Rapid-scan EPR with triangular scans and fourier deconvolution to recover the slow-scan spectrum

Joshi, Janhavi P.; Ballard, John R.; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

doi:10.1016/j.jmr.2005.03.013

Cited by 81 publications

(110 citation statements)

References 25 publications

(38 reference statements)

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“…The technique has evolved over two decades to become an important tool for studying free radicals in many branches of science [3][4][5] and has potential for the study of living biological systems [6][7][8][9]. Despite progress, high-quality EPR imaging has been limited by several technical factors including resolution, sensitivity, and acquisition time [10,11].…”

Section: Introductionmentioning

confidence: 99%

A parametric approach to spectral–spatial EPR imaging

Som

Potter

Ahmad

et al. 2007

Journal of Magnetic Resonance

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Continuous wave electron paramagnetic resonance imaging for in vivo mapping of spin distribution and spectral shape requires rapid data acquisition. A spectral-spatial imaging technique is presented that provides an order of magnitude reduction in acquisition time, compared to iterative tomographic reprojection. The proposed approach assumes that spectral shapes in the sample are wellapproximated by members from a parametric family of functions. A model is developed for the spectra measured with magnetic field modulation. Parameters defining the spin distribution and spectral shapes are then determined directly from the measurements using maximum a posteriori probability estimation. The approach does not suffer approximation error from limited sweep width of the main magnetic field and explicitly incorporates the variability in signal-to-noise ratio versus strength of magnetic field gradient. The processing technique is experimentally demonstrated on a one-dimensional phantom containing a nitroxide spin label with constant g-factor. Using an L-band EPR spectrometer, spectral shapes and spin distribution are accurately recovered from two projections and a spectral window which is comparable to the maximum linewidth of the sample.

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Section: Introductionmentioning

confidence: 99%

A parametric approach to spectral–spatial EPR imaging

Som

Potter

Ahmad

et al. 2007

Journal of Magnetic Resonance

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“…[11] are essentially identical and represent the variance 2 of the observed noise sample (r), and the last term measures the autocorrelation (r) between the adjacent points of (r). Therefore,…”

Section: Spikesmentioning

confidence: 99%

“…In the past few years, the potential applications of EPRI to studies of living biological systems have been recognized (6 -9). However, despite all of the progress made in the last two decades, the acquisition of high-quality images of biological samples has been limited by several technical factors, including gradient strength and accuracy, sensitivity, reliability, and speed of data acquisition (10,11).…”

mentioning

confidence: 99%

Automated on‐the‐fly detection and correction procedure for EPR imaging data acquisition

Ahmad

Vikram

Petryakov

et al. 2006

Magnetic Resonance in Med

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Fast and reliable data acquisition is a major requirement for successful and useful biological electron paramagnetic resonance imaging (EPRI) experiments. Even a technologically advanced and professionally supervised EPRI system can exhibit instabilities initiated by perturbations such as animal motion, microphonics, and temperature changes. As a result, part of an acquired data set may become corrupted with excessive noise and distortions, which in turn may degrade the quality of the reconstructed image. In this work an automated scheme to monitor the system performance and stability over the course of an experiment is demonstrated. This method ensures that the quality of the acquired data is maintained during the experiment. For this purpose, four parameters including noise content and integration of each acquired projection are quantified and measured against those of the zero-gradient (ZG) projection, which is set as a quality benchmark. Key words: noise; system stability; microphonics; motion artifacts Electron paramagnetic resonance imaging (EPRI) is a noninvasive technique that is capable of mapping the distribution of unpaired electrons (1,2). It has a distinct advantage for many medical applications (3-5) in which it can be used to directly measure both endogenous and introduced free radicals that carry unpaired electrons. In the past few years, the potential applications of EPRI to studies of living biological systems have been recognized (6 -9). However, despite all of the progress made in the last two decades, the acquisition of high-quality images of biological samples has been limited by several technical factors, including gradient strength and accuracy, sensitivity, reliability, and speed of data acquisition (10,11).In the past decade, advances in hardware (12-14), such as lumped circuit resonator designs and optimized automatic frequency control systems, have led to more stable and efficient EPRI systems, but system stability (15,16) still remains a serious issue that may limit the reproducibility and quality of the acquired data. In addition, electromagnetic interference, microphonics, temperature fluctuations, and animal motion may introduce unwanted noise or distortions to the data, which may leave the entire data set unusable even if only a small fraction of the data are affected. Testing the performance of the system hardware in advance does improve the chances of attaining sustained performance during the acquisition, but because of the complex nature of the system, there is no guarantee that it would behave as expected over the course of an experiment. Therefore, it would be extremely useful to constantly monitor the performance of a system to ensure the quality of data acquired during the experiment. In this work we present a procedure to identify any damaged projections. For this purpose we first quantify four parameters: the noise intensity, spike amplitude, and first and second integrations of the acquired projections. We then compare the monitored parameters (MPs) of each projection ...

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“…4, 6 The problem has been addressed by using rotating magnetic field gradients [10][11][12] and developing rapid-scan EPR techniques. [13][14][15] On the other hand, pulse EPR techniques, such as those using projection reconstruction from free induction decay or echo detected signals, or k-space sampling in the case of single-point imaging ͑SPI͒ are proving to be efficient in obtaining fast images. 16,17 In time-domain EPR imaging, there is usually no need to sweep the main magnetic field, and ideally all spectral frequency components are present in the acquired time-domain trace.…”

Section: Introductionmentioning

confidence: 99%

Multiple‐stepped Zeeman field offset method applied in acquiring enhanced resolution spin‐echo electron paramagnetic resonance images

Seifi¹,

Epel²,

Mailer³

et al. 2010

Medical Physics

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Purpose: Electron paramagnetic resonance ͑EPR͒ imaging techniques provide quantitative in vivo oxygen distribution images. Time-domain techniques including electron spin echo ͑ESE͒ imaging have been under study in recent years for their robustness and promising new features. One of the limitations of ESE imaging addressed here is the finite acquisition frequency bandwidth, which imposes limits on applied magnetic field gradients and the resulting image spatial resolution. In order to improve the image spatial resolution, we have extended the effective frequency bandwidth of the imaging system by acquiring projections at multiple Zeeman magnetic field offsets and combining them to restore complete projections obtained with more uniform frequency response, resulting in higher quality images. Methods: In multiple-stepped magnetic field or multi-B scheme, every projection of the three dimensional object is acquired at different main or Zeeman magnetic field ͑B͒ offset values. The data from field offset steps are combined, normalizing to the imaging system frequency acquisition window function, a sensitivity profile, to restore the complete projection. A multipurpose pulse EPR imager and phantoms containing the same type of spin probe ͑OX063H͒ used in routine animal imaging were also used in this study. Results: Using the multi-B method, we were able to acquire images of our phantoms with enhanced spatial resolution compared to the conventional ESE approach. Compared to standard single-B ESE images, the T 2 resolutions of multi-B images were superior using a high spatial-resolution regime. Image artifacts present in high-gradient single-B ESE images are also substantially reduced using in the multi-B scheme. Conclusions:The multi-B method is less susceptible to instrumental limitations for larger gradient fields and acquiring images with higher spatial resolution better overall quality, without the need to alter the existing pulse ESE image acquisition hardware.

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Rapid-scan EPR with triangular scans and fourier deconvolution to recover the slow-scan spectrum

Cited by 81 publications

References 25 publications

A parametric approach to spectral–spatial EPR imaging

A parametric approach to spectral–spatial EPR imaging

Automated on‐the‐fly detection and correction procedure for EPR imaging data acquisition

Multiple‐stepped Zeeman field offset method applied in acquiring enhanced resolution spin‐echo electron paramagnetic resonance images

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