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1.  Computationally Efficient Steady-State Solution of the Bloch Equations for Rapid Sinusoidal Scans Based on Fourier Expansion in Harmonics of the Scan Frequency 
Applied magnetic resonance  2013;44(12):1373-1379.
Rapid-scan EPR has been shown to improve the signal-to-noise ratio relative to conventional continuous wave spectroscopy. Equations are derived for the steady-state solution to the Bloch equations as a Fourier expansion in the harmonics of the scan frequency. This simulation method is about two orders of magnitude faster than time-domain numerical integration.
doi:10.1007/s00723-013-0494-2
PMCID: PMC3963382  PMID: 24678142
2.  [No title available] 
PMCID: PMC4291516  PMID: 25598580
3.  Probing Protein Secondary Structure using EPR: Investigating a Dynamic Region of Visual Arrestin 
Applied magnetic resonance  2012;43(3):405-419.
One key application of site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is the determination of sequence-specific secondary structure in proteins. Regular secondary structure leads to a periodic variation in both side chain motion and solvent accessibility, two properties easily monitored by EPR techniques. Specifically, saturation recovery (SR) EPR spectroscopy has proven to be useful for making accessibility measurements for multiple protein structure populations by determining individual accessibilities and is therefore well suited to study the structure of proteins exhibiting multiple conformations in equilibrium. Here we employ both continuous wave and SR EPR spectroscopy in combination to examine the secondary structure of a short sequence showing conformational heterogeneity in visual rod arrestin. The EPR data presented here clearly distinguish between the unstructured loop and the helical structure formed in the crystallographic tetramer of visual arrestin and show that this region is unstructured in solution.
doi:10.1007/s00723-012-0369-y
PMCID: PMC4240029  PMID: 25419051
4.  Optimization of pulsed DEER measurements for Gd-based labels: choice of operational frequencies, pulse durations and positions, and temperature 
Applied magnetic resonance  2013;44(6):10.1007/s00723-012-0434-6.
In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14–17 K, while in W-band the optimal temperatures are between 6–9 K; (iii) W-band is preferable to Ka-band for DEER measurements. Recent achievements and the conditions necessary for short-distance measurements (<15 Å) are also briefly discussed.
doi:10.1007/s00723-012-0434-6
PMCID: PMC3654798  PMID: 23687407
Gd(III) spin labels; long distance pulsed DEER; Ka -and W-microwave bands
5.  Temperature Dependence of Electron Spin Relaxation of 2,2-diphenyl-1-picrylhydrazyl in Polystyrene 
Applied magnetic resonance  2012;44(4):509-517.
The electron spin relaxation rates for the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) doped into polystyrene were studied by inversion recovery and electron spin echo at X-band and Q-band between 20 and 295 K. At low concentration (340 μM, 0.01%) spin-lattice relaxation was dominated by the Raman process and a local mode. At high concentration (140 mM, 5%) relaxation is orders of magnitude faster than at the lower concentration, and 1/T1 is approximately linearly dependent on temperature. Spin lattice relaxation rates are similar at X-band and Q-band. The temperature dependence of spin echo dephasing was faster at about 140 K than at higher or lower temperatures, which is attributed to a wagging motion of the phenyl groups.
doi:10.1007/s00723-012-0417-7
PMCID: PMC3616442  PMID: 23565040
6.  Phase Correction-Adaptive Line Enhancement for Noise Reduction of Low-Field NMR 
Applied Magnetic Resonance  2013;44(12):1381-1391.
The amplitude of low-field nuclear magnetic resonance (NMR) is weak, and the echo is buried in the noise. The reduction of noise is critical to accurately extract echo amplitude. Phase correction-adaptive line enhancement (PC-ALE) is proposed to noise suppression based on the principle of ALE and NMR spin-echo characteristics. The echo amplitude is calculated after two-stage processes; phase shift from time-delay and filter tap would be compensated effectively in frequency domain. Simulation and experiments show that PC-ALE has prominent performance on noise suppression, envelope recovery, as well as the correction of the phase shift. The amplitude from the method of sample average nearby the middle of the echo is more accurate than the maximum peak when the PC-ALE is applied to noise suppression of spin-echo.
doi:10.1007/s00723-013-0486-2
PMCID: PMC3835948  PMID: 24273386
7.  Application of EPR Spectroscopy to Examination of Free Radical Formation in Thermally Sterilized Flumetasone 
Applied Magnetic Resonance  2013;44(12):1431-1443.
Thermal formation of free radicals in flumetasone sterilized according to the pharmaceutical norms at 160, 170 and 180 °C was examined by electron paramagnetic resonance (EPR) spectroscopy. The microbiological analysis was done. Similar free radical concentrations were measured for flumetasone sterilized at 160 and 170 °C. The concentration was considerably higher than that for flumetasone sterilized at 180 °C. Fast spin–lattice relaxation processes, homogeneously broadened EPR lines, and complex free radicals system characterize the heated flumetasone. Free radicals were not observed 30 days after thermal sterilization. Optimal temperatures of sterilization of flumetasone are 160 and 170 °C.
doi:10.1007/s00723-013-0490-6
PMCID: PMC3835947  PMID: 24273387
8.  Frequency-Selective Fat Suppression Radiofrequency Pulse Train to Remove Olefinic Fats 
Applied Magnetic Resonance  2013;44(10):1213-1221.
CHESS pulse can suppress the signal originating from aliphatic fat protons but cannot suppress the signal from olefinic fat protons, which is near the resonance frequency of water protons. Adipose tissue contains various fat species; aliphatic fat comprises about 90 % and olefinic fat about 10 % of adipose tissue. Thus, CHESS pulse cannot be used to suppress the signal from adipose tissue completely. The purpose of this study was to find a method to suppress the signal from adipose tissue completely. The Fatsat train pulse, created with an arbitrary flip angle and insensitive to B1 inhomogeneity, was used. Because B1 inhomogeneity is larger on higher field magnetic resonance imaging, the fat suppression radiofrequency pulse needs to be B1-insensitive. To investigate a percentage of olefinic fat in adipose tissues, the excitation frequency of the Fatsat train pulse was varied from −240 to +400 Hz and the images and fat-suppressed images were obtained. The presence of olefinic fat comprising about 10 % of abdominal adipose tissue was identified. The result agreed with some previous papers. Complete fat suppression could be achieved by partial (10 %) inversion of longitudinal aliphatic fat magnetization and by canceling out the two fat magnetizations. The flip angle was identified to about 95°. In conclusion, the cause that the signal from adipose tissues cannot be suppressed completely has been found. Improved images that signals from adipose tissues were suppressed completely have been demonstrated. This technique can also be applied to several pulse sequences.
doi:10.1007/s00723-013-0474-6
PMCID: PMC3751390  PMID: 23990698
9.  Impact of SOD-Mimetic Manganoporphyrins on Spin Trapping of Superoxide and Related Artifacts 
Applied magnetic resonance  2011;40(1):125-134.
The superoxide dismutase (SOD)-mimetic effectiveness of [meso-tetrakis (R)porphyrinato]manganese with R = 1,3-di-N-ethylimidazolium-2-yl (Mn-TDEIP), 1,3-di-N-methylimidazolium-2-yl (Mn-TDMIP), 1,3-di-N-propylimidazolium-2-yl (Mn-TDPIP), N-ethyl-2-pyridyl (Mn-T2EPyP), 4-sulphonatophenyl (Mn-TSP), 1-methyl-4-pyridyl (Mn-T4PyP), 4-carboxyphenyl (Mn-TBAP), and β-octabromomeso-tetrakis(4-carboxyphenyl porphyrinato)manganese (MnBr8TBAP) was compared with Cu, Zn SOD. Superoxide generated by reaction of xanthine oxidase with hypoxanthine was trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO), forming BMPO–OOH, which was monitored by electron paramagnetic resonance. Manganoporphyrins with redox potentials ranging from −0.190 to 0.346 V relative to the standard hydrogen electrode were selected for this study. With 0.1 µM manganoporphyrins and 20 mM BMPO, the effectiveness of the manganoporphyrins in inhibiting formation of BMPO–OOH increases in the order Mn-TSP < Mn-TBAP < MnBr8TBAP < Mn-T4PyP < Mn-T2EPyP < Mn-TDEIP ~ Mn-TDMIP ~ Mn-TDPIP ~ Cu, Zn SOD. However, at higher concentrations of manganoporphyrin and BMPO, a BMPO–OH signal was observed. The formation of BMPO–OH was not inhibited by catalase or dimethylsulfoxide, which demonstrated that it was not produced from hydroxyl radical. The artifactual formation of BMPO–OH is attributed to oxidation of the water adduct of BMPO by the manganoporphyrins or decomposition of BMPO–OOH. Although spin trapping is an effective method for evaluating SOD-mimetic efficacy, caution must be exercised to ensure that artifact signals are not interpreted improperly.
doi:10.1007/s00723-010-0188-y
PMCID: PMC3708493  PMID: 23853422
10.  Electron Spin Resonance (ESR) Dating of Calcareous Fault Gouge of the Ushikubi Fault, Central Japan 
Applied Magnetic Resonance  2013;44(9):1105-1123.
The ages of fault events of active faults have been estimated using electron spin resonance (ESR) signals of siliceous gouges. This technique of ESR method is limited by obtaining only ages that are greater than tens of millennia. So this study focuses on developing a new technique of using calcareous gouges to gain an insight into the ages of latest seismogenic event within the Holocene. For the first time, signal B of the ESR method has been used to estimate the age of the Ushikubi fault from calcareous gouge. This technique proved reliable because the mean age (1.9 ka) obtained agrees with previous works on indirect age determination of latest fault events by utilizing radiocarbon dating in the study area. However, the result from the ESR technique showed an increase relative to the age of 1 ka that was obtained by the radiocarbon dating method. This disparity may be due to a high dose rate value of 50 Gy/h of artificial irradiation that was used to determine the equivalent dose (ED). Moreover, isochronal experiment revealed that the gouge did not comprise pure carbonates but consisted of a mixture of calcite and quartz grains. A younger age value would have been obtained if a lower artificial irradiation dose rate and a relatively pure carbonate fault gouge were used in the ED determination.
doi:10.1007/s00723-013-0471-9
PMCID: PMC3731512  PMID: 23914073
11.  Dielectric Resonator for Ka-Band Pulsed EPR Measurements at Cryogenic Temperatures: Probehead Construction and Applications 
Applied magnetic resonance  2012;42(4):441-452.
The construction and performance of a Ka-band pulsed electron paramagnetic resonance (EPR) cryogenic probehead that incorporates dielectric resonator (DR) is presented. We demonstrate that the use of DR allows one to optimize pulsed double electron–electron resonance (DEER) measurements utilizing large resonator bandwidth and large amplitude of the microwave field B1. In DEER measurements of Gd-based spin labels, use of this probe finally allows one to implement the potentials of Gd-based labels in distance measurements. Evidently, this DR is well suited to any applications requiring large B1-fields and resonator bandwidths, such as electron spin echo envelope modulation spectroscopy of nuclei having low magnetic moments and strong hyperfine interactions and double quantum coherence dipolar spectroscopy as was recently demonstrated in the application of a similar probe based on an loop-gap resonator and reported by Forrer et al. (J Magn Reson 190:280, 2008).
doi:10.1007/s00723-012-0313-1
PMCID: PMC3634706  PMID: 23626406
12.  A Solid-State NMR Investigation of MQ Silicone Copolymers 
Applied Magnetic Resonance  2013;44(9):1015-1025.
The structure of MQ copolymers of the general chemical formula [(CH3)3SiO0.5]m [SiO2]n was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. 29Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) 29Si{1H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH3)3) and two types of tetrafunctional Q units: Q4 ((≡SiO)4Si) and Q3 ((≡SiO)3SiOH). Spin–lattice relaxation times T1 measurements of 29Si nuclei and analysis of 29Si{1H} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.
doi:10.1007/s00723-013-0456-8
PMCID: PMC3731513  PMID: 23914072
13.  Calculations of B1 Distribution, Specific Energy Absorption Rate, and Intrinsic Signal-to-Noise Ratio for a Body-Size Birdcage Coil Loaded with Different Human Subjects at 64 and 128 MHz 
Applied magnetic resonance  2005;29(1):5-18.
A numerical model of a female body is developed to study the effects of different body types with different coil drive methods on radio-frequency magnetic (B1) field distribution, specific energy absorption rate (SAR), and intrinsic signal-to-noise ratio (ISNR) for a body-size birdcage coil at 64 and 128 MHz. The coil is loaded with either a larger, more muscular male body model (subject 1) or a newly developed female body model (subject 2), and driven with two-port (quadrature), four-port, or many (ideal) sources. Loading the coil with subject 1 results in significantly less homogeneous B1 field, higher SAR, and lower ISNR than those for subject 2 at both frequencies. This dependence of MR performance and safety measures on body type indicates a need for a variety of numerical models representative of a diverse population for future calculations. The different drive methods result in similar B1 field patterns, SAR, and ISNR in all cases.
doi:10.1007/BF03166953
PMCID: PMC3615460  PMID: 23565039
14.  Modeling Spectroscopic Properties of Ni2+ Ions in the Haldane Gap System Y2BaNiO5 
Applied Magnetic Resonance  2013;44(8):899-915.
Modeling of spin Hamiltonian parameters enables correlation of crystallographic, spectroscopic, and magnetic data for transition ions in crystals. In this paper, based on the crystallographic data and utilizing the point-charge model and superposition model, the crystal field parameters (CFPs) are estimated for Ni2+(3d8) ions in the Haldane gap system Y2BaNiO5. The CFPs serve as input for the perturbation theory expressions and the crystal field analysis package for microscopic spin Hamiltonian modeling of the zero-field splitting parameters (ZFSPs) D and E. Results of an extensive literature search of the pertinent crystallographic data, experimental ZFSPs, and model parameters are briefly outlined. The modeling aims at verification of the experimental ‘single ion anisotropy’ parameters and explanation of the controversy concerning the maximal rhombic distortion |E/D| ≈1/3 reported for Ni2+ ions in Y2BaNiO5. The preliminary results call for reanalysis of some magnetic studies of the Haldane gap systems.
doi:10.1007/s00723-013-0448-8
PMCID: PMC3728452  PMID: 23914071
15.  Transceiver-Phased Arrays for Human Brain Studies at 7 T 
Applied magnetic resonance  2011;41(2-4):483-506.
The paper describes technological advances in high-field (7 T) transceiver-phased arrays developed for magnetic resonance imaging of the human brain. The first part of this work describes an 8-element inductively decoupled split elliptical transceiver-phased array with selectable geometry, which provides an easy and efficient way of compensating for changes in mutual inductive coupling associated with difference in loading due to variability in head shape and size. The second part of the work describes a double-row 16-element (2 × 8) transceiver array to extend the homogeneous transmit B1 profile in the longitudinal direction. Multiplexing eight transmit channels between the two rows of the array provides homogeneous excitation over the entire volume. The final section describes design and construction of a double-tuned 31P/1H 16-element (8 at each frequency) array. The array improves transmission efficiency and B1 homogeneity at 1H frequency in comparison with 31P/1H quadrature transverse electromagnetic volume coil. For 31P studies, the array also improves transmission efficiency (38%), signal-to-noise ratio (SNR) for central brain locations (20%) and provides substantially greater SNR (up to 400%) for peripheral locations.
doi:10.1007/s00723-011-0280-y
PMCID: PMC3600590  PMID: 23516332
16.  Electron Paramagnetic Resonance and Electron Spin Echo Studies of Co2+ Coordination by Nicotinamide Adenine Dinucleotide (NAD+) in Water Solution 
Applied Magnetic Resonance  2013;44(7):817-826.
Co2+ binding to the nicotinamide adenine dinucleotide (NAD+) molecule in water solution was studied by electron paramagnetic resonance (EPR) and electron spin echo at low temperatures. Cobalt is coordinated by NAD+ when the metal is in excess only, but even in such conditions, the Co/NAD+ complexes coexist with Co(H2O)6 complexes. EPR spin-Hamiltonian parameters of the Co/NAD+ complex at 6 K are gz = 2.01, gx = 2.38, gy = 3.06, Az = 94 × 10−4 cm−1, Ax = 33 × 10−4 cm−1 and Ay = 71 × 10−4 cm−1. They indicate the low-spin Co2+ configuration with S = 1/2. Electron spin echo envelope modulation spectroscopy with Fourier transform of the modulated spin echo decay shows a strong coordination by nitrogen atoms and excludes the coordination by phosphate and/or amide groups. Thus, Co2+ ion is coordinated in pseudo-tetrahedral geometry by four nitrogen atoms of adenine rings of two NAD+ molecules.
doi:10.1007/s00723-013-0444-z
PMCID: PMC3677979  PMID: 23766555
17.  Analysis of Uniformity of Magnetic Field Generated by the Two-Pair Coil System 
Applied Magnetic Resonance  2013;44(5):605-618.
In this paper we use a simple analysis based on properties of the axial field generated by symmetrical multipoles to reveal all possible distributions of two coaxial pairs of circular windings, which result in systems featuring zero octupole and 32 pole magnetic moments (six-order systems). Homogeneity of magnetic field of selected systems is analyzed. It has been found that one of the derived systems generates homogenous magnetic field whose volume is comparable to that yielded by the eight-order system. The influence of the current distribution and the windings placement on the field homogeneity is considered. The table, graphs and equations given in the paper facilitate the choice of the most appropriate design for a given problem. The systems presented may find applications in low field electron paramagnetic resonance imaging, some functional f-MRI (nuclear magnetic resonance imaging) and bioelectromagnetic experiments requiring the access to the working space from all directions.
doi:10.1007/s00723-012-0427-5
PMCID: PMC3677240  PMID: 23761951
18.  Antiferromagnetic Ordering of Magnetic Clusters Units in Nb6F15 
Applied Magnetic Resonance  2012;44(1-2):143-151.
We have studied the magnetic cluster compound Nb6F15 which has an odd number of 15 valence electrons per (Nb6F12)3+ cluster core, as a function of temperature using nuclear magnetic resonance, magnetic susceptibility, electron magnetic resonance and neutron powder diffraction. Nuclear magnetic resonance of the 19F nuclei shows two lines corresponding to the apical Fa−a nucleus, and to the inner Fi nuclei. The temperature dependence of the signal from the Fi nuclei reveals an antiferromagnetic ordering at T < 5 K, with a hyperfine field of ~2 mT. Magnetic susceptibility exhibits a Curie–Weiss behavior with TN ~5 K, and μeff ~1.57 μB close to the expected theoretical value for one unpaired electron (1.73 μB). Electron magnetic resonance linewidth shows a transition at 5 K. Upon cooling from 10 to 1.4 K, the neutron diffraction shows a decrease in the intensity of the low-angle diffuse scattering below Q ~0.27 Å−1. This decrease is consistent with emergence of magnetic order of large magnetic objects (clusters). This study shows that Nb6F15 is paramagnetic at RT and undergoes a transition to antiferromagnetic order at 5 K. This unique antiferromagnetic ordering results from the interaction between magnetic spins delocalized over each entire (Nb6F12i)3+ cluster core, rather than the common magnetic ordering.
doi:10.1007/s00723-012-0426-6
PMCID: PMC3549236  PMID: 23349566
19.  A simple model for understanding the origin of the amide proton transfer MRI signal in tissue 
Applied magnetic resonance  2012;42(3):393-402.
Amide proton transfer (APT) imaging is a new molecular MRI technique that gives contrast at the cellular protein level. To better understand the origin of the APT signal in tissue, fresh and cooked hen eggs (n = 4) were imaged at 4.7 Tesla. The APT effect was quantified using the asymmetry in the magnetization transfer ratio (MTRasym) at the composite amide proton resonance frequency (3.5 ppm from the water resonance). The measured APT signals were significantly higher in the fresh egg white (20.1% ± 0.9%) than in the fresh egg yolk (−1.4% ± 1.1%; P < 0.001), and in the cooked egg white (2.8% ± 0.7%; P < 0.001), all of which have similar absolute protein contents. The data support the notion that the APT effect observed in vivo is associated with mobile proteins in tissue, such as those in the cytoplasm.
doi:10.1007/s00723-011-0306-5
PMCID: PMC3520492  PMID: 23243339
APT; CEST; magnetization transfer; egg white; protein
20.  Configuration and Performance of a Mobile 129Xe Polarizer 
Applied Magnetic Resonance  2012;44(1-2):65-80.
A stand-alone, self-contained and transportable system for the polarization of 129Xe by spin exchange optical pumping with Rb is described. This mobile polarizer may be operated in batch or continuous flow modes with medium amounts of hyperpolarized 129Xe for spectroscopic or small animal applications. A key element is an online nuclear magnetic resonance module which facilitates continuous monitoring of polarization generation in the pumping cell as well as the calculation of the absolute 129Xe polarization. The performance of the polarizer with respect to the crucial parameters temperature, xenon and nitrogen partial pressures, and the total gas flow is discussed. In batch mode the highest 129Xe polarization of PXe = 40 % was achieved using 0.1 mbar xenon partial pressure. For a xenon flow of 6.5 and 26 mln/min, PXe = 25 % and PXe = 13 % were reached, respectively. The mobile polarizer may be a practical and efficient means to make the applicability of hyperpolarized 129Xe more widespread.
doi:10.1007/s00723-012-0425-7
PMCID: PMC3549238  PMID: 23349565
21.  Simplified THz Instrumentation for High-Field DNP-NMR Spectroscopy 
Applied magnetic resonance  2012;43(1-2):181-94.
We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE01 circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE01 or TE11 mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible for the DNP effect using the TE11 or the TE01 mode are comparable to that generated by the HE11 mode and a corrugated waveguide. The choice of the TE11/TE01 mode allows the use of a smooth-walled, oversized waveguide that is easier to fabricate and less expensive than a corrugated waveguide required for transmission of the HE11 mode. Also, the choice of the TE01 mode can lead to a simplification of gyrotron oscillators that operate in the TE0n mode, by employing an on-axis rippled-wall mode converter to convert the TE0n mode into the TE01 mode either inside or outside of the gyrotron tube. These novel concepts will lead to a significant simplification of the gyrotron, the transmission line and the THz coupler, which are the three main components of a DNP system.
doi:10.1007/s00723-012-0360-7
PMCID: PMC3439215  PMID: 22977293
22.  The Instrument Set for Generating Fast Adiabatic Passage 
Applied Magnetic Resonance  2012;43(3):331-340.
The design and construction of a high-performance, low-cost, and easy to assemble adiabatic extension set for homebuilt and commercial spectrometers is described. Described apparatus set was designed for the fast adiabatic passage generation and is based on direct digital synthesizer DDS. This solution gives generator high signal to noise ratio, phase stability even during frequency change which is only possible in expansive commercial high-end hardware. Critical synchronization and timing issues are considered and solutions are discussed. Different experimental conditions and techniques for the measurements are briefly discussed. The proposed system is very flexible and might be used for the measurement of low-frequency nuclear magnetic resonance.
doi:10.1007/s00723-012-0372-3
PMCID: PMC3459077  PMID: 23144535
23.  EADC Values in Diagnosis of Renal Lesions by 3.0 T Diffusion-Weighted Magnetic Resonance Imaging: Compared with the ADC Values 
Applied Magnetic Resonance  2012;44(3):349-363.
Exponential apparent diffusion coefficient (EADC) is an indicator of diffusion-weighted imaging (DWI) and reflects the pathological changes of tissues quantitatively. However, no study has been investigated in the space-occupying kidney disease using EADC values. This study aims to evaluate the diagnostic role of EADC values at a high magnetic field strength (3.0 T) in kidney neoplastic lesions, compared with that of the ADC values. Ninety patients with suspected renal tumors (including 101 suspected renal lesions) and 20 healthy volunteers were performed MRI scanning. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar imaging (SE-EPI) sequence at a diffusion gradient of b = 500 s/mm2. We found renal cell carcinoma (RCC) can be distinguished from angiomyolipoma, and clear cell carcinoma can be distinguished from non-clear cell carcinoma by EADC value. There was significant difference in overall EADC values between renal cell carcinoma (0.150 ± 0.059) and angiomyolipoma (0.270 ± 0.108) when b value was 500 s/mm2. When receiver operating characteristic (ROC) was higher than 0.192, the sensitivity and specificity of EADC value of renal cell carcinoma were 84.6 and 81.1 %, respectively. In conclusion, EADC map shows the internal structure of the kidney tumor more intuitively than the ADC map dose, and is also in line with the observation habits of the clinicians. EADC can be used as an effective imaging method for tumor diagnosis.
doi:10.1007/s00723-012-0376-z
PMCID: PMC3585986  PMID: 23476099
24.  Comparison of Overhauser DNP at 0.34 and 3.4 T with Frémy’s Salt 
Applied Magnetic Resonance  2012;43(1-2):129-138.
Dynamic nuclear polarization (DNP) is investigated in the liquid state using a model system of Frémy’s salt dissolved in water. Nuclear magnetic resonance signal enhancements at 0.34 and 3.4 T of the bulk water protons are recorded as a function of the irradiation time and the polarizer concentration. The build-up rates are consistent with the T1n of the observed water protons at room temperature (for 9 GHz/0.34 T) and for about 50 ± 10 °C at 94 GHz/3.4 T. At 94 GHz/3.4 T, we observe in our setup a maximal enhancement of −50 at 25 mM polarizer concentration. The use of Frémy’s salt allows the determination of the saturation factors at 94 GHz by pulsed ELDOR experiments. The results are well consistent with the Overhauser DNP mechanism and indicate that higher enhancements at this intermediate frequency require higher sample temperatures.
doi:10.1007/s00723-012-0362-5
PMCID: PMC3396338  PMID: 22815593
25.  EPR Studies of DOPA–Melanin Complexes with Netilmicin and Cu(II) at Temperatures in the Range of 105–300 K 
Applied Magnetic Resonance  2012;43(3):341-351.
The application of electron paramagnetic resonance (EPR) spectroscopy in pharmacy of melanin complexes with netilmicin and Cu(II) was presented. The continuous microwave saturation of EPR spectra of DOPA–melanin and the complexes was performed. EPR spectra were measured on an X-band (9.3 GHz) spectrometer at temperatures in the range of 105–300 K. Paramagnetic copper ions decrease the intensity of the EPR lines of melanin’s free radicals. It was found that fast spin–lattice relaxation characterizes DOPA–melanin–Cu(II) complexes. Slow spin–lattice relaxation processes exist in melanin’s paramagnetic centers of DOPA–melanin and DOPA–melanin–netilmicin, [DOPA–melanin–netilmicin]–Cu(II), [DOPA–melanin–Cu(II)]–netilmicin complexes. Spin–lattice relaxation processes are faster at higher temperatures. The homogeneous broadening of EPR lines for melanin complexes was observed. The practical consequences of differences between paramagnetic properties of melanin complexes with netilmicin and the complexes with Cu(II) were discussed.
doi:10.1007/s00723-012-0340-y
PMCID: PMC3459086  PMID: 23144536

Results 1-25 (66)