A novel Electron Paramagnetic Resonance (EPR) oximetry
technique will help clinicians directly measure oxygen and schedule treatments
at times of high oxygen levels in cancer and stroke patients to improve outcomes,
the EPR team at Dartmouth's Geisel School of Medicine has found.
The team, led by Harold Swartz, MD, PhD, published their groundbreaking progress on the decades-old conundrum of how to measure oxygenation in deep-sited tissue in a paper titled, 'Deep-Tissue Oxygen Monitoring in the Brain of Rabbits for Stroke Research,' published in Stroke.
Nadeem Khan, PhD, first author said, "This is a major step forward. It brings EPR oximetry technique to the forefront of biomedical research for clinical applications."
The effectiveness of several therapies also depends on the oxygen levels in a malignancy. For example, a very low level of oxygen in cancer is known to develop aggressive phenotypes, varies with the growth of tumors, and also compromises the effectiveness of chemotherapy and radiation. Hence, it is very important to directly measure oxygen levels to understand disease progression, develop strategies to improve oxygen levels, and optimize the efficacy of therapies.
Oxygen measurement in deep-sited tissue has been a challenge for several techniques, which has unfortunately limited the understanding of various pathologies in large animals and humans. To solve the problem, Dartmouth's EPR team developed implantable resonators made of thin nonmagnetic copper wire to facilitate direct and repeated measurement of tissue oxygenation at any depth from the surface. In their most recent experiment, which demonstrated the efficacy of in vivo EPR oximetry, they used a one-time implementation of the oxygen probes in the brain of a rabbit and successfully monitored oxygen levels for several weeks.
"Other than the implantation, which is done under anesthesia, the rest of the procedure for oxygen measurements is entirely non-invasive. We anticipate that a better understanding of oxygen levels in stroke, for instance, will guide the development of strategies to significantly improve oxygen levels in the ischemic regions of the brain and thereby improve outcomes," explained Khan.
The investigators conclude that real-time monitoring of tissue oxygenation using implantable resonators will be a powerful tool in stroke and cancer research.