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Dynamic monitoring of localized tumor oxygenation changes using RF pulsed electron paramagnetic resonance in conscious mice
Author(s) -
Matsumoto Shingo,
Espey Michael Graham,
Utsumi Hideo,
Devasahayam Nallathamby,
Matsumoto KenIchiro,
Matsumoto Atsuko,
Hirata Hiroshi,
Wink David A.,
Kuppusamy Periannan,
Subramanian Sankaran,
Mitchell James B.,
Krishna Murali C.
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21500
Subject(s) - electron paramagnetic resonance , continuous wave , chemistry , oxygenation , nuclear magnetic resonance , pulsed epr , magnetic resonance imaging , nuclear medicine , medicine , spin echo , laser , radiology , physics , optics
Oxygenation status is a key determinant in both tumor growth and responses to therapeutic interventions. The oxygen partial pressure (pO 2 ) was assessed using a novel pulsed electron paramagnetic resonance (EPR) spectroscopy at 750 MHz. Crystals of lithium phthalocyanine (LiPc) implanted into either squamous cell carcinoma (SCC) tumor or femoral muscle on opposing legs of mice were tested by pulsed EPR. The results showed pO 2 of SCC tumor was 2.7 ± 0.4 mmHg, while in the femoral muscle it was 6.1 ± 0.9 mmHg. A major advantage of pulsed EPR oximetry over conventional continuous‐wave (CW) EPR oximetry is the lack of influence from subject motion, while avoiding artifacts associated with modulation or power saturation. Resonators in pulsed EPR are overcoupled to minimize recovery time. This makes changes in coupling associated with object motion minimal without influencing spectral quality. Consequently, pulsed EPR oximetry enables approximately a temporal resolution of ∼ one second in pO 2 monitoring in conscious subjects, avoiding significant influence of anesthetics on the physiology being studied. The pO 2 in SCC tumor and muscle was found to be higher without anesthesia (3.9 ± 0.5 mmHg for tumor, 8.8 ± 1.2 mmHg for muscle). These results support the advantage of pulsed EPR in examining pO 2 in conscious animals with LiPc chronically implanted in predetermined regions. Magn Reson Med, 2008. © 2008 Wiley‐Liss, Inc.