Pictures shown for the brain

With functional magnetic resonance imaging, it is not only possible to see cross-sectional images of the human body but also to watch how the brain processes different tasks. A new optical projection system delivers pictures to the test subject inside the scanner. Functional magnetic resonance imaging fMRI is a fascinating means of observing what happens in the living brain when it is thinking, feeling an emotion or carrying out a movement. If, for instance, a doctor wants to investigate how someone processes visual impressions, a  series of pictures are shown to the subject while he or she is lying in the tunnel of the scanner. While the subject looks at the pictures, the scanner records cross-sectional images of the organ. In addition to the conventional MRI scan, a fMRI system records neural activity by measuring local and temporal changes in the concentration of oxygen in blood and tissue. Subsequent computer analysis produces the familiar pictures with colored patches indicating different levels of activity in different parts of the brain. What makes things a bit more complicated is that the scanner operator cannot simply hand photos to the person lying in the narrow tunnel of the machine. And the subject is not allowed to move, because this would distort the measurements. The pictures are therefore displayed using a projection system, which not only has to be extremely compact. In addition, it also must not contain any ferromagnetic materials such as iron – for these would distort the magnetic field. Moreover, the display has to be of a type that is more or less immune to the presence of the field. Anyone who has held a magnet next to a CRT monitor knows what happens: the picture on the screen goes haywire. Scientists at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena have developed a projection system specifically for this purpose, using microdisplays made up of luminescent organic light-emitting diodes (OLEDs). Because it has separate eyepieces for each eye, it even allows the scanner to be used for testing stereoscopic vision. The lens system also permits the observer to see which part of the picture the subject’s eyes are focused on, providing an additional source of information for neurological studies. The complete system is being built by the Norwegian company NordicNeuroLab that commissioned the research. “There is a growing need for projection systems for medical applications, and also for use in virtual reality systems,” reports Stefan Riehemann of the IOF department for optical systems. “We are often asked to design such specialized systems – especially for cases where it is not possible to use conventional hardware.” The IOF researchers employ different types of microdisplays in their solutions, based on liquid crystals and micromirrors in addition to OLEDs. "Source":[ http://www.fraunhofer.de/fhg/EN/press/pi/2006/01/1-2006-Topic5.jsp]

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