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Innovation in moving organs MRI November 10, 2007

Isis Innovation, a spinoff of the University of Oxford, has developed new software for existing MRI machines to reduce breathing artifacts in medical images of moving organs, such as liver that sits just below the diaphragm.

Typically in magnetic resonance imaging, to acquire an image of the whole liver, you would need somebody to hold their breath for 60 seconds. Chances are that the patient is not particularly healthy, so it is expecting quite a lot. In existing methods of magnetic resonance imaging, the patient holds his or her breath for 20 seconds at a time while the machine takes an image of the liver in slices. After 60 seconds the slices are then put back together to form a whole image. Because the liver may move in between breath holds, some of the slices may overlap, or they might be put together incorrectly.

The researchers claim the new technology would eliminate this problem by aligning the slices of the liver image to a reference volume, an outline image of the liver taken before the more detailed slices, automatically checking for overlaps or missing slices. The reference image is acquired with a T1 weighted fast spoiled gradient echo (FSPGR) image. T2 images always take longer to acquire, so you break it down into several. You need both the T1 and T2 images to make the diagnoses, as they provide complementary information.(Source: The Engineer)

Worldwide over 1 million people are diagnosed with colorectal cancer annually, with a great proportion developing metastatic liver disease requiring follow up with abdominal Magnetic Resonance Imaging (MRI). Radiographers and Radiologists have raised breathing artefacts as a major issue in accurate diagnosis and estimation of tumour volumes. With current methods, in 19% of cases at least 5% of the liver is missed. Indeed, for lesions between 6 and 30mm in diameter, 3% are missed completely with a further 21% being incorrectly staged, leading to false diagnosis of disease progression or regression.

Working closely with clinical staff, Oxford scientists have used their expertise to find a robust solution. On the left, is an image that is reconstructed from a series of slices. The liver boundary is not smooth and the tumour seems to consist of multiple parts. After application of the Oxford technology, the liver outline is much smoother and the tumour well represented by a spherical shape. The technology significantly improves patient comfort by reducing scan duration and avoiding recalls. The improved quality and accuracy of the dataset provides meaningful estimation of tumour volumes for more precise chemotherapy dose calculation. It is estimated that 25% of the annual 2 million abdominal MRI scans worldwide would benefit from this innovation. The invention reached the Finals of the 2007 Medical Futures Innovation Awards and was also the subject of a recent paper in the European Journal of Radiology. (source:Isis Innovation)

The advantage of the technique is that it is applicable to organs subject to large uncontrolled amounts of motion. An extension of the technology would be the imaging of the head or body parts of patients who suffer from Parkinson’s disease and cannot control their motions.