reduce radiation exposure in CT scans

A study from Rensselaer Polytechnic Institute in the US is the first to calculate exactly how much additional radiation obese patients receive from a CT scan. Research results show the internal organs of obese men receive 62 per cent more radiation during a CT scan than those of normal-weight men. For obese women, it was an increase of 59 per cent.

Technology developed at Rensselaer by nuclear engineering expert Xie George Xu could help solve this problem. Xu’s research team created realistic 3D computer models of overweight and obese men and women, and used computer simulations to determine how X-rays interact with the different body types.

These models, known as ‘phantoms’, can help physicians to configure and optimise CT scanning devices in such a way that minimises how much radiation a patient receives.

‘Radiation exposure is cumulative over a patient’s lifetime,’ said Xu, head of the Nuclear Engineering Program and a professor in the Department of Mechanical, Aerospace and Nuclear Engineering (MANE) at Rensselaer.

‘The risk associated with a radiation dose from a single CT scan is relatively small when compared with the clinical benefit of the procedure. But patients are increasingly undergoing multiple CT scans and other radiation-based procedures, which can lead to unnecessary radiation risk… Our new study brings us one step closer to minimising radiation exposure and mitigating this risk to patients.’

If technicians use current equipment settings to perform a CT scan on an obese patient, the resulting images are blurry as the X-ray photons have to travel further and make their way through layers of fat.

As a result, technicians generally adjust the equipment to a more powerful setting, which produces a better image but exposes the obese patient to additional radiation. There is no mechanism for discerning the setting levels that will provide an optimal balance of the highest image clarity and the lowest radiation dose.

These new phantoms for overweight and obese patients will be part of a forthcoming software package, VirtualDose, developed by Xu and his team. VirtualDose aims to enable the creation of a personalised, ultra-realistic phantom of any patient undergoing a CT scan.

The program takes into consideration a patient’s individual characteristics, including age, sex, height, weight, and even if a woman is pregnant. By entering this data into the software, VirtualDose quickly creates a phantom that accurately models the patient’s internal organs.

These phantoms will allow physicians and researchers to compare the radiation doses a patient will get from different CT scanner settings and then choose the most appropriate configuration.

VirtualDose will also enable physicians to keep a highly accurate record of how much radiation patients are exposed to over their lifetime. California recently became the first state in the US to require radiation dose records for patients undergoing CT examinations.

Results of the team’s study have been published in the journal Physics in Medicine & Biology.