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Biofilm formation protects bacteria from antibiotic treatment and host immune responses, making biofilm infections difficult to treat. Within biofilms, bacterial cells are entangled in a self‐produced extracellular matrix that typically includes exopolysaccharides. Molecular‐level descriptions of biofilm matrix components, especially exopolysaccharides, have been challenging to attain due to their complex nature and lack of solubility and crystallinity. Solid‐state nuclear magnetic resonance (NMR) has emerged as a key tool to determine the structure of biofilm matrix exopolysaccharides without degradative sample preparation. In this review, we discuss challenges of studying biofilm matrix exopolysaccharides and opportunities to develop solid‐state NMR approaches to study these generally intractable materials. We specifically highlight investigations of the exopolysaccharide called Pel made by the opportunistic pathogen, Pseudomonas aeruginosa. We provide a roadmap for determining exopolysaccharide structure and discuss future opportunities to study such systems using solid‐state NMR. The strategies discussed for elucidating biofilm exopolysaccharide structure should be broadly applicable to studying the structures of other glycans. [ABSTRACT FROM AUTHOR]

Potentiometry is the primary pH measurement method, but alternatives are sought beyond glass electrodes operative limitations. In nuclear magnetic resonance (NMR) experiments, electrodeless pH sensing is important to track changes along titrations, during chemical reactions or inside compartmentalized environments inaccessible to electrodes, for instance. Although several interesting NMR pH indicators have been already presented, the potential of inorganic phosphate is overlooked, despite its common presence in NMR samples as the buffer main component. Its use for electrodeless pH determination can be expanded by exploiting all its three proton dissociations. This study was aimed at verifying the use of inorganic phosphate 31P chemical shift to sense pH variations, and at exploring the complementary use of pyrophosphate ions to cover a wide pH range. A simple set of equations is presented to utilize both phosphate and pyrophosphate 31P chemical shift in combination for accurate pH determination without a glass electrode over the 5–12 pH range, and without affecting the spectrum of other nuclei. The present study demonstrated an average deviation of 0.09 (maximum <0.2) pH unit from glass electrode measurements. The trimethylphosphate can be used as a suitable chemical shift reference for both 31P and 1H (also 13C), with its hydrolysis being significant only at pH > 12. The method was also demonstrated by determining the pKa of three distinct molecules in a mixture and by comparing the results to those obtained when the glass electrode was used to measure the pH. The approach shown here can be easily tuned to different experimental conditions. [ABSTRACT FROM AUTHOR]

Motivation: 31P magnetic resonance spectroscopic imaging (31P MRSI) is a powerful technique for investigating the metabolic effects of treatments for heart failure in vivo, allowing a better understanding of their mechanism of action in patient cohorts. Unfortunately, cardiac 31P MRSI is fundamentally limited by low SNR, which leads to compromises in acquisition, such as no cardiac or respiratory gating or low spatial resolution, in order to achieve reasonable scan times. Spectroscopy with linear algebra modeling (SLAM) reconstruction may be able to address these challenges and therefore improve repeatability by incorporating a segmented localizer into the reconstruction. Methods: Six healthy volunteers were scanned twice in a test-retest procedure to allow quantification of repeatability. Each scan consisted of anatomical localizers and two acquisition-weighted (AW) 31P MRSI acquisitions, which were acquired with and without cardiac gating. Five patients with heart failure with a preserved ejection fraction were then scanned with the same 31P MRSI sequence without cardiac gating. All 31P MRSI datasets were reconstructed with both conventional Fourier transform (FT)-based reconstruction and SLAM reconstruction, which were compared statistically. The effect of shifting the 31P MRSI acquisition field of view was also investigated. Results: In the healthy volunteer cohort, the spectral fit of the SLAM reconstructions had significantly improved Cramer-Rao lower bounds (CRLBs) compared to the FT-based reconstruction of non-cardiac gated data, as well as improved coefficients of variability and repeatability. The SLAM reconstruction found a significant difference in the PCr/ATP ratio between the healthy volunteer and patient cohorts, which the FT-based reconstruction did not find. Furthermore, the SLAM reconstruction was less influenced by the placement of the field of view (FOV) of the 31P MRSI acquisition in post hoc analysis. Discussion: The experimental benefits of the SLAM reconstruction for AW data were demonstrated by the improvements in fit confidence and repeatability seen in the healthy volunteer cohort and post hoc FOV analysis. The benefit of SLAM reconstruction of AW data for clinical studies was then illustrated by the patient cohort, which suggested improved sensitivity to clinically significant changes in the PCr/ATP ratio. [ABSTRACT FROM AUTHOR]

Motivation:31P magnetic resonance spectroscopic imaging (31P MRSI) is a powerful technique for investigating the metabolic effects of treatments for heart failure in vivo, allowing a better understanding of their mechanism of action in patient cohorts. Unfortunately, cardiac 31P MRSI is fundamentally limited by low SNR, which leads to compromises in acquisition, such as no cardiac or respiratory gating or low spatial resolution, in order to achieve reasonable scan times. Spectroscopy with linear algebra modeling (SLAM) reconstruction may be able to address these challenges and therefore improve repeatability by incorporating a segmented localizer into the reconstruction.Methods: Six healthy volunteers were scanned twice in a test–retest procedure to allow quantification of repeatability. Each scan consisted of anatomical localizers and two acquisition-weighted (AW) 31P MRSI acquisitions, which were acquired with and without cardiac gating. Five patients with heart failure with a preserved ejection fraction were then scanned with the same 31P MRSI sequence without cardiac gating. All 31P MRSI datasets were reconstructed with both conventional Fourier transform (FT)-based reconstruction and SLAM reconstruction, which were compared statistically. The effect of shifting the 31P MRSI acquisition field of view was also investigated.Results: In the healthy volunteer cohort, the spectral fit of the SLAM reconstructions had significantly improved Cramer–Rao lower bounds (CRLBs) compared to the FT-based reconstruction of non-cardiac gated data, as well as improved coefficients of variability and repeatability. The SLAM reconstruction found a significant difference in the PCr/ATP ratio between the healthy volunteer and patient cohorts, which the FT-based reconstruction did not find. Furthermore, the SLAM reconstruction was less influenced by the placement of the field of view (FOV) of the 31P MRSI acquisition in post hoc analysis.Discussion: The experimental benefits of the SLAM reconstruction for AW data were demonstrated by the improvements in fit confidence and repeatability seen in the healthy volunteer cohort and post hoc FOV analysis. The benefit of SLAM reconstruction of AW data for clinical studies was then illustrated by the patient cohort, which suggested improved sensitivity to clinically significant changes in the PCr/ATP ratio.

Proton nuclear (¹H) is the observed nucleus on which most magnetic resonance imaging (MRI) applications depend. Most traditional ¹H MRI can provide structural and functional information about organisms, while various non-proton nuclei (X-nuclei) MRI can provide more metabolic information. However, due to the relatively poor signal-to-noise ratio (SNR) of X-nuclei MRI, their applications are quite rare compared to ¹H. Benefit from the rapid developments of MRI hardware and software technologies, X-nuclei MRI has recently attracted increasing interests in biomedical research. This review firstly introduces some current methods to improve the SNR of X-nuclei MRI. Secondly, this review describes biomedical applications of X-nuclei MRI, especially focusing on the current use of X-nuclei (13C, 17O, 19F, 23Na and 31P) MRI to study related diseases in different organs, including the brain, liver, kidney, heart and bone. Finally, perspectives studies on X-nuclei imaging and its potential applications are described in biomedical research. [ABSTRACT FROM AUTHOR]

Even at 7 T, cardiac 31P magnetic resonance spectroscopic imaging (MRSI) is fundamentally limited by low signal‐to‐noise ratio (SNR), leading to long scan times and poor temporal and spatial resolutions. Compartment‐based reconstruction algorithms such as magnetic resonance spectroscopy with linear algebraic modeling (SLAM) and spectral localization by imaging (SLIM) may improve SNR or reduce scan time without changes to acquisition. Here, we compare the repeatability and SNR performance of these compartment‐based methods, applied to three different acquisition schemes at 7 T. Twelve healthy volunteers were scanned twice. Each scan session consisted of a 6.5‐min 3D acquisition‐weighted (AW) cardiac 31P phase encode‐based MRSI acquisition and two 6.5‐min truncated k‐space acquisitions with increased averaging (4 × 4 × 4 central k‐space phase encodes and fractional SLAM [fSLAM] optimized k‐space phase encodes). Spectra were reconstructed using (i) AW Fourier reconstruction; (ii) AW SLAM; (iii) AW SLIM; (iv) 4 × 4 × 4 SLAM; (v) 4 × 4 × 4 SLIM; and (vi) fSLAM acquisition–reconstruction combinations. The phosphocreatine‐to‐adenosine triphosphate (PCr/ATP) ratio, the PCr SNR, and spatial response functions were computed, in addition to coefficients of reproducibility and variability. Using the compartment‐based reconstruction algorithms with the AW 31P acquisition resulted in a significant increase in SNR compared with previously published Fourier‐based MRSI reconstruction methods while maintaining the measured PCr/ATP ratio and improving interscan reproducibility. The alternative acquisition strategies with truncated k‐space performed no better than the common AW approach. Compartment‐based spectroscopy approaches provide an attractive reconstruction method for cardiac 31P spectroscopy at 7 T, improving reproducibility and SNR without the need for a dedicated k‐space sampling strategy. [ABSTRACT FROM AUTHOR]

Introduction: Nuclear magnetic resonance (NMR) is widely used in metabolomics but it focusses on 1H over other NMR-active nuclei. Objectives: To evaluate the potential of alternative NMR-sensitive nuclei to generate useful metabolomic data. Method: Proton, carbon, phosphorus, and nitrogen-based NMR metabolomics was undertaken on extracts from mint and European honey bee tissue. Results: Carbon NMR provided useful information but required larger sample sizes. Phosphorus produced overlapping peaks in one dimensional (1D) analysis but showed potential in 2D experiments. 15N NMR was found to not be sensitive enough for general metabolomic work. Conclusions: Alternative NMR active nuclei are useful for metabolomics. [ABSTRACT FROM AUTHOR]

A three‐dimensional (3D), density‐weighted, concentric rings trajectory (CRT) magnetic resonance spectroscopic imaging (MRSI) sequence is implemented for cardiac phosphorus (31P)‐MRS at 7 T. The point‐by‐point k‐space sampling of traditional phase‐encoded chemical shift imaging (CSI) sequences severely restricts the minimum scan time at higher spatial resolutions. Our proposed CRT sequence implements a stack of concentric rings, with a variable number of rings and planes spaced to optimise the density of k‐space weighting. This creates flexibility in acquisition time, allowing acquisitions substantially faster than traditional phase‐encoded CSI sequences, while retaining high signal‐to‐noise ratio (SNR). We first characterise the SNR and point‐spread function of the CRT sequence in phantoms. We then evaluate it at five different acquisition times and spatial resolutions in the hearts of five healthy participants at 7 T. These different sequence durations are compared with existing published 3D acquisition‐weighted CSI sequences with matched acquisition times and spatial resolutions. To minimise the effect of noise on the short acquisitions, low‐rank denoising of the spatiotemporal data was also performed after acquisition. The proposed sequence measures 3D localised phosphocreatine to adenosine triphosphate (PCr/ATP) ratios of the human myocardium in 2.5 min, 2.6 times faster than the minimum scan time for acquisition‐weighted phase‐encoded CSI. Alternatively, in the same scan time, a 1.7‐times smaller nominal voxel volume can be achieved. Low‐rank denoising reduced the variance of measured PCr/ATP ratios by 11% across all protocols. The faster acquisitions permitted by 7‐T CRT 31P‐MRSI could make cardiac stress protocols or creatine kinase rate measurements (which involve repeated scans) more tolerable for patients without sacrificing spatial resolution. [ABSTRACT FROM AUTHOR]

The creatine kinase (CK) is a key enzyme involved in brain bioenergetics, playing a key role in brain function and the pathogenesis of neurological and psychiatric diseases, but imaging its activity noninvasively in the human brain in vivo remains a significant challenge. This study aims to advance the magnetization transfer (MT)- 31 P magnetic resonance fingerprinting (MRF) for 3D Creatine Kinase Imaging (CKI). The method was implemented and validated on a clinical 7 Tesla MRI scanner. It enables whole-brain mapping of CK reaction rates for the first time, showing robust reproducibility for 25-minute scan sessions. CKI acquisition also provided simultaneous mapping of adenosine triphosphate and phosphocreatine concentration ratios, phosphocreatine longitudinal relaxation time, and B 0 maps. Furthermore, a functional CKI (fCKI) study demonstrated the first CK activation map in response to visual stimulation, revealing a mean 15% increase in CK rates in the visual cortex. The novel imaging modalities, CKI and fCKI, have the potential to offer new insights into brain bioenergetics both at rest and during activity., Competing Interests: Declarations Conflict of interest Yun Jiang receives research grant support from Siemens Healthineers.

1H nucleus is the most commonly used nucleus for magnetic resonance imaging (MRI) due to its high natural abundance in organisms and high MR sensitivity. However, other nuclei are distinctive in physiological processes, such as 31P that is important in the energy metabolisms. The development of high-field MRI allows for MRI research based on 31P nucleus, while high-quality 1H/31P dual-tuned radio frequency (RF) coil is essential for such applications. This article summarized the researches and applications of various 1H/31P dual-tuned RF coils, and presented in vivo 1H MRI and 31P MR spectra of mouse brain at 9.4 T. Potential applications of 1H/31P dual-tuned RF coil for high field were discussed.

The study of stroke has historically made use of traditional spectroscopy techniques to provide the ground truth for parameters like pH. However, techniques like 31P spectroscopy have limitations, in particular poor temporal and spatial resolution, coupled with a need for a high field strength and specialized coils. More modern magnetic resonance spectroscopy (MRS)-based imaging techniques like chemical exchange saturation transfer (CEST) have been developed to counter some of these limitations but lack the definitive gold standard for pH that 31P spectroscopy provides. In this perspective, both the traditional (31P spectroscopy) and emerging (CEST) techniques in the measurement of pH for ischemic imaging will be discussed. Although each has its own advantages and limitations, it is likely that CEST may be preferable simply due to the hardware, acquisition time and image resolution advantages. However, more experiments on CEST are needed to determine the specificity of endogenous CEST to absolute pH, and 31P MRS can be used to calibrate CEST for pH measurement in the preclinical model to enhance our understanding of the relationship between CEST and pH. Combining the two imaging techniques, one old and one new, we may be able to obtain new insights into stroke physiology that would not be possible otherwise with either alone. [ABSTRACT FROM AUTHOR]

The study of stroke has historically made use of traditional spectroscopy techniques to provide the ground truth for parameters like pH. However, techniques like 31P spectroscopy have limitations, in particular poor temporal and spatial resolution, coupled with a need for a high field strength and specialized coils. More modern magnetic resonance spectroscopy (MRS)-based imaging techniques like chemical exchange saturation transfer (CEST) have been developed to counter some of these limitations but lack the definitive gold standard for pH that 31P spectroscopy provides. In this perspective, both the traditional (31P spectroscopy) and emerging (CEST) techniques in the measurement of pH for ischemic imaging will be discussed. Although each has its own advantages and limitations, it is likely that CEST may be preferable simply due to the hardware, acquisition time and image resolution advantages. However, more experiments on CEST are needed to determine the specificity of endogenous CEST to absolute pH, and 31P MRS can be used to calibrate CEST for pH measurement in the preclinical model to enhance our understanding of the relationship between CEST and pH. Combining the two imaging techniques, one old and one new, we may be able to obtain new insights into stroke physiology that would not be possible otherwise with either alone.

Over the past 50 years, 31P NMR has proven a powerful tool for obtaining information on cellular biochemistry. Here we use this technique for the first time to study intracellular phosphorous metabolites in skeletal muscle tissue of wild and farmed salmon, to investigate possible effects due to differences in diet and way of life. The wild salmon sample shows a significantly more diverse composition of metabolites compared to the farmed salmon sample. The differences are evident in the entire spectrum, including regions displaying resonances from phosphomonoesters and sugar phosphates, as well as other molecules important for phospholipid metabolism.It is demonstrated that 31P MAS NMR can be used to study a broad range of phosphorus metabolites ex vivo, which can give useful information, both on its own or as a supplement to other extraction-based analyses. Further 31P MAS NMR investigations on farmed salmon raised under different controlled conditions may give important insights into the broad array of health issues seen in farmed salmon.

Phosphorus magnetic resonance spectroscopic imaging (31P MRSI) is of particular interest for investigations of patients with brain tumors as it enables to non-invasively assess altered energy and phospholipid metabolism in vivo. However, the limited sensitivity of 31P MRSI hampers its broader application at clinical field strengths. This study aimed to identify the additional value of 31P MRSI in patients with glioma at ultra-high B 0 = 7T, where the increase in signal-to-noise ratio may foster its applicability for clinical research. High-quality, 3D 31P MRSI datasets with an effective voxel size of 5.7 ml were acquired from the brains of seven patients with newly diagnosed glioma. An optimized quantification model was implemented to reliably extract an extended metabolic profile, including low-concentrated metabolites such as extracellular inorganic phosphate, nicotinamide adenine dinucleotide [NAD(H)], and uridine diphosphoglucose (UDPG), which may act as novel tumor markers; a background signal was extracted as well, which affected measures of phosphomonoesters beneficially. Application of this model to the MRSI datasets yielded high-resolution maps of 12 different 31P metabolites, showing clear metabolic differences between white matter (WM) and gray matter, and between healthy and tumor tissues. Moreover, differences between tumor compartments in patients with high-grade glioma (HGG), i.e., gadolinium contrast-enhancing/necrotic regions (C+N) and peritumoral edema, could also be suggested from these maps. In the group of patients with HGG, the most significant changes in metabolite intensities were observed in C+N compared to WM, i.e., for phosphocholine +340%, UDPG +54%, glycerophosphoethanolamine −45%, and adenosine-5′-triphosphate −29%. Furthermore, a prominent signal from mobile phospholipids appeared in C+N. In the group of patients with low-grade glioma, only the NAD(H) intensity changed significantly by −28% in the tumor compared to WM. Besides the potential of 31P MRSI at 7T to provide novel insights into the biochemistry of gliomas in vivo , the attainable spatial resolutions improve the interpretability of 31P metabolite intensities obtained from malignant tissues, particularly when only subtle differences compared to healthy tissues are expected. In conclusion, this pilot study demonstrates that 31P MRSI at 7T has potential value for the clinical research of glioma. [ABSTRACT FROM AUTHOR]

Surgery for tongue cancer often results in a major loss in quality of life. While MRI may be used to minimise the volume of excised tissue, often the full tumour extent is missed. This tumour extent may be detected with metabolic imaging. One of the main reasons for the lack of metabolic information on tongue cancer would be the absence of an x-nuclear coil with the tongue as a focus target. Metabolic MRI through 31P MRSI is known as a powerful tool to non-invasively study elevated cell proliferation and disturbed energy metabolism in tumours. Severe magnetic field non-uniformities are inherently caused by the substantial difference in magnetic susceptibilities of tissue and air in the mouth and its environs. Despite this, the wide chemical shift dispersion of 31P could still facilitate precise detection of the cell proliferation biomarkers, phospomonoesters and diesters, as well as energy metabolites ATP, inorganic phosphate, and phosphocreatine potentially mapped over the tongue or tumour in vivo. In this study, we present the first 31P MRSI data of the human tongue in vivo from healthy volunteers and a patient with a tongue tumour at 7 T MRI using a 1H 8-channel transceiver setup placed inside a body 31P transmitter, which is able to get a uniform excitation from the tongue while providing comfortable access to the patient. In addition, a user-friendly external 31P receiver array is used to provide high sensitivity (80%) comparable to an uncomfortable inner mouth loop coil positioned on the tongue. The primary aim is the demonstration of 31P metabolite profiles in the tongue and the differences between healthy and malignant tissue. Indeed, clear elevated cell proliferation expressed as enhanced phosphomonoesters is observed in the tumour vs. the healthy part of the tongue. This can be performed within a total scan duration of 30 min, comparable to clinical scans, with a spatial resolution of 1.5 cm for the 10-min 31P MRSI scan. [ABSTRACT FROM AUTHOR]

Phosphorus magnetic resonance spectroscopic imaging (31P MRSI) is of particular interest for investigations of patients with brain tumors as it enables to non-invasively assess altered energy and phospholipid metabolism in vivo. However, the limited sensitivity of 31P MRSI hampers its broader application at clinical field strengths. This study aimed to identify the additional value of 31P MRSI in patients with glioma at ultra-high B0 = 7T, where the increase in signal-to-noise ratio may foster its applicability for clinical research. High-quality, 3D 31P MRSI datasets with an effective voxel size of 5.7 ml were acquired from the brains of seven patients with newly diagnosed glioma. An optimized quantification model was implemented to reliably extract an extended metabolic profile, including low-concentrated metabolites such as extracellular inorganic phosphate, nicotinamide adenine dinucleotide [NAD(H)], and uridine diphosphoglucose (UDPG), which may act as novel tumor markers; a background signal was extracted as well, which affected measures of phosphomonoesters beneficially. Application of this model to the MRSI datasets yielded high-resolution maps of 12 different 31P metabolites, showing clear metabolic differences between white matter (WM) and gray matter, and between healthy and tumor tissues. Moreover, differences between tumor compartments in patients with high-grade glioma (HGG), i.e., gadolinium contrast-enhancing/necrotic regions (C+N) and peritumoral edema, could also be suggested from these maps. In the group of patients with HGG, the most significant changes in metabolite intensities were observed in C+N compared to WM, i.e., for phosphocholine +340%, UDPG +54%, glycerophosphoethanolamine −45%, and adenosine-5′-triphosphate −29%. Furthermore, a prominent signal from mobile phospholipids appeared in C+N. In the group of patients with low-grade glioma, only the NAD(H) intensity changed significantly by −28% in the tumor compared to WM. Besides the potential of 31P MRSI at 7T to provide novel insights into the biochemistry of gliomas in vivo, the attainable spatial resolutions improve the interpretability of 31P metabolite intensities obtained from malignant tissues, particularly when only subtle differences compared to healthy tissues are expected. In conclusion, this pilot study demonstrates that 31P MRSI at 7T has potential value for the clinical research of glioma.

Surgery for tongue cancer often results in a major loss in quality of life. While MRI may be used to minimise the volume of excised tissue, often the full tumour extent is missed. This tumour extent may be detected with metabolic imaging. One of the main reasons for the lack of metabolic information on tongue cancer would be the absence of an x-nuclear coil with the tongue as a focus target. Metabolic MRI through 31P MRSI is known as a powerful tool to non-invasively study elevated cell proliferation and disturbed energy metabolism in tumours. Severe magnetic field non-uniformities are inherently caused by the substantial difference in magnetic susceptibilities of tissue and air in the mouth and its environs. Despite this, the wide chemical shift dispersion of 31P could still facilitate precise detection of the cell proliferation biomarkers, phospomonoesters and diesters, as well as energy metabolites ATP, inorganic phosphate, and phosphocreatine potentially mapped over the tongue or tumour in vivo. In this study, we present the first 31P MRSI data of the human tongue in vivo from healthy volunteers and a patient with a tongue tumour at 7 T MRI using a 1H 8-channel transceiver setup placed inside a body 31P transmitter, which is able to get a uniform excitation from the tongue while providing comfortable access to the patient. In addition, a user-friendly external 31P receiver array is used to provide high sensitivity (80%) comparable to an uncomfortable inner mouth loop coil positioned on the tongue. The primary aim is the demonstration of 31P metabolite profiles in the tongue and the differences between healthy and malignant tissue. Indeed, clear elevated cell proliferation expressed as enhanced phosphomonoesters is observed in the tumour vs. the healthy part of the tongue. This can be performed within a total scan duration of 30 min, comparable to clinical scans, with a spatial resolution of 1.5 cm for the 10-min 31P MRSI scan.

Skeletal muscle phosphorus‐31 31P MRS is the oldest MRS methodology to be applied to in vivo metabolic research. The technical requirements of 31P MRS in skeletal muscle depend on the research question, and to assess those questions requires understanding both the relevant muscle physiology, and how 31P MRS methods can probe it. Here we consider basic signal‐acquisition parameters related to radio frequency excitation, TR, TE, spectral resolution, shim and localisation. We make specific recommendations for studies of resting and exercising muscle, including magnetisation transfer, and for data processing. We summarise the metabolic information that can be quantitatively assessed with 31P MRS, either measured directly or derived by calculations that depend on particular metabolic models, and we give advice on potential problems of interpretation. We give expected values and tolerable ranges for some measured quantities, and minimum requirements for reporting acquisition parameters and experimental results in publications. Reliable examination depends on a reproducible setup, standardised preconditioning of the subject, and careful control of potential difficulties, and we summarise some important considerations and potential confounders. Our recommendations include the quantification and standardisation of contraction intensity, and how best to account for heterogeneous muscle recruitment. We highlight some pitfalls in the assessment of mitochondrial function by analysis of phosphocreatine (PCr) recovery kinetics. Finally, we outline how complementary techniques (near‐infrared spectroscopy, arterial spin labelling, BOLD and various other MRI and 1H MRS measurements) can help in the physiological/metabolic interpretation of 31P MRS studies by providing information about blood flow and oxygen delivery/utilisation. Our recommendations will assist in achieving the fullest possible reliable picture of muscle physiology and pathophysiology. [ABSTRACT FROM AUTHOR]

7Li, 31P, and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy was used to investigate the local arrangement of oxygen and fluorine in LiVPO4F1‐yOy materials, interesting as positive electrode materials for Li‐ion batteries. From the evolution of the 1D spectra versus y, 2D 7Li radiofrequency‐driven recoupling (RFDR) experiments combined, and a tentative signal assignment based on density functional theory (DFT) calculations, it appears that F and O are not randomly dispersed on the bridging X position between two X–VO4–X octahedra (X = O or F) but tend to segregate at a local scale. Using DFT calculations, we analyzed the impact of the different local environments on the local electronic structure. Depending on the nature of the VO4X2 environments, vanadium ions are either in the +III or in the +IV oxidation state and can exhibit different distributions of their unpaired electron(s) on the d orbitals. Based on those different local electronic structures and on the computed Fermi contact shifts, we discuss the impact on the spin transfer mechanism on adjacent nuclei and propose tentative signal assignments. The O/F clustering tendency is discussed in relation with the formation of short VIVO vanadyl bonds with a very specific electronic structure and possible cooperative effect along the chain. [ABSTRACT FROM AUTHOR]

The fully deprotonated anion of 1,3,5-benzene-triphosphonic acid 1,3,5-C6H3[PO32−]3 gives rise to deceptively simple 1H and 31P NMR spectra due to a corresponding [AX]3 spin system. The 13C{1H} NMR spectrum reveals two 13C isotopomers which are identified via AXX′2 systems. Results from analysis and iteration are described. [ABSTRACT FROM AUTHOR]

Purpose: The design and performance of a novel head coil setup for 31P spectroscopy at ultra‐high field strengths (7T) is presented. The described system supports measurements at both the 1H and 31P resonance frequencies. Methods: The novel coil consists of 2, actively detunable, coaxial birdcage coils to give homogeneous transmit, combined with a double resonant 30 channel receive array. This allows for anatomical imaging combined with 31P acquisitions over the whole head, without changing coils or disturbing the subject. A phosphate buffer phantom and 3 healthy volunteers were scanned with a pulse acquire CSI sequence using both the novel array coil and a conventional transceiver birdcage. Four different methods of combining the array channels were compared at 3 different levels of SNR. Results: The novel coil setup delivers significantly increased 31P SNR in the peripheral regions of the brain, reaching up to factor 8, while maintaining comparable performance relative to the birdcage in the center. Conclusions: The new system offers the potential to acquire whole brain 31P MRSI with superior signal relative to the standard options. [ABSTRACT FROM AUTHOR]

Abstract Background The correction of γ-photon attenuation in PET-MRI remains a critical issue, especially for bone attenuation. This problem is of great importance for brain studies due to the density of the skull. Current techniques for skull attenuation correction (AC) provide indirect estimates of cortical bone density, leading to inaccurate estimates of brain activity. The purpose of this study was to develop an alternate method for bone attenuation correction based on NMR. The proposed approach relies on the detection of hydroxyapatite crystals by zero echo time (ZTE) MRI of 31P, providing individual and quantitative assessment of bone density. This work presents a proof of concept of this approach. The first step of the method is a calibration experiment to determine the conversion relationship between the 31P signal and the linear attenuation coefficient μ. Then 31P-ZTE was performed in vivo in rodent to estimate the μ-map of the skull. 18F-FDG PET data were acquired in the same animal and reconstructed with three different AC methods: 31P-based AC, AC neglecting the bone and the gold standard, CT-based AC, used to comparison for the other two methods. Results The calibration experiment provided a conversion factor of 31P signal into μ. In vivo 31P-ZTE made it possible to acquire 3D images of the rat skull. Brain PET images showed underestimation of 18F activity in peripheral regions close to the skull when AC neglected the bone (as compared with CT-based AC). The use of 31P-derived μ-map for AC leads to increased peripheral activity, and therefore a global overestimation of brain 18F activity. Conclusions In vivo 31P-ZTE MRI of hydroxyapatite provides μ-map of the skull, which can be used for attenuation correction of 18F-FDG PET images. This study is limited by several intrinsic biases associated with the size of the rat brain, which are unlikely to affect human data on a clinical PET-MRI system.

Potentiometry is the primary pH measurement method, but alternatives are sought beyond glass electrodes operative limitations. In nuclear magnetic resonance (NMR) experiments, electrodeless pH sensing is important to track changes along titrations, during chemical reactions or inside compartmentalized environments inaccessible to electrodes, for instance. Although several interesting NMR pH indicators have been already presented, the potential of inorganic phosphate is overlooked, despite its common presence in NMR samples as the buffer main component. Its use for electrodeless pH determination can be expanded by exploiting all its three proton dissociations. This study was aimed at verifying the use of inorganic phosphate 31 P chemical shift to sense pH variations, and at exploring the complementary use of pyrophosphate ions to cover a wide pH range. A simple set of equations is presented to utilize both phosphate and pyrophosphate 31 P chemical shift in combination for accurate pH determination without a glass electrode over the 5-12 pH range, and without affecting the spectrum of other nuclei. The present study demonstrated an average deviation of 0.09 (maximum <0.2) pH unit from glass electrode measurements. The trimethylphosphate can be used as a suitable chemical shift reference for both 31 P and 1 H (also 13 C), with its hydrolysis being significant only at pH > 12. The method was also demonstrated by determining the pKa of three distinct molecules in a mixture and by comparing the results to those obtained when the glass electrode was used to measure the pH. The approach shown here can be easily tuned to different experimental conditions., (© 2024 John Wiley & Sons Ltd.)

Motivation: 31 P magnetic resonance spectroscopic imaging ( 31 P MRSI) is a powerful technique for investigating the metabolic effects of treatments for heart failure in vivo , allowing a better understanding of their mechanism of action in patient cohorts. Unfortunately, cardiac 31 P MRSI is fundamentally limited by low SNR, which leads to compromises in acquisition, such as no cardiac or respiratory gating or low spatial resolution, in order to achieve reasonable scan times. Spectroscopy with linear algebra modeling (SLAM) reconstruction may be able to address these challenges and therefore improve repeatability by incorporating a segmented localizer into the reconstruction. Methods: Six healthy volunteers were scanned twice in a test-retest procedure to allow quantification of repeatability. Each scan consisted of anatomical localizers and two acquisition-weighted (AW) 31 P MRSI acquisitions, which were acquired with and without cardiac gating. Five patients with heart failure with a preserved ejection fraction were then scanned with the same 31 P MRSI sequence without cardiac gating. All 31 P MRSI datasets were reconstructed with both conventional Fourier transform (FT)-based reconstruction and SLAM reconstruction, which were compared statistically. The effect of shifting the 31 P MRSI acquisition field of view was also investigated. Results: In the healthy volunteer cohort, the spectral fit of the SLAM reconstructions had significantly improved Cramer-Rao lower bounds (CRLBs) compared to the FT-based reconstruction of non-cardiac gated data, as well as improved coefficients of variability and repeatability. The SLAM reconstruction found a significant difference in the PCr/ATP ratio between the healthy volunteer and patient cohorts, which the FT-based reconstruction did not find. Furthermore, the SLAM reconstruction was less influenced by the placement of the field of view (FOV) of the 31 P MRSI acquisition in post hoc analysis. Discussion: The experimental benefits of the SLAM reconstruction for AW data were demonstrated by the improvements in fit confidence and repeatability seen in the healthy volunteer cohort and post hoc FOV analysis. The benefit of SLAM reconstruction of AW data for clinical studies was then illustrated by the patient cohort, which suggested improved sensitivity to clinically significant changes in the PCr/ATP ratio., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Tyler, Hundertmark, Miller, Rider, Tyler and Valkovič.)

• We studied the 31P(d,d 0) elastic scattering at energies and detection angles suitable for IBA. • We measured differential cross sections. • We benchmarked the obtained results. The differential cross sections of deuteron elastic scattering on 31P were determined in the present work for the first time, in the projectile energy range E d,lab = 900–2400 keV (in energy steps of ~10–30 keV), suitable for analytical purposes. The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of N.C.S.R. "Demokritos", Athens, Greece. The experimental setup consisted of five silicon surface barrier (SSB) detectors, placed at the angles between 130° and 170° (in steps of 10°) in a high-precision goniometer. The implemented target was a thin GaP layer evaporated on top of a thin carbon foil. The obtained differential cross-section datasets were benchmarked against a polished GaP crystal and the deviations from the corresponding ones using Rutherford's formula will be discussed and analyzed. [ABSTRACT FROM AUTHOR]

Purpose: In vivo1H and 31P magnetic resonance spectroscopic imaging (MRSI) provide complementary information on the biology of prostate cancer. In this work we demonstrate the feasibility of performing multiparametric imaging (mpMRI) and 1H and 31P spectroscopic imaging of the prostate using a 31P and 1H endorectal radiofrequency coil (ERC) in combination with a multitransmit body array at 7 Tesla (T). Methods: An ERC with a 31P transceiver loop coil and 1H receive (Rx) asymmetric microstrip (31P/1H ERC) was designed, constructed and tested in combination with an external 8‐channel 1H transceiver body array coil (8CH). Electromagnetic field simulations and measurements and in vivo temperature measurements of the ERC were performed for safety validation. In addition, the signal‐to‐noise (SNR) benefit of the 1H microstrip with respect to the 8CH was evaluated. Finally, the feasibility of the setup was tested in one volunteer and three patients with prostate cancer by performing T2‐weighted and diffusion‐weighted imaging in combination with 1H and 31P spectroscopic imaging. Results: Electromagnetic field simulations of the 31P loop coil showed no differences in the E‐ and B‐fields of the 31P/1H ERC compared with a previously safety validated ERC without 1H microstrip. The hotspot of the specific absorption rate (SAR) at the feed point of the 31P/1H ERC loop coil was 9.42 W/kg when transmitting on 31P at 1 W. Additional in vivo measurements showed a maximum temperature increase at the SAR hotspot of 0.7°C over 6 min on 31P at 1.9 W transmit (Tx) power, indicating safe maximum power levels. When transmitting with the external 1H body array at 40W for 2:30 min, the temperature increase around the ERC was < 0.3°C. Up to 3.5 cm into the prostate the 1H microstrip of the ERC provided higher SNR than the 8CH. The total coil combination allowed acquisition of an mpMRI protocol and the assessment of 31P and 1H metabolites of the prostate in all test subjects. Conclusion: We developed a setup with a 31P transceiver and 1H Rx endorectal coil in combination with an 8‐channel transceiver external body array coil and demonstrated its safety and feasibility for obtaining multiparametric imaging and 1H and 31P MRSI at 7T in patients with prostate cancer within one MR examination. [ABSTRACT FROM AUTHOR]

Polyphosphate (poly-P) is a major constituent in activated sludge from wastewater treatment plants with enhanced biological phosphorus removal due to poly-P synthesis by poly-P accumulating organisms where it plays an important role for recovery of phosphorus from waste water. Our aim was to develop a reliable protocol for poly-P quantification by 31P NMR spectroscopy. This has so far been complicated by the risks of inefficient extraction and poly-P hydrolysis in the extracts. A protocol for complete extraction, identification and quantification of poly-P in activated sludge from a waste water treatment plant was identified based on test and evaluation of existing extraction protocols in combination with poly-P determination and quantification by solution and solid state 31P NMR spectroscopy. The total poly-P middle group content was quantified by solid state NMR for comparison with the poly-P middle groups quantified by solution NMR, which is novel. Three different extraction protocols previously used in literature were compared: 1) a single 0.25 M NaOH-0.05 M EDTA extraction, 2) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH main extraction and 3) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH-0.05 M EDTA main extraction. The results showed that the extraction protocol 2 was optimal for fresh activated sludge, extracting 10.8 ± 0.4 to 11.4 ± 1.2 mgP/gDW poly-P. Extraction protocols 1 and 3 extracted less than 9.4 ± 0.5 mgP/gDW poly-P. A comparison of the quantification of poly-P by 31P solution NMR and by 31P solid state NMR spectroscopy of lyophilised activated sludge showed 86 ± 9% extraction efficiency of poly-P, which confirms that the extraction protocol recovered most of the poly-P from the samples without pronounced poly-P degradation. Image 1 • 31P solution NMR spectroscopy for quantification of poly-P extracted from activated sludge. • Three extraction protocols for poly-P from activated sludge were compared. • Two-step EDTA and NaOH extraction extracts all poly-P from activated sludge. • Rotary evaporation of extracts gives less poly-P degradation than lyophilisation. • Poly-P extraction efficiency was evaluated by comparison with solid state NMR results. [ABSTRACT FROM AUTHOR]

The 31P chemical shift anisotropy (CSA) offers a potential source of new information to help determine the structures of aluminophosphate (AlPO) framework materials. We investigate how to measure the CSAs, which are small (span of ~20–30 ppm) for AlPOs, demonstrating the need for CSA‐amplification experiments (often in conjunction with 27Al and/or 1H decoupling) at high magnetic field (20.0 T) to obtain accurate values. We show that the most shielded component of the chemical shift tensor, δ33, is related to the length of the shortest P─O bond, whereas the more deshielded components, δ11 and δ22 can be related more readily to the mean P─O bond lengths and P─O─Al angles. Using the case of Mg‐doped STA‐2 as an example, the CSA is shown to be much larger for P(OAl)4–n(OMg)n environments, primarily owing to a much shorter P─O(Mg) bond affecting δ33, however, because the mean P─O bond lengths and P─O─T (T = Al, Mg) bond angles do not change significantly between P(OAl)4 and P(OAl)4–n(OMg)n sites, the isotropic chemical shifts for these species are similar, leading to overlapped spectral lines. When the CSA information is included, spectral assignment becomes unambiguous, therefore, although the specialist conditions required might preclude the routine measurement of 31P CSAs in AlPOs, in some cases (particularly doped materials), the experiments can still provide valuable additional information for spectral assignment. [ABSTRACT FROM AUTHOR]

For the first time, pore spaces in the Zr (IV) phosphonate (1) as a representative of layered metal (IV) phosphonate materials have been investigated by studying mobility of guest molecules, benzene‐d6, and toluene‐d8. Guest molecules located in micropores of 1 have been characterized by solid‐state 13C{1H} and 2H NMR spectra in static samples with varying temperatures. At moderately low temperatures, the benzene and toluene molecules experience fast isotropic reorientations and show the motionally averaged liquid‐like carbon and deuterium line shapes in the NMR spectra. At lower temperatures, two anisotropic motional modes have been found for benzene molecules by analyzing the 2H NMR line shapes: the well‐known in‐plane C6 rotation and composite motions. Interpretation of the variable‐temperature 2H T1 relaxation times identifies the composite motions as 120° flips around the C6 axis perpendicular to the molecular plane and the rotations around the molecular para‐C‐C axis. The data obtained resulted in the idealized (cylinder‐shaped) model of micropores in compound 1 with the diameter of 20–30 Å. Furthermore, the activation energy of 20.1 kJ/mol determined for the benzene motions classifies the molecule–surface interactions as weak but enough for absorption. The temperature dependence of the 2H T1 time characterizing molecular reorientations of benzene molecules in pores of the layered Zr phosphonate. [ABSTRACT FROM AUTHOR]

Purpose: To determine the phosphorus‐31 T2s of phosphomonoesters, phosphodiesters, and inorganic phosphate in the healthy human brain at 7T. Methods: A 3D chemical shift imaging multi‐echo sequence with composite block pulses for refocusing was used to measure one free induction decay (FID) and seven full echoes with an echo spacing of 45 ms on the brain of nine healthy volunteers (age range 22–45 years; average age 27 ± 8 years). Spectral fitting was used to determine the change in metabolic signal amplitude with echo time. Results: The average apparent T2s with their standard deviation were 202 ± 6 ms, 129 ± 6 ms, 86 ± 2 ms, 214 ± 10 ms, and 213 ± 11 ms for phosphoethanolamine, phosphocholine, inorganic phosphate, glycerophosphoethanolamine, and glycerophosphocholine, respectively. Conclusion: The determined apparent T2 for phosphoethanolamine, glycerophosphocholine, and glycerophosphoethanolamine is approximately 200 ms. The lower apparent T2 value for phosphocholine is attributed to the overlap of this resonance with the 3‐phosphorous resonance of 2,3‐diphosphoglycerate from blood, with an apparent shorter T2. Omitting the FID signal and the first echo of phosphocholine leads to a T2 of 182 ± 7 ms, whereas a biexponential analysis leads to 203 ± 4 ms. These values are more in line with phosphoethanolamine and the phosphodiesters. The short T2 of inorganic phosphate is subscribed to the fast reversible exchange with γ‐adenosine triphosphate, which is mediated by glyceraldehyde‐3‐phosphate dehydrogenase and phosphoglycerate kinase within the glycolytic pathway. Magn Reson Med 80:29–35, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. [ABSTRACT FROM AUTHOR]

Multinuclear solid‐state NMR and powder X‐ray diffraction data collected for phosphonate materials Zr(O3PC6H4PO3) · 3.6H2O and Sn(O3PC6H4PO3)0.85(O3POH)0.30 · 3.09H2O have resulted in the layered structure, where the phosphonic acids cross‐link the layers. The main structural motif (the 111 connectivity in the PO3 group) has been established by determination of chemical shift anisotropy parameters for phosphorus nuclei in the phosphonate groups. An analysis of the variable‐temperature 31P T1 measurements and the shapes of the phosphorus resonances in the 31P static NMR spectra have resulted in the dipolar mechanism of the phosphorus spin‐lattice relaxation, where the rotating phenylene rings reorient dipolar vectors P…H as a driving force of the relaxation process. It has been found that water protons do not affect the 31P T1 times. The activation energy of the phenylene rotation in both compounds has been determined as low as 12.5 kJ/mol. The interpretation of the phosphorus relaxation data has been independently confirmed by the measurements of 1H T1 times for protons of the phenylene rings. [ABSTRACT FROM AUTHOR]

Magnetic Resonance Spectroscopy (MRS) allows for a non-invasive and non-ionizing determination of in vivo tissue concentrations and metabolic turn-over rates of more than 20 metabolites and compounds in the central nervous system of humans. The aim of this review is to give a comprehensive overview about the advantages, challenges and advances of ultra-high field MRS with regard to methodological development, discoveries and applications from its beginnings around 15 years ago up to the current state. The review is limited to human brain and spinal cord application at field strength of 7T and 9.4T and includes all relevant nuclei ( 1 H, 31 P, 13 C). [ABSTRACT FROM AUTHOR]

Purpose: Conventional 31P chemical shift imaging is time‐consuming and yields only limited spatial resolution. The purpose of this study was to demonstrate feasibility of 31P echo‐planar spectroscopic imaging (EPSI) in vivo at 7T. Methods: A 3D 31P EPSI sequence with trapezoidal‐shaped gradient pulses was implemented on a 7T MR scanner. To increase spectral width with reduced demand on gradient performance, a multishot approach was chosen. Acquisition weighting and 31P–{1H} double resonance for nuclear Overhauser signal enhancement were applied to increase sensitivity. Results: 3D 31P–{1H} EPSI data from model solution and from human calf muscle and brain were obtained from voxels with effective sizes of 4.1 to 16.2 cm3 in measurement times of approximately 10 min. Individual spectra showed well‐resolved resonances of endogenous 31P‐metabolites without artifacts. Volumetric high‐resolution 31P‐metabolite maps in vivo showed metabolic heterogeneity of different tissues. Conclusion: In vivo 31P EPSI at 7T yields high‐quality metabolic images. The proposed multishot EPSI technique reduces the measurement times for acquisition of volumetric high‐resolution maps of 31P‐metabolites or intracellular pH in human studies. Magn Reson Med 79:1251–1259, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

The study of a layered crystalline Sn(IV) phosphate by solid-state NMR has demonstrated that the 31P T 1 relaxation of phosphate groups, dependent on spinning rate is completely controlled by the limited spin diffusion to paramagnetic ions found by EPR. The spin-diffusion constant, D(SD), was estimated as 2.04 10−14 cm2s−1. The conclusion was supported by the 31P T 1 time measurements in zirconium phosphate 1 – 1 , also showing paramagnetic ions and in diamagnetic compound (NH 4) 2 HPO 4. [Display omitted] • The 31P T 1 relaxation of phosphate groups in a layered crystalline Sn(IV) phosphate depends on spinning rates. • Due to the presence of metal paramagnetic ions, the phosphorus nuclei relax via the limited spin diffusion mechanism. [ABSTRACT FROM AUTHOR]

The new zincophosphate of chemical formula [C6H10N2][ZnP2O8H2]·0.6H2O was hydrothermally synthesized with p-phenylenediamine as structure-directing agent. The title compound crystallizes in the trigonal symmetry (proposed space group P3m1), where inorganic zincophosphate chains form layers due to the half occupancy of the unique crystallographic zinc site. The layers are separated from each other by p-phenylenediammonium dications with hydrogen bonding scheme involving the ammonium protons that reveals a pillar-like 3D structure aspect. The compound was characterized by powder X-ray diffraction, multinuclear solid-state NMR, scanning electron microscopy, chemical analysis, and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Purpose Phosphorus (31P) metabolites are emerging liver disease biomarkers. Of particular interest are phosphomonoester and phosphodiester (PDE) 'peaks' that comprise multiple overlapping resonances in 31P spectra. This study investigates the effect of improved spectral resolution at 7 Tesla (T) on quantifying hepatic metabolites in cirrhosis. Methods Five volunteers were scanned to determine metabolite T1s. Ten volunteers and 11 patients with liver cirrhosis were scanned at 7T. Liver spectra were acquired in 28 min using a 16-channel 31P array and 3D chemical shift imaging. Concentrations were calculated using γ-adenosine-triphosphate (γ-ATP) = 2.65 mmol/L wet tissue. Results T1 means ± standard deviations: phosphatidylcholine 1.05 ± 0.28 s, nicotinamide-adenine-dinucleotide (NAD+) 2.0 ± 1.0 s, uridine-diphosphoglucose (UDPG) 3.3 ± 1.4 s. Concentrations in healthy volunteers: α-ATP 2.74 ± 0.11 mmol/L wet tissue, inorganic phosphate 2.23 ± 0.20 mmol/L wet tissue, glycerophosphocholine 2.34 ± 0.46 mmol/L wet tissue, glycerophosphoethanolamine 1.50 ± 0.28 mmol/L wet tissue, phosphocholine 1.06 ± 0.16 mmol/L wet tissue, phosphoethanolamine 0.77 ± 0.14 mmol/L wet tissue, NAD+ 2.37 ± 0.14 mmol/L wet tissue, UDPG 2.00 ± 0.22 mmol/L wet tissue, phosphatidylcholine 1.38 ± 0.31 mmol/L wet tissue. Inorganic phosphate and phosphatidylcholine concentrations were significantly lower in patients; glycerophosphoethanolamine concentrations were significantly higher ( P < 0.05). Conclusion We report human in vivo hepatic T1s for phosphatidylcholine, NAD+, and UDPG for the first time at 7T. Our protocol allows high signal-to-noise, repeatable measurement of metabolite concentrations in human liver. The splitting of PDE into its constituent peaks at 7T may allow more insight into changes in metabolism. Magn Reson Med 78:2095-2105, 2017. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. [ABSTRACT FROM AUTHOR]

Purpose Phosphorus magnetic resonance spectroscopy (31P-MRS) provides a unique tool for assessing cardiac energy metabolism, often quantified using the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio. Surface coils are typically used for excitation for 31P-MRS, but they create an inhomogeneous excitation field across the myocardium, producing undesirable, spatially varying partial saturation. Therefore, we implemented adiabatic excitation in a 3D chemical shift imaging (CSI) sequence for cardiac 31P-MRS at 7 Tesla (T). Methods We optimized an adiabatic half passage pulse with bandwidth sufficient to excite PCr and γ-ATP together. In addition, the CSI sequence was modified to allow interleaved excitation of PCr and γ-ATP, then 2,3-DPG, to enable PCr/ATP determination with blood correction. Nine volunteers were scanned at 2 transmit voltages to confirm that measured PCr/ATP was independent of [ABSTRACT FROM AUTHOR]

The 1H, 13C{1H}, and 31P NMR spectral parameters of some pyrophosphates were determined in CDCl3. The most complicated 1H spectrum can be solved fully only as (A3MN)R6XX′R6′(MNA3)′, where R6 (= -N(CH3)2) is coupled only to phosphorus (X). Second-order coupling between phosphorus was found and solved with iterative analysis. A signal shape of one of the carbon resonance cannot be explained only with couplings. Explanation for exceptional shape was searched from molecular modeling results. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]