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Komarov DA, Samouilov A, Hirata H, Zweier JL. High fidelity triangular sweep of the magnetic field for millisecond scan EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 329:107024. [PMID: 34198184 PMCID: PMC8316393 DOI: 10.1016/j.jmr.2021.107024] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/28/2021] [Accepted: 06/07/2021] [Indexed: 06/13/2023]
Abstract
Linearity of the magnetic field sweep is important for high resolution continuous wave EPR imaging. Driving the field with triangular wave function is the most efficient way to scan EPR projections. However, the magnetic field sweep profile can be significantly distorted during fast millisecond projection scan. In this work, we introduce a method to generate highly linear and properly symmetrical triangular sweeps of the magnetic field using calibrated harmonics of the triangular wave function. First, the frequency response function of the EPR magnet and its power circuitry was obtained. For this, the field sweeping coil was driven with sinusoidal signals of different frequencies and the actual magnetic field inside the magnet was recorded. To cover wide range of frequencies, the measurements were carried out independently using gaussmeter, Hall-effect linear sensor integrated circuit, and an inductance coil. For each frequency, the system gain and the phase delay were determined. These data were used to adjust the amplitudes and the phases of individual harmonics of the triangular wave function. After the calibration, the maximum deviation of the magnetic field from the linear function was 0.05% of sweep width for 4 ms scan. The maximum discrepancy between the forward and the reverse scan was less than 0.04%. Sweep overhead time for changing the scan direction was 5%. The proposed approach allows generation of high fidelity triangular magnetic field sweeps with accuracy better than 0.1% for the range of the magnetic field sweep widths up to 48 G and scan duration from 10 s down to 1 ms.
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Affiliation(s)
- Denis A Komarov
- The EPR Center and Department of Internal Medicine, Division of Cardiovascular Medicine, Davis Heart and Lung Institute, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Alexandre Samouilov
- The EPR Center and Department of Internal Medicine, Division of Cardiovascular Medicine, Davis Heart and Lung Institute, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Hiroshi Hirata
- Division of Bioengineering and Bioinformatics, Faculty of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo 060-0814, Japan
| | - Jay L Zweier
- The EPR Center and Department of Internal Medicine, Division of Cardiovascular Medicine, Davis Heart and Lung Institute, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
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2
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Tseytlin O, Guggilapu P, Bobko AA, AlAhmad H, Xu X, Epel B, O'Connell R, Hoblitzell EH, Eubank TD, Khramtsov VV, Driesschaert B, Kazkaz E, Tseytlin M. Modular imaging system: Rapid scan EPR at 800 MHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 305:94-103. [PMID: 31238278 PMCID: PMC6656609 DOI: 10.1016/j.jmr.2019.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 06/04/2019] [Accepted: 06/05/2019] [Indexed: 06/05/2023]
Abstract
An electron paramagnetic resonance (EPR) imaging system has been custom built for use in pre-clinical and, potentially, clinical studies. Commercial standalone modules have been used in the design that are MATLAB-controlled. The imaging system combines digital and analog technologies. It was designed to achieve maximum flexibility and versatility and to perform standard and novel user-defined experiments. This design goal is achieved by frequency mixing of an arbitrary waveform generator (AWG) output at the intermediate frequency (IF) with a constant source frequency (SF). Low noise SF at 250, 750, and 1000 MHz are available in the system. A wide range of frequencies from near-baseband to L-band can be generated as a result. Two-stage downconversion at the signal detection side is implemented that enables multi-frequency EPR capability. In the first stage, the signal frequency is converted to IF. A novel AWG-enabled digital auto-frequency control method that operates at IF is described that is used for automatic resonator tuning. Quadrature baseband EPR signal is generated in the second downconversion step. The semi-digital approach of mixing low-noise frequency sources with an AWG permits generation of arbitrary excitation patterns that include but are not limited to frequency sweeps for resonator tuning and matching, continuous-wave, and pulse sequences. Presented in this paper is the demonstration of rapid scan (RS) EPR imaging implemented at 800 MHz. Generation of stable magnetic scan waveforms is critical for the RS method. A digital automatic scan control (DASC) system was developed for sinusoidal magnetic field scans. DASC permits tight control of both amplitude and phase of the scans. A surface loop resonator was developed using 3D printing technology. RS EPR imaging system was validated using sample phantoms. In vivo imaging of a breast cancer mouse model is demonstrated.
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Affiliation(s)
- Oxana Tseytlin
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Priyaankadevi Guggilapu
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Andrey A Bobko
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Hussien AlAhmad
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA; Department of Industrial & Management Systems Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Xuan Xu
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Boris Epel
- Center for EPR Imaging In Vivo Physiology, University of Chicago, IL 60637, USA
| | - Ryan O'Connell
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Emily H Hoblitzell
- In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA; Department of Microbiology, Immunology & Cell Biology, West Virginia University School of Medicine, Morgantown, WV 26506, USA
| | - Timothy D Eubank
- In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA; Department of Microbiology, Immunology & Cell Biology, West Virginia University School of Medicine, Morgantown, WV 26506, USA
| | - Valery V Khramtsov
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Benoit Driesschaert
- In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA; Department of Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506, USA
| | - Eiad Kazkaz
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA
| | - Mark Tseytlin
- Biochemistry Department, West Virginia University, Morgantown, WV 26506, USA; In Vivo Multifunctional Magnetic Resonance Center at Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA.
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Tseytlin M. Full Cycle Rapid Scan EPR Deconvolution Algorithm. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 281:272-278. [PMID: 28666168 PMCID: PMC5568913 DOI: 10.1016/j.jmr.2017.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/09/2017] [Accepted: 06/10/2017] [Indexed: 05/12/2023]
Abstract
Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan period. Separation of the interfering up- and down-field scan responses remains a challenge for reaching the full potential of this new method. For this reason, only a factor of two increase in the scan rate was achieved, in comparison with the standard half-scan RS EPR algorithm. It is important for practical use that faster scans not necessarily increase the signal bandwidth because acceleration of the Larmor frequency driven by the changing magnetic field changes its sign after passing the inflection points on the scan. The half-scan and full-scan algorithms are compared using a LiNC-BuO spin probe of known line-shape, demonstrating that the new method produces stable solutions when RS signals do not completely decay by the end of each half-scan.
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Affiliation(s)
- Mark Tseytlin
- Department of Biochemistry, School of Medicine, West Virginia University, Morgantown, West Virginia, USA
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
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Eaton SS, Shi Y, Woodcock L, Buchanan LA, McPeak J, Quine RW, Rinard GA, Epel B, Halpern HJ, Eaton GR. Rapid-scan EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 280:140-148. [PMID: 28579099 PMCID: PMC5523658 DOI: 10.1016/j.jmr.2017.02.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 02/17/2017] [Accepted: 02/18/2017] [Indexed: 05/12/2023]
Abstract
In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250MHz.
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Affiliation(s)
- Sandra S Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Yilin Shi
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Lukas Woodcock
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Laura A Buchanan
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Joseph McPeak
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Richard W Quine
- School of Engineering and Computer Science and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - George A Rinard
- School of Engineering and Computer Science and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States
| | - Boris Epel
- Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, IL 60637, United States
| | - Howard J Halpern
- Department of Radiation and Cellular Oncology and Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, IL 60637, United States
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80210, United States.
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Jones CE, Berliner LJ. Nitroxide Spin-Labelling and Its Role in Elucidating Cuproprotein Structure and Function. Cell Biochem Biophys 2016; 75:195-202. [PMID: 27342129 DOI: 10.1007/s12013-016-0751-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/11/2016] [Indexed: 10/21/2022]
Abstract
Copper is one of the most abundant biological metals, and its chemical properties mean that organisms need sophisticated and multilayer mechanisms in place to maintain homoeostasis and avoid deleterious effects. Studying copper proteins requires multiple techniques, but electron paramagnetic resonance (EPR) plays a key role in understanding Cu(II) sites in proteins. When spin-labels such as aminoxyl radicals (commonly referred to as nitroxides) are introduced, then EPR becomes a powerful technique to monitor not only the coordination environment, but also to obtain structural information that is often not readily available from other techniques. This information can contribute to explaining how cuproproteins fold and misfold. The theory and practice of EPR can be daunting to the non-expert; therefore, in this mini review, we explore how nitroxide spin-labelling can be used to help the inorganic biochemist gain greater understanding of cuproprotein structure and function in vitro and how EPR imaging may help improve understanding of copper homoeostasis in vivo.
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Affiliation(s)
- Christopher E Jones
- The School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2759, Australia.
| | - Lawrence J Berliner
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO, 80208-0183, USA
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Abstract
Rapid-scan electron paramagnetic resonance is based on continuous direct detection of the spin response as the magnetic field is scanned upfield and downfield through resonance thousands of times per second. The method provides improved signal-to-noise for a wide range of samples, including rapidly tumbling and immobilized radicals. This chapter provides an introduction to the method and practical examples of implementation for organic radicals.
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Affiliation(s)
- Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, USA
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, USA.
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7
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Spitzbarth M, Drescher M. Simultaneous iterative reconstruction technique software for spectral-spatial EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 257:79-88. [PMID: 26102454 DOI: 10.1016/j.jmr.2015.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 05/31/2015] [Accepted: 06/01/2015] [Indexed: 05/13/2023]
Abstract
Continuous wave electron paramagnetic resonance imaging (EPRI) experiments often suffer from low signal to noise ratio. The increase in spectrometer time required to acquire data of sufficient quality to allow further analysis can be counteracted in part by more processing effort during the image reconstruction step. We suggest a simultaneous iterative reconstruction algorithm (SIRT) for reconstruction of continuous wave EPRI experimental data as an alternative to the widely applied filtered back projection algorithm (FBP). We show experimental and numerical test data of 2d spatial images and spectral-spatial images. We find that for low signal to noise ratio and spectral-spatial images that are limited by the maximum magnetic field gradient strength SIRT is more suitable than FBP.
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Affiliation(s)
- Martin Spitzbarth
- University of Konstanz, Department of Chemistry, 78457 Konstanz, Germany
| | - Malte Drescher
- University of Konstanz, Department of Chemistry, 78457 Konstanz, Germany.
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Czechowski T, Chlewicki W, Baranowski M, Jurga K, Szczepanik P, Szulc P, Tadyszak K, Kedzia P, Szostak M, Malinowski P, Wosinski S, Prukala W, Jurga J. Two-dimensional EPR imaging with the rapid scan and rotated magnetic field gradient. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:126-30. [PMID: 25442781 DOI: 10.1016/j.jmr.2014.09.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 07/13/2014] [Accepted: 09/23/2014] [Indexed: 05/12/2023]
Abstract
A new method for fast 2D Electron Paramagnetic Resonance Imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradient, whose orientation is changed at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to reduce the image acquisition time up to 10 ms for 2D EPRI, and to detect the sinogram with infinitesimal angular step between projections.
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Affiliation(s)
- T Czechowski
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland.
| | - W Chlewicki
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland; Faculty of Electrical Engineering, West Pomeranian University of Technology, 70-310 Szczecin, Poland
| | - M Baranowski
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland; Department of Physics, Adam Mickiewicz University, 61-614 Poznan, Poland
| | - K Jurga
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - P Szczepanik
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - P Szulc
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - K Tadyszak
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 14, PL 61614 Poznan, Poland
| | - P Kedzia
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - M Szostak
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - P Malinowski
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - S Wosinski
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
| | - W Prukala
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland; Department of Organometalic Chemistry, Adam Mickiewicz University, 60-780 Poznan, Poland
| | - J Jurga
- Laboratory of EPR Tomography, Poznan University of Technology, 60-965 Poznan, Poland
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