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Giovannetti G, Frijia F. Use of the Perturbing Sphere Method for the Estimation of Radiofrequency Coils' Efficiency in Magnetic Resonance Applications: Experience from an Electromagnetic Laboratory. SENSORS (BASEL, SWITZERLAND) 2024; 24:5705. [PMID: 39275616 PMCID: PMC11397733 DOI: 10.3390/s24175705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Revised: 08/19/2024] [Accepted: 08/28/2024] [Indexed: 09/16/2024]
Abstract
Radiofrequency (RF) transmitter and receiver coils are employed in in magnetic resonance (MR) applications to, respectively, excite the nuclei in the object to be imaged and to pick up the signals emitted by the nuclei with a high signal-to-noise ratio (SNR). The ability to obtain high-quality images and spectra in MR strongly depends on the RF coil's efficiency. Local coil efficiency can be estimated with magnetic field mapping methods evaluated at a fixed point in space. Different methods have been described in the literature, divided into electromagnetic bench tests and MR techniques. In this paper, we review our experience in designing and testing RF coils for MR in our electromagnetic laboratory with the use of the perturbing sphere method, which permits coil efficiency and magnetic field mapping to be estimated with great accuracy and in a short space of time, which is useful for periodic coil quality control checks. The method's accuracy has been verified with simulations and workbench tests performed on RF coils with different surfaces and of different volumes. Furthermore, all the precautions taken to improve the measurement sensitivity are also included in this review, in addition to the various applications of the method that have been described over the last twenty years of research in our electromagnetic laboratory.
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Affiliation(s)
- Giulio Giovannetti
- Institute of Clinical Physiology, National Council of Research, 56124 Pisa, Italy
| | - Francesca Frijia
- Bioengineering Unit, Fondazione Toscana G. Monasterio, 56124 Pisa, Italy
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2
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Flood AB, Sidabras JW, Swarts SG, Buehler PW, Schreiber W, Grinberg O, Swartz HM. Benefits and challenges of in vivo EPR nail biodosimetry in a second tier of medical triage in response to a large radiation event. RADIATION PROTECTION DOSIMETRY 2023; 199:1539-1550. [PMID: 37721065 PMCID: PMC10505939 DOI: 10.1093/rpd/ncad022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 09/19/2023]
Abstract
Following large-scale radiation events, an overwhelming number of people will potentially need mitigators or treatment for radiation-induced injuries. This necessitates having methods to triage people based on their dose and its likely distribution, so life-saving treatment is directed only to people who can benefit from such care. Using estimates of victims following an improvised nuclear device striking a major city, we illustrate a two-tier approach to triage. At the second tier, after first removing most who would not benefit from care, biodosimetry should provide accurate dose estimates and determine whether the dose was heterogeneous. We illustrate the value of using in vivo electron paramagnetic resonance nail biodosimetry to rapidly assess dose and determine its heterogeneity using independent measurements of nails from the hands and feet. Having previously established its feasibility, we review the benefits and challenges of potential improvements of this method that would make it particularly suitable for tier 2 triage. Improvements, guided by a user-centered approach to design and development, include expanding its capability to make simultaneous, independent measurements and improving its precision and universality.
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Affiliation(s)
- Ann Barry Flood
- Radiology Department, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH, USA
- Clin-EPR, LLC, Lyme, NH, USA
| | - Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Steven G Swarts
- Department of Radiation Oncology, University of Florida, Gainesville, FL, USA
| | - Paul W Buehler
- Department of Pathology, University of Maryland, Baltimore, MD, USA
| | | | | | - Harold M Swartz
- Radiology Department, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH, USA
- Clin-EPR, LLC, Lyme, NH, USA
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3
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Samouilov A, Komarov D, Petryakov S, Iosilevich A, Zweier JL. Development of an L-band resonator optimized for fast scan EPR imaging of the mouse head. Magn Reson Med 2021; 86:2316-2327. [PMID: 33938574 PMCID: PMC8295191 DOI: 10.1002/mrm.28821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 12/11/2022]
Abstract
PURPOSE To develop a novel resonator for high-quality fast scan electron paramagnetic resonance (EPR) and EPR/NMR co-imaging of the head and brain of mice at 1.25 GHz. METHODS Resonator dimensions were scaled to fit the mouse head with maximum filling factor. A single-loop 6-gap resonator of 20 mm diameter and 20 mm length was constructed. High resonator stability was achieved utilizing a fixed position double coupling loop. Symmetrical mutually inverted connections rendered it insensitive to field modulation and fast scan. Coupling adjustment was provided by a parallel-connected variable capacitor located at the feeding line at λ/4 distance. To minimize radiation loss, the shield around the resonator was supplemented with a planar conductive disc that focuses return magnetic flux. RESULTS Coupling of the resonator loaded with the mouse head was efficient and easy. This resonator enabled high-quality in vivo 3D EPR imaging of the mouse head following intravenous infusion of nitroxide probes. With this resonator and rapid scan EPR system, 4 ms scans were acquired in forward and reverse directions so that images with 2-scan 3,136 projections were acquired in 25 s. Head images were achieved with resolutions of 0.4 mm, enabling visualization of probe localization and uptake across the blood-brain barrier. CONCLUSIONS This resonator design provides good sensitivity, high stability, and B1 field homogeneity for in vivo fast scan EPR of the mouse head and brain, enabling faster measurements and higher resolution imaging of probe uptake, localization, and metabolism than previously possible.
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Affiliation(s)
- Alexandre Samouilov
- Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210 USA
| | - Denis Komarov
- Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210 USA
| | - Sergey Petryakov
- Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210 USA
| | - Arkadiy Iosilevich
- Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210 USA
| | - Jay L. Zweier
- Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH 43210 USA
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Implantable microchip containing oxygen-sensing paramagnetic crystals for long-term, repeated, and multisite in vivo oximetry. Biomed Microdevices 2019; 21:71. [PMID: 31286244 DOI: 10.1007/s10544-019-0421-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
EPR oximetry is established as a viable method for measuring the tissue oxygen level (partial pressure of oxygen, pO2) in animal models; however, it has not yet been established for measurements in humans. EPR oximetry requires an oxygen-sensing paramagnetic probe (molecular or particulate) to be placed at the site/organ of measurement, which may pose logistical and safety concerns, including invasiveness of the probe-placement procedure as well as lack of temporal stability and sensitivity for long-term (repeated) measurements, and possible toxicity in the short- and long-term. In the past, we have developed an implantable oxygen-sensing probe, called OxyChip, which we have successfully established for oximetry in pre-clinical animal models (Hou et al. Biomed. Microdevices 20, 29, 2018). Currently, OxyChip is being evaluated in a limited clinical trial in cancer patients. A major limitation of OxyChip is that it is a large (1.4 mm3) implant and hence not suitable for measuring oxygen heterogeneity that may be present in solid tumors, chronic wounds, etc. In this report, we describe the development of a substantially smaller version of OxyChip (0.07 mm3 or 70 cubic micron), called mChip, that can be placed in the tissue of interest using a 23G syringe-needle with minimal invasiveness. Using in vitro and in vivo models, we have shown that the microchip provides adequate EPR sensitivity, stability, and biocompatibility and thus enables robust, repeated, and simultaneous measurement from multiple implants providing mean and median pO2 values in the implanted region. The mChips will be particularly useful for those applications that require repeated measurements of mean/median pO2 in superficial tissues and malignancies.
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Rinard GA, Quine RW, Buchanan LA, Eaton SS, Eaton GR, Epel B, Sundramoorthy SV, Halpern HJ. Resonators for In Vivo Imaging: Practical Experience. APPLIED MAGNETIC RESONANCE 2017; 48:1227-1247. [PMID: 29391664 PMCID: PMC5788320 DOI: 10.1007/s00723-017-0947-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Resonators for preclinical electron paramagnetic resonance imaging have been designed primarily for rodents and rabbits and have internal diameters between 16 and 51 mm. Lumped circuit resonators include loop-gap, Alderman-Grant, and saddle coil topologies and surface coils. Bimodal resonators are useful for isolating the detected signal from incident power and reducing dead time in pulse experiments. Resonators for continuous wave, rapid scan, and pulse experiments are described. Experience at the University of Chicago and University of Denver in design of resonators for in vivo imaging is summarized.
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Affiliation(s)
- George A Rinard
- Center for EPR Imaging In Vivo Physiology, Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, CO 80210, USA
| | - Richard W Quine
- Center for EPR Imaging In Vivo Physiology, Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, CO 80210, USA
| | - Laura A Buchanan
- Center for EPR Imaging In Vivo Physiology, Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, CO 80210, USA
| | - Sandra S Eaton
- Center for EPR Imaging In Vivo Physiology, Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, CO 80210, USA
| | - Gareth R Eaton
- Center for EPR Imaging In Vivo Physiology, Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, CO 80210, USA
| | - Boris Epel
- Center for EPR Imaging In Vivo Physiology, Department of Radiation and Cellular Oncology, University of Chicago, IL, USA
| | - Subramanian V Sundramoorthy
- Center for EPR Imaging In Vivo Physiology, Department of Radiation and Cellular Oncology, University of Chicago, IL, USA
| | - Howard J Halpern
- Center for EPR Imaging In Vivo Physiology, Department of Radiation and Cellular Oncology, University of Chicago, IL, USA
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Li Y, Cai M, Sun Q, Liu Z, Cardounel AJ, Swartz HM, He G. Hyperoxia and transforming growth factor β1 signaling in the post-ischemic mouse heart. Life Sci 2013; 92:547-54. [PMID: 23352974 DOI: 10.1016/j.lfs.2013.01.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/18/2012] [Accepted: 01/08/2013] [Indexed: 11/24/2022]
Abstract
AIMS Following ischemic injury, myocardial healing and remodeling occur with characteristic myofibroblast trans-differentiation and scar formation. The current study tests the hypothesis that hyperoxia and nitric oxide (NO) regulate TGF-β1 signaling in the post-ischemic myocardium. MAIN METHODS C57BL/6 wild-type (WT), endothelial and inducible nitric oxide synthase knockout (eNOS(-/-) and iNOS(-/-)) mice were subjected to 30-min left anterior descending coronary artery occlusion followed by reperfusion. Myocardial tissue oxygenation was monitored with electron paramagnetic resonance oximetry. Protein expressions of TGF-β1, receptor-activated small mothers against decapentaplegic homolog (Smad), p21 and α-smooth muscle actin (α-SMA) were measured with enzyme-linked immunosorbent assay (ELISA), Western immunoblotting, and immunohistochemical staining. KEY FINDINGS There was a hyperoxic state in the post-ischemic myocardial tissue. Protein expressions of total and active TGF-β1, p-Smad2/3 over t-Smad2/3 ratio, p21, and α-SMA were significantly increased in WT mice compared to Sham control. Knockout of eNOS or iNOS further increased protein expression of these signals. The expression of α-SMA was more abundant in the infarct of eNOS(-/-) and iNOS(-/-) mice than WT mice. A protein band indicating nitration of TGF-β type-II receptor (TGFβRII) was observed from WT heart. Carbogen (95% O2 plus 5% CO2) treatment increased the ratio of p-Smad2/t-Smad2, which was inhibited by 10006329 EUK (EUK134) and sodium nitroprusside (SNP). In conclusion, hyperoxia up-regulated and NO/ONOO(-) inhibited cardiac TGF-β1 signaling and myofibroblast trans-differentiation. SIGNIFICANCE These findings may provide new insights in myocardial infarct healing and repair.
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Affiliation(s)
- Yuanjing Li
- Davis Heart and Lung Research Institute and Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
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Enomoto A, Hirata H. Sequential CW-EPR image acquisition with 760-MHz surface coil array. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 209:244-249. [PMID: 21320789 DOI: 10.1016/j.jmr.2011.01.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 01/19/2011] [Accepted: 01/19/2011] [Indexed: 05/30/2023]
Abstract
This paper describes the development of a surface coil array that consists of two inductively coupled surface-coil resonators, for use in continuous-wave electron paramagnetic resonance (CW-EPR) imaging at 760 MHz. To make sequential EPR image acquisition possible, we decoupled the surface coils using PIN-diode switches, to enable the shifting of the resonators resonance frequency by more than 200 MHz. To assess the effectiveness of the surface coil array in CW-EPR imaging, two-dimensional images of a solution of nitroxyl radicals were measured with the developed coil array. Compared to equivalent single coil acquired images, we found the visualized area to be extended approximately 2-fold when using the surface coil array. The ability to visualize larger regions of interest through the use of a surface coil array, may offer great potential in future EPR imaging studies.
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Affiliation(s)
- Ayano Enomoto
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo 060-0814, Japan
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Abstract
Reactive oxygen/nitrogen species (ROS/RNS) have been increasingly recognized as important mediators and play a number of critical roles in cell injury, metabolism, disease pathology, diagnosis, and clinical treatment. Electron paramagnetic resonance (EPR) spectroscopy enables the spectral information at certain spatial position, and, from the observed line-width and signal intensity, the localized tissue oxygenation, and tissue redox status can be determined. We applied in vivo EPR oximetry and redoximetry technique and implemented its physiological/pathophysiological applications, along with the use of biocompatible lithium pthalocyanine (liPc) and nitroxide redox sensitive probes, on in vivo tissue oxygenation and redox profile of the ischemic and reperfused heart in living animals. We have observed that the hypoxia during myocardial ischemia limited mitochondrial respiration and caused a shift of tissue redox status to a more reduced state. ROS/RNS generated at the beginning of reperfusion not only caused a shift of redox status to a more oxidized state which may contribute to the postischemic myocardial injury, but also a marked suppression of in vivo tissue O(2) consumption in the postischemic heart through modulation of mitochondrial respiration based on alterations in enzyme activity and mRNA expression of NADH dehydrogenase (NADH-DH) and cytochrome c oxidase (CcO). In addition, ischemic preconditioning was found to be able to markedly attenuate postischemic myocardial hyperoxygenation with less ROS/RNS generation and preservation of mitochondrial O(2) metabolism, due to conserved NADH-DH and CcO activities. These studies have demonstrated that EPR oximetry and redoximetry techniques have advanced to a stage that enables in-depth insight in the process of ischemia reperfusion injury.
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Affiliation(s)
- Guanglong He
- The Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute and Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH, USA.
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Petryakov S, Samouilov A, Chzhan-Roytenberg M, Kesselring E, Sun Z, Zweier JL. Segmented surface coil resonator for in vivo EPR applications at 1.1GHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 198:8-14. [PMID: 19268615 PMCID: PMC2919311 DOI: 10.1016/j.jmr.2008.12.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 12/03/2008] [Accepted: 12/15/2008] [Indexed: 05/21/2023]
Abstract
A four-loop segmented surface coil resonator (SSCR) with electronic frequency and coupling adjustments was constructed with 18mm aperture and loading capability suitable for in vivo Electron Paramagnetic Resonance (EPR) spectroscopy and imaging applications at L-band. Increased sample volume and loading capability were achieved by employing a multi-loop three-dimensional surface coil structure. Symmetrical design of the resonator with coupling to each loop resulted in high homogeneity of RF magnetic field. Parallel loops were coupled to the feeder cable via balancing circuitry containing varactor diodes for electronic coupling and tuning over a wide range of loading conditions. Manually adjusted high Q trimmer capacitors were used for initial tuning with subsequent tuning electronically controlled using varactor diodes. This design provides transparency and homogeneity of magnetic field modulation in the sample volume, while matching components are shielded to minimize interference with modulation and ambient RF fields. It can accommodate lossy samples up to 90% of its aperture with high homogeneity of RF and modulation magnetic fields and can function as a surface loop or a slice volume resonator. Along with an outer coaxial NMR surface coil, the SSCR enabled EPR/NMR co-imaging of paramagnetic probes in living rats to a depth of 20mm.
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Affiliation(s)
| | | | | | | | | | - Jay L. Zweier
- Corresponding author. Fax: +1 614 247 7845. (J.L. Zweier)
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Hirata H, He G, Deng Y, Salikhov I, Petryakov S, Zweier JL. A loop resonator for slice-selective in vivo EPR imaging in rats. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 190:124-34. [PMID: 18006343 PMCID: PMC2615245 DOI: 10.1016/j.jmr.2007.10.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 10/24/2007] [Accepted: 10/24/2007] [Indexed: 05/05/2023]
Abstract
A loop resonator was developed for 300 MHz continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy and imaging in live rats. A single-turn loop (55 mm in diameter) was used to provide sufficient space for the rat body. Efficiency for generating a radiofrequency magnetic field of 38 microT/W(1/2) was achieved at the center of the loop. For the resonator itself, an unloaded quality factor of 430 was obtained. When a 350 g rat was placed in the resonator at the level of the lower abdomen, the quality factor decreased to 18. The sensitive volume in the loop was visualized with a bottle filled with an aqueous solution of the nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-CP). The resonator was shown to enable EPR imaging in live rats. Imaging was performed for 3-CP that had been infused intravenously into the rat and its distribution was visualized within the lower abdomen.
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Affiliation(s)
- Hiroshi Hirata
- Department of Electrical Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan.
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Dhimitruka I, Velayutham M, Bobko AA, Khramtsov VV, Villamena FA, Hadad CM, Zweier JL. Large-scale synthesis of a persistent trityl radical for use in biomedical EPR applications and imaging. Bioorg Med Chem Lett 2007; 17:6801-5. [PMID: 17964156 DOI: 10.1016/j.bmcl.2007.10.030] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Revised: 10/09/2007] [Accepted: 10/10/2007] [Indexed: 11/26/2022]
Abstract
Tetrathiatriarylmethyl radicals are ideal spin probes for biological electron paramagnetic resonance (EPR) spectroscopy and imaging. The wide application of trityl radicals as biosensors of oxygen or other biological radicals was hampered by the lack of affordable large-scale syntheses. We report the large-scale synthesis of the Finland trityl radical using an improved addition protocol of the aryl lithium monomer to methylchloroformate. A new reaction for the formal one-electron reduction of trityl alcohols to trityl radicals using neat trifluoroacetic acid is reported as well. Initial applications show that the compound is very sensitive to molecular oxygen. It has already provided high-resolution EPR images on large aqueous samples and should be suitable for a broad range of in vivo applications.
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Affiliation(s)
- Ilirian Dhimitruka
- Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
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Petryakov S, Samouilov A, Kesselring E, Wasowicz T, Caia GL, Zweier JL. Single loop multi-gap resonator for whole body EPR imaging of mice at 1.2 GHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 188:68-73. [PMID: 17625940 PMCID: PMC2714052 DOI: 10.1016/j.jmr.2007.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 04/13/2007] [Accepted: 05/18/2007] [Indexed: 05/05/2023]
Abstract
For whole body EPR imaging of small animals, typically low frequencies of 250-750 MHz have been used due to the microwave losses at higher frequencies and the challenges in designing suitable resonators to accommodate these large lossy samples. However, low microwave frequency limits the obtainable sensitivity. L-band frequencies can provide higher sensitivity, and have been commonly used for localized in vivo EPR spectroscopy. Therefore, it would be highly desirable to develop an L-band microwave resonator suitable for in vivo whole body EPR imaging of small animals such as living mice. A 1.2 GHz 16-gap resonator with inner diameter of 42 mm and 48 mm length was designed and constructed for whole body EPR imaging of small animals. The resonator has good field homogeneity and stability to animal-induced motional noise. Resonator stability was achieved with electrical and mechanical design utilizing a fixed position double coupling loop of novel geometry, thus minimizing the number of moving parts. Using this resonator, high quality EPR images of lossy phantoms and living mice were obtained. This design provides good sensitivity, ease of sample access, excellent stability and uniform B(1) field homogeneity for in vivo whole body EPR imaging of mice at 1.2 GHz.
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Affiliation(s)
- Sergey Petryakov
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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Williams BB, Sucheta A, Dong R, Sakata Y, Iwasaki A, Burke G, Grinberg O, Lesniewski P, Kmiec M, Swartz HM. Experimental Procedures for Sensitive and Reproducible In Situ EPR Tooth Dosimetry. RADIAT MEAS 2007; 42:1094-1098. [PMID: 18591989 DOI: 10.1016/j.radmeas.2007.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In vivo electron paramagnetic resonance (EPR) tooth dosimetry provides a means for non-invasive retrospective assessment of personal radiation exposure. While there is a clear need for such capabilities following radiation accidents, the most pressing need for the development of this technology is the heightened likelihood of terrorist events or nuclear conflicts. This technique will enable such measurements to be made at the site of an incident, while the subject is present, to assist emergency personnel as they perform triage for the affected population. At Dartmouth Medical School this development is currently being tested with normal volunteers with irradiated teeth placed in their mouths and with patients who have undergone radiation therapy. Here we describe progress in practical procedures to provide accurate and reproducible in vivo dose estimates.
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Samouilov A, Caia GL, Kesselring E, Petryakov S, Wasowicz T, Zweier JL. Development of a hybrid EPR/NMR coimaging system. Magn Reson Med 2007; 58:156-166. [PMID: 17659621 PMCID: PMC2919286 DOI: 10.1002/mrm.21205] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Accepted: 01/12/2007] [Indexed: 11/08/2022]
Abstract
Electron paramagnetic resonance imaging (EPRI) is a powerful technique that enables spatial mapping of free radicals or other paramagnetic compounds; however, it does not in itself provide anatomic visualization of the body. Proton magnetic resonance imaging (MRI) is well suited to provide anatomical visualization. A hybrid EPR/NMR coimaging instrument was constructed that utilizes the complementary capabilities of both techniques, superimposing EPR and proton-MR images to provide the distribution of paramagnetic species in the body. A common magnet and field gradient system is utilized along with a dual EPR and proton-NMR resonator assembly, enabling coimaging without the need to move the sample. EPRI is performed at approximately 1.2 GHz/ approximately 40 mT and proton MRI is performed at 16.18 MHz/ approximately 380 mT; hence the method is suitable for whole-body coimaging of living mice. The gradient system used is calibrated and controlled in such a manner that the spatial geometry of the two acquired images is matched, enabling their superposition without additional postprocessing or marker registration. The performance of the system was tested in a series of phantoms and in vivo applications by mapping the location of a paramagnetic probe in the gastrointestinal (GI) tract of mice. This hybrid EPR/NMR coimaging instrument enables imaging of paramagnetic molecules along with their anatomic localization in the body.
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Affiliation(s)
- Alexandre Samouilov
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
| | - George L. Caia
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
| | - Eric Kesselring
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
| | - Sergey Petryakov
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
| | - Tomasz Wasowicz
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
| | - Jay L. Zweier
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Ohio State University, Columbus, Ohio, USA
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Lund LP, Timmins GS. Melanoma, long wavelength ultraviolet and sunscreens: Controversies and potential resolutions. Pharmacol Ther 2007; 114:198-207. [PMID: 17376535 DOI: 10.1016/j.pharmthera.2007.01.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Accepted: 01/30/2007] [Indexed: 12/31/2022]
Abstract
Although sunlight is known to cause melanoma, there has been considerable controversy as to the importance of short (UVB) and long (UVA) ultraviolet (UV) wavelengths in causing melanoma, leading to uncertainty in how best to prevent this cancer. This uncertainty has been compounded by the difficulties in assaying the UVA protection abilities of sunscreens, as compared to widely accepted measures of UVB screening by the sun protection factor (SPF). This review discusses the controversies surrounding UVA causation of melanoma in both human and animal models and the use of sunscreens to prevent melanoma. In addition, it details the development of an electron paramagnetic resonance (EPR) technique, initially used to determine the wavelength dependence (or action spectrum) of intramelanocyte radical generation to resolve these controversies in the Xiphophorus model. It is shown how this EPR technique allows a sunscreen protection factor to be determined, that is weighted to the melanocyte, and how this also allows study of the wavelength-dependent screening ability of sunscreens.
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Affiliation(s)
- Leslie P Lund
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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Som S, Potter LC, Ahmad R, Kuppusamy P. A parametric approach to spectral-spatial EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 186:1-10. [PMID: 17276111 PMCID: PMC2020527 DOI: 10.1016/j.jmr.2006.12.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 12/12/2006] [Accepted: 12/16/2006] [Indexed: 05/13/2023]
Abstract
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 well-approximated 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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Affiliation(s)
- Subhojit Som
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Lee C. Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
- * Corresponding Author. Fax: +1-614-292-7596, E-mail address: (Lee C. Potter)
| | - Rizwan Ahmad
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Periannan Kuppusamy
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA
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Zhu X, Zuo L, Cardounel AJ, Zweier JL, He G. Characterization of in vivo tissue redox status, oxygenation, and formation of reactive oxygen species in postischemic myocardium. Antioxid Redox Signal 2007; 9:447-55. [PMID: 17280486 DOI: 10.1089/ars.2006.1389] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The current study aims to characterize the alterations of in vivo tissue redox status, oxygenation, formation of reactive oxygen species (ROS), and their effects on the postischemic heart. Mouse heart was subjected to 30 min LAD occlusion, followed by 60 min reperfusion. In vivo myocardial redox status and oxygenation were measured with electron paramagnetic resonance (EPR). In vivo tissue NAD(P)H and formation of ROS were monitored with fluorometry. Tissue glutathione/glutathione disulfide (GSH/GSSG) levels were detected with high-performance liquid chromatography (HPLC). These experiments demonstrated that tissue reduction rate of nitroxide was increased 100% during ischemia and decreased 33% after reperfusion compared to the nonischemic tissue. There was an overshoot of tissue oxygenation after reperfusion. Tissue NAD(P)H levels were increased during and after ischemia. There was a burst formation of ROS at the beginning of reperfusion. Tissue GSH/GSSG level showed a 48% increase during ischemia and 29% decrease after reperfusion. In conclusion, the hypoxia during ischemia limited mitochondrial respiration and caused a shift of tissue redox status to a more reduced state. ROS generated at the beginning of reperfusion caused a shift of redox status to a more oxidized state, which may contribute to the postischemic myocardial injury.
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Affiliation(s)
- Xuehai Zhu
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
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Ahmad R, Clymer B, Vikram DS, Deng Y, Hirata H, Zweier JL, Kuppusamy P. Enhanced resolution for EPR imaging by two-step deblurring. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 184:246-57. [PMID: 17113800 PMCID: PMC1866261 DOI: 10.1016/j.jmr.2006.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 10/11/2006] [Accepted: 10/16/2006] [Indexed: 05/12/2023]
Abstract
The broad spectrum of spin probes used for electron paramagnetic resonance imaging (EPRI) result in poor spatial resolution of the reconstructed images. Conventional deconvolution procedures can enhance the resolution to some extent but obtaining high resolution EPR images is still a challenge. In this work, we have implemented and analyzed the performance of a postacquisition deblurring technique to enhance the spatial resolution of the EPR images. The technique consists of two steps; noniterative deconvolution followed by iterative deconvolution of the acquired projections which are then projected back using filtered backprojection (FBP) to reconstruct a high resolution image. Further, we have proposed an analogous technique for iterative reconstruction algorithms such as multiplicative simultaneous iterative reconstruction technique (MSIRT) which can be a method of choice for many applications. The performance of the suggested deblurring approach is evaluated using computer simulations and EPRI experiments. Results suggest that the proposed procedure is superior to the standard FBP and standard iterative reconstruction algorithms in terms of mean-square-error (MSE), spatial resolution, and visual judgment. Although the procedure is described for 2D imaging, it can be readily extended to 3D imaging.
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Affiliation(s)
- Rizwan Ahmad
- Department of Electrical and Computer Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Bradley Clymer
- Department of Electrical and Computer Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
- Department of Biomedical Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
| | - Deepti S. Vikram
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Yuanmu Deng
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Hiroshi Hirata
- Department of Electrical Engineering, Yamagata University, Johnan, Yonezawa 992-8510, Japan
| | - Jay L. Zweier
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Periannan Kuppusamy
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
- Address for correspondence: * Periannan Kuppusamy, PhD, Davis Heart and Lung Research Institute, The Ohio State University, 420 West 12 Ave, Room 114, Columbus, OH 43210. Phone: 614-292-8998, E-mail:
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19
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Ahmad R, Deng Y, Vikram DS, Clymer B, Srinivasan P, Zweier JL, Kuppusamy P. Quasi Monte Carlo-based isotropic distribution of gradient directions for improved reconstruction quality of 3D EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 184:236-45. [PMID: 17095271 PMCID: PMC1892230 DOI: 10.1016/j.jmr.2006.10.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 10/11/2006] [Accepted: 10/16/2006] [Indexed: 05/11/2023]
Abstract
In continuous wave (CW) electron paramagnetic resonance imaging (EPRI), high quality of reconstructed image along with fast and reliable data acquisition is highly desirable for many biological applications. An accurate representation of uniform distribution of projection data is necessary to ensure high reconstruction quality. The current techniques for data acquisition suffer from nonuniformities or local anisotropies in the distribution of projection data and present a poor approximation of a true uniform and isotropic distribution. In this work, we have implemented a technique based on Quasi-Monte Carlo method to acquire projections with more uniform and isotropic distribution of data over a 3D acquisition space. The proposed technique exhibits improvements in the reconstruction quality in terms of both mean-square-error and visual judgment. The effectiveness of the suggested technique is demonstrated using computer simulations and 3D EPRI experiments. The technique is robust and exhibits consistent performance for different object configurations and orientations.
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Affiliation(s)
- Rizwan Ahmad
- Department of Electrical and Computer Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Yuanmu Deng
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Deepti S. Vikram
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Bradley Clymer
- Department of Electrical and Computer Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
- Department of Biomedical Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
| | | | - Jay L. Zweier
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
| | - Periannan Kuppusamy
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, College of Medicine, Columbus, Ohio 43210, USA
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Kawada Y, Hirata H, Fujii H. Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 184:29-38. [PMID: 17029883 DOI: 10.1016/j.jmr.2006.09.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 09/12/2006] [Accepted: 09/12/2006] [Indexed: 05/12/2023]
Abstract
This article reports experimental investigations on the use of RF resonators for continuous-wave electron paramagnetic resonance (cw-EPR) and proton nuclear magnetic resonance (NMR) imaging. We developed a composite resonator system with multi-coil parallel-gap resonators for co-registration EPR/NMR imaging. The resonance frequencies of each resonator were 21.8MHz for NMR and 670MHz for EPR. A smaller resonator (22mm in diameter) for use in EPR was placed coaxially in a larger resonator (40mm in diameter) for use in NMR. RF magnetic fields in the composite resonator system were visualized by measuring a homogeneous 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-hydroxy-TEMPO) solution in a test tube. A phantom of five tubes containing distilled water and 4-hydroxy-TEMPO solution was also measured to demonstrate the potential usefulness of this composite resonator system in biomedical science. An image of unpaired electrons was obtained for 4-hydroxy-TEMPO in three tubes, and was successfully mapped on the proton image for five tubes. Technical problems in the implementation of a composite resonator system are discussed with regard to co-registration EPR/NMR imaging for animal experiments.
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Affiliation(s)
- Yuuki Kawada
- Department of Electrical Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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21
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Matsumoto S, Yamada K, Hirata H, Yasukawa K, Hyodo F, Ichikawa K, Utsumi H. Advantageous application of a surface coil to EPR irradiation in overhauser-enhanced MRI. Magn Reson Med 2007; 57:806-11. [PMID: 17390363 DOI: 10.1002/mrm.21198] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The present study describes the advantageous application of a surface coil to electron paramagnetic resonance (EPR) irradiation in Overhauser-enhanced MRI (OMRI). OMRI is a double-resonance method for imaging free radicals based on the Overhauser effect. Proton NMR images are recorded without and with EPR irradiation of the free radical resonance, which results in a difference proton image that shows signal enhancement in spatial regions that contain the free radical. To obtain good signal enhancement in OMRI, very high RF power and a long EPR irradiation time are required. To improve sensitivity and shorten the image acquisition time, especially for localized (and topical) applications, we developed and tested a surface-coil-type EPR irradiation coil. Theoretical calculations and experimental data showed that EPR irradiation through the surface coil could ameliorate the localized Overhauser enhancement, which was related to the ratio of B(1) surface coil/B(1) volume coil in the region of interest (ROI), as expected. The increased sensitivity could also be converted into a shortened EPR irradiation time, resulting in fast data acquisition. For biomedical applications, the use of a surface coil (as opposed to a conventional volume coil) could decrease the total RF power deposition in the sample required to obtain the same Overhauser enhancement in the ROI.
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Affiliation(s)
- Shingo Matsumoto
- Department of Biofunctional Science, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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22
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Ahmad R, Clymer B, Deng Y, He G, Vikram D, Kuppusamy P, Zweier JL. Optimization of data acquisition for EPR imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 179:263-72. [PMID: 16458030 DOI: 10.1016/j.jmr.2005.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2005] [Revised: 12/24/2005] [Accepted: 12/27/2005] [Indexed: 05/06/2023]
Abstract
In electron paramagnetic resonance imaging (EPRI), long data acquisition time is one of the major problems limiting successful and useful biological EPRI experiments. Depending on the configuration (spatial distribution of paramagnetic species), information embedded in some objects can be characterized using a smaller number of projections, while others may require significantly larger number of projections to generate similar results. In order to optimize the acquisition process, it is therefore important to acquire a different number of projections for different objects. In this paper, a prediction scheme is demonstrated that can determine the number of projections required to achieve a preset reconstruction quality for a given object. After acquiring first few projections, corresponding partially filled k-space is analyzed. The complexity of data (to interpolate) in k-space is quantified and used to predict the number of required projections. All the projections are acquired using a mean-square difference-based adaptive acquisition technique that is also demonstrated in this work. The purpose of this non-uniform acquisition is to reduce redundancy in the acquired data which in turn decreases the number of projections required for the given object. It is also demonstrated that the performance of non-uniform acquisition is content dependant, and for certain configurations it may not be as effective as uniform acquisition in preserving signal from low intensity regions. The prediction scheme along with the non-uniform acquisition is tested using computer simulations, imaging of experimental phantoms, and in vivo imaging. Results indicate that the proposed method may save up to 50% of acquisition time. The techniques in this manuscript are described for 2D spatial imaging but can be extended to 3D imaging.
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Affiliation(s)
- Rizwan Ahmad
- Department of Electrical and Computer Engineering, The Ohio State University, College of Engineering, Columbus, Ohio 43210, USA
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Takeshita K, Chi C, Hirata H, Ono M, Ozawa T. In vivo generation of free radicals in the skin of live mice under ultraviolet light, measured by L-band EPR spectroscopy. Free Radic Biol Med 2006; 40:876-85. [PMID: 16520239 DOI: 10.1016/j.freeradbiomed.2005.10.049] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 09/27/2005] [Accepted: 10/16/2005] [Indexed: 11/18/2022]
Abstract
Although free radicals may be involved in various types of UV-induced injuries, only a few in vivo studies of the generation of free radicals, including oxygen radicals, during exposure to ultraviolet light (UV) have been reported. In this study, the nitroxyl probe 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl was intravenously injected into hairless mice, and its decay was monitored in the skin with an in vivo EPR spectrometer equipped with a surface-coil-type resonator. The rate of decay of the EPR signal increased during UV (UVA+B) irradiation. This increase in signal decay was suppressed by preadministration of a spin trap, N-tert-butyl-alpha-phenylnitrone (PBN). PBN did not change the rate of signal decay in nonirradiated mice. The correlation between signal decay rate and physiological parameters such as blood velocity, blood mass, or skin temperature was low. The decay rate responded rapidly and reversibly to starting and stopping the UV illumination. Hydroxyl and peroxyl radicals caused reduction of the probe signal in vitro, and PBN inhibited only the peroxyl radical-induced signal reduction. These observations suggest that peroxyl radicals are generated in the skin of live mice during UVA+B irradiation.
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Affiliation(s)
- Keizo Takeshita
- Faculty of Pharmaceutical Sciences, Sojo University, Ikeda, Kumamoto, Japan.
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Lichy MP, Wietek BM, Mugler JP, Horger W, Menzel MI, Anastasiadis A, Siegmann K, Niemeyer T, Königsrainer A, Kiefer B, Schick F, Claussen CD, Schlemmer HP. Magnetic Resonance Imaging of the Body Trunk Using a Single-Slab, 3-Dimensional, T2-weighted Turbo-Spin-Echo Sequence With High Sampling Efficiency (SPACE) for High Spatial Resolution Imaging. Invest Radiol 2005; 40:754-60. [PMID: 16304477 DOI: 10.1097/01.rli.0000185880.92346.9e] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The authors conducted a clinical evaluation of single-slab, 3-dimensional, T2-weighted turbo-spin-echo (TSE) with high sampling efficiency (SPACE) for high isotropic body imaging with large field-of-view (FoV). MATERIALS AND METHODS Fifty patients were examined in clinical routine with SPACE (regions of interest: pelvis n=30, lower spine n=12, upper spine n=6, extremities n=4) at 1.5 T. For achieving a high sampling efficiency, parallel imaging, high turbofactor, and magnetization restore pulses were used. In contrast to a conventional TSE imaging technique with constant flip angle refocusing, the refocusing pulse train of the SPACE sequence consists of variable flip angle radiofrequency pulses along the echo train. RESULTS Signal-to-noise ratio and contrast-to-noise ratio of SPACE images were of sufficient diagnostic value. The possibility of image reconstruction in multiple planes was of clinical relevance in all cases and simplified data analysis. CONCLUSION The achievement of 3-dimensional, T2-weighted TSE magnetic resonance imaging with isotropic and high spatial resolution and interactive 3-dimensional visualization essentially improve the diagnostic potential of magnetic resonance imaging.
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Mikuni T, He G, Petryakov S, Fallouh MM, Deng Y, Ishihara R, Kuppusamy P, Tatsuta M, Zweier JL. In vivo detection of gastric cancer in rats by electron paramagnetic resonance imaging. Cancer Res 2004; 64:6495-502. [PMID: 15374960 DOI: 10.1158/0008-5472.can-04-0319] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Electron paramagnetic resonance imaging (EPRI) enables noninvasive spatial mapping of free radical metabolism and has recently been shown to provide in vivo physiologic information regarding alterations in the redox state of tumors and neoplastic tissues. With the use of nitroxide spin probes, it has been shown that certain tumors possess a highly reduced state. To determine whether EPRI can be used for early detection and visualization of gastric carcinoma based on its altered redox metabolism, studies were performed in a rat gastric cancer model induced by 1-methyl-3-nitro-1-nitrosoguanidine. Using a specialized 750 MHz resonator and EPRI instrument, a technique was developed for imaging nitroxide radicals in the whole stomach. In vivo three-dimensional EPRI of the stomach of rats with continuous intravenous administration of nitroxide 3-carboxamido-2,2,5,5-tetramethylpyrrolidine-N-oxyl (3-carbamoyl-proxyl) [3-CP] was performed. Whereas electron paramagnetic resonance images from untreated controls provide a uniform visualization of the stomach mucosa and wall, in the treated rats with gastric cancer, holes were present in the image at the locations of tumors. With localized spectroscopy, it was confirmed that the tumor regions were devoid of signal, and this was largely due to the presence of a more reduced state with rapid reduction of nitroxide. Pharmacokinetic studies indicated that 3-CP in tumors was rapidly reduced to an undetectable level, whereas the 3-CP levels in normal stomach tissue persisted. Near-infrared reflectance measurements of indocyanine green dye uptake indicated that there were no significant differences in tumor versus normal mucosal perfusion. From these results, we concluded that gastric cancer tumors could be distinguished from normal tissue based primarily on the marked difference in their rate of radical metabolism. Because alterations in cellular redox state and radical metabolism are of critical importance in tumor biology and treatment, this methodology should provide an important new tool for the study and visualization of gastric carcinoma and may also be of use in other cancer models.
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Affiliation(s)
- Tomiko Mikuni
- Center for Biomedical Electron Paramagnetic Resonance Spectroscopy and Imaging, Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, Ohio, USA
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Ilangovan G, Liebgott T, Kutala VK, Petryakov S, Zweier JL, Kuppusamy P. EPR oximetry in the beating heart: myocardial oxygen consumption rate as an index of postischemic recovery. Magn Reson Med 2004; 51:835-42. [PMID: 15065258 DOI: 10.1002/mrm.20000] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Oxygen plays a critical role in the pathophysiology of myocardial injury during both ischemia and subsequent reperfusion (I/R). Thus, oxygen concentration is an important variable to measure during I/R. In the present work, electron paramagnetic resonance (EPR)-based oximetry was used to measure the oxygen concentration during a series of I/R episodes and oxygenation levels were correlated with the contractile and hemodynamic functions of the heart. A custom-developed electronically tunable surface coil resonator working at 1.1 GHz was used to determine tissue pO(2) in the beating heart. Microcrystalline particulate of lithium phthalocyanine was used as an EPR oximetry probe. Isolated and perfused rat hearts were subjected to 1 or 3 hr durations of preischemic perfusion, followed by 15-min I/R cycles. In hearts perfused for 3 hr prior to 15-min I/R cycles, the myocardial pO(2) decreased gradually on subsequent reperfusions of three successive I/R cycles. However, in hearts perfused for 1 hr there was almost 100% recovery of myocardial pO(2) in all three I/R cycles. The extent of oxygenation recovered in each reperfusion cycle correlated with the recovery of hemodynamic and contractile function. The results also showed that the oxygen consumption rate of the heart at the end of each I/R episode decreased in direct proportion to the functional recovery. In summary, it was observed that the amount of myocardial oxygen consumption during I/R could provide a reliable index of functional impairment in the heart.
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