Post date: Nov 26, 2012 1:45:56 PM
You might expect twins to share the womb happily during their mother's pregnancy, but striking new MRI images show fetal life isn't quite so harmonious. Used by London doctors, the scanning method also offers improved medical diagnosis for sufferers of twin-to-twin transfusion syndrome, a potentially life-threatening condition. Jim Drury has more.
The images were made possible by a recently developed cine-MRI scan used by clinicians at London's Center for Fetal Care.
Dr Marisa Taylor-Clarke says the technology offers new perspectives on dual pregnancies.
DR MARISA TAYLOR-CLARKE, CLINICAL RESEARCH FELLOW AT CENTRE FOR FETAL CARE & ROBERT STEINER MR UNIT,
"We haven't really been able to see before in such real-time complete pictures how twins interact and what this cine lets us do is see their positions in relation to each other and how much space they have, how much space they occupy, and how they might move around and push each other out of the way. So that's something that you can see snapshots of on ultrasound and small parts of it, but you don't get the view of the whole room, as it were, the room being the womb."
The scan uses a technique known as oversampling, which provides a far more detailed picture than conventional MRIs.
DR MARISA TAYLOR-CLARKE, CLINICAL RESEARCH FELLOW AT CENTRE FOR FETAL CARE & ROBERT STEINER MR UNIT,
"What we do differently is much thinner slices of the brain, so the pictures that we take are much, much thinner, just a couple of millimetre thickness regions and we overlap them, so that means that even if the baby moves we've over-sampled the brains, so when we come back to looking at them then if we want to reconstruct the 3D volume of the brain we've got extra data, which means we're not missing out any key regions."
Doctors here use the technique to study twin-to-twin transfusion syndrome, found in twins whose blood supplies are connected. In TTTS one sibling, called the recipient, takes
too much blood from the other - the donor twin - who can suffer stunted growth as a result.
Foetal laser surgery can successfully interrupt the blood flow, but in the worst case scenario TTTS can cause the deaths of both twins.
Although conventional ultrasound detects the syndrome, MRI scans pinpoint signs of brain injury earlier and in more detail, allowing treatment to be better targeted.
First-time mother Stephanie undergoes a scan as one of the centre's healthy volunteers. She's expecting a single child in January.
Despite the striking clarity offered by these scans, Taylor-Clarke doesn't advocate their use for routine pregnancies like Stephanie's.
DR MARISA TAYLOR-CLARKE, CLINICAL RESEARCH FELLOW AT CENTRE FOR FETAL CARE & ROBERT STEINER MR UNIT,
"I think MRI scanning is a very specialised technique and the vast majority of women have healthy pregnancies without any problems and deliver well, healthy babies and if we were to scan all pregnant women we would pick up a very very small number of abnormalities and potentially pick up things that we didn't know how to interpret that might be quite stressful for some mothers."
The Fetal Center is seeking further modifications of the cine MRI technique to help improve the chances of TTTS sufferers, and provide an even clearer picture of sibling rivalry.