Towards Human Oxygen Images with Electron Paramagnetic Resonance Imaging

Area of Science:

• Medical Imaging
• Biophysics
• Biomedical Engineering

Background:

• Electron paramagnetic resonance imaging (EPRI) noninvasively provides 3D images of absolute oxygen concentration (pO2) with high spatial (~1 mm) and pO2 (1-3 mmHg) resolution.
• Preclinical EPRI studies show promise for investigating oxygen-dependent physiological processes and diseases like cancer hypoxia.

Purpose of the Study:

• To detail recent advancements in EPRI technology aimed at enabling human applications.
• To highlight the development of novel hardware and methods for improved EPRI imaging in humans.

Main Methods:

• Development of a bimodal crossed-wire surface coil for localized pO2 imaging in superficial human tumors.
• Construction of a large 9 mT EPRI magnet capable of accommodating human subjects for whole-body imaging.
• Investigation of intratumoral (IT) injections of the EPRI spin probe (trityl) to significantly reduce required doses compared to intravenous administration.

Main Results:

• The surface coil demonstrated high isolation, potentially enabling safer human imaging by reducing specific absorption rate limitations.
• The large magnet supports imaging of local anatomy in entire human subjects.
• Intratumoral injections reduced trityl probe requirements by a factor of 2000, addressing a key obstacle for human use.

Conclusions:

• Advancements in surface coils, large magnets, and reduced spin probe doses via IT injections are critical steps towards human EPRI applications.
• EPRI has the potential to image pO2 in superficial tumors and investigate various diseases including peripheral vascular disease, heart disease, and stroke.