When viewed in a rotating frame of reference, a transverse-plane radiofrequency (RF) field manifests as a longitudinal field component called the fictitious field. By modulating the RF field and thus the fictitious field, detectable longitudinal magnetization patterns have previously been shown to be measurable. By combining fictitious-field modulation and longitudinal detection, here we demonstrate EPR spectroscopy and one-dimensional imaging in a custom-built longitudinal detection system operating at an ultra-low frequency (24 MHz) for detecting electron spins with short (~nanoseconds) relaxation times. Simultaneous transmit and receive with low transmitter leakage level (~80 dB isolation) is also demonstrated.
Bibliographical noteFunding Information:
This research has been supported by the National Institutes of Health [ U01 EB025153 ] and the Malcolm B. Hanson Endowed Chair in Radiology. The authors would like to thank Jerahmie Radder, Russell Lagore and Steven Jungst for technical support. We are also grateful to Donald Garwood, Kalkidan Molla, Michael Mullen, Hattie Ring, Lance DelaBarre and Paul Wang for valuable discussions and their inspiring thoughts. Furthermore, we appreciate the constructive comments provided by the referees, which improved the paper.
- Electron paramagnetic resonance
- Fictitious field
- Iron-oxide nanoparticles
- Longitudinal detection
- Simultaneous transmit and receive