Early or Delayed Enteral Feeding for Infants with Abnormal Antenatal Doppler Flow Patterns

Introdução: O principal objetivo deste estudo foi determinar o efeito da introdução de alimentação entérica precoce comparado com introdução tardia, na incidência de morbilidade gastrointestinal e tempo até alimentação entérica total, em recém- -nascidos com alteração de fluxos em ecografia pré-natal. Métodos: Análise retrospetiva dos recém-nascidos internados numa unidade de cuidados intensivos neonatais de nível III, em Portugal, entre janeiro de 2004 e dezembro de 2013 com alteração de fluxos em ecografia pré-natal. Foram criados dois grupos baseados no tempo até introdução de primeira alimentação entérica: grupo de alimentação precoce (≤48 horas) e grupo de alimentação tardia (> 48 horas). Os resultados principais foram morbilidade gastrointestinal e mortalidade devido a complicações gastrointestinais. Resultados: Foram incluídos 46 (47%) de recém-nascidos no grupo de alimentação precoce e 52 (53%) no grupo de alimentação tardia. Não houve diferenças significativas na morbilidade gastrointestinal, incluindo enterocolite necrosante, perfuração ou cirurgia gastrointestinal, íleus séptico ou intolerância alimentar. A alimentação precoce resultou numa diminuição significativa da sepsis tardia (p=0,016; odds ratio 0,276; intervalo de confiança 95% 0,096-0,789). Discussão: A introdução precoce de alimentação entérica poderá não ter efeitos significativos na incidência de morbilidade gastrointestinal em recém-nascidos com alteração de fluxos em ecografia pré-natal. Houve uma redução significativa na sepsis tardia, sem condicionar um aumento de risco de morbilidade gastrointestinal.Introduction: The main objective of this study was to determine the effect of early versus late enteral feeding on the incidence of gastrointestinal morbidity and on time to establish full enteral feeding in neonates with abnormal antenatal Doppler flow patterns. Methods: We retrospectively analysed neonates admitted to a level III neonatal intensive care unit in Portugal between January 2004 and December 2013 with abnormal antenatal Doppler flow patterns. Two groups were created based on the time of first enteral feeding: early feeding group (≤48 hours) and late feeding group (> 48 hours). Primary outcomes were gastrointestinal morbidity and death due to gastrointestinal complications. Results: Forty-six (47%) infants were included in the early feeding group and 52 (53%) in the late feeding group. There was no statistical difference in gastrointestinal morbidity, including necrotising enterocolitis, gastrointestinal perforation or surgery, septic ileus or feeding intolerance. Early feeding resulted in a significant decrease in late-onset sepsis (p=0.016; odds ratio 0.276; 95% confidence interval 0.096-0.789). Discussion: Early introduction of enteral feeding may not have a significant effect on the incidence of gastrointestinal morbidity in neonates with abnormal antenatal Doppler flow patterns. There was a significant reduction in late-onset sepsis, without incurring an increased risk of gastrointestinal morbidity.info:eu-repo/semantics/publishedVersio

Fluorine-19 MRI at 21.1 T: enhanced spin-lattice relaxation of perfluoro-15-crown-5-ether and sensitivity as demonstrated in ex vivo murine neuroinflammation

OBJECTIVE: Fluorine MR would benefit greatly from enhancements in signal-to-noise ratio (SNR). This study examines the sensitivity gain of (19)F MR that can be practically achieved when moving from 9.4 to 21.1 T. MATERIALS AND METHODS: We studied perfluoro-15-crown-5-ether (PFCE) at both field strengths (B(0)), as a pure compound, in the form of nanoparticles (NP) as employed to study inflammation in vivo, as well as in inflamed tissue. Brains, lymph nodes (LNs) and spleens were obtained from mice with experimental autoimmune encephalomyelitis (EAE) that had been administered PFCE NPs. All samples were measured at both B(0) with 2D-RARE and 2D-FLASH using (19)F volume radiofrequency resonators together. T(1) and T(2) of PFCE were measured at both B(0) strengths. RESULTS: Compared to 9.4 T, an SNR gain of > 3 was observed for pure PFCE and > 2 for PFCE NPs at 21.1 T using 2D-FLASH. A dependency of (19)F T(1) and T(2) relaxation on B(0) was demonstrated. High spatially resolved (19)F MRI of EAE brains and LNs at 21.1 T revealed signals not seen at 9.4 T. DISCUSSION: Enhanced SNR and T(1) shortening indicate the potential benefit of in vivo (19)F MR at higher B(0) to study inflammatory processes with greater detail

Fiber-orientation independent component of R2* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm

The effective transverse relaxation rate (R2*) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R2* degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R2,iso*) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β1, can be biophysically related to R2,iso* when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimental and simulated data with variable g-ratio and fibre dispersion. We found that the fitted β1 can estimate R2,iso* using meGRE with long maximum-echo time (TEmax ≈ 54 ms), but not accurately captures its microscopic dependence on the g-ratio (error 84%). We proposed a new heuristic expression for β1 that reduced the error to 12% for ex vivo compartmental R2 values. Using the new expression, we could estimate an MW fraction of 0.14 for fibres with negligible dispersion in a fixed human optic chiasm for the ex vivo compartmental R2 values but not for the in vivo values. M2 and the HCFM-based simulations failed to explain the measured R2*-orientation-dependence around the magic angle for a typical in vivo meGRE protocol (with TEmax ≈ 18 ms). In conclusion, further validation and the development of movement-robust in vivo meGRE protocols with TEmax ≈ 54 ms are required before M2 can be used to estimate R2,iso* in subjects

Experimental MRI monitoring of renal blood volume fraction variations en route to renal magnetic resonance oximetry

Diagnosis of early-stage acute kidney injury (AKI) will benefit from a timely identification of local tissue hypoxia. Renal tissue hypoxia is an early feature in AKI pathophysiology, and renal oxygenation is increasingly being assessed through T(2)*-weighted magnetic resonance imaging (MRI). However, changes in renal blood volume fraction (BVf) confound renal T(2)*. The aim of this study was to assess the feasibility of intravascular contrast-enhanced MRI for monitoring renal BVf during physiological interventions that are concomitant with variations in BVf and to explore the possibility of correcting renal T(2)* for BVf variations. A dose-dependent study of the contrast agent ferumoxytol was performed in rats. BVf was monitored throughout short-term occlusion of the renal vein, which is known to markedly change renal blood partial pressure of O(2) and BVf. BVf calculated from MRI measurements was used to estimate oxygen saturation of hemoglobin (SO(2)). BVf and SO(2) were benchmarked against cortical data derived from near-infrared spectroscopy. As estimated from magnetic resonance parametric maps of T(2) and T(2)*, BVf was shown to increase, whereas SO(2) was shown to decline during venous occlusion (VO). This observation could be quantitatively reproduced in test-retest scenarios. Changes in BVf and SO(2) were in good agreement with data obtained from near-infrared spectroscopy. Our findings provide motivation to advance multiparametric MRI for studying AKIs, with the ultimate goal of translating MRI-based renal BVf mapping into clinical practice en route noninvasive renal magnetic resonance oximetry as a method of assessing AKI and progression to chronic damage

Thermal magnetic resonance: physics considerations and electromagnetic field simulations up to 23.5 Tesla (1GHz)

Background: Glioblastoma multiforme is the most common and most aggressive malign brain tumor. The 5-year survival rate after tumor resection and adjuvant chemoradiation is only 10 %, with almost all recurrences occurring in the initially treated site. Attempts to improve local control using a higher radiation dose were not successful so that alternative additive treatments are urgently needed. Given the strong rationale for hyperthermia as part of a multimodal treatment for patients with glioblastoma, non-invasive radio frequency (RF) hyperthermia might significantly improve treatment results. Methods: A non-invasive applicator was constructed utilizing the magnetic resonance (MR) spin excitation frequency for controlled RF hyperthermia and MR imaging in an integrated system, which we refer to as thermal MR. Applicator designs at RF frequencies 300 MHz, 500 MHz and 1GHz were investigated and examined for absolute applicable thermal dose and temperature hotspot size. Electromagnetic field (EMF) and temperature simulations were performed in human voxel models. RF heating experiments were conducted at 300 MHz and 500 MHz to characterize the applicator performance and validate the simulations. Results: The feasibility of thermal MR was demonstrated at 7.0 T. The temperature could be increased by ~11 °C in 3 min in the center of a head sized phantom. Modification of the RF phases allowed steering of a temperature hotspot to a deliberately selected location. RF heating was monitored using the integrated system for MR thermometry and high spatial resolution MRI. EMF and thermal simulations demonstrated that local RF hyperthermia using the integrated system is feasible to reach a maximum temperature in the center of the human brain of 46.8 °C after 3 min of RF heating while surface temperatures stayed below 41 °C. Using higher RF frequencies reduces the size of the temperature hotspot significantly. Conclusion: The opportunities and capabilities of thermal magnetic resonance for RF hyperthermia interventions of intracranial lesions are intriguing. Employing such systems as an alternative additive treatment for glioblastoma multiforme might be able to improve local control by "fighting fire with fire". Interventions are not limited to the human brain and might include temperature driven targeted drug and MR contrast agent delivery and help to understand temperature dependent bio- and physiological processes in-vivo

Diffusion-weighted renal MRI at 9.4 Tesla using RARE to improve anatomical integrity

Diffusion-weighted magnetic resonance imaging (DWI) is a non-invasive imaging technique sensitive to tissue water movement. By enabling a discrimination between tissue properties without the need of contrast agent administration, DWI is invaluable for probing tissue microstructure in kidney diseases. DWI studies commonly make use of single-shot Echo-Planar Imaging (ss-EPI) techniques that are prone to suffering from geometric distortion. The goal of the present study was to develop a robust DWI technique tailored for preclinical magnetic resonance imaging (MRI) studies that is free of distortion and sensitive to detect microstructural changes. Since fast spin-echo imaging techniques are less susceptible to B(0) inhomogeneity related image distortions, we introduced a diffusion sensitization to a split-echo Rapid Acquisition with Relaxation Enhancement (RARE) technique for high field preclinical DWI at 9.4 T. Validation studies in standard liquids provided diffusion coefficients consistent with reported values from the literature. Split-echo RARE outperformed conventional ss-EPI, with ss-EPI showing a 3.5-times larger border displacement (2.60 vs. 0.75) and a 60% higher intra-subject variability (cortex = 74%, outer medulla = 62% and inner medulla = 44%). The anatomical integrity provided by the split-echo RARE DWI technique is an essential component of parametric imaging on the way towards robust renal tissue characterization, especially during kidney disease

Renal MRI diffusion: experimental protocol

Renal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis

Simultaneous T(2) and T(2)* mapping of multiple sclerosis lesions with radial RARE-EPI

PURPOSE: The characteristic MRI features of multiple sclerosis (MS) lesions make it conceptually appealing to pursue parametric mapping techniques that support simultaneous generation of quantitative maps of 2 or more MR contrast mechanisms. We present a modular rapid acquisition with relaxation enhancement (RARE)‐EPI hybrid that facilitates simultaneous T(2) and T(2)* mapping (2in1‐RARE‐EPI). METHODS: In 2in1‐RARE‐EPI the first echoes in the echo train are acquired with a RARE module, later echoes are acquired with an EPI module. To define the fraction of echoes covered by the RARE and EPI module, an error analysis of T(2) and T(2)* was conducted with Monte Carlo simulations. Radial k‐space (under)sampling was implemented for acceleration (R = 2). The feasibility of 2in1‐RARE‐EPI for simultaneous T(2) and T(2)* mapping was examined in a phantom study mimicking T(2) and T(2)* relaxation times of the brain. For validation, 2in1‐RARE‐EPI was benchmarked versus multi spin‐echo (MSE) and multi gradient‐echo (MGRE) techniques. The clinical applicability of 2in1‐RARE‐EPI was demonstrated in healthy subjects and MS patients. RESULTS: There was a good agreement between T(2)/T(2)* values derived from 2in1‐RARE‐EPI and T(2)/T(2)* reference values obtained from MSE and MGRE in both phantoms and healthy subjects. In patients, MS lesions in T(2) and T(2)* maps deduced from 2in1‐RARE‐EPI could be just as clearly delineated as in reference maps calculated from MSE/MGRE. CONCLUSION: This work demonstrates the feasibility of radially (under)sampled 2in1‐RARE‐EPI for simultaneous T(2) and T(2)* mapping in MS patients

Open‐source magnetic resonance imaging: improving access, science, and education through global collaboration

Open-source practices and resources in magnetic resonance imaging (MRI) have increased substantially in recent years. This trend started with software and data being published open-source and, more recently, open-source hardware designs have become increasingly available. These developments towards a culture of sharing and establishing nonexclusive global collaborations have already improved the reproducibility and reusability of code and designs, while providing a more inclusive approach, especially for low-income settings. Community-driven standardization and documentation efforts are further strengthening and expanding these milestones. The future of open-source MRI is bright and we have just started to discover its full collaborative potential. In this review we will give an overview of open-source software and open-source hardware projects in human MRI research

Fiber-orientation independent component of R(2)* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm

The effective transverse relaxation rate (R(2)*) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R(2)* degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R(2,iso)*) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β(1), can be biophysically related to R(2,iso)* when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimental and simulated data with variable g-ratio and fibre dispersion. We found that the fitted β(1) can estimate R(2,iso)* using meGRE with long maximum-echo time (TE(max) ≈ 54 ms), but not accurately captures its microscopic dependence on the g-ratio (error 84%). We proposed a new heuristic expression for β(1) that reduced the error to 12% for ex vivo compartmental R(2) values. Using the new expression, we could estimate an MW fraction of 0.14 for fibres with negligible dispersion in a fixed human optic chiasm for the ex vivo compartmental R(2) values but not for the in vivo values. M2 and the HCFM-based simulations failed to explain the measured R(2)*-orientation-dependence around the magic angle for a typical in vivo meGRE protocol (with TE(max) ≈ 18 ms). In conclusion, further validation and the development of movement-robust in vivo meGRE protocols with TE(max) ≈ 54 ms are required before M2 can be used to estimate R(2,iso)* in subjects