New spectral–spatial imaging algorithm for full EPR spectra of multiline nitroxides and pH sensitive trityl radicals

Abstract

An algorithm is derived and demonstrated that reconstructs an EPR spectral-spatial image from projections with arbitrarily selected gradients. This approach permits imaging wide spectra without the use of the very large sweep widths and gradients that would be required for spectral-spatial imaging with filtered backprojection reconstruction. Each projection is defined as the sum of contributions at the set of locations in the object. At each location gradients shift the spectra in the magnetic field domain, which is equivalent to a phase change in the Fourier-conjugate frequency domain. This permits solution of the problem in the frequency domain. The method was demonstrated for 2D images of phantoms consisting of (i) two tubes containing 14N and 15N nitroxide and (ii) two tubes containing a pH sensitive trityl radical at pH 7.0 and 7.2. In each case spectral slices through the image agree well with the full spectra obtained in the absence of gradient.

Exchange Phenomena in the Electron Paramagnetic Resonance Spectra of the Nitroxyl and Trityl Radicals: Multifunctional Spectroscopy and Imaging of Local Chemical Microenvironment

“…The proposed future directions include advances in the synthesis of multifunctional paramagnetic probes and progress in EPR-based imaging techniques such as RS EPR imaging 87 and Overhauser-enhanced MRI. 59,91 …”

“…A new approach to image reconstruction is being evaluated that is based on the concept of solving the inverse problem in a form of large system of linear equations using Tikhonov regularization. 87 It was demonstrated that the size of the problem can be reduce by one in the Fourier domain, which makes it possible to handle with a modern desktop computer. The new method has been shown to work in a less computationally demanding two-dimensional case.…”

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters <em>In Vivo</em>

“…Note: Specific instructions related to analysis of phantoms containing BMPO-OH 24 , pH sensitive TAM radicals 19,27 and redox sensitive dinitroxides 28 are provided in the literature.…”

“…Magnetic field gradients are used to encode spatial information into EPR spectra, which are called projections. The spectral-spatial image is reconstructed from these projections 18,19 .…”

Rapid-Scan EPR of Nitroxide Spin Labels and Semiquinones

“…Krishna laboratory (Subramanian et al, 2007). Published rapid-scan imaging experiments have been performed with phantoms of TCNQ (Subramanian et al, 2007), LiPc (Czechowski et al, 2014), nitroxides (Aminov, Tseitlin, & Salikhov, 1999; Biller et al, 2015; Biller et al, 2014b; M. Tseitlin et al, 2014) and pH-sensitive amino substituted trityl radicals (Elajaili, Biller, Tseitlin, et al, 2015).…”