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		Charles S. Springer, Jr. Adjunct Professor (Brookhaven National Laboratory) B.S., 1962, St. Louis University; M.Sc., 1964, Ph.D., 1967, Ohio State University; U.S. Air Force Research and Development Award, 1967; Research Associate, Wright-Patterson Air Force Base, 1968; Visiting Research Associate, CalTech, 1976-77; Visiting Associate Professor of Medicine, Harvard Medical School, 1983-84; Visiting Associate Professor of Radiology, New England Deaconess Hospital, 1985; Adjunct Professor of Radiology, College of Physicians and Surgeons of Columbia University, 1989-present. Professor of Radiology, 1991-93; Board of Trustees, Int. Soc. for Magn. Reson. in Med. 1994-97; Assistant Professor, Associate Professor, Professor, State University of New York at Stony Brook, 1968 - 1996; Senior Chemist, Brookhaven National Laboratory, 1996-present; Editorial Board, NMR Biomed. , 1997- present. (631) 344-3109 Email: springer@bnl.gov Publications

	IN VIVO NMR The biological tissue NMR signal-to-noise ratio (SNR) scales with the field strength (measured as flux density, B0) of the instrument magnet, to at least the first power. Higher SNR translates into better temporal resolution, better spatial resolution (in MRI), or both. The very high field magnets (ex., 14T (Tesla)) used for high resolution chemical and biochemical molecular structure studies have very small bore sizes of vertical orientation. The largest field strength currently used for human subjects is 4T (170 MHz for 1 H). There are only eight such instruments in the world. We are very fortunate to have one of these in the High-Field MRI Laboratory at Brookhaven National Laboratory.It joins the PET (Positron Emission Tomography) Laboratory as part of the Brookhaven Center for Imaging and Neuroscience. Each of these laboratories is part of the BNL Chemistry Department. There are three current general themes in the High-Field MRI Laboratory programs. The first is to integrate MRI data with those obtained from the PET experiment. With some prudence, MR images constructed from the 1 H2O signal can be used to display very fine anatomical detail (sub-mm resolution). On the other hand, PET images can discern sub-nanomolar concentrations of any of the vast array of bioactive compounds that clever organic chemists can label with the PET isotopes of nature. The PET images, however, suffer resolution an order of magnitude poorer than that of MRI. We convolve Fourier-space MR and PET images of the same subject. A double Fourier transformation of such a convolution produces a positron emission magnetic resonance image (PEMRI), which exhibits the sensitivity of PET and the resolution of MRI. A second major effort involves the dramatic new methods to study brain function in a completely noninvasive way. These approaches, so-called functional MRI (fMRI), are rapidly sweeping the neuroscience world. They basically involve detecting changes in the oxygenation level of blood that occur in a region of neuronal activity. This is measurable by NMR because, while the oxygenated hemoglobin iron atom is diamagnetic, the deoxygenated iron atom - with four unpaired electrons - is paramagnetic. Thus, a change in the oxygenation state of blood is manifest as a change in the bulk magnetic susceptibility (BMS) of the blood. Changes in blood BMS values in microscopic regions of brain activity cause localized changes in the intensities of the MRI signals from those regions. Our research group has studied the fundamental aspects of BMS effects on NMR parameters for almost ten years. Gratifyingly, fMRI changes are significantly larger at 4T than those observed at the clinical field strengths of 2T or less. In fact, some very important aspects of neuronal activity can hardly be detected by fMRI even at 3T. Finally, 99% of all MR images are made from the 1 H2O signal, which is at least four orders of magnitude greater than any other from tissue. However, the tissue distribution of H2O is reasonably uniform. What heterogeneity exists is not sufficient to produce significant contrast between tissue types in an MR image. Thus, contrast in MRI is always produced by taking advantage of differences in the relaxation times (T1, T2) of signals in various tissues. However, this means that some of the 1 H2O signal is always discarded. We have developed a new approach that can produce contrast while at the same time preserving the entire signal. We produce images from discrete portions of the relaxation time distribution that describes the return of the nuclear magnetization to equilibrium. Since we refer to this distribution as a relaxogram, we call these relaxographic images.

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