Imaging radio frequency electron-spin-resonance spectrometer with high resolution and sensitivity for i
 n v
 i
 v
 o measurements

Halpern, Howard J.; Spencer, David P.; Polen, Jerry van; Bowman, Michael K.; Nelson, Aimee J.; Dowey, Elizabeth M.; Teicher, Beverly A.

doi:10.1063/1.1140314

Cited by 205 publications

(133 citation statements)

References 11 publications

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“…An extension of this is the use of techniques previously reserved for the laboratory such as EPR imaging which detects unpaired electrons in such species as transition metal complexes and free radicals [39][40][41]. Unpaired electrons are extremely rare in normal tissues, so little if any EPR signal is detected in biological tissues.…”

Section: Functional Imagingmentioning

confidence: 99%

The chemistry and biology of nitroxide compounds

Soule

Hyodo

Matsumoto

et al. 2007

Free Radical Biology and Medicine

459

387

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Cyclic nitroxides are a diverse range of stable free radicals that have unique antioxidant properties. Because of their ability to interact with free radicals, they have been used for many years as biophysical tools. During the past 15-20 years, however, many interesting biochemical interactions have been discovered and harnessed for therapeutic applications. Biologically relevant effects of nitroxides have been described including their ability to degrade superoxide and peroxide, inhibit Fenton reactions and undergo radical-radical recombination. Cellular studies defined the activity of nitroxides in vitro. By modifying oxidative stress and altering the redox status of tissues, nitroxides have been found to interact with and alter many metabolic processes. These interactions can be exploited for therapeutic and research use including protection against ionizing radiation, as probes in functional magnetic resonance imaging, cancer prevention and treatment, control of hypertension and weight, and protection from damage resulting from ischemia/reperfusion injury. While much remains to be done, many applications have been well studied and some are presently being tested in clinical trials. The therapeutic and research uses of nitroxide compounds are reviewed here with a focus on the progress from initial development to modern trials.

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Section: Functional Imagingmentioning

confidence: 99%

The chemistry and biology of nitroxide compounds

Soule

Hyodo

Matsumoto

et al. 2007

Free Radical Biology and Medicine

459

387

View full text Add to dashboard Cite

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“…Electron paramagnetic resonance imaging (EPRI) has been widely used to map the distribution and metabolism of paramagnetic species in isolated organs and other ex vivo and in vivo biological systems (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). However, in contrast to proton NMR-based MRI, EPRI only detects the distribution and kinetics of free radicals, and consequently these images may not resemble the anatomic structure of the imaged object.…”

mentioning

confidence: 99%

EPR/NMR co‐imaging for anatomic registration of free‐radical images

Deng

et al. 2002

Magnetic Resonance in Med

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While electron paramagnetic resonance imaging (EPRI) enables spatial mapping of free radicals in the whole body of small animals, it solely visualizes the free-radical distribution and does not typically provide anatomic visualization of the body. However, anatomic registration is often required for meaningful interpretation of the EPRI-derived free-radical images. An approach is reported for whole-body, EPRI-based, free-radical imaging along with proton MRI in mice. EPRI instrumentation with a 750-MHz narrow band microwave bridge and transverse oriented electric field reentrant resonator, with automatic coupling control and automatic tuning control capability, was used to map the spatial distribution of nitroxide free radicals in phantoms and in living mice, while low-field proton MRI at 16 MHz was used to define the anatomic structure to register the EPR images. Small capillary tubes containing an aqueous radical label were used as markers to enable image superimposition. With this coregistration technique, the EPRI free-radical images were precisely registered, enabling assignment of the location of the observed free-radical distribution within the organs of the mice. Key words: in vivo EPR; in vivo NMR; proton MRI; co-imaging; automatic tuning; automatic couplingElectron paramagnetic resonance imaging (EPRI) has been widely used to map the distribution and metabolism of paramagnetic species in isolated organs and other ex vivo and in vivo biological systems (1-10). However, in contrast to proton NMR-based MRI, EPRI only detects the distribution and kinetics of free radicals, and consequently these images may not resemble the anatomic structure of the imaged object. Therefore, development of independent approaches for anatomic registration of EPR image data is of critical importance to facilitate accurate assignment of the distribution of free radicals within the body.Proton MRI has been well established over the last two decades as a precise method for the noninvasive delineation of internal anatomic structure, and has been widely applied in a wide range of research and clinical applications. As an MR technique, it is particularly powerful for anatomic mapping due to the high concentration and narrow linewidth of water protons in biological systems (11)(12)(13)(14)(15). By employing NMR images to define the anatomic structure with appropriate markers visualized by both EPRI and proton MRI, appropriate superimposition/registration can in principle be performed. This EPR/NMR coimaging (ENCI), while a seemingly simple concept, presents a number of unique technical challenges. These problems are primarily based on the need for high-resolution EPRI mapping of the registration markers and biological samples, appropriate NMR/EPR-detectable markers, and mechanical and computational approaches to appropriately fix the sample orientations and superimpose the images obtained. Largely because of these challenges, this type of co-imaging technique with 2D or 3D EPR image registration has not been previously achieved.App...

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“…Even if a trimmer capacitor C M is adjustable, critical coupling of the resonator could only be achieved when the other capacitors were appropriately adjusted. For several EPR resonators, remote tuning and matching circuits with varactor diodes have been reported [28][29][30][31]. Since the varactor diodes are usually used in applications with small signals, e.g., tuning of RF oscillators and radio/television receivers, non-linearity of the varactor diodes will appear in high-power applications.…”

Section: Resonator Designmentioning

confidence: 99%

A loop resonator for slice-selective in vivo EPR imaging in rats

Hirata

Deng

et al. 2008

Journal of Magnetic Resonance

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A loop resonator was developed for 300-MHz continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy and imaging in live rats. A single-turn loop (55 mm in diameter) was used to provide sufficient space for the rat body. Efficiency for generating a radiofrequency magnetic field of 38 µT/W 1/2 was achieved at the center of the loop. For the resonator itself, an unloaded quality factor of 430 was obtained. When a 350 g rat was placed in the resonator at the level of the lower abdomen, the quality factor decreased to 18. The sensitive volume in the loop was visualized with a bottle filled with an aqueous solution of the nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-CP). The resonator was shown to enable EPR imaging in live rats. Imaging was performed for 3-CP that had been infused intravenously into the rat and its distribution was visualized within the lower abdomen.

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Imaging radio frequency electron-spin-resonance spectrometer with high resolution and sensitivity for i n v i v o measurements

Cited by 205 publications

References 11 publications

The chemistry and biology of nitroxide compounds

The chemistry and biology of nitroxide compounds

EPR/NMR co‐imaging for anatomic registration of free‐radical images

A loop resonator for slice-selective in vivo EPR imaging in rats

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