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PURPOSE: Motion artifact limits the clinical translation of high-field MR. We present an optical prospective motion correction system for 7 Tesla MRI using a custom-built, within-coil camera to track an optical marker mounted on a subject. METHODS: The camera was constructed to fit between the transmit-receive coils with direct line of sight to a forehead-mounted marker, improving upon prior mouthpiece work at 7 Tesla MRI. We validated the system by acquiring a 3D-IR-FSPGR on a phantom with deliberate motion applied. The same 3D-IR-FSPGR and a 2D gradient echo were then acquired on 7 volunteers, with/without deliberate motion and with/without motion correction. Three neuroradiologists blindly assessed image quality. In 1 subject, an ultrahigh-resolution 2D gradient echo with 4 averages was acquired with motion correction. Four single-average acquisitions were then acquired serially, with the subject allowed to move between acquisitions. A fifth single-average 2D gradient echo was acquired following subject removal and reentry. RESULTS: In both the phantom and human subjects, deliberate and involuntary motion were well corrected. Despite marked levels of motion, high-quality images were produced without spurious artifacts. The quantitative ratings confirmed significant improvements in image quality in the absence and presence of deliberate motion across both acquisitions (P < .001). The system enabled ultrahigh-resolution visualization of the hippocampus during a long scan and robust alignment of serially acquired scans with interspersed movement. CONCLUSION: We demonstrate the use of a within-coil camera to perform optical prospective motion correction and ultrahigh-resolution imaging at 7 Tesla MRI. The setup does not require a mouthpiece, which could improve accessibility of motion correction during 7 Tesla MRI exams.

PURPOSE Although 1 H spin coupling is generally avoided in probes for hyperpolarized (HP) 13 C MRI, enzymatic transformations of biological interest can introduce large 13 C-1 H couplings in vivo. The purpose of this study was to develop and investigate the application of 1 H decoupling for enhancing the sensitivity for detection of affected HP 13 C metabolic products. METHODS A standalone 1 H decoupler system and custom concentric 13 C/1 H paddle coil setup were integrated with a clinical 3T MRI scanner for in vivo 13 C MR studies using HP [2-13 C]dihydroxyacetone, a novel sensor of hepatic energy status. Major 13 C-1 H coupling JCH = ∼150 Hz) is introduced after adenosine triphosphate-dependent enzymatic transformation of HP [2-13 C]dihydroxyacetone to [2-13 C]glycerol-3-phosphate in vivo. Application of WALTZ-16 1 H decoupling for elimination of large 13 C-1 H couplings was first tested in thermally polarized glycerol phantoms and then for in vivo HP MR studies in three rats, scanned both with and without decoupling. RESULTS As configured, 1 H-decoupled 13 C MR of thermally polarized glycerol and the HP metabolic product [2-13 C]glycerol-3-phosphate was achieved at forward power of approximately 15 W. High-quality 3-s dynamic in vivo HP 13 C MR scans were acquired with decoupling duty cycle of 5%. Application of 1 H decoupling resulted in sensitivity enhancement of 1.7-fold for detection of metabolic conversion of [2-13 C]dihydroxyacetone to HP [2-13 C]glycerol-3-phosphate in vivo. CONCLUSIONS Application of 1 H decoupling provides significant sensitivity enhancement for detection of HP 13 C metabolic products with large 1 H spin couplings, and is therefore expected to be useful for preclinical and potentially clinical HP 13 C MR studies. Magn Reson Med 80:36-41, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose Hyperpolarization of carbon-13 (13C) nuclei by dissolution dynamic nuclear polarization increases signal-to-noise ratio (SNR) by >10,000-fold for metabolic imaging, but care must be taken when transferring hyperpolarized (HP) samples from polarizer to MR scanner. Some 13C substrates relax rapidly in low ambient magnetic fields. A handheld electromagnet carrier was designed and constructed to preserve polarization by maintaining a sufficient field during sample transfer. Methods The device was constructed with a solenoidal electromagnet, powered by a nonmagnetic battery, holding the HP sample during transfer. A specially designed switch automated deactivation of the field once transfer was complete. Phantom and rat experiments were performed to compare MR signal enhancement with or without the device for HP [13C]urea and [1-13C]pyruvate. Results The magnetic field generated by this device was tested to be >50 G over a 6-cm central section. In phantom and rat experiments, [13C]urea transported via the device showed SNR improvement by a factor of 1.8–1.9 over samples transferred through the background field. Conclusion A device was designed and built to provide a suitably high yet safe magnetic field to preserve hyperpolarization during sample transfer. Comparative testing demonstrated SNR improvements of approximately two-fold for [13C]urea while maintaining SNR for [1-13C]pyruvate. Magn Reson Med 75:917–922, 2016. © 2015 Wiley Periodicals, Inc.

The Aspergillus nidulans stcL gene is predicted to encode a cytochrome P-450 monooxygenase and is located within a cluster of other genes that are required for synthesis of sterigmatocystin. Inactivation of stcL resulted in strains that accumulate dihydrosterigmatocystin, a tetrahydrobisfuran containing molecule that is very similar to the unsaturated product of the wild-type pathway, sterigmatocystin. This observation led us to hypothesize that the A. nidulans sterigmatocystin biosynthetic pathway is branched similarly to the aflatoxin pathway in Aspergillus parasiticus and Aspergillus flavus and that StcL is required for the desaturation of the bisfuran moiety in the sterigmatocystin/aflatoxin precursor versicolorin B. This prediction was confirmed by feeding the stcL mutant with the subsequent pathway intermediate, versicolorin A, which resulted in accumulation of both sterigmatocystin and dihydrosterigmatocystin, indicating that StcL functions before versicolorin A synthesis. A. nidulans stcU was shown previously to encode a ketoreductase required to convert versicolorin A to demethylsterigmatocystin and an stcL, stcU double mutant strain was shown here to accumulate only versicolorin B. These results indicate that both versicolorin A and versicolorin B can serve as substrates for StcU, resulting in a branched pathway. The final product of each branch are sterigmatocystin and dihydrosterigmatocystin, respectively.

We report a high-resolution 42-MHz[sup 1]HFT-NMR instrument that is suitable for use as a process analyzer and demonstrate its use in the determination of methyl tert-butyl ether (MTBE) in a flowing stream of gasoline. This spectrometer is based on a 55-kg permanent magnet with essentially no fringe field. A spectral resolution of 3 Hz was typically obtained for spinning samples, and this performance was only slightly degraded with flowing samples. We report a procedure for magnet drift compensation using a software procedure rather than a field-frequency lock channel. This procedure allowed signal averaging without loss of resolution. Regulatory changes to be implemented in the near future have created a need for the development of methods for the determination of MTBE and other oxygenates in reformulated gasolines. Existing methods employing gas chromatography are not fast enough for process control of a gasoline blender and suffer from other limitations. This study demonstrates that process analysis NMR is well-suited to the determination of MTBE in a simulated gasoline blender. The detection limit of 0.5 vol % MTBE was obtained with a measurement time of 1 min. The absolute standard deviation of independent determinations was 0.17% when the MTBE concentration was 10%, a nominalmore » value. Preliminary results also suggest that the method may be applicable to gasolines containing mixtures of oxygenate additives as well as the measurement of aromatic and olefinic hydrogens. 33 refs., 9 figs.« less

In nur 170 Millisekunden kann in dem rechts gezeigten Katalysereaktor das Katalysatorbett um 150 K abgekuhlt werden. Dadurch ist die NMR-spektroskopische Untersuchung von Produkten moglich, die nach sehr kurzen Kontaktzeiten und unter realen Katalysebedingungen gebildet wurden.

Only 170 milliseconds are required to cool the catalyst bed by 150 K in the catalytic reactor shown on the right. Thus, NMR spectroscopic investigations can be carried out on products that are formed after very short contact times and under real catalysis conditions.

Only 170 milliseconds are required to cool the catalyst bed by 150 K in the catalytic reactor shown on the right. Thus, NMR spectroscopic investigations can be carried out on products that are formed after very short contact times and under real catalysis conditions.

In situ 13 C MAS NMR characterization following UV irradiation of two FAU zeolites with adsorbed benzaldehyde or acetophenone and toluene allows observation of photoproducts and subsequent acid-catalysed chemistry.

Poly (vinyl cinnamate), PVCN, is one of the more important polymers used in NLO research. It is frequently used as a host polymer into which suitable dyes are introduced, especially those with limited solubilities in other polymers. During the poling process, the polymer may be irradiated with UV light to yield a material with superior SHG retention and reduced solubility. This is frequently. This is frequently assumed to be due to photocrosslinking reactions between cinnamoyl groups in different chains or alternatively between cinnamoyl groups and NLO dye molecules with suitable structures. The mechanism of this crosslinking is proposed to be 2 + 2 cycloaddition of the olefinic groups to yield four-membered-ring crosslink sites. Although this mechanism is appealing in that it is consistent with well characterized reactions in solution, experimental evidence for this important reaction in NLO polymers has been lacking, and its acceptance has not been universal.