The patient lies in the bore, keeping as still as he can - but he finds it very hard to remain immobile for so long. If he moves too much, he risks causing errors - known by experts as artifacts - in the magnetic resonance image. This problem is particularly critical when high-resolution images are needed, as in an examination of the brain. If the patient is a child, or is seriously ill, it may even be necessary to administer an anesthetic to prevent him or her from moving. Until now, it has only been possible to correct artifacts after a delay of several seconds or after completing the scan. What is more, artifacts prolong and disturb the examinations.
Motion artifacts in magnetic resonance imaging will soon be a thing of the past: The PROMO technique developed by researchers at the Fraunhofer Institute for Computer Graphics IGD corrects errors caused by motion while the scan is still in progress. "PROMO determines the patients current head position immediately prior to each individual scan," explains IGD project manager Christian Dold. "The system transmits the exact position to the scanner of the tomograph sixty times a second. Before the scanner takes another picture, it adjusts the scanning image section to the current head position." PROMO is an optical recognition system: The patient bites for a few seconds on an individually fitted bite bar that is held in place by a slight vacuum. Attached to the bite bar is a frame with reflective markers. PROMO determines the spatial position of the markers and immediately transmits the information to the scanner. Thereafter, even the slightest head movement is immediately detected and compensated for.
Since even the position of patients who are used to keeping still may shift by one to three millimeters, PROMO improves the image quality even for these people. This means that functional magnetic resonance imaging (fMRT), for example, could become a routine procedure. A technique for displaying metabolic changes, fMRT requires extremely high-resolution images that can be distorted by even tiny head movements of less than one millimeter. In a first series of tests conducted with colleagues at Freiburg university hospital, PROMO proved to be very successful. It significantly improved the quality of the fMRT images even for patients who had frequently moved their heads. PROMO is already patented in Germany, and a patent is pending in the USA. The developers are confident that PROMO will be in use in hospitals within the next two years.
Contact:
Christian Dold
Phone: +49 6151 155-523
Fax: +49 6151 155-559
Fraunhofer-Institut für Graphische Datenverarbeitung
IGD
Fraunhoferstraße 5
64283 Darmstadt
For further information, please visit:
http://www.igd.fhg.de