Lightweight, open, mobile, cheaper MRI brain scanner prototype working in lab

Attila Csordas — Wed, 17 Sep 2008 15:13:20 -0700

Description

Those giant, claustrophobic, tunnel forming magnets used for magnetic resonance imaging (MRI) in labs and hospitals look so last century! They are pricey and heavy, making MRI systems immobile and demanding to install. Any alternative? Yes by implementing the pre-polarized MRI concept introduced some 15 years ago:

"Writing in the Journal of Magnetic Resonance, Vadim Zotev and colleagues report success in imaging a human brain using a different type of MRI system: lightweight, open, mobile and significantly cheaper.

By dividing the functions of these large-field magnets between two sets of magnets with different characteristics, Zotev et al. have produced the prototype of a machine that would be smaller and more open, as well as being capable of performing magnetic resonance imaging and magnetoencephalography at the same time.

Conventional MRI machines reconcile these different requirements by using magnets that are both powerful and homogeneous. But could the same effect be achieved by using two simpler magnets and switching between them? The first magnet, strong but relatively inhomogeneous, would polarize the sample, whereas the second, weak but highly homogeneous, would be optimized for collecting resonance signals. This concept, termed pre-polarized MRI, was originally introduced by Macovski and Conolly2 some 15 years ago, and has been pursued by several research teams since.

Zotev et al. now report obtaining images of a living human brain using pre-polarization at 30 millitesla (mT) and image data collection at just 46 microT, a similar strength to that of Earth's magnetic field and about 30,000 times weaker than that of typical clinical MRI machines. Using such small magnetic fields means that the frequencies of the signals produced by the oscillating nuclear spins are similarly reduced from the usual radiofrequency range to around 2 kilohertz — a frequency readily audible to the human ear (approximately three octaves above middle C)."

Biomedical Sciences and Biotechnology

Source

Klaas P. Pruessmann: Medical imaging: Less is more
Nature 455, 43-44 (4 September 2008) | doi:10.1038/455043a
http://www.nature.com/nature/journal/v455/n7209/full/455043a.html

Zotev et al.: Microtesla MRI of the human brain combined with MEG.
J Magn Reson. 2008 Sep;194(1):115-20.
http://www.ncbi.nlm.nih.gov/pubmed/18619876?dopt=Abstract&holding=npg

Microfabrication to develop a family of magnetic microstructures to enhance the sensitivity of magnetic resonance images

jorgemata — Wed, 18 Jun 2008 14:29:02 -0700

Description

Engineering of 'coloured' agents that greatly enhance the sensitivity of magnetic resonance images

Magnetic resonance imaging (MRI) is widely used in medicine as a diagnostic and a research tool, but has so far been limited by having to rely on 'grey-scale' contrast agents to highlight biological areas of interest. A paper in tomorrow's Nature describes the engineering of 'coloured' agents that greatly enhance the sensitivity of the technique.

US scientists use microfabrication to develop a family of magnetic microstructures. They show that careful control of the geometry of these magnetic particles yields well-defined spectral signatures in the radio-frequency spectrum used for MRI - effectively giving them characteristic 'colours' that can be readily distinguished from one another.

The microstructures also function as subcellular-sized spectral radio-frequency identification tags, enabling increased MRI functionality, high sensitivity and greatly extended spectral ranges.

Abstract:

In recent years, biotechnology and biomedical research have benefited from the introduction of a variety of specialized nanoparticles whose well-defined, optically distinguishable signatures enable simultaneous tracking of numerous biological indicators. Unfortunately, equivalent multiplexing capabilities are largely absent in the field of magnetic resonance imaging (MRI). Comparable magnetic-resonance labels have generally been limited to relatively simple chemically synthesized superparamagnetic microparticles that are, to a large extent, indistinguishable from one another. Here we show how it is instead possible to use a top-down microfabrication approach to effectively encode distinguishable spectral signatures into the geometry of magnetic microstructures. Although based on different physical principles from those of optically probed nanoparticles, these geometrically defined magnetic microstructures permit a multiplexing functionality in the magnetic resonance radio-frequency spectrum that is in many ways analogous to that permitted by quantum dots in the optical spectrum. Additionally, in situ modification of particle geometries may facilitate radio-frequency probing of various local physiological variables.

Source

Micro-engineered local field control for high-sensitivity multispectral MRI. Gary Zabow1,2, Stephen Dodd1, John Moreland2 & Alan Koretsky1. Nature, June 19, 2008

1Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
2Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado, USA.