Four-year-old Amy Morrell is a world first after a pioneering treatment helped save her life - and spared her a heavy dose of radiation.

Little Amy was born with a rare heart condition and has already been through two operations, one after birth and one at six months.

Doctors needed to check whether her heart, which was too small when she was born, was ready for a third operation before her fourth birthday.

The tests usually require a substantial dose of X-rays to check the organ's condition.

But breakthrough technology meant surgeons at Guy's Hospital in London were able to carry out the procedure without subjecting Amy, from Brighton, to the potentially damaging radiation.

She is now on the way to making a full recovery.

The hospital team used a new XMR facility, which integrates magnetic resonance imaging (MRI) with conventional X-rays, to create a 3D computer model of her heart. They then inspected the model to ensure she was ready for the op.

Amy's mother, Joanne, said: "It was great that we could have the test done with less radiation, and the extra information obtained reassured us that the operation was likely to be successful."

Dr Derek Hill, of Guy's, King's and St Thomas' School of Medicine at King's College London, said: "It's like being able to see the model of a house rather than a floor plan."

The XMR facility located at Guy's is the first of its type in the UK and the first in the world to carry out these pioneering procedures on children with heart defects.