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1.
J Orthop Surg Res ; 14(1): 299, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31488174

RESUMO

PURPOSE: Our purpose was to combine intravoxel incoherent motion diffusion-weighted MR imaging (IVIM-DWI) and magnetic resonance spectroscopy (MRS) to differentiate osteoporotic fractures from osteolytic metastatic vertebral compression fractures (VCFs). METHODS: A total of 70 patients with VCFs were included and divided into two groups, according to their causes of fractures based on pathological findings or clinical follow-up. All patients underwent conventional sagittal T1WI, T2WI, STIR, IVIM-DWI, and single-voxel MRS. The diffusion coefficient (D), pseudo diffusion (D*), and perfusion fraction (f) parameters from IVIM-DWI and the lipid water ratio (LWR) and fat fraction (FF) parameters from MRS were obtained and compared among groups. Furthermore, the diagnostic performance of MRS, IVIM-DWI, and IVIM-DWI combined with MRS for differentiation between osteoporotic and osteolytic metastatic VCFs was assessed by using receiver operating characteristic (ROC) curve analysis. RESULTS: Compared with the osteoporotic group, the metastatic group had significantly lower values for f, D, and FF, but higher D* (all P < 0.05). The area under the receiver operating characteristic (ROC) curve of MRS, IVIM-DWI, and IVIM-DWI combined with MRS were 0.73, 0.88, and 0.94, respectively. Among these, the IVIM-DWI combined with MRS showed the highest sensitivity, specificity, and accuracy, which are 90.63% (29/32), 97.37 % (37/38), and 94.29% (66/70), respectively. CONCLUSIONS: IVIM-DWI combined with MRS can be more accurate and efficient for differentiation between osteoporotic and osteolytic metastatic VCFs than single MRS or IVIM-DWI.


Assuntos
Imagem de Difusão por Ressonância Magnética/métodos , Fraturas por Compressão/diagnóstico por imagem , Espectroscopia de Ressonância Magnética/métodos , Fraturas por Osteoporose/diagnóstico por imagem , Fraturas da Coluna Vertebral/diagnóstico por imagem , Neoplasias da Coluna Vertebral/diagnóstico por imagem , Idoso , Diagnóstico Diferencial , Imagem de Difusão por Ressonância Magnética/normas , Feminino , Fraturas por Compressão/metabolismo , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/lesões , Vértebras Lombares/metabolismo , Espectroscopia de Ressonância Magnética/normas , Masculino , Pessoa de Meia-Idade , Fraturas por Osteoporose/metabolismo , Fraturas da Coluna Vertebral/metabolismo , Neoplasias da Coluna Vertebral/metabolismo , Vértebras Torácicas/diagnóstico por imagem , Vértebras Torácicas/lesões , Vértebras Torácicas/metabolismo
2.
Anal Chim Acta ; 1081: 131-137, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31446950

RESUMO

In the absence of adequate reference material, a problem often encountered in natural product chemistry, we investigated the use of surrogate standards in two-dimensional qNMR for the quantification of anthraquinones in the bark of alder buckthorn (Frangula alnus). Using the integrals of cross signals in the HSQC spectrum obtained from commercial standards rutin and duroquinone and adapting the delays for the 1JCH coupling, we quantified the total amount of anthraquinones and anthraquinone glucosides, as well as the content of the value-determining glucofrangulins and frangulins. Thereby, duroquinone was used as an external standard to establish the calibration curve for the methylated anthraquinone scaffold, whereas calibration curves for the glycosides were obtained using the anomeric proton signals of the rutinose disaccharide. The method was validated for accuracy, precision, specificity, linearity and limit of quantitation and shows clear advantages over the method of the European Pharmacopeia, especially in terms of specificity and meaningfulness of the results. Apart from being a useful alternative in the quality control of alder buckthorn, the presented approach demonstrates, moreover, the versatility of sophisticated 2D measurements in quantitative NMR.


Assuntos
Antraquinonas/análise , Glicosídeos/análise , Rhamnus/química , Benzoquinonas/normas , Espectroscopia de Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/normas , Padrões de Referência , Rutina/normas
3.
PLoS One ; 14(6): e0218549, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31220183

RESUMO

INTRODUCTION: It is crucial to understand the factors that introduce variability before applying metabolomics to clinical and biomarker research. OBJECTIVES: We quantified technical and biological variability of both fasting and postprandial metabolite concentrations measured using 1H NMR spectroscopy in plasma samples. METHODS: In the Netherlands Epidemiology of Obesity study (n = 6,671), 148 metabolite concentrations (101 metabolites belonging to lipoprotein subclasses) were measured under fasting and postprandial states (150 minutes after a mixed liquid meal). Technical variability was evaluated among 265 fasting and 851 postprandial samples, with the identical blood plasma sample being measured twice by the same laboratory protocol. Biological reproducibility was assessed by measuring 165 individuals twice across time for evaluation of short- (<6 months) and long-term (>3 years) biological variability. Intra-class coefficients (ICCs) were used to assess variability. The ICCs of the fasting metabolites were compared with the postprandial metabolites using two-sided paired Wilcoxon test separately for short- and long-term measurements. RESULTS: Both fasting and postprandial metabolite concentrations showed high technical reproducibility using 1H NMR spectroscopy (median ICC = 0.99). Postprandial metabolite concentrations revealed slightly higher ICC scores than fasting ones in short-term repeat measures (median ICC in postprandial and fasting metabolite concentrations 0.72 versus 0.67, Wilcoxon p-value = 8.0×10-14). Variability did not increase further in a long-term repeat measure, with median ICC in postprandial of 0.64 and in fasting metabolite concentrations 0.66. CONCLUSION: Technical reproducibility is excellent. Biological reproducibility of postprandial metabolite concentrations showed a less or equal variability than fasting metabolite concentrations over time.


Assuntos
Jejum/sangue , Espectroscopia de Ressonância Magnética/normas , Metaboloma , Metabolômica/normas , Análise de Variância , Variação Biológica da População , Biomarcadores/sangue , Análise Química do Sangue/normas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Período Pós-Prandial , Reprodutibilidade dos Testes
4.
J Agric Food Chem ; 67(24): 6902-6910, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31132263

RESUMO

The autoxidation kinetics of stripped sunflower oil (SSO), squalene (SQ), and p-cymene ( p-C) initiated by 2,2'-azobis(isobutyronitrile) at 303 K were investigated under controlled conditions by differential oximetry in order to build reference model systems that are representative of the natural variability of oxidizable materials, for quantitative antioxidant testing. Rate constants for oxidative chain propagation ( kp) and chain termination (2 kt) and the oxidizability ( kp/√2 kt) were measured using 2,6-di- tert-butyl-4-methoxyphenol, 2,2,5,7,8-pentamethyl-6-chromanol, BHT, and 4-methoxyphenol as reference antioxidants. Measured values of kp (M-1 s-1)/2 kt (M-1 s-1)/oxidizability (M-1/2 s-1/2) at 303 K in chlorobenzene were 66.9/3.45 × 106/3.6 × 10-2, 68.0/7.40 × 106/2.5 × 10-2, and 0.83/2.87 × 106/4.9 × 10-4, respectively, for SSO, SQ, and p-C. Quercetin, magnolol, caffeic acid phenethyl ester, and 2,4,6-trimethylphenol were investigated to validate calibrations. The distinctive usefulness of the three substrates in testing antioxidants is discussed.


Assuntos
Antioxidantes/análise , Espectroscopia de Ressonância Magnética/normas , Monoterpenos/análise , Espectrofotometria Infravermelho/normas , Esqualeno/análise , Óleo de Girassol/química , Calibragem , Cimenos , Oxirredução
5.
Neuroimage Clin ; 23: 101835, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31035232

RESUMO

OBJECTIVES: To investigate the association between proton magnetic resonance spectroscopy (1H-MRS) metabolic features and the grade of gliomas, and to establish a machine-learning model to predict the glioma grade. METHODS: This study included 112 glioma patients who were divided into the training (n = 74) and validation (n = 38) sets based on the time of hospitalization. Twenty-six metabolic features were extracted from the preoperative 1H-MRS image. The Student's t-test was conducted to screen for differentially expressed features between low- and high-grade gliomas (WHO grades II and III/IV, respectively). Next, the minimum Redundancy Maximum Relevance (mRMR) algorithm was performed to further select features for a support vector machine (SVM) classifier building. Performance of the predictive model was evaluated both in the training and validation sets using ROC curve analysis. RESULTS: Among the extracted 1H-MRS metabolic features, thirteen features were differentially expressed. Four features were further selected as grade-predictive imaging signatures using the mRMR algorithm. The predictive performance of the machine-learning model measured by the AUC was 0.825 and 0.820 in the training and validation sets, respectively. This was better than the predictive performances of individual metabolic features, the best of which was 0.812. CONCLUSIONS: 1H-MRS metabolic features could help in predicting the grade of gliomas. The machine-learning model achieved a better prediction performance in grading gliomas than individual features, indicating that it could complement the traditionally used metabolic features.


Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Glioma/diagnóstico por imagem , Espectroscopia de Ressonância Magnética/normas , Cuidados Pré-Operatórios/normas , Máquina de Vetores de Suporte/normas , Adulto , Neoplasias Encefálicas/metabolismo , Feminino , Glioma/metabolismo , Humanos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Gradação de Tumores/métodos , Gradação de Tumores/normas , Cuidados Pré-Operatórios/métodos , Estudos Retrospectivos
6.
J Neurointerv Surg ; 11(10): 1019-1023, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30842309

RESUMO

BACKGROUND: To date, very little study of the importance of a volumetric T2-weighted MR sequence in the evaluation of spinal vascular malformations (SVMs) has been carried out. OBJECTIVE: To determine the utility and accuracy of a volumetric T2 MR sequence compared with conventional T2 in the diagnosis of SVMs. METHODS: Retrospective analysis of all patients who underwent spinal DSA for suspected SVMs was conducted. Conventional T2 and volumetric T2 MR images were analysed for the presence of flow voids and parenchymal changes, and SVMs were characterized. The sensitivity, specificity, and overall diagnostic accuracy of these MRI diagnoses were calculated. RESULTS: Of 89 subjects included in the final analysis, 70 patients had angiographically proved SVMs (38 patients with spinal cord arteriovenous malformations [SCAVM-intramedullary or perimedullary] and 32 cases of spinal dural arteriovenous fistula (SDAVF)) and the remaining 19 subjects were normal. The sensitivity and specificity for identification of SVMs were 98.1% and 90% for volumetric T2 sequences, compared with 82.8% and 89.4% for conventional T2 MRI, respectively. For characterization of spinal vascular lesions, volumetric MRI showed high sensitivity, specificity, and accuracy for SDAVF (100%, 90%, 97%, respectively) compared with conventional T2 MRI (71.8%, 89%, 79%, respectively). The positive likelihood ratio was high and negative likelihood ratio was zero for volumetric MRI evaluation of SDAVF, while these ratios were comparable between the two sequences for SCAVM. CONCLUSION: Volumetric T2 MRI is highly sensitive for the detection of SVMs, especially for SDAVF. Volumetric T2 MRI could be introduced into routine clinical practice in the screening of suspected SVMs.


Assuntos
Malformações Vasculares do Sistema Nervoso Central/diagnóstico por imagem , Imagem por Ressonância Magnética/normas , Espectroscopia de Ressonância Magnética/normas , Medula Espinal/diagnóstico por imagem , Adulto , Idoso , Estudos de Casos e Controles , Feminino , Humanos , Imagem por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Medula Espinal/irrigação sanguínea
7.
Neuroimage ; 191: 537-548, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-30840905

RESUMO

Accurate and reliable quantification of brain metabolites measured in vivo using 1H magnetic resonance spectroscopy (MRS) is a topic of continued interest. Aside from differences in the basic approach to quantification, the quantification of metabolite data acquired at different sites and on different platforms poses an additional methodological challenge. In this study, spectrally edited γ-aminobutyric acid (GABA) MRS data were analyzed and GABA levels were quantified relative to an internal tissue water reference. Data from 284 volunteers scanned across 25 research sites were collected using GABA+ (GABA + co-edited macromolecules (MM)) and MM-suppressed GABA editing. The unsuppressed water signal from the volume of interest was acquired for concentration referencing. Whole-brain T1-weighted structural images were acquired and segmented to determine gray matter, white matter and cerebrospinal fluid voxel tissue fractions. Water-referenced GABA measurements were fully corrected for tissue-dependent signal relaxation and water visibility effects. The cohort-wide coefficient of variation was 17% for the GABA + data and 29% for the MM-suppressed GABA data. The mean within-site coefficient of variation was 10% for the GABA + data and 19% for the MM-suppressed GABA data. Vendor differences contributed 53% to the total variance in the GABA + data, while the remaining variance was attributed to site- (11%) and participant-level (36%) effects. For the MM-suppressed data, 54% of the variance was attributed to site differences, while the remaining 46% was attributed to participant differences. Results from an exploratory analysis suggested that the vendor differences were related to the unsuppressed water signal acquisition. Discounting the observed vendor-specific effects, water-referenced GABA measurements exhibit similar levels of variance to creatine-referenced GABA measurements. It is concluded that quantification using internal tissue water referencing is a viable and reliable method for the quantification of in vivo GABA levels.


Assuntos
Encéfalo/metabolismo , Espectroscopia de Ressonância Magnética/normas , Ácido gama-Aminobutírico/análise , Adolescente , Adulto , Conjuntos de Dados como Assunto , Feminino , Humanos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Valores de Referência , Água , Adulto Jovem
8.
Neuroimage ; 189: 425-431, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30682536

RESUMO

Spectral editing allows direct measurement of low-concentration metabolites, such as GABA, glutathione (GSH) and lactate (Lac), relevant for understanding brain (patho)physiology. The most widely used spectral editing technique is MEGA-PRESS, which has been diversely implemented across research sites and vendors, resulting in variations in the final resolved edited signal. In this paper, we describe an effort to develop a new universal MEGA-PRESS sequence with HERMES functionality for the major MR vendor platforms with standardized RF pulse shapes, durations, amplitudes and timings. New RF pulses were generated for the universal sequence. Phantom experiments were conducted on Philips, Siemens, GE and Canon 3 T MRI scanners using 32-channel head coils. In vivo experiments were performed on the same six subjects on Philips and Siemens scanners, and on two additional subjects, one on GE and one on Canon scanners. On each platform, edited MRS experiments were conducted with the vendor-native and universal MEGA-PRESS sequences for GABA (TE = 68 ms) and Lac editing (TE = 140 ms). Additionally, HERMES for GABA and GSH was performed using the universal sequence at TE = 80 ms. The universal sequence improves inter-vendor similarity of GABA-edited and Lac-edited MEGA-PRESS spectra. The universal HERMES sequence yields both GABA- and GSH-edited spectra with negligible levels of crosstalk on all four platforms, and with strong agreement among vendors for both edited spectra. In vivo GABA+/Cr, Lac/Cr and GSH/Cr ratios showed relatively low variation between scanners using the universal sequence. In conclusion, phantom and in vivo experiments demonstrate successful implementation of the universal sequence across all four major vendors, allowing editing of several metabolites across a range of TEs.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/normas , Adulto , Feminino , Glutationa/metabolismo , Humanos , Ácido Láctico/metabolismo , Espectroscopia de Ressonância Magnética/instrumentação , Masculino , Ácido gama-Aminobutírico/metabolismo
9.
Radiology ; 291(1): 131-138, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30694162

RESUMO

Purpose To investigate metabolic changes in chronic spinal cord injury (SCI) by applying MR spectroscopy in the cervical spinal cord. Materials and Methods Single-voxel short-echo spectroscopic data in study participants with chronic SCI and healthy control subjects were prospectively acquired in the cervical spinal cord at C2 above the level of injury between March 2016 and January 2017 and were compared between groups. Concentrations of total N-acetylaspartate (tNAA), myo-inositol (mI), total choline-containing compounds (tCho), creatine, and glutamine and glutamate complex were estimated from the acquired spectra. Participants were assessed with a comprehensive clinical evaluation investigating sensory and motor deficits. Correlation analysis was applied to investigate relationships between observed metabolic differences, lesion severity, and clinical outcome. Results There were 18 male study participants with chronic SCI (median age, 51 years; range, 30-68 years) and 11 male healthy control subjects (median age, 45 years; range, 30-67 years). At cervical level C2, tNAA/mI and tCho/mI ratios were lower in participants with SCI (tNAA/mI: -26%, P = .003; tCho/mI: -18%; P = .04) than in healthy control subjects. The magnitude of difference was greater with the severity of cord atrophy (tNAA/mI: R2 = 0.44, P = .003; tCho/mI: R2 = 0.166, P = .09). Smaller tissue bridges at the lesion site correlated with lower ratios of tNAA/mI (R2 = 0.69, P = .006) and tCho/mI (R2 = 0.51, P = .03) at the C2 level. Lower tNAA/mI and tCho/mI ratios were associated with worse sensory and motor outcomes (P < .05). Conclusion Supralesional metabolic alterations are observed in chronic spinal cord injury, likely reflecting neurodegeneration, demyelination, and astrocytic gliosis in the injured cervical cord. Lesion severity and greater clinical impairment are both linked to the biochemical changes in the atrophied cervical cord after spinal cord injury. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Lin in this issue.


Assuntos
Vértebras Cervicais/patologia , Espectroscopia de Ressonância Magnética/métodos , Traumatismos da Medula Espinal/patologia , Adulto , Idoso , Atrofia/patologia , Estudos de Casos e Controles , Doença Crônica , Humanos , Espectroscopia de Ressonância Magnética/normas , Masculino , Pessoa de Meia-Idade , Paraplegia/patologia , Quadriplegia/patologia
10.
J Electromyogr Kinesiol ; 43: 127-139, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30273920

RESUMO

The importance of surface-EMG placement for development and interpretation of EMG-assisted biomechanical models is well established. Since MR has become a reliable noninvasive cervical spine musculoskeletal diagnostic tool, this investigation attempted to illustrate the anatomical relationships of individual cervical spine muscles with their paired surface-EMG electrodes. The secondary purpose of this investigation was to provide an MR cross-sectional pictorial and descriptive guideline of the cervical spine musculature. MR scans were performed on a healthy adult male subject from skull to manubrium of the sternum. Prior to scanning, MR safe markers were placed over neck muscles following surface EMG placement recommendations. Twenty-three neck muscles were traced manually in each of 267 scan slices. 3-D models of the neck musculoskeletal structure were constructed to aid with understanding the complex anatomy of the region as well as to identify correct EMG electrode locations and to identify muscles' curved lines-of-action. 3D models of the MR-safe markers were constructed relative to the target muscles. Based on the findings of this study, muscle palpation and bony landmarks can be used to effectively identify appropriate surface EMG electrode locations to record upper trapezius, middle trapezius, semispinalis capitis, splenius capitis, levator scapulae, scalenus, sternocleidomastoid and hyoid muscles activities.


Assuntos
Vértebras Cervicais/fisiologia , Eletromiografia/normas , Espectroscopia de Ressonância Magnética/normas , Músculos do Pescoço/fisiologia , Guias de Prática Clínica como Assunto/normas , Adulto , Estudos Transversais , Eletromiografia/métodos , Humanos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Músculos Paraespinais/fisiologia , Reprodutibilidade dos Testes
11.
Nutrients ; 10(9)2018 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-30149663

RESUMO

Human milk contains a complex combination of lipids, proteins, carbohydrates, and minerals, which are essential for infant growth and development. While the lipid portion constitutes only 5% of the total human milk composition, it accounts for over 50% of the infant's daily energy intake. Human milk lipids vary throughout a feed, day, and through different stages of lactation, resulting in difficulties in sampling standardization and, like blood, human milk is bioactive containing endogenous lipases, therefore appropriate storage is critical in order to prevent lipolysis. Suitable sample preparation, often not described in studies, must also be chosen to achieve the aims of the study. Gas chromatography methods have classically been carried out to investigate the fatty acid composition of human milk lipids, but with the advancement of other chromatographic techniques, such as liquid and supercritical fluid chromatography, as well as mass spectrometry, intact lipids can also be characterized. Despite the known importance, concise and comprehensive analysis of the human milk lipidome is limited, with gaps existing in all areas of human milk lipidomics, discussed in this review. With appropriate methodology and instrumentation, further understanding of the human milk lipidome and the influence it has on infant outcomes can be achieved.


Assuntos
Bioquímica/métodos , Cromatografia Líquida , Lipídeos/análise , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Leite Humano/química , Bioquímica/instrumentação , Bioquímica/normas , Cromatografia Gasosa , Cromatografia Líquida/instrumentação , Cromatografia Líquida/normas , Feminino , Humanos , Metabolismo dos Lipídeos , Espectroscopia de Ressonância Magnética/instrumentação , Espectroscopia de Ressonância Magnética/normas , Espectrometria de Massas/instrumentação , Espectrometria de Massas/normas , Leite Humano/metabolismo , Valor Nutritivo , Reprodutibilidade dos Testes
13.
Phys Chem Chem Phys ; 20(23): 15807-15816, 2018 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-29845162

RESUMO

Hybrid cyclic α/ß-peptides, in which one or more ß-amino acids are incorporated into the backbone, are gaining increasing interest as potential therapeutics, thanks to their ability to achieve enhanced binding affinities for a biological target through pre-organization in solution. The in silico prediction of their three dimensional structure through strategies such as MD simulations would substantially advance the rational design process. However, whether the molecular mechanics force fields are accurate in sampling highly constrained cyclopeptides containing ß-amino acids remains to be verified. Here, we present a systematic assessment of the ability of 8 widely used force fields to reproduce 79 NMR observables (including chemical shifts and 3J scalar couplings) on five cyclic α/ß-peptides that contain the integrin recognition motif isoDGR. Most of the investigated force fields, which include force fields from AMBER, OPLS, CHARMM and GROMOS families, display very good agreement with experimental 3J(HN,Hα), suggesting that MD simulations could be an appropriate tool in the rational design of therapeutic cyclic α-peptides. However, for NMR observables directly related to ß-amino acids, we observed a poor agreement with experiments and a remarkable dependence of our evaluation on the choice of Karplus parameters. The force field weaknesses herein unveiled might constitute a source of inspiration for further force field optimization.


Assuntos
Aminoácidos/química , Espectroscopia de Ressonância Magnética , Peptídeos Cíclicos/química , Desenho de Fármacos , Espectroscopia de Ressonância Magnética/normas , Simulação de Dinâmica Molecular , Ligação Proteica
14.
Sci Rep ; 8(1): 4249, 2018 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-29523811

RESUMO

Non-uniform sampling (NUS) allows the accelerated acquisition of multidimensional NMR spectra. The aim of this contribution was the systematic evaluation of the impact of various quantitative NUS parameters on the accuracy and precision of 2D NMR measurements of urinary metabolites. Urine aliquots spiked with varying concentrations (15.6-500.0 µM) of tryptophan, tyrosine, glutamine, glutamic acid, lactic acid, and threonine, which can only be resolved fully by 2D NMR, were used to assess the influence of the sampling scheme, reconstruction algorithm, amount of omitted data points, and seed value on the quantitative performance of NUS in 1H,1H-TOCSY and 1H,1H-COSY45 NMR spectroscopy. Sinusoidal Poisson-gap sampling and a compressed sensing approach employing the iterative re-weighted least squares method for spectral reconstruction allowed a 50% reduction in measurement time while maintaining sufficient quantitative accuracy and precision for both types of homonuclear 2D NMR spectroscopy. Together with other advances in instrument design, such as state-of-the-art cryogenic probes, use of 2D NMR spectroscopy in large biomedical cohort studies seems feasible.


Assuntos
Espectroscopia de Ressonância Magnética/métodos , Urinálise/métodos , Aminoácidos/análise , Feminino , Humanos , Espectroscopia de Ressonância Magnética/normas , Amostragem , Ureia/química , Urinálise/normas
15.
J Neurosci Methods ; 303: 86-94, 2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29476871

RESUMO

BACKGROUND: The relationships between scan duration, signal-to-noise ratio (SNR) and sample size must be considered and understood to design optimal GABA-edited magnetic resonance spectroscopy (MRS) studies. NEW METHOD: Simulations investigated the effects of signal averaging on SNR, measurement error and group-level variance against a known ground truth. Relative root mean square errors (measurement error) and coefficients of variation (group-level variance) were calculated. GABA-edited data from 18 participants acquired from five voxels were used to examine the relationships between scan duration, SNR and quantitative outcomes in vivo. These relationships were then used to determine the sample sizes required to observe different effect sizes. RESULTS: In both simulated and in vivo data, SNR increased with the square root of the number of averages. Both measurement error and group-level variance were shown to follow an inverse-square-root function, indicating no significant impact of cumulative artifacts. Comparisons between the first two-thirds of the data and the full dataset showed no statistical difference in group-level variance. There was, however, some variability across the five voxels depending on SNR, which impacted the sample sizes needed to detect group differences in specific brain regions. COMPARISON WITH EXISTING METHODS: Typical scan durations can be reduced if taking into account a statistically acceptable amount of variance and the magnitudes of predicted effects. CONCLUSIONS: While scan duration in GABA-edited MRS has typically been considered in terms of SNR, it is more appropriate to think in terms of the amount of measurement error and group-level variance that provides sufficient statistical power.


Assuntos
Córtex Cerebral/diagnóstico por imagem , Espectroscopia de Ressonância Magnética/métodos , Neuroimagem/métodos , Projetos de Pesquisa , Tamanho da Amostra , Razão Sinal-Ruído , Ácido gama-Aminobutírico , Adulto , Córtex Cerebral/metabolismo , Simulação por Computador , Feminino , Humanos , Espectroscopia de Ressonância Magnética/normas , Masculino , Neuroimagem/normas , Projetos de Pesquisa/normas , Adulto Jovem
16.
J Magn Reson ; 287: 110-112, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29335163

RESUMO

We demonstrate that N,N-Diethylmethylamine (DEMA) is a useful compound for shimming the magnetic field when doing NMR experiments at room temperature and 130 K, near the temperature used in many dynamic nuclear polarization (DNP) experiments. The resonance assigned to the N-methyl carbon in DEMA at 14.7 T and 140 K has a full-width-half-max linewidth of <4 Hz and has a spin-lattice relaxation time of 0.17 ±â€¯0.03 s.


Assuntos
Dietilaminas/química , Espectroscopia de Ressonância Magnética/normas , Pressão , Temperatura
17.
Metabolomics ; 14(3): 28, 2018 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-30830358

RESUMO

INTRODUCTION: Comparative metabolic profiling of different human cancer cell lines can reveal metabolic pathways up-regulated or down-regulated in each cell line, potentially providing insight into distinct metabolism taking place in different types of cancer cells. It is noteworthy, however, that human cell lines available from public repositories are deposited with recommended media for optimal growth, and if cell lines to be compared are cultured on different growth media, this introduces a potentially serious confounding variable in metabolic profiling studies designed to identify intrinsic metabolic pathways active in each cell line. OBJECTIVES: The goal of this study was to determine if the culture media used to grow human cell lines had a significant impact on the measured metabolic profiles. METHODS: NMR-based metabolic profiles of hydrophilic extracts of three human pancreatic cancer cell lines, AsPC-1, MiaPaCa-2 and Panc-1, were compared after culture on Dulbecco's Modified Eagle Medium (DMEM) or Roswell Park Memorial Institute (RPMI-1640) medium. RESULTS: Comparisons of the same cell lines cultured on different media revealed that the concentrations of many metabolites depended strongly on the choice of culture media. Analyses of different cell lines grown on the same media revealed insight into their metabolic differences. CONCLUSION: The choice of culture media can significantly impact metabolic profiles of human cell lines and should be considered an important variable when designing metabolic profiling studies. Also, the metabolic differences of cells cultured on media recommended for optimal growth in comparison to a second growth medium can reveal critical insight into metabolic pathways active in each cell line.


Assuntos
Meios de Cultura/farmacologia , Metaboloma/efeitos dos fármacos , Linhagem Celular Tumoral , Humanos , Espectroscopia de Ressonância Magnética/normas
18.
J Pharm Biomed Anal ; 147: 485-492, 2018 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-28648253

RESUMO

BACKGROUND: Time dependent quantification of endogenous metabolites in biological samples (blood, urine, biological tissues extracts) in normal and pathological conditions as well as following therapeutic protocols is well established. In the clinical practice, such a dynamic flux of information allows the physician to identify and appreciate alterations associated to biochemical pathways of specific organs. In the years, many biochemical assays have been developed to detect, selectively, this vast array of molecules. METHODS: The Proton Nuclear Magnetic Resonance (1H NMR) spectrum allows the identification and quantification of more than 30 RBC-associated metabolites with minimum manipulation of the sample. To validate the use of 1H NMR spectroscopy for quality control purposes in transfusion medicine, a series of statistical tools have been employed to analyse and compare accuracy and precision of the 1H NMR results with respect to the ones obtained by standard biochemical assays. RESULTS: Among the many metabolites that can be detected and quantified by 1H NMR spectroscopy we selected creatinine and lactate, since they are routinely quantified by standard biochemical assays and because they are characterized by a wide concentration dynamic range. We show that 1D 1H NMR spectroscopy is an accurate a precise method for metabolite quantification. CONCLUSION: These results validate the use of 1H NMR spectroscopy in transfusion medicine as a method to evaluate the quality of RBC packed units and to develop novel and more efficient RBCs storage protocols.


Assuntos
Transfusão de Sangue/normas , Eritrócitos/química , Espectroscopia de Ressonância Magnética/normas , Controle de Qualidade , Adulto , Bioensaio/normas , Bioensaio/estatística & dados numéricos , Transfusão de Sangue/estatística & dados numéricos , Humanos , Espectroscopia de Ressonância Magnética/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Prótons
19.
Neuroimage ; 168: 509-531, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-28179167

RESUMO

The three goals of this paper are: 1) to evaluate the improvements in technology for increasing magnetic flux density (magnetic field) to 14T in the next few years and eventually to 20T; 2) to highlight neuroscience opportunities enabled by these advances; and, 3) to evaluate the physiological and biophysical effects associated with MRI at very high performance levels. Substantial recent advances in magnet technology including superconductor developments enable neuroscience goals that are not obtainable at contemporary magnetic fields. Ten areas of brain neuroscience include potential improvements in resolution for functional MRI(BOLD), diffusion weighted MRI, tractography, susceptibility weighted MR, neuronal architecture patterns related to human behavior, proton spectroscopy of small brain biochemicals, chemical exchange saturation transfer (CEST), dynamic contrast enhanced MRI, brain energy metabolism using 13C, 17O, and 31P; and brain electrolyte physiology using 23Na, 35Cl, and 39K. Physiological phenomena and safety aspects include: absorbed RF power, acoustic sound pressure levels, induced electric fields, Lorentz forces, magnetohydrodynamic forces, and biophysical phenomena in cells and tissues. Where feasible, effects are quantified for magnetic fields beyond 7T with the conclusion that there are no foreseen barriers either in the technical or human safety aspects of brain MRI and MRS at fields up to 20T. This conclusion is conditioned on results of recommended experiments to verify the predicted level of physiological effects beyond 9.4T. This technology is predicted to enable quantification of biochemical components of the functioning brain not detectable heretofore.


Assuntos
Encéfalo/diagnóstico por imagem , Imagem de Tensor de Difusão , Neuroimagem Funcional , Campos Magnéticos , Imagem por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Neurociências , Imagem de Tensor de Difusão/instrumentação , Imagem de Tensor de Difusão/métodos , Imagem de Tensor de Difusão/normas , Imagem de Tensor de Difusão/tendências , Neuroimagem Funcional/instrumentação , Neuroimagem Funcional/métodos , Neuroimagem Funcional/normas , Neuroimagem Funcional/tendências , Humanos , Campos Magnéticos/efeitos adversos , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Imagem por Ressonância Magnética/normas , Imagem por Ressonância Magnética/tendências , Espectroscopia de Ressonância Magnética/instrumentação , Espectroscopia de Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/normas , Neurociências/instrumentação , Neurociências/métodos , Neurociências/normas , Neurociências/tendências
20.
Neuroimage ; 168: 199-210, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-27825954

RESUMO

MRSI in the brain at ≥7 T is a technique of great promise, but has been limited mainly by low B0/B1+-homogeneity, specific absorption rate restrictions, long measurement times, and low spatial resolution. To overcome these limitations, we propose an ultra-high resolution (UHR) MRSI sequence that provides a 128×128 matrix with a nominal voxel volume of 1.7×1.7×8mm3 in a comparatively short measurement time. A clinically feasible scan time of 10-20min is reached via a short TR of 200 ms due to an optimised free induction decay-based acquisition with shortened water suppression as well as parallel imaging (PI) using Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration (CAIPIRINHA). This approach is not limited to a rectangular region of interest in the centre of the brain, but also covers cortical brain regions. Transversal pulse-cascaded Hadamard encoding was able to further extend the coverage to 3D-UHR-MRSI of four slices (100×100×4 matrix size), with a measurement time of 17min. Lipid contamination was removed during post-processing using L2-regularisation. Simulations, phantom and volunteer measurements were performed. The obtained single-slice and 3D-metabolite maps show the brain in unprecedented detail (e.g., hemispheres, ventricles, gyri, and the contrast between grey and white matter). This facilitates the use of UHR-MRSI for clinical applications, such as measurements of the small structures and metabolic pathologic deviations found in small Multiple Sclerosis lesions.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Processamento de Imagem Assistida por Computador/métodos , Espectroscopia de Ressonância Magnética/métodos , Neuroimagem/métodos , Adulto , Artefatos , Estudos de Viabilidade , Feminino , Humanos , Espectroscopia de Ressonância Magnética/instrumentação , Espectroscopia de Ressonância Magnética/normas , Masculino , Neuroimagem/instrumentação , Neuroimagem/normas , Imagens de Fantasmas
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