Development of a resonator with automatic tuning and coupling capability to minimize sample motion noise for in vivo EPR spectroscopy.
EPR spectroscopy has been applied to measure free radicals in vivo; however, respiratory, cardiac, and other movements of living animals are a major source of noise and spectral distortion. Sample motions result in changes in resonator frequency, Q, and coupling. These instabilities limit the applications that can be performed and the quality of data that can be obtained. Therefore, it is of great importance to develop resonators with automatic tuning and automatic coupling capability. We report the development of automatic tuning and automatic coupling provisions for a 750-MHz transversely oriented electric field reentrant resonator using two electronically tunable high Q hyperabrupt varactor diodes and feedback loops. In both moving phantoms and living mice, these automatic coupling control and automatic tuning control provisions resulted in an 8- to 10-fold increase in signal-to-noise ratio.
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EPR Center and Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, Maryland 21224, USA.
Petryakov
S
S
Samouilov
A
A
Chzhan
M
M
Kuppusamy
P
P
Zweier
J L
JL
D000818:Animals; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D051379:Mice; D008809:Mice, Inbred C3H; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation