Abstract: Methods and kits useful in the detection of occult blood in biological samples and specimens, for example to screen for colorectal cancer or detect blood in samples ex vivo, e.g., at a crime scene. Also provided are methods useful in diagnosing whether a subject is predisposed to, or suffers from, an occult-blood related disorder; and methods for direct micro-mapping of the distribution of occluded vessels associated with cerebral vascular injury.

Abstract: The invention provides apparatus and methods for measuring oxygen tensions in biological systems utilizing physiologically acceptable paramagnetic material, such as India ink or carbon black, and electron paramagnetic resonance (EPR) oximetry. India ink is introduced to the biological system and exposed to a magnetic field and an electromagnetic field in the 1-2 GHz range. The EPR spectra is then measured at the biological system to determine oxygen concentration. The EPR spectra is determined by an EPR spectrometer that adjusts the resonator to a single resonator frequency to compensate for movements of the biological system, such as a human or animal. The biological system can also include other in vivo tissues, cells, and cell cultures to directly measure pO.sub.2 non-destructively.