Faculty Spotlight

Archive - 2004

Portable scanners moving closer to reality

Alex Pines

Although nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) provide crucial diagnostic information, these sophisticated techniques are typically immobile, intimidating to patients, and expensive to use.

Limitations on the use of these techniques are numerous. NMR and MRI devices can fill a room and cost millions of dollars. A significant number of patients suffer claustrophobia during the procedure. Also, many potential objects or subjects for analysis are unmovable, fragile, or in some other way not suited to examination in a fixed bore with limited accessibility.

QB3 faculty affiliate Alexander Pines and his collaborators are seeking ways to turn these costly, challenging behemoths into potentially user-friendly, portable, and inexpensive devices that might be used in the doctor’s office.

Pines, the Glenn T. Seaborg Professor of Chemistry at UC Berkeley and senior scientist at Lawrence Berkeley National Laboratory (LBNL), has pioneered the development of novel approaches to NMR spectroscopy, a technique for detecting and studying molecular structures in samples from polymers and catalysts to biomolecules and tissue.

His collaborators include Thomas Budinger, UC Berkeley professor of bioengineering and e lectrical engineering and computer sciences, UC San Francisco professor of radiology, and head of LBNL’s Department of Nuclear Medicine & Functional Imaging ; John Clarke, UC Berkeley professor of physics and LNBL Material Science Division investigator; Jeffrey Reimer, UC Berkeley professor of chemical engineering and LBNL faculty scientist; Peter Schultz, director of the Genomics Institute of the Novartis Research Foundation; and David Wemmer, UC Berkeley professor of chemistry.

Along with Pines, Budinger and Wemmer are also QB3 faculty affiliates.

Both NMR and MRI techniques are based on the fact that nuclei within the body’s atoms act like minuscule magnetic moments that resonate at characteristic frequencies when placed in a magnetic field. NMR and MRI are typically performed by placing samples, either molecules for NMR or some part of an object or subject for MRI, in a high-field superconducting magnet of several Tesla, 10,000 to 100,000 times stronger than the Earth’s magnetic field.

Clarke’s and Pines’s groups have developed a way to enhance the scanning process without using large magnets by employing prepolarization and superconducting quantum interference devices (SQUIDs) for signal detection at ultralow frequencies. The combination of SQUIDs with modern developments in NMR pulse sequences, switched magnetic fields, and gradients to detect spatially encoded signals has produced encouraging micro-Tesla images of samples from plants to the human forearm. Furthermore, researchers can obtain images in the presence of metals, even of objects within a metal container, circumstances under which normal high-field MRI is impossible.

Budinger, Pines, and their research groups have developed an additional technique that “lights up” NMR and MRI images to greatly improve the image contrast. Pines and Budinger created a patented process in which living tissue is injected with polarized xenon gas, an inert gas that does not react with living cells but can create a local magnetic field detectable by MRI scanners. Their process has been licensed and is a candidate for clinical trials designed to improve cardiovascular imaging with MRI.

Together with Schultz, Wemmer and Pines have further enhanced the capabilities of laser-polarized xenon as a molecular and imaging diagnostic tool by developing a “functionalized” xenon-based biosensor for protein and metabolite targets. In one recent incarnation of their work, the NMR and MRI are detected remotely, up to several meters away, thus making it possible to separately optimize the NMR/MRI encoding of the concentrated gas for observation by ultrasensitive detectors such as SQUIDs and laser magnetometers.

By combining these techniques, which take advantage of ultra-low magnetic fields, Pines and his colleagues are paving the way for a future in which chemists, molecular biologists, and physicians can use handheld scanners to obtain molecular and structural details and images previously available only through access to the currently prevailing lab-bound machines.

Related link

Alex Pine's lab