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1.
Magn Reson Med ; 87(2): 574-588, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34545962

RESUMO

PURPOSE: Low-rank denoising of MRSI data results in an apparent increase in spectral SNR. However, it is not clear if this translates to a lower uncertainty in metabolite concentrations after spectroscopic fitting. Estimation of the true uncertainty after denoising is desirable for downstream analysis in spectroscopy. In this work, the uncertainty reduction from low-rank denoising methods based on spatiotemporal separability and linear predictability in MRSI are assessed. A new method for estimating metabolite concentration uncertainty after denoising is proposed. Automatic rank threshold selection methods are also assessed in simulated low SNR regimes. METHODS: Assessment of denoising methods is conducted using Monte Carlo simulation of proton MRSI data and by reproducibility of repeated in vivo acquisitions in 5 subjects. RESULTS: In simulated and in vivo data, spatiotemporal based denoising is shown to reduce the concentration uncertainty, but linear prediction denoising increases uncertainty. Uncertainty estimates provided by fitting algorithms after denoising consistently underestimate actual metabolite uncertainty. However, the proposed uncertainty estimation, based on an analytical expression for entry-wise variance after denoising, is more accurate. It is also shown automated rank threshold selection using Marchenko-Pastur distribution can bias the data in low SNR conditions. An alternative soft-thresholding function is proposed. CONCLUSION: Low-rank denoising methods based on spatiotemporal separability do reduce uncertainty in MRS(I) data. However, thorough assessment is needed as assessment by SNR measured from residual baseline noise is insufficient given the presence of non-uniform variance. It is also important to select the right rank thresholding method in low SNR cases.

2.
Elife ; 102021 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-34622779

RESUMO

The brain has a remarkable capacity to acquire and store memories that can later be selectively recalled. These processes are supported by the hippocampus which is thought to index memory recall by reinstating information stored across distributed neocortical circuits. However, the mechanism that supports this interaction remains unclear. Here, in humans, we show that recall of a visual cue from a paired associate is accompanied by a transient increase in the ratio between glutamate and GABA in visual cortex. Moreover, these excitatory-inhibitory fluctuations are predicted by activity in the hippocampus. These data suggest the hippocampus gates memory recall by indexing information stored across neocortical circuits using a disinhibitory mechanism.


Assuntos
Hipocampo/fisiologia , Rememoração Mental , Neocórtex/fisiologia , Inibição Neural , Plasticidade Neuronal , Estimulação Acústica , Associação , Vias Auditivas/fisiologia , Percepção Auditiva , Mapeamento Encefálico , Sinais (Psicologia) , Feminino , Ácido Glutâmico/metabolismo , Hipocampo/diagnóstico por imagem , Hipocampo/metabolismo , Humanos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Masculino , Neocórtex/diagnóstico por imagem , Neocórtex/metabolismo , Estimulação Luminosa , Fatores de Tempo , Vias Visuais/fisiologia , Percepção Visual , Adulto Jovem , Ácido gama-Aminobutírico/metabolismo
3.
Eur Heart J ; 2021 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-34542592

RESUMO

AIMS: We sought to determine if myocardial energetics could distinguish obesity cardiomyopathy as a distinct entity from dilated cardiomyopathy. METHODS AND RESULTS: Sixteen normal weight participants with dilated cardiomyopathy (DCMNW), and 27 with DCM and obesity (DCMOB), were compared to 26 normal weight controls (CTLNW). All underwent cardiac magnetic resonance imaging and 31P spectroscopy to assess function and energetics. Nineteen DCMOB underwent repeat assessment after a dietary weight loss intervention. Adenosine triphosphate (ATP) delivery through creatine kinase (CK flux) was 55% lower in DCMNW than in CTLNW (P = 0.004), correlating with left ventricular ejection fraction (LVEF, r = 0.4, P = 0.015). In contrast, despite similar LVEF (DCMOB 41 ± 7%, DCMNW 38 ± 6%, P = 0.14), CK flux was two-fold higher in DCMOB (P < 0.001), due to higher rate through CK [median kf 0.21 (0.14) vs. 0.11 (0.12) s-1, P = 0.002]. During increased workload, the CTLNW heart increased CK flux by 97% (P < 0.001). In contrast, CK flux was unchanged in DCMNW and fell in DCMOB (by >50%, P < 0.001). Intentional weight loss was associated with positive left ventricular remodelling, with reduced left ventricular end-diastolic volume (by 8%, P < 0.001) and a change in LVEF (40 ± 9% vs. 45 ± 10%, P = 0.002). This occurred alongside a fall in ATP delivery rate with weight loss (by 7%, P = 0.049). CONCLUSIONS: In normal weight, DCM is associated with reduced resting ATP delivery. In obese DCM, ATP demand through CK is greater, suggesting reduced efficiency of energy utilization. Dietary weight loss is associated with significant improvement in myocardial contractility, and a fall in ATP delivery, suggesting improved metabolic efficiency. This highlights distinct energetic pathways in obesity cardiomyopathy, which are both different from dilated cardiomyopathy, and may be reversible with weight loss.

4.
Neuroimage ; 241: 118430, 2021 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-34314848

RESUMO

PURPOSE: Heating of gradient coils and passive shim components is a common cause of instability in the B0 field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites. METHOD: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors. Phantom water signals were acquired before and after an EPI sequence. The protocol consisted of: minimal preparatory imaging; a short pre-fMRI PRESS; a ten-minute fMRI acquisition; and a long post-fMRI PRESS acquisition. Both pre- and post-fMRI PRESS were non-water suppressed. Real-time frequency stabilization/adjustment was switched off when appropriate. Sixty scanners repeated the protocol for a second dataset. In addition, a three-hour post-fMRI MRS acquisition was performed at one site to observe change of gradient temperature and drift rate. Spectral analysis was performed using MATLAB. Frequency drift in pre-fMRI PRESS data were compared with the first 5:20 minutes and the full 30:00 minutes of data after fMRI. Median (interquartile range) drifts were measured and showed in violin plot. Paired t-tests were performed to compare frequency drift pre- and post-fMRI. A simulated in vivo spectrum was generated using FID-A to visualize the effect of the observed frequency drifts. The simulated spectrum was convolved with the frequency trace for the most extreme cases. Impacts of frequency drifts on NAA and GABA were also simulated as a function of linear drift. Data from the repeated protocol were compared with the corresponding first dataset using Pearson's and intraclass correlation coefficients (ICC). RESULTS: Of the data collected from 99 scanners, 4 were excluded due to various reasons. Thus, data from 95 scanners were ultimately analyzed. For the first 5:20 min (64 transients), median (interquartile range) drift was 0.44 (1.29) Hz before fMRI and 0.83 (1.29) Hz after. This increased to 3.15 (4.02) Hz for the full 30 min (360 transients) run. Average drift rates were 0.29 Hz/min before fMRI and 0.43 Hz/min after. Paired t-tests indicated that drift increased after fMRI, as expected (p < 0.05). Simulated spectra convolved with the frequency drift showed that the intensity of the NAA singlet was reduced by up to 26%, 44 % and 18% for GE, Philips and Siemens scanners after fMRI, respectively. ICCs indicated good agreement between datasets acquired on separate days. The single site long acquisition showed drift rate was reduced to 0.03 Hz/min approximately three hours after fMRI. DISCUSSION: This study analyzed frequency drift data from 95 3T MRI scanners. Median levels of drift were relatively low (5-min average under 1 Hz), but the most extreme cases suffered from higher levels of drift. The extent of drift varied across scanners which both linear and nonlinear drifts were observed.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Análise de Dados , Bases de Dados Factuais/normas , Imageamento por Ressonância Magnética/normas , Espectroscopia de Ressonância Magnética/normas , Humanos , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos
5.
Magn Reson Med ; 85(6): 2950-2964, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33280161

RESUMO

PURPOSE: We introduce FSL-MRS, an end-to-end, modular, open-source MRS analysis toolbox. It provides spectroscopic data conversion, preprocessing, spectral simulation, fitting, quantitation, and visualization. METHODS: The FSL-MRS package is modular. Its programs operate on data in a standard format (Neuroimaging Informatics Technology Initiative [NIfTI]) capable of storing single-voxel and multivoxel spectroscopy, including spatial orientation information. The FSL-MRS toolbox includes tools for preprocessing of raw spectroscopy data, including coil combination, frequency and phase alignment, and filtering. A density matrix simulation program is supplied for generation of basis spectra from simple text-based descriptions of pulse sequences. Fitting is based on linear combination of basis spectra and implements Markov chain Monte Carlo optimization for the estimation of the full posterior distribution of metabolite concentrations. Validation of the fitting is carried out on independently created simulated data, phantom data, and three in vivo human data sets (257 single-voxel spectroscopy and 8 MRSI data sets) at 3 T and 7 T. Interactive HTML reports are automatically generated by processing and fitting stages of the toolbox. The FSL-MRS package can be used on the command line or interactively in the Python language. RESULTS: Validation of the fitting shows low error in simulation (median error of 11.9%) and in phantom (3.4%). Average correlation between a third-party toolbox (LCModel) and FSL-MRS was high (0.53-0.81) in all three in vivo data sets. CONCLUSION: The FSL-MRS toolbox is designed to be flexible and extensible to new forms of spectroscopic acquisitions. Custom fitting models can be specified within the framework for dynamic or multivoxel spectroscopy. It is available as part of the FMRIB Software Library.


Assuntos
Neuroimagem , Software , Simulação por Computador , Humanos , Espectroscopia de Ressonância Magnética , Imagens de Fantasmas
6.
Clin Gastroenterol Hepatol ; 19(4): 839-841.e2, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-32147594

RESUMO

Comparison data regarding anti-tumor necrosis factor drug concentrations in inflammatory bowel disease (IBD) between the enzyme-linked immunosorbent assay (ELISA) and the homogenous mobility shift assay (HMSA) are scarce.1-3 As decisions in clinical practice depend on the thresholds that define a therapeutic drug concentration, it is important to determine if this varies based on the type of assay used for therapeutic drug monitoring.4 We recently showed a discrepancy between a commercially available ELISA and the HMSA for both infliximab and adalimumab concentrations in patients with IBD.5 Based on the results of the study, Prometheus Laboratories (San Diego, CA) initiated a comprehensive review of their HMSA assays and found that there was an upward drift for both infliximab (from December 2017 to May 2019) and adalimumab (from August 2017 to May 2019), including when our study was performed. Prometheus Laboratories corrected the errant values and reported the revised drug concentrations to physicians (Supplementary Methods). We aimed to compare the corrected infliximab and adalimumab concentrations with the original ELISA values.


Assuntos
Doenças Inflamatórias Intestinais , Adalimumab/uso terapêutico , Monitoramento de Medicamentos , Ensaio de Imunoadsorção Enzimática , Humanos , Doenças Inflamatórias Intestinais/tratamento farmacológico , Infliximab , Fator de Necrose Tumoral alfa
8.
Neuroimage ; 223: 117358, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32916289

RESUMO

INTRODUCTION: We present the reliability of ultra-high field T2* MRI at 7T, as part of the UK7T Network's "Travelling Heads" study. T2*-weighted MRI images can be processed to produce quantitative susceptibility maps (QSM) and R2* maps. These reflect iron and myelin concentrations, which are altered in many pathophysiological processes. The relaxation parameters of human brain tissue are such that R2* mapping and QSM show particularly strong gains in contrast-to-noise ratio at ultra-high field (7T) vs clinical field strengths (1.5-3T). We aimed to determine the inter-subject and inter-site reproducibility of QSM and R2* mapping at 7T, in readiness for future multi-site clinical studies. METHODS: Ten healthy volunteers were scanned with harmonised single- and multi-echo T2*-weighted gradient echo pulse sequences. Participants were scanned five times at each "home" site and once at each of four other sites. The five sites had 1× Philips, 2× Siemens Magnetom, and 2× Siemens Terra scanners. QSM and R2* maps were computed with the Multi-Scale Dipole Inversion (MSDI) algorithm (https://github.com/fil-physics/Publication-Code). Results were assessed in relevant subcortical and cortical regions of interest (ROIs) defined manually or by the MNI152 standard space. RESULTS AND DISCUSSION: Mean susceptibility (χ) and R2* values agreed broadly with literature values in all ROIs. The inter-site within-subject standard deviation was 0.001-0.005 ppm (χ) and 0.0005-0.001 ms-1 (R2*). For χ this is 2.1-4.8 fold better than 3T reports, and 1.1-3.4 fold better for R2*. The median ICC from within- and cross-site R2* data was 0.98 and 0.91, respectively. Multi-echo QSM had greater variability vs single-echo QSM especially in areas with large B0 inhomogeneity such as the inferior frontal cortex. Across sites, R2* values were more consistent than QSM in subcortical structures due to differences in B0-shimming. On a between-subject level, our measured χ and R2* cross-site variance is comparable to within-site variance in the literature, suggesting that it is reasonable to pool data across sites using our harmonised protocol. CONCLUSION: The harmonized UK7T protocol and pipeline delivers on average a 3-fold improvement in the coefficient of reproducibility for QSM and R2* at 7T compared to previous reports of multi-site reproducibility at 3T. These protocols are ready for use in multi-site clinical studies at 7T.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/anatomia & histologia , Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética , Adulto , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Reprodutibilidade dos Testes
9.
J Clin Med ; 9(9)2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32887317

RESUMO

An upward drift for both infliximab and adalimumab concentrations measured by the homogenous mobility shift assay (HMSA) was previously reported. We aimed to investigate the impact of this drift on clinical care of patients with inflammatory bowel disease. This was a retrospective, multicenter study. Providers reviewed the individual patient data and drug concentrations before and after the laboratory corrections and then documented whether a different clinical decision would have been made had the corrected drug concentration been originally reported. A multivariable Cox proportional hazards regression analysis was performed to investigate the association of a documented treatment change with treatment failure, defined as drug discontinuation for primary nonresponse, loss of response, or serious adverse event, adjusting for confounding factors. The study population consisted of 479 patients (infliximab, n = 219; adalimumab, n = 260). Upon review, 14.9% (71/479) patients would have had a different treatment decision made had the corrected drug concentration been initially reported. After a median follow-up of 10.6 months, 25.7% of patients (123/479) had treatment failure. A theoretical different clinical decision based on the corrected drug concentrations was not associated with treatment failure (adjusted hazard ratio (HR): 1.452; 95% confidence interval (CI): 0.805-2.618; p = 0.216), which was consistent for both infliximab (adjusted HR: 1.977; 95% CI: 0.695-5.627; p = 0.201) and adalimumab (adjusted HR: 1.484; 95% CI: 0.721-3.054; p = 0.284). The drift in infliximab and adalimumab concentrations in the HMSA assay affected treatment decisions in 15% of cases. However, this discrepancy was not associated with a higher cumulative probability for treatment failure.

10.
Circulation ; 141(24): 1971-1985, 2020 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-32438845

RESUMO

BACKGROUND: Why some but not all patients with severe aortic stenosis (SevAS) develop otherwise unexplained reduced systolic function is unclear. We investigate the hypothesis that reduced creatine kinase (CK) capacity and flux is associated with this transition. METHODS: We recruited 102 participants to 5 groups: moderate aortic stenosis (ModAS) (n=13), SevAS, left ventricular (LV) ejection fraction ≥55% (SevAS-preserved ejection fraction, n=37), SevAS, LV ejection fraction <55% (SevAS-reduced ejection fraction, n=15), healthy volunteers with nonhypertrophied hearts with normal systolic function (normal healthy volunteer, n=30), and patients with nonhypertrophied, non-pressure-loaded hearts with normal systolic function undergoing cardiac surgery and donating LV biopsy (non-pressure-loaded heart biopsy, n=7). All underwent cardiac magnetic resonance imaging and 31P magnetic resonance spectroscopy for myocardial energetics. LV biopsies (AS and non-pressure-loaded heart biopsy) were analyzed for CK total activity, CK isoforms, citrate synthase activity, and total creatine. Mitochondria-sarcomere diffusion distances were calculated by using serial block-face scanning electron microscopy. RESULTS: In the absence of failure, CK flux was lower in the presence of AS (by 32%, P=0.04), driven primarily by reduction in phosphocreatine/ATP (by 17%, P<0.001), with CK kf unchanged (P=0.46). Although lowest in the SevAS-reduced ejection fraction group, CK flux was not different from the SevAS-preserved ejection fraction group (P>0.99). Accompanying the fall in CK flux, total CK and citrate synthase activities and the absolute activities of mitochondrial-type CK and CK-MM isoforms were also lower (P<0.02, all analyses). Median mitochondria-sarcomere diffusion distances correlated well with CK total activity (r=0.86, P=0.003). CONCLUSIONS: Total CK capacity is reduced in SevAS, with median values lowest in those with systolic failure, consistent with reduced energy supply reserve. Despite this, in vivo magnetic resonance spectroscopy measures of resting CK flux suggest that ATP delivery is reduced earlier, at the moderate AS stage, where LV function remains preserved. These findings show that significant energetic impairment is already established in moderate AS and suggest that a fall in CK flux is not by itself a necessary cause of transition to systolic failure. However, because ATP demands increase with AS severity, this could increase susceptibility to systolic failure. As such, targeting CK capacity and flux may be a therapeutic strategy to prevent and treat systolic failure in AS.


Assuntos
Estenose da Valva Aórtica/sangue , Creatina Quinase/sangue , Metabolismo Energético/fisiologia , Volume Sistólico/fisiologia , Disfunção Ventricular Esquerda/sangue , Função Ventricular Esquerda/fisiologia , Trifosfato de Adenosina/sangue , Adulto , Idoso , Idoso de 80 Anos ou mais , Estenose da Valva Aórtica/diagnóstico , Estenose da Valva Aórtica/fisiopatologia , Biomarcadores/sangue , Feminino , Humanos , Espectroscopia de Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Disfunção Ventricular Esquerda/diagnóstico , Disfunção Ventricular Esquerda/fisiopatologia
11.
Circulation ; 141(14): 1152-1163, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32138541

RESUMO

BACKGROUND: Obesity is strongly associated with exercise intolerance and the development of heart failure. Whereas myocardial energetics and diastolic function are impaired in obesity, systolic function is usually preserved. This suggests that the rate of ATP delivery is maintained, but this has never been explored in human obesity. We hypothesized that ATP transfer rate through creatine kinase (CK) (kfCKrest) would be increased, compensating for depleted energy stores (phosphocreatine/ATP), but potentially limiting greater ATP delivery during increased workload. We hypothesized that these changes would normalize with weight loss. METHODS: We recruited 80 volunteers (35 controls [body mass index 24±3 kg/m2], 45 obese [body mass index 35±5 kg/m2]) without coexisting cardiovascular disease. Participants underwent body composition analysis, magnetic resonance imaging of abdominal, liver, and myocardial fat content, left ventricular function, and 31P magnetic resonance spectroscopy to assess phosphocreatine/ATP and CK kinetics, at rest and during dobutamine stress. Obese volunteers were assigned to a dietary weight loss intervention, before reexamination. RESULTS: At rest, although myocardial phosphocreatine/ATP was 14% lower in obesity (1.9±0.3 versus 2.2±0.2, P<0.001), kfCkrest was 33% higher (0.23±0.07 s-1 versus 0.16±0.08 s-1, P=0.002), yielding no difference in overall resting ATP delivery (obese 2.5±0.9 µmol·g-1·s-1 versus control 2.2±1.1 µmol·g-1·s-1, P=0.232). In controls, increasing cardiac workload led to an increase in both kfCK (+86%, P<0.001) and ATP delivery (+80%, P<0.001). However, in obesity, similar stress led to no significant increase in either kfCK (P=0.117) or ATP delivery (P=0.608). This was accompanied by reduced systolic augmentation (absolute increase in left ventricular ejection fraction, obese +16±7% versus control +21±4%, P=0.031). Successful weight loss (-11±5% body weight) was associated with improvement of these energetic changes such that there was no significant difference in comparison with controls. CONCLUSIONS: In the obese resting heart, the myocardial CK reaction rate is increased, maintaining ATP delivery despite reduced phosphocreatine/ATP. During increased workload, although the nonobese heart increases ATP delivery through CK, the obese heart does not; this is associated with reduced systolic augmentation and exercise tolerance. Weight loss reverses these energetic changes. This highlights myocardial energy delivery through CK as a potential therapeutic target to improve symptoms in obesity-related heart disease, and a fascinating modifiable pathway involved in the progression to heart failure, as well.


Assuntos
Trifosfato de Adenosina/genética , Creatina Quinase/metabolismo , Metabolismo Energético/fisiologia , Espectroscopia de Ressonância Magnética/métodos , Miocárdio/patologia , Obesidade/genética , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Perda de Peso
12.
Magn Reson Med ; 84(2): 777-786, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-31971634

RESUMO

PURPOSE: To improve the labeling efficiency of pseudo-continuous arterial spin labeling (PCASL) at 7T using parallel transmission (pTx). METHODS: Five healthy subjects were scanned on an 8-channel-transmit 7T human MRI scanner. Time-of-flight (TOF) angiography was acquired to identify regions of interest (ROIs) around the 4 major feeding arteries to the brain, and B 1 + and B0 maps were acquired in the labeling plane for tagging pulse design. Complex weights of the labeling pulses for each of the 8 transmit channels were calculated to produce a homogenous radiofrequency (RF) -shimmed labeling across the ROIs. Variable-Rate Selective Excitation (VERSE) pulses were also implemented as a part of the labeling pulse train. Whole-brain perfusion-weighted images were acquired under conditions of RF shimming, VERSE with RF shimming, and standard circularly polarized (CP) mode. The same subjects were scanned on a 3T scanner for comparison. RESULTS: In simulation, VERSE with RF shimming improved the flip-angles across the ROIs in the labeling plane by 90% compared with CP mode. VERSE with RF shimming improved the temporal signal-to-noise ratio by 375% compared with CP mode, but did not outperform a matched 3T sequence with a matched flip-angle. CONCLUSION: We have demonstrated improved PCASL tagging at 7T using VERSE with RF shimming on a commercial head coil under conservative SAR limits at 7T. However, improvements of 7T over 3T may require strategies with less conservative SAR restrictions.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Artérias , Encéfalo/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Marcadores de Spin
13.
Neuroimage ; 206: 116335, 2020 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-31712167

RESUMO

Increasing numbers of 7 T (7 T) magnetic resonance imaging (MRI) scanners are in research and clinical use. 7 T MRI can increase the scanning speed, spatial resolution and contrast-to-noise-ratio of many neuroimaging protocols, but technical challenges in implementation have been addressed in a variety of ways across sites. In order to facilitate multi-centre studies and ensure consistency of findings across sites, it is desirable that 7 T MRI sites implement common high-quality neuroimaging protocols that can accommodate different scanner models and software versions. With the installation of several new 7 T MRI scanners in the United Kingdom, the UK7T Network was established with an aim to create a set of harmonized structural and functional neuroimaging sequences and protocols. The Network currently includes five sites, which use three different scanner platforms, provided by two different vendors. Here we describe the harmonization of functional and anatomical imaging protocols across the three different scanner models, detailing the necessary changes to pulse sequences and reconstruction methods. The harmonized sequences are fully described, along with implementation details. Example datasets acquired from the same subject on all Network scanners are made available. Based on these data, an evaluation of the harmonization is provided. In addition, the implementation and validation of a common system calibration process is described.


Assuntos
Encéfalo/diagnóstico por imagem , Imageamento por Ressonância Magnética/instrumentação , Neuroimagem/normas , Calibragem , Neuroimagem Funcional/métodos , Neuroimagem Funcional/normas , Humanos , Neuroimagem/métodos , Padrões de Referência , Reprodutibilidade dos Testes , Reino Unido
15.
World J Gastroenterol ; 25(30): 4148-4157, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31435169

RESUMO

Patients with long-standing inflammatory bowel disease (IBD) involving at least 1/3 of the colon are at increased risk for colorectal cancer (CRC). Advancements in CRC screening and surveillance and improved treatment of IBD has reduced CRC incidence in patients with ulcerative colitis and Crohn's colitis. Most cases of CRC are thought to arise from dysplasia, and recent evidence suggests that the majority of dysplastic lesions in patients with IBD are visible, in part thanks to advancements in high definition colonoscopy and chromoendoscopy. Recent practice guidelines have supported the use of chromoendoscopy with targeted biopsies of visible lesions rather than traditional random biopsies. Endoscopists are encouraged to endoscopically resect visible dysplasia and only recommend surgery when a complete resection is not possible. New technologies such as virtual chromoendoscopy are emerging as potential tools in CRC screening. Patients with IBD at increased risk for developing CRC should undergo surveillance colonoscopy using new approaches and techniques.


Assuntos
Neoplasias Colorretais/prevenção & controle , Detecção Precoce de Câncer/normas , Doenças Inflamatórias Intestinais/patologia , Lesões Pré-Cancerosas/patologia , Conduta Expectante/normas , Biópsia , Colonografia Tomográfica Computadorizada/métodos , Colonografia Tomográfica Computadorizada/normas , Colonoscopia/métodos , Colonoscopia/normas , Neoplasias Colorretais/patologia , Progressão da Doença , Detecção Precoce de Câncer/métodos , Ressecção Endoscópica de Mucosa/normas , Humanos , Doenças Inflamatórias Intestinais/diagnóstico por imagem , Doenças Inflamatórias Intestinais/cirurgia , Mucosa Intestinal/diagnóstico por imagem , Mucosa Intestinal/patologia , Mucosa Intestinal/cirurgia , Programas de Rastreamento/métodos , Programas de Rastreamento/normas , Guias de Prática Clínica como Assunto , Lesões Pré-Cancerosas/diagnóstico por imagem , Lesões Pré-Cancerosas/cirurgia
17.
J Viral Hepat ; 26(10): 1164-1169, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31134715

RESUMO

We have previously shown that ultrasound identifies significant steatosis in patients with chronic HBV (CHB). However, the relationship between CHB, metabolic syndrome (MS) and steatosis is poorly understood. In this tertiary care, single-centre retrospective cohort study of 617 CHB patients, we examined the prevalence of MS and steatosis in a predominantly Asian US cohort. Patients were predominantly male (57%) with a mean age of 53 years, Asian (88%), on HBV therapy (64%) and had undetectable DNA (65%). 21% had MS, of which hypertension (41%), dyslipidemia (41%) and obesity (32%) were most common. Patients with MS were more likely to be older (60 vs 52 [P < 0.001]), have steatosis (40% vs 17% [P < 0.001]) and have a higher ALT (29 vs 25 [P = 0.003]). Of the 22% of patients with steatosis by ultrasound, a higher prevalence of MS (38% vs 16% [P < 0.001]) and higher ALT (31 vs 24 [P < 0.001]) was observed. Asian patients had a lower BMI than non-Asians (mean 24 vs 26 [P = 0.001]) but similar prevalence of MS risk factors and steatosis. Asian patients with a BMI between 25 and 30 and two other MS risk factors had steatosis at the same rate as patients with a BMI > 30 and at least two other MS risk factors. We found a strong association between MS, steatosis and elevated ALT in HBV patients. Asian HBV patients have lower BMI than non-Asians yet have the same prevalence of steatosis and other MS risk factors, supporting guidelines for lower BMI targets in Asians.


Assuntos
Americanos Asiáticos , Índice de Massa Corporal , Fígado Gorduroso/complicações , Fígado Gorduroso/patologia , Hepatite B Crônica/complicações , Síndrome Metabólica/complicações , Síndrome Metabólica/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Centros de Atenção Terciária , Estados Unidos , Adulto Jovem
18.
J Cardiovasc Magn Reson ; 21(1): 19, 2019 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-30871562

RESUMO

BACKGROUND: Cardiovascular phosphorus MR spectroscopy (31P-CMRS) is a powerful tool for probing energetics in the human heart, through quantification of phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio. In principle, 31P-CMRS can also measure cardiac intracellular pH (pHi) and the free energy of ATP hydrolysis (ΔGATP). However, these require determination of the inorganic phosphate (Pi) signal frequency and amplitude that are currently not robustly accessible because blood signals often obscure the Pi resonance. Typical cardiac 31P-CMRS protocols use low (e.g. 30°) flip-angles and short repetition time (TR) to maximise signal-to-noise ratio (SNR) within hardware limits. Unfortunately, this causes saturation of Pi with negligible saturation of the flowing blood pool. We aimed to show that an adiabatic 90° excitation, long-TR, 7T 31P-CMRS protocol will reverse this balance, allowing robust cardiac pHi measurements in healthy subjects and patients with hypertrophic cardiomyopathy (HCM). METHODS: The cardiac Pi T1 was first measured by the dual TR technique in seven healthy subjects. Next, ten healthy subjects and three HCM patients were scanned with 7T 31P-MRS using long (6 s) TR protocol and adiabatic excitation. Spectra were fitted for cardiac metabolites including Pi. RESULTS: The measured Pi T1 was 5.0 ± 0.3 s in myocardium and 6.4 ± 0.6 s in skeletal muscle. Myocardial pH was 7.12 ± 0.04 and Pi/PCr ratio was 0.11 ± 0.02. The coefficients of repeatability were 0.052 for pH and 0.027 for Pi/PCr quantification. The pH in HCM patients did not differ (p = 0.508) from volunteers. However, Pi/PCr was higher (0.24 ± 0.09 vs. 0.11 ± 0.02; p = 0.001); Pi/ATP was higher (0.44 ± 0.14 vs. 0.24 ± 0.05; p = 0.002); and PCr/ATP was lower (1.78 ± 0.07 vs. 2.10 ± 0.20; p = 0.020), in HCM patients, which is in agreement with previous reports. CONCLUSION: A 7T 31P-CMRS protocol with adiabatic 90° excitation and long (6 s) TR gives sufficient SNR for Pi and low enough blood signal to permit robust quantification of cardiac Pi and hence pHi. Pi was detectable in every subject scanned for this study, both in healthy subjects and HCM patients. Cardiac pHi was unchanged in HCM patients, but both Pi/PCr and Pi/ATP increased that indicate an energetic impairment in HCM. This work provides a robust technique to quantify cardiac Pi and pHi.


Assuntos
Trifosfato de Adenosina/metabolismo , Cardiomiopatia Hipertrófica/metabolismo , Metabolismo Energético , Espectroscopia de Ressonância Magnética , Miocárdio/metabolismo , Fosfatos/metabolismo , Fosfocreatina/metabolismo , Adulto , Idoso , Biomarcadores/metabolismo , Estudos de Casos e Controles , Feminino , Humanos , Concentração de Íons de Hidrogênio , Hidrólise , Masculino , Pessoa de Meia-Idade , Isótopos de Fósforo , Reprodutibilidade dos Testes , Adulto Jovem
19.
NMR Biomed ; 32(6): e4095, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30924566

RESUMO

PURPOSE: We test the reproducibility of human cardiac phosphorus MRS (31 P-MRS) at ultra-high field strength (7 T) for the first time. The primary motivation of this work was to assess the reproducibility of a 'rapid' 6½ min 31 P three-dimensional chemical shift imaging (3D-CSI) sequence, which if sufficiently reproducible would allow the study of stress-response processes. We compare this with an established 28 min protocol, designed to record high-quality spectra in a clinically feasible scan time. Finally, we use this opportunity to compare the effect of per-subject B0 shimming on data quality and reproducibility in the 6½ min protocol. METHODS: 10 healthy subjects were scanned on two occasions: one to test the 28 min 3D-CSI protocol, and one to test the 6½ min protocol. Spectra were fitted using the OXSA MATLAB toolbox. The phosphocreatine to adenosine triphosphate concentration ratio (PCr/ATP) from each scan was analysed for intra- and intersubject variability. The impact of different strategies for voxel selection was assessed. RESULTS: There were no significant differences between repeated measurements in the same subject. For the 28 min protocol, PCr/ATP in the midseptal voxel across all scans was 1.91 ± 0.36 (mean ± intersubject SD). For the 6½ min protocol, PCr/ATP in the midseptal voxel was 1.76 ± 0.40. The coefficients of reproducibility (CRs) were 0.49 (28 min) and 0.67 (6½ min). Per-subject B0 shimming improved the fitted PCr/ATP precision (for 6½ min scans), but had negligible effect on the CR (0.67 versus 0.66). CONCLUSIONS: Both 7 T protocols show improved reproducibility compared with a previous 3 T study by Tyler et al. Our results will enable informed power calculations and protocol selection for future clinical research studies.


Assuntos
Espectroscopia de Ressonância Magnética , Miocárdio/metabolismo , Fósforo/metabolismo , Trifosfato de Adenosina/metabolismo , Adulto , Feminino , Humanos , Masculino , Fosfocreatina/metabolismo , Reprodutibilidade dos Testes , Tamanho da Amostra , Fatores de Tempo
20.
NMR Biomed ; 32(6): e4085, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30920054

RESUMO

Changes in the kinetics of the creatine kinase (CK) shuttle are sensitive markers of cardiac energetics but are typically measured at rest and in the prone position. This study aims to measure CK kinetics during pharmacological stress at 3 T, with measurement in the supine position. A shorter "stressed saturation transfer" (StreST) extension to the triple repetition time saturation transfer (TRiST) method is proposed. We assess scanning in a supine position and validate the MR measurement against biopsy assay of CK activity. We report normal ranges of stress CK forward rate (kf CK ) for healthy volunteers and obese patients. TRiST measures kf CK in 40 min at 3 T. StreST extends the previously developed TRiST to also make a further kf CK measurement during <20 min of dobutamine stress. We test our TRiST implementation in skeletal muscle and myocardium in both prone and supine positions. We evaluate StreST in the myocardium of six healthy volunteers and 34 obese subjects. We validated MR-measured kf CK against biopsy assays of CK activity. TRiST kf CK values matched literature values in skeletal muscle (kf CK  = 0.25 ± 0.03 s-1 vs 0.27 ± 0.03 s-1 ) and myocardium when measured in the prone position (0.32 ± 0.15 s-1 ), but a significant difference was found for TRiST kf CK measured supine (0.24 ± 0.12 s-1 ). This difference was because of different respiratory- and cardiac-motion-induced B0 changes in the two positions. Using supine TRiST, cardiac kf CK values for normal-weight subjects were 0.15 ± 0.09 s-1 at rest and 0.17 ± 0.15 s-1 during stress. For obese subjects, kf CK was 0.16 ± 0.07 s-1 at rest and 0.17 ± 0.10 s-1 during stress. Rest myocardial kf CK and CK activity from LV biopsies of the same subjects correlated (R = 0.43, p = 0.03). We present an independent implementation of TRiST on the Siemens platform using a commercially available coil. Our extended StreST protocol enables cardiac kf CK to be measured during dobutamine-induced stress in the supine position.


Assuntos
Creatina Quinase/metabolismo , Coração/fisiopatologia , Espectroscopia de Ressonância Magnética , Descanso , Estresse Fisiológico , Adulto , Biópsia , Estudos de Casos e Controles , Feminino , Humanos , Cinética , Masculino , Pessoa de Meia-Idade , Miocárdio/metabolismo , Obesidade/enzimologia , Obesidade/fisiopatologia , Postura , Reprodutibilidade dos Testes , Respiração
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