Modified Pulse Sequence Research Articles

A Standardized MRI Phantom for Dissolved Phase 129Xe MRI.

Pulmonary MRI of hyperpolarized xenon-129 (hp129Xe) dissolved in the lung parenchyma and vascular phase is gaining increasing attention for clinical assessment of gas exchange in multiple diseases. These conditions can involve thickening of barrier tissues due to fibrotic scarring or reduced capillary blood flow leading to diminished gas-blood exchange hence, the ratios between hp129Xe signals arising from the lung membrane (M), the red blood cells (RBC), and the gas phase hold significant diagnostic value. However, comparing hp129Xe signal ratios quantitatively across different studies may pose challenges due to varied experimental conditions and slightly modified pulse sequence protocols.A solution to this problem arises from materials science applications of hp129Xe where xenon dissolved in porous materials or polymers can display chemical shifts similar to the M and RBC shift in lungs. This work explored the generation of MR spectral profiles with respect to chemical shift and signal intensity ratios that closely resemble spectral profiles observed in human lungs in health and disease. At ambient temperatures, reticulated open cell polyurethane foam treated with olive oil as a fatty phase produced dissolved phase 129Xe chemical shifts of 215 ppm and 196 ppm, respectively, that emulate typical RBC and M signals. The uptake kinetics into the non-toxic materials was sufficiently similar to pulmonary signal uptake to enable hp129Xe MRI with dissolved phase ratios that closely resemble clinical data.A phantom assembly was devised to allow for gas handling protocols that match clinical protocols. The current iteration of the developed phantom enabled rapid testing of basic experimental protocols and can be used for training purposes without regulatory approval and governance. Furthermore, the introduced concept shows a pathway for the development of a quantitative universal phantom standard for dissolved phase pulmonary hp129Xe MRI. A robust phantom standard will require materials with longer shelf lifetime than the oil-foam system and would benefit from a more defined microstructure.

Quantitative 1H Magnetic Resonance Imaging on Normal and Pathologic Rat Bones by Solid-State 1H ZTE Sequence with Water and Fat Suppression.

Osteoporosis (OP) and osteomalacia (OM) are metabolic bone diseases characterized by mineral and matrix density changes. Quantitative bone matrix density differentiates OM from OP. MRI is a noninvasive and nonionizing imaging technique that can measure bone matrix density quantitatively in ex vivo and in vivo. To demonstrate water + fat suppressed 1H MRI to compute bone matrix density in ex vivo rat femurs in the preclinical model. Prospective. Fifteen skeletally mature female Sprague-Dawley rats, five per group (normal, ovariectomized (OVX), partially nephrectomized/vitamin D (Vit-D) deficient), 250-275 g, ∼15 weeks old. 7T, zero echo time sequence with water + fat (VAPOR) suppression capability, μCT imaging, and gravimetric measurements. Cortical and trabecular bone segments from normal and disease models were scanned in the same coil along with a dual calibration phantom for quantitative assessment of bone matrix density. ANOVA and linear regression were used for data analysis, with P-values <0.05 statistically significant. The MRI-derived three-density PEG pellet densities have a strong linear relationship with physical density measures (r2 = 0.99). The Vit-D group had the lowest bone matrix density for cortical bone (0.47 ± 0.16 g cm-3), whereas the OVX had the lowest bone matrix density for trabecular bone (0.26 ± 0.04 g cm-3). Gravimetry results confirmed these MRI-based observations for Vit-D cortical (0.51 ± 0.07 g cm-3) and OVX trabecular (0.26 ± 0.03 g cm-3) bone groups. Rat femur images were obtained using a modified pulse sequence and a custom-designed double-tuned (1H/31P) transmit-receive solenoid-coil on a 7T preclinical MRI scanner. Phantom experiments confirmed a strong linear relation between MRI-derived and physical density measures and quantitative bone matrix densities in rat femurs from normal, OVX, and Vit-D deficient/partially nephrectomized animals were computed. 2 TECHNICAL EFFICACY: Stage 2.

Modified Pulse Sequences Based on Barker Codes

The article considers an approach to the modification of manipulative impulse sequences based on Barker codes. It is proposed to change the structure of the encoded pulses by the duration of the elementary message, taking into account the change in the duty cycle of their repetition while maintaining the total average energy. Numerical relations are obtained that determine the spectral and temporal parameters for a seven-element pulse sequence, with an increase in the pulse repetition rate by two and three times. Numerical values are calculated that determine the ratio of the duration of the peaks of the cross-correlation functions between the modified and canonical forms of pulse sequences. Reasonable estimates are presented that characterize the increase in the resolution of the peaks of the cross-correlation functions by 4.43 times in the transition to the proposed modified structure of the pulse sequence.

Application of NMR and Chemometrics for the Profiling and Classification of Ale and Lager American Craft Beer.

In this paper, Nuclear Magnetic Resonance spectroscopy (NMR)-based metabolomics were applied for the discrimination of ale and lager craft American beers. A modified pulse sequence that allows the efficient suppression of the water and ethanol peaks was used to achieve high-quality spectra with minimal sample preparation. The initial chemometrics analysis generated models of low predictive power, indicating the high variability in the groups. Due to this variability, we tested the effect of various data pretreatment and chemometrics approaches to improve the model’s performance. Spectral alignment was found to improve the classification significantly, while the type of normalization also played an important role. NMR combined with statistical and machine-learning techniques such as orthogonal projection to latent structures discriminant analysis (OPLS-DA) and random forest was able to discriminate between ale and lager beers, thus providing an important tool for the quality control and analysis of these products.

Robotically Assisted Sonic Therapy (RAST) for Noninvasive Hepatic Ablation in a Porcine Model: Mitigation of Body Wall Damage with a Modified Pulse Sequence.

Robotically assisted sonic therapy (RAST) is a nonthermal, noninvasive ablation method based on histotripsy. Prior animal studies have demonstrated the ability to create hepatic ablation zones at the focal point of an ultrasound therapy transducer; however, these treatments resulted in thermal damage to the body wall within the path of ultrasound energy delivery. The purpose of this study was to evaluate the efficacy and safety of a pulse sequence intended to mitigate prefocal body wallinjury. Healthy swine (n = 6) underwent hepatic RAST (VortxRx software version 1.0.1.3, HistoSonics, Ann Arbor MI) in the right hepatic lobe. A 3.0cm spherical ablation zone was prescribed for each. Following treatment, animals underwent MRI which was utilized for ablation zone measurement, evaluation of prefocal injury, and assessment of complications. Each animal was euthanized, underwent necropsy, and thetissuewas processed for histopathologic analysis of the ablation zone and any other sites concerning for injury. No prefocal injury was identified by MRI or necropsy in the body wall or tissues overlying the liver. Ablation zones demonstrated uniform cell destruction, were nearly spherical (sphericity index = 0.988), and corresponded closely to the prescribed size (3.0 × 3.1 × 3.4cm, p = 0.70, 0.36, and 0.01, respectively). Ablation zones were associated with portal vein (n = 3, one occlusive) and hepatic vein thrombosis (n = 4, one occlusive); however, bile ducts remained patent within ablation zones (n = 2). Hepatic RAST performed with a modified ultrasound pulse sequence in a porcine model can mitigate prefocal body wall injuries while maintaining treatment efficacy. Further study of hepatic RAST appears warranted, particularly in tumor models.

Simultaneous detection of intra- and inter-molecular paramagnetic relaxation enhancements in protein complexes.

Paramagnetic relaxation enhancement (PRE) measurements constitute a powerful approach for detecting both permanent and transient protein-protein interactions. Typical PRE experiments require an intrinsic or engineered paramagnetic site on one of the two interacting partners; while a second, diamagnetic binding partner is labeled with stable isotopes (15N or 13C). Multiple paramagnetic labeled centers or reversed labeling schemes are often necessary to obtain sufficient distance restraints to model protein-protein complexes, making this approach time consuming and expensive. Here, we show a new strategy that combines a modified pulse sequence (1HN-Γ2-CCLS) with an asymmetric labeling scheme to enable the detection of both intra- and inter-molecular PREs simultaneously using only one sample preparation. We applied this strategy to the non-covalent dimer of ubiquitin. Our method confirmed the previously identified binding interface for the transient di-ubiquitin complex, and at the same time, unveiled the internal structural dynamics rearrangements of ubiquitin upon interaction. In addition to reducing the cost of sample preparation and speed up PRE measurements, by detecting the intra-molecular PRE this new strategy will make it possible to measure and calibrate inter-molecular distances more accurately for both symmetric and asymmetric protein-protein complexes.

Implementation of fast macromolecular proton fraction mapping on 1.5 and 3 Tesla clinical MRI scanners: preliminary experience

Macromolecular proton fraction (MPF) is a biophysical parameter describing the amount of macromolecular protons involved into magnetization exchange with water protons in tissues. MPF represents a significant interest as a magnetic resonance imaging (MRI) biomarker of myelin for clinical applications. A recent fast MPF mapping method enabled clinical translation of MPF measurements due to time-efficient acquisition based on the single-point constrained fit algorithm. However, previous MPF mapping applications utilized only 3 Tesla MRI scanners and modified pulse sequences, which are not commonly available. This study aimed to test the feasibility of MPF mapping implementation on a 1.5 Tesla clinical scanner using standard manufacturer’s sequences and compare the performance of this method between 1.5 and 3 Tesla scanners. MPF mapping was implemented on 1.5 and 3 Tesla MRI units of one manufacturer with either optimized custom-written or standard product pulse sequences. Whole-brain three-dimensional MPF maps obtained from a single volunteer were compared between field strengths and implementation options. MPF maps demonstrated similar quality at both field strengths. MPF values in segmented brain tissues and specific anatomic regions appeared in close agreement. This experiment demonstrates the feasibility of fast MPF mapping using standard sequences on 1.5 T and 3 T clinical scanners.

Perturbative harmonic modulation of longitudinal electron-spin magnetization for short [formula omitted] determination

Longitudinally detected T1 measurement scheme (LOD-T1) is studied in detail. In contrast to the original work on LOD-T1, using high power microwave pulses, this work deals with general and practically frequent cases in which perfect inversion of the electron-spin magnetization is not feasible due to the effect of relaxation during microwave pulses. Theoretical studies, numerical simulations, and experiments reveal a pair of separate contributions of the dynamics of the longitudinal magnetization to the LOD signal, namely, the periodic modulation and the relaxation contributions. The latter alone which is of interest can be extracted to give relaxation curves. In addition, it is shown that T1 information can be obtained even when the available microwave power is so low that the electron magnetization can only be perturbatively modulated, at the cost of reduced sensitivity. To overcome this, a modified pulse sequence is proposed. In this new method, the pulse excitations are repeated during half a period of the resonance of the longitudinal detection circuit. The method is called the perturbative harmonic modulation method for longitudinally detected T1 measurement (HM-LOD-T1). HM-LOD-T1 experiments are demonstrated in 2,2-diphenyl-1-picrylhydrazyl (DPPH).

A modified design of pulse sequence and inversion method for D-T2 two-dimensional NMR

In face of the increasingly complicated exploration targets, D-T2 2D NMR technology cannot balance the range of diffusion coefficient and transverse relaxation resolution in practice. As the key technique of D-T2 2D NMR, the property of pulse sequence affects its application. A modified design of bivariate D-T2 pulse sequence based on pulsed field gradient is proposed after summarizing the technical characteristics of PFG, STE-PFG, BP-PFG, modified CPMG, “diffusion editing” and multi echo interval CPMG pulse sequences, which effectively integrates the advantages of D-T2 pulse sequences based on pulsed field gradient and constant field gradient. In order to reduce the difficulties that the existing D-T2 inversion methods cannot balance the inversion efficiency and accuracy, we propose a joint TSVD inversion method which sets the echos from the second window as the main part supplemented by the echos from the first window. Numerical simulation results for gas-water, oil-water, heavy oil and gas-oil-water models in different SNRs indicate that the D-T2 modified pulse sequence can balance the diffusion coefficient measureflent range and transverse relaxation resolution successfully, and the joint TSVD inversion method balances the inversion efficiency and accuracy successfully. Above all, the D-T2 modified pulse sequence and the joint TSVD inversion method have wide applications in the exploration and formation evaluation for unconventional reflervoir, and create favorable conditions for the development of D-T2 2D NMR technology.

Quantitation of Iron in Brain Structures of Children with Sickle Cell Disease and Transfusion Hemosiderosis

Introduction:Children with sickle cell disease (SCD) and abnormal cerebral blood flow often receive cyclic blood transfusions (CTx) to reduce risk of stroke. While effective for stroke prevention, CTx causes systemic iron accumulation that may damage multiple organs (Harmatz P., Blood 2000). Iron toxicity from CTx is poorly described for the brain, in comparison to the liver and heart. Quantifying iron in the subcortical structures and the choroid plexus is of renewed clinical importance, due to recent findings that iron accumulation in these regions may predict CNS injury in neurodegenerative disorders. In this study, a new imaging protocol is applied to quantify iron levels and measure structural volumes for the subcortical structures and choroid plexus of children with SCD on CTx, using healthy children for comparison.Methods:SCD patients were eligible if at least 12 consecutive months of CTx were received for abnormal transcranial doppler. Patients with history of CVA were excluded, due to potential confounding effects of prior ischemic damage.Healthysiblings and relatives were used as ethnic- and age-matched controls.MRI scans of the liver and brain, using a Siemens 3T Trio scanner, was performed without sedation for all subjects. A modified pulse sequence (R2*) for the 3T scanner was used to determine liver iron concentration. T1-weighted imaging sequence with MPRAGE was used for anatomical identification and volume measurements of brain regions (Kirk G., Cerebral Cortex 2009). A 3D multi-echo gradient-echo sequence (FOV=256x192mm, Matrix=256x192, Slice thickness = 2mm, 72 slices, TR = 50 ms, first TE = 3.7ms, 12 echoes, echo spacing = 3.8ms) was used for the quantitative susceptibility mapping (QSM), a MRI method that is sensitive to tissue iron (Shmueli K., Magn Reson Med 2009). Iron levels were generated with a post-processing protocol developed for this application (modification of Qiu D., AJNR 2014). To compare iron levels between the two groups a general linear model (GLM) was used that incorporated the ages of the subjects into the comparison. For the patients, an additional GLM analysis was performed to determine if iron level when in each region when corrected for age was associated duration of transfusions, liver R2* and average serum ferritins.Results:MRI scans were evaluable for 25 SCD patients on CTx and 23 controls. There were no significant differences between patients and healthy controls with respect to age, sex or ethnicity. The average duration of CTx was 6.0 (1.5-12.6) yrs and the average serum ferritin and liver iron R2* were 2540 ng/ml and 819 Hz (~14.8mg/g dry weight), respectively. As anticipated, iron level in the choroid plexus was significantly elevated in patients compared to controls (p=1.4x10-7), and levels correlated well with serum ferritin (p=0.0003) and liver R2* (p=0.001) (panel a). While there were no significant differences detected between the groups with respect to iron levels in the subcortical structures, there was a trend to increasing differences between the groups with age in the Substanita Nigra, Red Nucleus and Dentate Nucleus (panels b,c,d). In the GLM analysis, age was significantly associated with iron levels in the subcortical structures, not in the choroid plexus. Although iron levels in some of the subcortical structures were associated with duration of CTx, ferritin and liver R2*, the significance was predominately lost when corrected for age. These observations suggest additional studies with older subjects may reveal increased differences. Volumetric analysis was performed to assess potential injury to deep gray matter. The measured volumes of the subcortical structures were not statistically different between the groups, with a noted exception of the caudate nucleus (p=0.021), a region of known predisposition to injury in SCD (Steen R., Ann Neurol 1999).Conclusions: The MRI protocol successfully quantified iron in brain structures, associated with neurodegenerative disorders. Iron accumulation in the choroid plexus was significant in SCD patients on CTx, and correlated with other markers of iron overload. While iron was detectable in subcortical structures, the levels were not significant different from controls after adjusting for age. These finding should be helpful in planning for a longitudinal study that includes a broader age range. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Dual-optimized 1Jcc-edited 1,n-adequate: A novel NMR structure elucidation technique

Establishing the carbon skeleton of a molecule is an integral aspect of structure elucidation. Recent advances in ADEQUATE experiments have highlighted their potential; 1,1-ADEQUATE, provides direct 13C-13C correlation via 1 J CC; and 1,n-ADEQUATE yields both long-range (typically 3 J CC) and direct 1 J CC correlation. Direct and long-range correlations are unfortunately indistinguishable in 1,n-ADEQUATE. A modified pulse sequence was developed in 2012 that inverted 1 J CC correlations in 1,n-ADEQUATE spectra. This change provided a significant improvement, allowing 1 J CC and n J CC correlations to be differentiated in the same spectrum. Careful matching of the amplitude transfer function with 1 J CC coupling constants was required with that version of the experiment to achieve near uniform inversion. Some 1 J CC correlations could still have positive intensity due to the oscillatory nature of the transfer function. Those shortcomings significantly limited application of the method. We now report a dual-optimized 1 J CC-edited 1,n-ADEQUATE experiment, that provides uniform inversion of 1 J CC correlations across the range of 29 – 82 Hz. Fine-tuning for a molecule's 1 J CC coupling constant values is not required. Beneficially, the dual-optimized version provides up to two-fold improvement in signal-to-noise for some long-range correlations. Using modern, cryogenically-cooled probes, the experiment can be successfully applied to samples as small as 1 mg. In addition to strychnine, examples of applications of the method to staurosporine and coniothyrione are also presented.

Characterisation and evaluation of paramagnetic fluorine labelled glycol chitosan conjugates for 19F and 1H magnetic resonance imaging

Medium molecular weight glycol chitosan conjugates have been prepared, linked by an amide bond to paramagnetic Gd(III), Ho(III) and Dy(III) macrocyclic complexes in which a trifluoromethyl reporter group is located 6.5 Å from the paramagnetic centre. The faster relaxation of the observed nucleus allows modified pulse sequences to be used with shorter acquisition times. The polydisperse materials have been characterised by gel permeation chromatography, revealing an average molecular weight on the order of 13,800 (Gd), 14,600 (Dy) and 16,200 (Ho), consistent with the presence of 8.5, 9.5 and 13 complexes, respectively. The gadolinium conjugate was prepared for both a q = 1 monoamide tricarboxylate conjugate (r1p 11.2 mM(-1) s(-1), 310 K, 1.4 T) and a q = 0 triphosphinate system, and conventional contrast-enhanced proton MRI studies at 7 T were undertaken in mice bearing an HT-29 or an HCT-116 colorectal tumour xenograft (17 μmol/kg). Enhanced contrast was observed following injection in the tail vein in tumour tissue, with uptake also evident in the liver and kidney with a tumour-to-liver ratio of 2:1 at 13 min, and large amounts in the kidney and bladder consistent with predominant renal clearance. Parallel experiments observing the (19)F resonance in the holmium conjugate complex using a surface coil did not succeed owing to its high R2 value (750 Hz, 7 T). However, the fluorine signal in the dysprosium triphosphinate chitosan conjugate [R1/R2 = 0.6 and R1 = 145 Hz (7 T)] was sharper and could be observed in vivo at -65.7 ppm, following intravenous tail vein injection of a dose of 34 μmol/kg.

Broadband inversion of 1JCC responses in 1,n-ADEQUATE spectra

Establishing the carbon skeleton of a molecule greatly facilitates the process of structure elucidation, both manual and computer-assisted. Recent advances in the family of ADEQUATE experiments demonstrated their potential in this regard. 1,1-ADEQUATE, which provides direct 13C–13C correlation via 1JCC, and 1,n-ADEQUATE, which typically yields 3JCC and 1JCC correlations, are more sensitive and more widely applicable experiments than INADEQUATE and PANACEA. A recently reported modified pulse sequence that semi-selectively inverts 1JCC correlations in 1,n-ADEQUATE spectra provided a significant improvement, allowing 1JCC and nJCC correlations to be discerned in the same spectrum. However, the reported experiment requires a careful matching of the amplitude transfer function with 1JCC coupling constants in order to achieve the inversion, and even then some 1JCC correlations could still have positive intensity due to the oscillatory nature of the transfer function. Both shortcomings limit the practicality of the method. We now report a new, dual-optimized inverted 1JCC 1,n-ADEQUATE experiment, which provides more uniform inversion of 1JCC correlations across the range of 29–82Hz. Unlike the original method, the dual optimization experiment does not require fine-tuning for the molecule’s 1JCC coupling constant values. Even more usefully, the dual-optimized version provides up to two-fold improvement in signal-to-noise for some long-range correlations. Using modern, cryogenically-cooled probes, the experiment can be successfully applied to samples of ∼1mg under favorable circumstances. The improvements afforded by dual optimization inverted 1JCC 1,n-ADEQUATE experiment make it a useful and practical tool for NMR structure elucidation and should facilitate the implementation and utilization of the experiment.

Short TE7Li-MRS confirms Bi-exponential lithium T2 relaxation in humans and clearly delineates two patient subtypes

(i) To develop an MRS technique to measure (7) Li levels in human brain in a reasonable scan time, (ii) to develop a technique to quantify (7) Li T2 relaxation times as measured from human brain in patients taking lithium for the treatment of their bipolar disorder, and (iii) to confirm or refute the presence of bi-exponential (7) Li T2 relaxation in human brain. We modified a spin-echo MRS pulse sequence to decrease its minimum echo time. With IRB approval, we performed lithium MRS with the modified pulse sequence on 13 euthymic bipolar patients stable on long-term lithium to treat their disease. We were able to achieve a total scan time per sample of 8:20; total scan time including imaging, calibration and MRS was approximately 1 h 15 min. We observed bi-exponential T2 relaxation in the majority of patients, with an average short decay time of 5.3 ± 1.4 ms and an average long decay time of 68.2 ± 10.2 ms. However, in two patients we observed strongly mono-exponential T2 relaxation with an average decay time of 47.4 ± 1.3 ms. (7) Li relaxation patterns may prove useful to distinguish between lithium-responsive and lithium nonresponsive bipolar patients.

Fidelity of a Rydberg-blockade quantum gate from simulated quantum process tomography

We present a detailed error analysis of a Rydberg blockade mediated controlled-NOT quantum gate between two neutral atoms as demonstrated recently in Phys. Rev. Lett. 104, 010503 (2010) and Phys. Rev. A 82, 030306 (2010). Numerical solutions of a master equation for the gate dynamics, including all known sources of technical error, are shown to be in good agreement with experiments. The primary sources of gate error are identified and suggestions given for future improvements. We also present numerical simulations of quantum process tomography to find the intrinsic fidelity, neglecting technical errors, of a Rydberg blockade controlled phase gate. The gate fidelity is characterized using trace overlap and trace distance measures. We show that the trace distance is linearly sensitive to errors arising from the finite Rydberg blockade shift and introduce a modified pulse sequence which corrects the linear errors. Our analysis shows that the intrinsic gate error extracted from simulated quantum process tomography can be under 0.002 for specific states of $^{87}$Rb or Cs atoms. The relation between the process fidelity and the gate error probability used in calculations of fault tolerance thresholds is discussed.

Compensated second-order recoupling: application to third spin assisted recoupling.

We consider the effect of phase shifts in the context of second-order recoupling techniques in solid-state NMR. Notably we highlight conditions leading to significant improvements for the Third Spin Assisted Recoupling (TSAR) mechanism and demonstrate the benefits of resulting techniques for detecting long-distance transfer in biomolecular systems. The modified pulse sequences of PAR and PAIN-CP, Phase-Shifted Proton Assisted Recoupling (AH-PS-PAR) and Phase-Shifted Proton-Assisted Insensitive Nuclei Cross Polarization (ABH-PS-PAIN-CP), still rely on cross terms between heteronuclear dipolar couplings involving assisting protons that mediate zero-quantum polarization transfer between low-γ nuclei ((13)C-(13)C, (15)N-(15)N, (15)N-(13)C polarization transfer). Using Average Hamiltonian Theory we show that phase inversion compensates off-resonance contributions and yields improved polarization transfer as well as substantial broadening of the matching conditions. PS-TSAR greatly improves on the standard TSAR based methods because it alleviates their sensitivity to precise RF settings which significantly enhances robustness of the experiments. We demonstrate these new methods on a 19.6 kDa protein (U-[(15)N, (13)C]-YajG) at high magnetic fields (up to 900 MHz (1)H frequency) and fast sample spinning (up to 65 kHz MAS frequency).

Short echo time in vivo prostate 1H-MRSI

Visualization of short echo time (TE) metabolites in prostate magnetic resonance spectroscopic imaging is difficult due to lipid contamination and pulse timing constraints. In this work, we present a modified pulse sequence to permit short echo time (TE=40ms) acquisitions with reduced lipid contamination for the detection of short TE metabolites. The modified pulse sequence employs the conformal voxel MRS (CV-MRS) technique, which automatically optimizes the placement of spatial saturation planes to adapt the excitation volume to the shape of the prostate, thus reducing lipid contamination in prostate magnetic resonance spectroscopic imaging (MRSI). Metabolites were measured and assessed using a modified version of LCModel for analysis of in vivo prostate spectra. We demonstrate the feasibility of acquiring high quality spectra at short TEs, and show the measurement of short TE metabolites, myo-inositol, scyllo-inositol, taurine and glutamine/glutamate for both single and multi-voxel acquisitions. In single voxels experiments, the reduction in TE resulted in 57% improvement in the signal-to-noise ratio (SNR). Additional 3D MRSI experiments comparing short (TE=40 ms), and long (TE=130 ms) TE acquisitions revealed a 35% improvement in the number of adequately fitted metabolite peaks (775 voxels over all subjects). This resulted in a 42±24% relative improvement in the number of voxels with detectable citrate that were well-fitted using LCmodel. In this study, we demonstrate that high quality prostate spectra can be obtained by reducing the TE to 40 ms to detect short T2 metabolites, while maintaining positive signal intensity of the spin-coupled citrate multiplet and managing lipid suppression.

Pulse voltage operation of two-to-four-phase voltage-induction-type electrostatic motor

This paper analyzes pulse voltage operations of a two-to-four phase voltage-induction-type electrostatic motor (VITEM) to clarify the appropriate driving sequences. The paper also evaluates transient charge effects that can possibly enhance the thrust force. VITEM has been studied as a novel centimeter-sized electrostatic film motor whose power to the slider is supplied indirectly through its induction electrodes. Since a smooth synchronous driving was aimed in the past stud- ies, high-frequency AC voltages have been used for the driving. This paper demonstrates that straightforward usage of simple pulse sequences cannot realize continuous stepping driving, and proposes several different sets of modified pulse sequences to realize continuous stepping driving using low-switching-rate pulse voltages. In the experiments, the motor showed continuous stepwise driving with a step width of about half of the electrode pitch. In addition, transient characteristics of charges on films were evaluated experimentally under the pulse driving condition, and contribution for thrust force enhancement was clarified.

Getting to know the nitrogen next door: HNMBC measurements of amino sugars

Long-range 1H– 15N correlations detected by the heteronuclear multiple-bond correlation (HMBC) experiment are explored for the characterization of amino sugars. The gradient-enhanced HMBC, IMPACT-HMBC, and a modified pulse sequence with the 1 J-filters removed, IMPACT-HNMBC, are compared for sensitivity and resolution. 15N chemical shifts and long-range proton correlations are reported using the IMPACT-HNMBC experiment for N-acetyl-glucosamine, N-acetyl-galactosamine, and for a series of glucosamine analogs with an N-sulfo substitution, unmodified amino group, and 6- O-sulfonation. As is common with sugars, for all the compounds examined both anomeric forms are present in solution. For each compound studied, the 15N chemical shifts of the α anomer are downfield of the β form. For the N-acetylated sugars, the β anomer has a unique long-range 15N correlation to the anomeric proton not observed for the α anomer. Though N-sulfonation results in a significant change in the 15N chemical shift of the glucosamine analogs, 6- O sulfo substitution has no significant effect on the local environment of the amino nitrogen. For N-acetylated sugars in D 2O solution, peaks in the 15N projection of the HMBC spectrum appear as triplets as a result of J-modulation due to 2H– 15N coupling.

In vivo lactate signal enhancement using binomial spectral‐selective pulses in selective MQ coherence (SS‐SelMQC) spectroscopy

Tumor vasculature and tissue oxygen pressure can influence tumor growth, metastases, and patient survival. Elevated levels of lactate may be observed during the process of aggressive tumor development accompanied by angiogenesis (the evolution of the microenvironment). The noninvasive MR detection of lactate in tumor tissues as a potential biomarker is difficult due to the presence of co-resonating lipids that are present at high concentrations. Methods were previously reported for lactate editing using the SELective Multiple Quantum Coherence (SelMQC) method. Here we report a sequence "SS-SelMQC," Spectral-Selective SelMQC, which is a modified version of SelMQC using binomial pulses. Binomial pulses were employed in this editing sequence for frequency excitation or inversion of selective lactate resonances. Lactate detection has been demonstrated using SS-SelMQC, both in vitro (30 mM lactate/H(2)O doped with 25 microM Gd-DTPA) and in vivo (Dunning R3337-AT prostate tumors), and compared to similar measurements made with SelMQC. Lactate areas were measured from nonlocalized spectra, one-dimensional (1D) localized spectra, and two-dimensional chemical shift images (CSI) of the localized slice. In data from whole phantoms, the modified pulse sequence yielded enhancement of the lactate signal of 2.4 +/- 0.40 times compared to SelMQC. Similar in vivo lactate signal enhancement of 2.3 +/- 0.24 times was observed in 1D slice-localized experiment.