A bridged loop-gap S-band surface resonator for topical EPR spectroscopy.

The design and structure of a bridged loop-gap surface resonator developed for topical EPR spectroscopy and imaging of the distribution and metabolism of spin labels in in vivo skin is reported. The resonator is a one-loop, one-gap bridged structure. A pivoting single loop-coupling coil was used to couple the microwave power to the loop-gap resonant structure.

Development of a resonator with automatic tuning and coupling capability to minimize sample motion noise for in vivo EPR spectroscopy.

EPR spectroscopy has been applied to measure free radicals in vivo; however, respiratory, cardiac, and other movements of living animals are a major source of noise and spectral distortion. Sample motions result in changes in resonator frequency, Q, and coupling. These instabilities limit the applications that can be performed and the quality of data that can be obtained.

Noninvasive measurement of anatomic structure and intraluminal oxygenation in the gastrointestinal tract of living mice with spatial and spectral EPR imaging.

EPR imaging has emerged as an important tool for noninvasive three-dimensional (3D) spatial mapping of free radicals in biological tissues. Spectral-spatial EPR imaging enables mapping of the spectral information at each spatial position, and, from the observed line width, the localized tissue oxygenation can be mapped. We report the development of EPR imaging instrumentation enabling 3D spatial and spectral-spatial EPR imaging of small animals.

A tunable reentrant resonator with transverse orientation of electric field for in vivo EPR spectroscopy.

There has been a need for development of microwave resonator designs optimized to provide high sensitivity and high stability for EPR spectroscopy and imaging measurements of in vivo systems. The design and construction of a novel reentrant resonator with transversely oriented electric field (TERR) and rectangular sample opening cross section for EPR spectroscopy and imaging of in vivo biological samples, such as the whole body of mice and rats, is described. This design with its transversely oriented capacitive element enables wide and simple setting of the center frequency by trimming the dimensions of the capacitive plate over the range 100-900 MHz with unloaded Q values of approximately 1100 at 750 MHz, while the mechanical adjustment mechanism allows smooth continuous frequency tuning in the range +/-50 MHz.

Electron paramagnetic resonance imaging of the rat heart.

It has been hypothesized that free radical metabolism, oxygenation and nitric oxide generation in biological organs such as the heart may vary over the spatially defined tissue structure. To address fundamental questions regarding the role of spatially localized alterations in radical metabolism, oxygenation and nitric oxide in the pathophysiology of cellular injury during ischaemia, we have developed instrumentation optimized for 3D spatial and 3D or 4D spectral-spatial imaging of free radicals in the isolated perfused rat heart at 1.2 GHz.