James F. Glockner

Spectral-spatial ESR imaging as a method of noninvasive biological oximetry

Abstract Using a spectral range of 3.5 G, spectral-spatial ESR imaging has been applied to obtain noninvasively a quantitative spatial description of intracellular oxygen concentrations in vitro . The results of simulations and experiments with phantoms are presented to demonstrate the validity of this technique.

In Vivo EPR Oximetry Using Two Novel Probes: Fusinite and Lithium Phthalocyanine

The concentration of oxygen is an important variable in many physiological and pathological processes; it is not surprising, therefore, that a variety of methods have been developed to measure oxygen tensions in biological systems. Many techniques provide accurate and reliable determinations of in vitro oxygen tensions; in vivo measurements are more difficult, however, and the currently available methodologies have significant limitations. In this study we employ two novel EPR oximetric probes, fusinite and lithium phthalocyanine (LiPc), along with a low frequency (1.1 GHz) electron paramagnetic resonance (EPR) spectrometer and surface probe to measure intramuscular oxygen pressures in anesthetized mice. Principles of in vivo EPR oximetry are discussed in a preceding article by Swartz.

Oximetry in cells and tissues using a nitroxide-liposome system

In order to avoid the complication of reduction of nitroxides in biological media during oxygen measurements, liposomes containing a water-soluble nitroxide, 2,2,6,6-tetramethyl-piperidine-N-oxyl-4-trimethylammonium (Cat1), were used in studies of oxygen consumption by thymus-bone-marrow cells. The superhyperfine structure of Cat1 contained in liposomes was found to be sensitive to oxygen concentration in a fashion similar to that of free Cat1. Measurements of cellular respiration using Cat1 contained in liposomes agreed well with the results obtained using free Cat1. Using this nitroxide-liposome system, the respiration of liver slices was measured successfully, whereas such measurements using free cat1 were complicated by rapid reduction of the nitroxide. This nitroxide-liposome system also could be used in conjunction with a membrane permeable nitroxide and an extracellular broadening agent to measure intracellular and extracellular oxygen concentrations simultaneously.

Time-resolved contrast-enhanced MR angiography with single-echo Dixon fat suppression

Dixon‐based fat suppression has recently gained interest for dynamic contrast‐enhanced MRI, but multi‐echo techniques require longer scan times and reduce temporal resolution compared to single‐echo alternatives without fat suppression. The purpose of this work is to demonstrate accelerated single‐echo Dixon imaging with high spatial and temporal resolution.