Uniform spinning sampling gradient electron paramagnetic resonance imaging

Abstract

Purpose To improve the quality and speed of electron paramagnetic resonance imaging (EPRI) acquisition by combining a uniform sampling distribution with spinning gradient acquisition. Theory and Methods A uniform sampling distribution was derived for spinning gradient EPRI acquisition (Uniform Spinning Sampling, USS) and compared to the existing (Equilinear Spinning Sampling, ESS) acquisition strategy. Novel corrections were introduced to reduce artifacts in experimental data. Results Simulations demonstrated that USS puts an equal number of projections near each axis whereas ESS puts excessive projections at one axis, wasting acquisition time. Artifact corrections added to the magnetic gradient waveforms reduced noise and correlation between projections. USS images had higher SNR (85.9±0.8 vs. 56.2±0.8) and lower mean-squared error than ESS images. The quality of the USS images did not vary with the magnetic gradient orientation, in contrast to ESS images. The quality of rat heart images was improved using USS compared to that with ESS or traditional fast-scan acquisitions. Conclusion A novel EPRI acquisition which combines spinning gradient acquisition with a uniform sampling distribution was developed. This USS spinning gradient acquisition offers superior SNR and reduced artifacts compared to prior methods enabling potential improvements in speed and quality of EPR imaging in biological applications.

Development of a fast‐scan EPR imaging system for highly accelerated free radical imaging

“…Important steps were made in the optimization of image‐acquisition software and image‐reconstruction routines . Implementation of these approaches has been shown to allow reduction in the number of projections, resulting in reduction of total image‐acquisition time and achieving submillimeter resolution in images of isolated rat hearts infused with LiNcBuO suspension and acquired in 264 seconds …”

“…33 Important steps were made in the optimization of imageacquisition software and image-reconstruction routines. [36][37][38][39][40][41][42][43] Implementation of these approaches has been shown to allow reduction in the number of projections, resulting in reduction of total image-acquisition time and achieving submillimeter resolution in images of isolated rat hearts infused with LiNcBuO suspension and acquired in 264 seconds. 41,42,44 With regard to hardware development, construction of fast 3D gradients even in combination with high-inductance main magnet allowed significant reduction of CW-EPRI image-acquisition time.…”

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery

“…The signal dynamics were modeled by a single exponential decay, with the time constants (in minutes) listed in Figure 1, which shows three orthogonal slices passing through the center of the phantom. The projection data were simulated using these parameters: sweepwidth of 1.6 × 10 −3 T, field-of-view 64×64×64 mm 3 , number of samples per projection of 128, and golden angle radial sampling [17,35]. The lineshape was assumed to be the first derivative of the Lorentzian function.…”

“…Compared to a small number of high-SNR projections, collecting a larger number of projections with relatively low SNR improves information content of the data by reducing redundancies. Although increasing the scan speed and uniformly distributing the projections [17,18] lead to a more efficient acquisition, SNR may become the limiting factor for in vivo application. Therefore, for realistic SNR values, FA and uniform sampling of the projection data may not be adequate to achieve high-fidelity imaging of rapid dynamic processes.…”

Molecular Probes for Evaluation of Oxidative Stress by In Vivo EPR Spectroscopy and Imaging: State-of-the-Art and Limitations

“…The main advantage of such models is the ease of immobilization of these body parts. Indeed, compensation of contractile heart motion and animal breathing movements is still challenging in EPR imaging [84,85]. Only rare examples of the in vivo evaluation of the whole-body organ-specific redox state exist, such as EPR/MRI co-imaging of smoke-exposed mice [86].…”