At the University of California, Irvine, researchers can use a 200 million–pixel display system to develop medical imaging techniques for diagnostics.
Such a high level of visualization could help scientists understand brain diseases such as schizophrenia and Alzheimer's disease. “These diseases cause lesions, plaques, and other very small changes in the brain. In order to understand [them], we must look at the cellular level,” said Joerg Meyer during the ASME Frontiers in Biomedical Devices conference in June.
Meyer is an assistant professor in the electrical and computer engineering department at the university. “Our goal is to improve the quality of medical images and make the images representative of the actual body part,” he said.
The HIPerWall is an array of 50 flat-panel tiles that has the capacity to display more than 200 million pixels. Images at the cellular level can take up to 76 GB of space (enough to fill up one PC hard drive). Meyer said the greatest challenge they face is finding storage for the more than 1400 images the team has collected.
The system works by combining histological images, which are stacked to produce high-resolution renderings, and noninvasive methods such as computed tomography (CT) or magnetic resonance imaging, which is known for high alignment.
Researchers developed a visualization engine that produces three-dimensional (3-D) images from stacks of 2-D cross sections. In addition to the high-resolution images, annotated atlases can also be displayed at the same time, enabling simultaneous views of macro and microscopic structures from the same imaging set.
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Rendering combined with CT imaging enables visualization down to the cellular level, as demonstrated with this cross section of a monkey brain.
To demonstrate, Meyer presented high-resolution images of a rhesus monkey brain, which is about the size of a walnut. “We froze the brain and then cut it into 1400 very thin slices. Then we put the sections into a film scanner, which produced high-resolution digital images. The image quality is about 10 times better than with a typical 2-megapixel digital camera,” he said. The scanning was done at the Center for Neuroscience at the University of California, Davis. UCI processed the images, aligned them, and recombined them into a three-dimensional atlas of the monkey brain.
Meyer explains that there is one-to-one mapping between the functional regions and circuits of a monkey brain and a human brain. “We hope that our 3-D brain atlas will replace 2-D drawings in textbooks, because it is more intuitive and more instructive. It allows us to compute a virtual flight through the brain. We can zoom in and out, and we can navigate to every region of the brain and look at thecellular structure.”
Besides brain imaging, the researchers are also working on a computational heart-imaging model that has 22 million segments, rendered in real time. They are also looking at stem cells to map for differentiation.
And the team is also exploring ways to acquire images that do not rely on invasive histology. The engineers are working with a system called optical coherence tomography (OCT), which uses lasers to scan very thin layers of tissue, very close to the cellular level. “It is near the results we get from histology, which is the standard,” Meyer explained.
The National Institute of Mental Health funded the Monkey Brain Atlas project. The HIPerWall project was funded through a grant from the National Science Foundation.