Trials in measuring radiation doses accurately

Researchers have begun trials which will allow radiation doses in computed tomography (CT) scans to be estimated much more accurately.

Safer CT scans for children is the goal of a new approach to determining correct radiation dosages.

A multi-disciplinary team involving researchers from Westmead Hospital, The Children's Hospital at Westmead, Flinders and Sydney Universities, and CSIRO has begun trials of a new atlas of child body types which will allow radiation doses in computed tomography (CT) scans to be estimated much more accurately for children.

The method is based on new models of children's bodies at different ages, which have been developed by the Biomedical Image Analysis group at the CSIRO ICT Centre, led by Dr Sébastien Ourselin.

Associate Professor Donald McLean of Westmead Hospital's Medical Physics Department says that this will allow doses to be accurately known across the whole range of child sizes, and then made available clinically through a simple dose calculator.

"CT dose to children can vary by as much as 3600 per cent between different clinical centres," says Professor McLean.

"The use of an accurate CT dose calculator will allow radiographers to determine child doses before the examination and so result in significant dose reductions."

It is essential for clinicians to have an accurate idea of the amount of radiation energy deposited in various tissues of the body to correctly establish the child patient dose from a CT scan.

Dr Ourselin says that traditional model-based dose estimation has proven effective for adults but, in paediatric cases, they are less accurate because they are based on simple geometric models.

"This has resulted in incorrect radiation dosages being applied at times," says Dr Ourselin.

"Our new method is based on actual medical images of children in different age groups so it is a much more accurate tool for estimating energy deposition."

The new paediatric CT dosage model is being developed and clinically trialled with funding from a NH&MRC grant.

"Patients will benefit greatly from this new approach," says Dr McLean.

"The major benefits from CT for children will not be altered, but this new approach will assure that the dose to the child is appropriately low."