Monday, April 24, 2006

Bruce Rosen: brain imaging

Bruce Rosen started the colloquium by saying that it is useful to have two degrees - PhD and MD - because every time he gives a talk for the physicians, he may impress them by physics, and every time he speaks in front of the physicists, he may impress them by medicine. And he did.

Although there are many methods to study the anatomy and physiology of the brain - such as EEG and/or flattening the brain by a hammer which is what some of Rosen's students routinely do - Rosen considers NMR to be the epicenter of all these methods. (This is a conservative physics blog, so we still refer to these procedures as NMR and not MRI.) This bias should not be unexpected because Rosen's advisor was Ed Purcell.

Some of the results he shown were obtained by George Bush who is an extremely smart scientist as well as psychiatrist, besides being a good expert in B-physics.

Rosen has shown a lot of pictures and videosequences revealing how the activity of the brains depends on time in various situations, on the presence of various diseases, on the age, and on the precise way how the brains are being monitored. Many of these pictures were very detailed and methods already exist to extract useful data from the pictures and videos that can't be seen by a naked eye.

Human brains are being observed at 10 Tesla or so, and magnetic field of 15 Tesla is the state-of-the-art environment to scan the brains of smaller animals. The frequency used in these experiments is about half a gigahertz. Many tricks how to drastically reduce the required amount of drugs that the subject must take before the relevant structures are transparent have been found.

Most of the data comes from observations of water that is a dominant compound in the human body and not only the human body. It turns out that the blood that carries oxygen and the blood that carries carbon dioxide is diamagnetic and paramagnetic, respectively. That simplifies the NMR analysis considerably.

There's a lot of data in the field and fewer ways to draw the right conclusions and interpretations out of the data.

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