Clinical EPR: unique opportunities and some challenges.
Electron paramagnetic resonance (EPR) spectroscopy has been well established as a viable technique for measurement of free radicals and oxygen in biological systems, from in vitro cellular systems to in vivo small animal models of disease. However, the use of EPR in human subjects in the clinical setting, although attractive for a variety of important applications such as oxygen measurement, is challenged with several factors including the need for instrumentation customized for human subjects, probe, and regulatory constraints. This article describes the rationale and development of the first clinical EPR systems for two important clinical applications, namely, measurement of tissue oxygen (oximetry) and radiation dose (dosimetry) in humans. The clinical spectrometers operate at 1.2 GHz frequency and use surface-loop resonators capable of providing topical measurements up to 1 cm depth in tissues. Tissue pO2 measurements can be carried out noninvasively and repeatedly after placement of an oxygen-sensitive paramagnetic material (currently India ink) at the site of interest. Our EPR dosimetry system is capable of measuring radiation-induced free radicals in the tooth of irradiated human subjects to determine the exposure dose. These developments offer potential opportunities for clinical dosimetry and oximetry, which include guiding therapy for individual patients with tumors or vascular disease by monitoring of tissue oxygenation. Further work is in progress to translate this unique technology to routine clinical practice.
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766. Electronic address: Harold.M.Swartz@Dartmouth.edu.
Harold M
HM
Swartz
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766.
Benjamin B
BB
Williams
Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Bassem I
BI
Zaki
Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Alan C
AC
Hartford
Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Lesley A
LA
Jarvis
Department of Surgery, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Eunice Y
EY
Chen
Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Richard J
RJ
Comi
Department of Medicine, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH.
Marc S
MS
Ernstoff
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766.
Huagang
H
Hou
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766.
Nadeem
N
Khan
Dept. of Radiation Oncology, University of Florida, Gainesville, FL.
Steven G
SG
Swarts
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766.
Ann B
AB
Flood
Department of Radiology, Geisel School of Medicine at Dartmouth, Dartmouth College, 48 Lafayette Street, Lebanon, NH 03766.
Periannan
P
Kuppusamy
D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D010092:Oximetry / Q000295:instrumentation* / Q000379:methods*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*
Electron paramagnetic resonance; dosimetry; free radical; hyperoxygenation; oxygen; radiation therapy; tumor therapy