Tabletop 700 MHz electron paramagnetic resonance imaging spectrometer

Abstract

Low frequency electron paramagnetic resonance imaging is a powerful tool to non-invasively measure the physiological status of tumors. Here, we report on the design and functionality of a rapid scan and pulse table-top imaging spectrometer based around an arbitrary waveform generator and 25mm cross-loop resonator operating at 700 MHz. Two and four-dimensional rapid scan spectral-spatial images are presented. This table-top imager is a prototype for future pre-clinical imagers.

EPR Everywhere

“…At $300 for the SDR card, the addition of a laptop and supplies to build a coil enables the construction of an EPR spectrometer for ~ $1000. Given the bandwidth of the LimeSDR card (~ 3.5 GHz), it is also potentially a multi-frequency microwave source and detector for an inexpensive price, though practically the source noise may limit operation to low frequencies (< ~ 1 GHz) without the addition of a low noise fixed frequency source [ 77 , 150 ]. This same card was programmed to perform NMR experiments, so that one unit could provide stand-alone DNP hardware using both transmit and receive channels on a single card.…”

“…Rapid-scan is now routinely used in low-frequency applications at DU and has been used for 4D imaging [77], dynamic imaging of redox status [78] and multicomponent phantom imaging [79]. An even more recent development regarding the rapid-scan background is to remove its influence based on how the experiment is carried out, rather than modifying the rapid-scan resonator.…”

“…Qualitative differences between hyperfine splitting may be used as a "fingerprint" allowing an effective and efficient way to explore new applications using low-field EPR. This type of fingerprinting has been investigated at VHF and UHF (~ 250 MHz, 700 MHz) in the Eaton laboratory in 2D spectral-spatial imaging experiments of hybrid phantoms containing 14 N and 15 N nitroxides and trityl radicals recorded by rapid-scan with sufficient SNR to differentiate the signals of each isotope present [77,79]. Regardless of the type of information to be extracted from an EPR spectrum, the experiment can always be relied upon to generate more questions than those with which the operator started.…”

Cyclic Disulfide-Bridged Dinitroxide Biradical for Measuring Thiol Redox Status by Electron Paramagnetic Resonance

“…Rapid-scan EPR imaging of a phantom containing the biradical was performed at L-band (1 GHz) to demonstrate the feasibility of using cPxSSPx-1 as an in vivo reporter of cellular thiol redox status. 18 ■ METHODS Reagents. Lyophilized cPxSSPx-1 (40.5 mg) was dissolved in 8.1 mL of DMSO to make a 10 mM stock solution.…”

“…For rapid-scan EPR, a previously described benchtop spectrometer, modified to operate at 1 GHz, was used for spectroscopy and imaging. 18 A loop-gap resonator with an internal diameter of 2.5 cm was used. Resonated sinusoidal scans were taken at a scan frequency of 9.76 kHz for spectroscopy or 17.85 kHz for imaging, with a scan width of 6 mT.…”