Mid-Term Outcome after Extracorporeal Life Support in Postcardiotomy Cardiogenic Shock: Recovery and Quality of Life

Background: Extracorporeal life support (ECLS) therapy for refractory postcardiotomy cardiogenic shock (rPCS) is associated with high early mortality rates. This study aimed to identify negative predictors of mid-term survival and to assess health-related quality of life (HRQoL) and recovery of the survivors. Methods: Between 2017 and 2020, 142 consecutive patients received ECLS therapy following cardiac surgery. The median age was 66.0 [57.0–73.0] years, 67.6% were male and the median EuroSCORE II was 10.5% [4.2–21.3]. In 48 patients, HRQoL was examined using the 36-Item Short Form Survey (SF-36) and the modified Rankin-Scale (mRS) at a median follow-up time of 2.2 [1.9–3.2] years. Results: Estimated survival rates at 3, 12, 24 and 36 months were 47%, 46%, 43% and 43% (SE: 4%). Multivariable Cox Proportional Hazard regression analysis revealed preoperative EuroSCORE II (p = 0.013), impaired renal function (p = 0.010), cardiopulmonary bypass duration (p = 0.015) and pre-ECLS lactate levels (p = 0.004) as independent predictors of mid-term mortality. At the time of follow-up, 83.3% of the survivors were free of moderate to severe disability (mRS \u3c 3). SF-36 analysis showed a physical component summary of 45.5 ± 10.2 and a mental component summary of 50.6 ± 12.5. Conclusions: Considering the disease to be treated, ECLS for rPCS is associated with acceptable mid-term survival, health-related quality of life and functional status. Preoperative EuroSCORE II, impaired renal function, cardiopulmonary bypass duration and lactate levels prior to ECLS implantation were identified as negative predictors and should be included in the decision-making process

Across‐vendor standardization of semi‐LASER for single‐voxel MRS at 3T

The semi‐adiabatic localization by adiabatic selective refocusing (sLASER) sequence provides single‐shot full intensity signal with clean localization and minimal chemical shift displacement error and was recommended by the international MRS Consensus Group as the preferred localization sequence at high‐ and ultra‐high fields. Across‐vendor standardization of the sLASER sequence at 3 tesla has been challenging due to the B1 requirements of the adiabatic inversion pulses and maximum B1 limitations on some platforms. The aims of this study were to design a short‐echo sLASER sequence that can be executed within a B1 limit of 15 μT by taking advantage of gradient‐modulated RF pulses, to implement it on three major platforms and to evaluate the between‐vendor reproducibility of its perfomance with phantoms and in vivo. In addition, voxel‐based first and second order B0 shimming and voxel‐based B1 adjustments of RF pulses were implemented on all platforms. Amongst the gradient‐modulated pulses considered (GOIA, FOCI and BASSI), GOIA‐WURST was identified as the optimal refocusing pulse that provides good voxel selection within a maximum B1 of 15 μT based on localization efficiency, contamination error and ripple artifacts of the inversion profile. An sLASER sequence (30 ms echo time) that incorporates VAPOR water suppression and 3D outer volume suppression was implemented with identical parameters (RF pulse type and duration, spoiler gradients and inter‐pulse delays) on GE, Philips and Siemens and generated identical spectra on the GE ‘Braino’ phantom between vendors. High‐quality spectra were consistently obtained in multiple regions (cerebellar white matter, hippocampus, pons, posterior cingulate cortex and putamen) in the human brain across vendors (5 subjects scanned per vendor per region; mean signal‐to‐noise ratio [less than] 33; mean water linewidth between 6.5 Hz to 11.4 Hz). The harmonized sLASER protocol is expected to produce high reproducibility of MRS across sites thereby allowing large multi‐site studies with clinical cohorts

Frequency drift in MR spectroscopy at 3T

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B-0 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 &lt; 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.</p

1H MR Spektroskopie und Spektroskopische Bildgebung des In Vivo Gehirns bei 7 Tesla

Neurotransmitters and compounds of the brain’s energy metabolism are directly linked to brain function. In vivo magnetic resonance (MR) spectroscopy is a useful method to quantify the neurochemical profiles of localized brain regions noninvasively and to provide valuable information for medical treatment or for the study of underlying mechanisms. The concentrations of substances in the brain detectable by MR, however, are at best in the range of millimols and the sensitivity of MR methods that are based on the Boltzmann spin polarization is inherently low. Most anatomical or functional structures in the brain of humans and monkeys are in the millimeter range or below. The spatial resolution that would be necessary to account for the small target dimensions could not be realized so far in humans and with current MR systems. Reasonable signal strength could only be achieved at the cost of limited spatial specificity. The spectral quality of in vivo MR spectroscopy and the amount of information available from it strongly depend on the existence and strength of potential experimental artifacts like frequency drifts, localization errors or spectral contaminations. In addition, the homogeneity of the magnetic field within the sensitive probe volume is a critical issue. The goal of the thesis was to establish different methods for MR spectroscopy and chemical shift imaging at maximum spatial specificity and spectral quality. The methods were to be adopted for investigations of the non-human primate visual cortex, an area of intense study of the brain’s physiology and function. To maximize the sensitivity and the quality of the MR spectra, a number of methods have been implemented and optimized. Artifact sources were analyzed and methodological corrections were proposed to overcome them. For instance, strong limitations of the MR scanner’s built-in capacity to compensate actively for inhomogeneities of the magnetic field by electrical coils were overcome by newly designed ferromagnetic permalloy assemblies. A combined modular passive (ferromagnetic) and active (electrical) shimming method was developed that provides very strong and highly accurate correction fields for the homogenization of magnetic field distributions in the in vivo brain with reasonably low experimental effort. MR spectroscopy of the macaque primary visual cortex (V1) is challenging, because of its position adjacent to the skull bone and the cortical thickness of only 1.7–2.0 mm. A dedicated 7 Tesla high field MR setup, an anesthetized monkey preparation and optimized MR methods enabled single voxel MR spectroscopy from 40 microliter volumes of V1. Due to the varying magnetic susceptibility conditions around macaque V1 this region is prone for susceptibility induced field distortions. To achieve optimal field homogeneity, field distributions were analyzed, and an appropriate shimming strategy was developed. With the established methods the successful sampling from brain regions entirely confined within V1 gray matter is now possible. Chemical shift imaging methods were implemented and optimized to permit high resolution spatial mapping of metabolite distributions from the macaque visual cortex. The feasibility of chemical shift imaging along planar slices through the brain with a spatial resolution of 1–2 mm has been shown using conventional phase encoding. In addition, Hamming acquisition weighting was provided to improve the reliability of the metabolic mapping based on its favorable imaging properties. Applying the techniques developed in this thesis the achieved resolution limits for 1H MR spectroscopy and chemical shift imaging in monkeys were 2–3 orders of magnitude better compared to previous studies in humans. The spatial specificity now reaches the level of cortical dimensions which is the basis for the investigation of physiology and function in the primate visual system.Neurotransmitter und Metabolite des zerebralen Energiestoffwechsels sind unmittelbar mit Hirnaktivität korreliert. In vivo Magnetresonanzspektroskopie ermöglicht eine direkte, nicht-invasive Messung einer Vielzahl dieser chemischen Komponenten von lokalisierten Bereichen des Gehirns. Die so erzielbaren Erkenntnisse sind von hohem Wert für die medizinische Diagnostik auf der einen Seite sowie für die Erforschung der zugrunde liegenden Mechanismen auf der anderen. Die Konzentrationen der auf diese Weise detektierbaren Substanzen im Gehirn sind jedoch sehr gering und bestenfalls im Bereich weniger Millimol. Zusätzlich ist die Sensitivität von Magnetresonanzexperimenten an sich sehr begrenzt für Techniken, die auf der Boltzmann’schen Spinpolarisation beruhen. Die Dimensionen anatomischer und funktioneller Strukturen im Gehirn von Menschen und Affen liegen im Bereich von Millimetern oder darunter. Räumliche Auflösungen, die in der Lage wären solch kleine Meßobjekte zu erfassen sind bisher und mit heutigen MR Systemen am Menschen nicht realisierbar. Ausreichende Signalstärken konnten nur auf Kosten einer limitierten räumlichen Auflösung erreicht werden. Die spektrale Qualität von in vivo MR Spektren und der daraus zu erzielende Informationsgehalt hängen maßgeblich von der Existenz und Größenordung potentieller Meßartefakte wie Frequenzverschiebungen, Lokalisierungsfehlern und spektralen Verunreingungen ab. Inhomogenitäten des Magnetfeldes innerhalb des betrachteten Raumbereiches stellen ein weiteres, grundlegendes Problem dar. Das Ziel dieser Arbeit war die Etablierung von Methoden für MR Spektroskopie und spektroskopische Bildgebung mit maximaler räumlicher Spezifität und bestmöglicher spektraler Qualität. Diese waren so anzupassen, daß Untersuchungen der Sehrinde des nicht-menschlichen Primaten und die Erforschung von Hirnphysiologie und -funktion in diesem Bereich des Gehirns ermöglicht werden. Im Rahmen dieser Arbeit wurden verschiedene MR spektroskopische Methoden implementiert und bzgl. der speziellen Erfordernisse optimiert. Artefaktquellen wurden analysiert und methodische Korrekturen wurden vorgeschlagen, diese zu minimieren oder zu beheben. So wurden etwa starke Limitierungen zur aktiven Homogenisierung von Magnetfeldverteilungen mittels elektrischer Spulen des MR Tomographen durch eine neue Entwicklung von modularen, ferromagnetischen Mu-Metall-Anordnungen gelöst. Durch die Kombination von Methoden zur (ferromagnetischen) passiven und (elektronischen) aktiven Magnetfeldmodulierung ist es nun möglich, mit vertretbarem Aufwand sehr starke und trotzdem sehr präzise Magnetfeldverteilungen zur Korrektur von Feldinhomogenitäten im in vivo Gehirn zu generieren. MR Spektroskopie in der primären Sehrinde (V1) im Makaken ist eine besondere Herausforderung wegen der unmittelbaren Nähe von V1 zum Schädelknochen und weil die kortikale Dicke in diesem Bereich lediglich 1.7–2.0 mm beträgt. Die Verwendung eines spezialisierten 7 Tesla Hochfeld MR Tomographen, eine Anästhesiepräparation der Versuchstiere und optimierte MR Methoden waren nötig, um volumenselektive MR Spektroskopie aus 40 Mikroliter kleinen Volumina von V1 zu ermöglichen. Aufgrund der Regionen unterschiedlicher magnetischer Suszeptibilitäten im Bereich von Kortex, Schädelknochen und der den Kopf umgebenden Luft werden insbesondere dort Feldverzerrungen beobachtet. Die auftretenden Magnetfeldinhomogenitäten im Bereich der primären Sehrinde wurden daher vermessen, analysiert und es konnte eine Strategie vorgeschlagen werden, diese effizient zu minimieren. Mit den hier etablierten Methoden sind nun MR spektroskopische Untersuchungen von kleinsten Volumina möglich, die sich komplett innerhalb der primären Sehrinde befinden. Desweiteren wurden Methoden zur spektroskopischen Bildgebung implementiert und optimiert, um eine hochaufgelöste Kartierung der Metabolitenverteilung des visuellen Kortex zu ermöglichen. Mittels konventioneller Phasenkodierung wurde die Machbarkeit von spektroskopischen Karten der Sehrinde mit einer Ortsauflösung von 1–2 mm gezeigt. Zusätzlich wurden Methoden zur Hamming Akquisitionswichtung bereitgestellt, durch deren verbesserte Lokalisierungseigenschaften eine weitere Erhöhung der Verläßlichkeit erzielter metabolischer Karten zu erwarten ist. Die vorgelegte Dissertation beschreibt die Verbesserung der räumlichen Auflösung von MR Spektroskopie und spektroskopischer Bildgebung im Primaten von 2–3 Größenordnungen verglichen mit ähnlichen Studien am Menschen. Die räumliche Spezifizität hat somit ein kortikales Niveau erreicht, das die Grundlage darstellt für Studien von Physiologie und Funktion des visuellen Systems

Preprocessing, analysis and quantification in single-voxel magnetic resonance spectroscopy: experts' consensus recommendations.

Once an MRS dataset has been acquired, several important steps must be taken to obtain the desired metabolite concentration measures. First, the data must be preprocessed to prepare them for analysis. Next, the intensity of the metabolite signal(s) of interest must be estimated. Finally, the measured metabolite signal intensities must be converted into scaled concentration units employing a quantitative reference signal to allow meaningful interpretation. In this paper, we review these three main steps in the post-acquisition workflow of a single-voxel MRS experiment (preprocessing, analysis and quantification) and provide recommendations for best practices at each step

sj-docx-1-css-10.1177_24705470221128004 - Supplemental material for Proton Magnetic Resonance Spectroscopy in Post-Traumatic Stress Disorder—Updated Systematic Review and Meta-Analysis

Supplemental material, sj-docx-1-css-10.1177_24705470221128004 for Proton Magnetic Resonance Spectroscopy in Post-Traumatic Stress Disorder—Updated Systematic Review and Meta-Analysis by Kelley M. Swanberg, Leonardo Campos, Chadi G. Abdallah and Christoph Juchem in Chronic Stress</p

B(0)shimming for in vivo magnetic resonance spectroscopy: Experts' consensus recommendations

Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) allow the chemical analysis of physiological processes in vivo and provide powerful tools in the life sciences and for clinical diagnostics. Excellent homogeneity of the static B(0)magnetic field over the object of interest is essential for achieving high-quality spectral results and quantitative metabolic measurements. The experimental minimization of B(0)variation is performed in a process called B(0)shimming. In this article, we summarize the concepts of B(0)field shimming using spherical harmonic shimming techniques, specific strategies for B(0)homogenization and crucial factors to consider for implementation and use in both brain and body. In addition, experts' recommendations are provided for minimum requirements for B(0)shim hardware and evaluation criteria for the primary outcome of adequate B(0)shimming for MRS and MRSI, such as the water spectroscopic linewidth