Beyond blood brain barrier breakdown – in vivo detection of occult neuroinflammatory foci by magnetic nanoparticles in high field MRI

BACKGROUND: Gadopentate dimeglumine (Gd-DTPA) enhanced magnetic resonance imaging (MRI) is widely applied for the visualization of blood brain barrier (BBB) breakdown in multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). Recently, the potential of magnetic nanoparticles to detect macrophage infiltration by MRI was demonstrated. We here investigated a new class of very small superparamagnetic iron oxide particles (VSOP) as novel contrast medium in murine adoptive-transfer EAE. METHODS: EAE was induced in 17 mice via transfer of proteolipid protein specific T cells. MR images were obtained before and after application of Gd-DTPA and VSOP on a 7 Tesla rodent MR scanner. The enhancement pattern of the two contrast agents was compared, and correlated to histology, including Prussian Blue staining for VSOP detection and immunofluorescent staining against IBA-1 to identify macrophages/microglia. RESULTS: Both contrast media depicted BBB breakdown in 42 lesions, although differing in plaques appearances and shapes. Furthermore, 13 lesions could be exclusively visualized by VSOP. In the subsequent histological analysis, VSOP was localized to microglia/macrophages, and also diffusely dispersed within the extracellular matrix. CONCLUSION: VSOP showed a higher sensitivity in detecting BBB alterations compared to Gd-DTPA enhanced MRI, providing complementary information of macrophage/microglia activity in inflammatory plaques that has not been visualized by conventional means

32‐Channel self‐grounded bow‐tie transceiver array for cardiac MR at 7.0T

Purpose Design, implementation, evaluation, and application of a 32‐channel Self‐Grounded Bow‐Tie (SGBT) transceiver array for cardiac MR (CMR) at 7.0T. Methods The array consists of 32 compact SGBT building blocks. Transmission field (B1+) shimming and radiofrequency safety assessment were performed with numerical simulations and benchmarked against phantom experiments. In vivo B1+ efficiency mapping was conducted with actual flip angle imaging. The array’s applicability for accelerated high spatial resolution 2D FLASH CINE imaging of the heart was examined in a volunteer study (n = 7). Results B1+ shimming provided a uniform field distribution suitable for female and male subjects. Phantom studies demonstrated an excellent agreement between simulated and measured B1+ efficiency maps (7% mean difference). The SGBT array afforded a spatial resolution of (0.8 × 0.8 × 2.5) mm3 for 2D CINE FLASH which is by a factor of 12 superior to standardized cardiovascular MR (CMR) protocols. The density of the SGBT array supports 1D acceleration of up to R = 4 (mean signal‐to‐noise ratio (whole heart) ≥ 16.7, mean contrast‐to‐noise ratio ≥ 13.5) without impairing image quality significantly. Conclusion The compact SGBT building block facilitates a modular high‐density array that supports accelerated and high spatial resolution CMR at 7.0T. The array provides a technological basis for future clinical assessment of parallel transmission techniques.EC/H2020/743077/EU/Thermal Magnetic Resonance: A New Instrument to Define the Role of Temperature in Biological Systems and Disease for Diagnosis and Therapy/ThermalMRBMBF, 01QE1815, Verbundprojekt: Seeing is Believing: Revolution der bildgebenden Diagnostik und Therapiekontrolle des Körperstammes durch superaufgelöste Hochfeld-Magnetresonanztomographie; Teilprojekt: Industrielle Forschung und Entwicklung lokaler Radiofrequenz-Antennen für hochauflösende Hochfeld-MRT des Körperstamme

Oral High-Dose Atorvastatin Treatment in Relapsing-Remitting Multiple Sclerosis

BACKGROUND:Recent data from animal models of multiple sclerosis (MS) and from a pilot study indicated a possible beneficial impact of statins on MS. METHODOLOGY/PRINCIPAL FINDINGS:Safety, tolerability and effects on disease activity of atorvastatin given alone or in combination with interferon-beta (IFN-beta) were assessed in a phase II open-label baseline-to-treatment trial in relapsing-remitting MS (RRMS). Patients with at least one gadolinium-enhancing lesion (CEL) at screening by magnetic resonance imaging (MRI) were eligible for the study. After a baseline period of 3 monthly MRI scans (months -2 to 0), patients followed a 9-month treatment period on 80 mg atorvastatin daily. The number of CEL in treatment months 6 to 9 compared to baseline served as the primary endpoint. Other MRI-based parameters as well as changes in clinical scores and immune responses served as secondary endpoints. Of 80 RRMS patients screened, 41 were included, among them 16 with IFN-beta comedication. The high dose of 80 mg atorvastatin was well tolerated in the majority of patients, regardless of IFN-beta comedication. Atorvastatin treatment led to a substantial reduction in the number and volume of CEL in two-sided multivariate analysis (p = 0.003 and p = 0.008). A trend towards a significant decrease in number and volume of CEL was also detected in patients with IFN-beta comedication (p = 0.060 and p = 0.062), in contrast to patients without IFN-beta comedication (p = 0.170 and p = 0.140). Immunological investigations showed no suppression in T cell response but a significant increase in IL-10 production. CONCLUSIONS/SIGNIFICANCE:Our data suggest that high-dose atorvastatin treatment in RRMS is safe and well tolerated. Moreover, MRI analysis indicates a possible beneficial effect of atorvastatin, alone or in combination with IFN-beta, on the development of new CEL. Thus, our findings provide a rationale for phase II/III trials, including combination of atorvastatin with already approved immunomodulatory therapy regimens. TRIAL REGISTRATION:ClinicalTrials.gov NCT00616187

Wideband Self‐Grounded Bow‐Tie Antenna for Thermal MR

The objective of this study was the design, implementation, evaluation and application of a compact wideband self‐grounded bow‐tie (SGBT) radiofrequency (RF) antenna building block that supports anatomical proton (1H) MRI, fluorine (19F) MRI, MR thermometry and broadband thermal intervention integrated in a whole‐body 7.0 T system. Design considerations and optimizations were conducted with numerical electromagnetic field (EMF) simulations to facilitate a broadband thermal intervention frequency of the RF antenna building block. RF transmission (B1+) field efficiency and specific absorption rate (SAR) were obtained in a phantom, and the thigh of human voxel models (Ella, Duke) for 1H and 19F MRI at 7.0 T. B1+ efficiency simulations were validated with actual flip‐angle imaging measurements. The feasibility of thermal intervention was examined by temperature simulations (f = 300, 400 and 500 MHz) in a phantom. The RF heating intervention (Pin = 100 W, t = 120 seconds) was validated experimentally using the proton resonance shift method and fiberoptic probes for temperature monitoring. The applicability of the SGBT RF antenna building block for in vivo 1H and 19F MRI was demonstrated for the thigh and forearm of a healthy volunteer. The SGBT RF antenna building block facilitated 19F and 1H MRI at 7.0 T as well as broadband thermal intervention (234‐561 MHz). For the thigh of the human voxel models, a B1+ efficiency ≥11.8 μT/√kW was achieved at a depth of 50 mm. Temperature simulations and heating experiments in a phantom demonstrated a temperature increase ΔT >7 K at a depth of 10 mm. The compact SGBT antenna building block provides technology for the design of integrated high‐density RF applicators and for the study of the role of temperature in (patho‐) physiological processes by adding a thermal intervention dimension to an MRI device (Thermal MR).BMBF, 13GW0102A, KMU-Innovativ - Verbundprojekt: Forschung für Tumortherapie mit lokalisierter Hochfrequenz-Hyperthermie: Diagnostik, Therapiesteuerung und -kontrolle mit ultrahochfeld MRT (3-IN-1:THERAHEAT) - Teilvorhaben: Erforschung von Hochfrequenzantennen für Tumortherapie mittels kontrollierter Hochfrequenz-HyperthermieEC/H2020/EU/743077/Thermal Magnetic Resonance: A New Instrument to Define the Role of Temperature in Biological Systems and Disease for Diagnosis and Therapy/ThermalM

Perfluorocarbon Particle Size Influences Magnetic Resonance Signal and Immunological Properties of Dendritic Cells

The development of cellular tracking by fluorine (19F) magnetic resonance imaging (MRI) has introduced a number of advantages for following immune cell therapies in vivo. These include improved signal selectivity and a possibility to correlate cells labeled with fluorine-rich particles with conventional anatomic proton (1H) imaging. While the optimization of the cellular labeling method is clearly important, the impact of labeling on cellular dynamics should be kept in mind. We show by 19F MR spectroscopy (MRS) that the efficiency in labeling cells of the murine immune system (dendritic cells) by perfluoro-15-crown-5-ether (PFCE) particles increases with increasing particle size (560>365>245>130 nm). Dendritic cells (DC) are professional antigen presenting cells and with respect to impact of PFCE particles on DC function, we observed that markers of maturation for these cells (CD80, CD86) were also significantly elevated following labeling with larger PFCE particles (560 nm). When labeled with these larger particles that also gave an optimal signal in MRS, DC presented whole antigen more robustly to CD8+ T cells than control cells. Our data suggest that increasing particle size is one important feature for optimizing cell labeling by PFCE particles, but may also present possible pitfalls such as alteration of the immunological status of these cells. Therefore depending on the clinical scenario in which the 19F-labeled cellular vaccines will be applied (cancer, autoimmune disease, transplantation), it will be interesting to monitor the fate of these cells in vivo in the relevant preclinical mouse models

Identification of Cellular Infiltrates during Early Stages of Brain Inflammation with Magnetic Resonance Microscopy

A comprehensive view of brain inflammation during the pathogenesis of autoimmune encephalomyelitis can be achieved with the aid of high resolution non-invasive imaging techniques such as microscopic magnetic resonance imaging (μMRI). In this study we demonstrate the benefits of cryogenically-cooled RF coils to produce μMRI in vivo, with sufficient detail to reveal brain pathology in the experimental autoimmune encephalomyelitis (EAE) model. We could visualize inflammatory infiltrates in detail within various regions of the brain, already at an early phase of EAE. Importantly, this pathology could be seen clearly even without the use of contrast agents, and showed excellent correspondence with conventional histology. The cryogenically-cooled coil enabled the acquisition of high resolution images within short scan times: an important practical consideration in conducting animal experiments. The detail of the cellular infiltrates visualized by in vivo μMRI allows the opportunity to follow neuroinflammatory processes even during the early stages of disease progression. Thus μMRI will not only complement conventional histological examination but will also enable longitudinal studies on the kinetics and dynamics of immune cell infiltration

Metabolic Changes in the Visual Cortex Are Linked to Retinal Nerve Fiber Layer Thinning in Multiple Sclerosis

OBJECTIVE: To investigate the damage to the retinal nerve fiber layer as part of the anterior visual pathway as well as an impairment of the neuronal and axonal integrity in the visual cortex as part of the posterior visual pathway with complementary neuroimaging techniques, and to correlate our results to patients' clinical symptoms concerning the visual pathway. DESIGN, SUBJECTS AND METHODS: Survey of 86 patients with relapsing-remitting multiple sclerosis that were subjected to retinal nerve fiber layer thickness (RNFLT) measurement by optical coherence tomography, to a routine MRI scan including the calculation of the brain parenchymal fraction (BPF), and to magnetic resonance spectroscopy at 3 tesla, quantifying N-acetyl aspartate (NAA) concentrations in the visual cortex and normal-appearing white matter. RESULTS: RNFLT correlated significantly with BPF and visual cortex NAA, but not with normal-appearing white matter NAA. This was connected with the patients' history of a previous optic neuritis. In a combined model, both BPF and visual cortex NAA were independently associated with RNFLT. CONCLUSIONS: Our data suggest the existence of functional pathway-specific damage patterns exceeding global neurodegeneration. They suggest a strong interrelationship between damage to the anterior and the posterior visual pathway

Construction and Test of a new Ion-Guide-System for Ion-Molecule-Reactions

Titelblatt und Inhaltsverzeichnis 1 1\. Einleitung 5 2\. Theoretischer Teil 11 3\. Experimenteller Aufbau 43 4\. Ergebnisse und Diskussion 87 5\. Zusammenfassung 121 6\. Summary 125 7\. Ausblick 129 8\. Literaturverzeichnis 131 9\. Curriculum Vitae 147 10\. Anhang 153Im Rahmen dieser Arbeit wurde eine neue Apparatur zur Untersuchung von Ionen- Molekül-Reaktionen geplant und aufgebaut. Der Focus lag dabei auf der Analyse von Reaktionsgeschwindigkeitskonstanten bei unterschiedlichen und möglichst geringen c.m.-Stoßenergien. Um dieses zu ermöglichen, wurde ein "ion-guide" mit einem Quadrupol-Massenspektrometer kombiniert. Der "ion-guide" besteht dabei aus einem Drahtvierpol und wird im sogenannten "rf-only"-Betrieb, d.h. ohne Massendiskriminierung eingesetzt (Kapitel 3.2). Das Kernstück, der rf- Generator (Kapitel 3.3), wurde dabei nach einem effizienten Prinzip mittels zweier Röhren aufgebaut und Frequenz und Amplitude an das Experiment angepasst. Röhren haben gegenüber entsprechenden Halbleitern wesentliche Vorteile. Zum einen sind sie leistungsstärker und sehr kurzschlussfest und zum anderen kostengünstiger. Außerdem lässt sich der Aufbau mit wesentlich weniger Bauteilen realisieren, was den Tuningprozess und eine eventuelle Fehlersuche erheblich vereinfacht. Die Analyse der effektiven c.m.-Stoßenergie stellte sich als komplizierter heraus als zu Anfang angenommen. Multiple Effekte können Einfluss auf die c.m.-Stoßenergie haben. Nebst der eigentlichen Beschleunigungsenergie der Ionen muss man den Radialanteil durch das rf-Feld des ion-guides und die Dopplerverbreiterung durch die Maxwellsche Geschwindigkeitsverteilung der Target-Moleküle berücksichtigen (Kapitel 4.3.2). Der Radialanteil hängt dabei sehr stark von dem Entstehungspunkt der Ionen ab (Abb. 4 8) und muss bei einer Änderung am Experiment neu bestimmt werden. Da eine Messung des Radialanteils nicht möglich ist, muss man sich dabei auf Berechnungen mit SIMION 3D verlassen (Abb. 4 10). Die Dopplerverbreiterung tritt immer dann auf, wenn die Target-Moleküle eine Maxwellsche Geschwindigkeitsverteilung aufweisen, welche von der Temperatur abhängt. Beide Effekte, die Dopplerverbreiterung und der Radialanteil, fließen in die Fehlerberechnung für die c.m.-Stoßenergie ein (Kapitel 4.3.2). Der zweite Teil der vorliegenden Arbeit befasst sich mit der Untersuchung von vier Ionen-Molekül-Reaktionen. Mit Hilfe dieser Reaktionen konnte (i) die Funktionstüchtigkeit der Apparatur überprüft werden und (ii) erste k-Wert- Messungen bei c.m.-Stoßenergien (< 1 eV) durchgeführt werden. Die erste untersuchte Reaktion, HBr+ + HBr à H2Br+ + Br·, diente zur Überprüfung des Aufbaues und zur Ermittlung eines möglichst genauen k-Wertes bei einer definierten c.m.-Stoßenergie. Die Ergebnisse sind in Tab. 5 1 zusammengefasst. Der in dieser Arbeit ermittelte k-Wert stimmt gut mit den Theoriewerten und mit einem von Zare & Mitarbeiter gemessenen k-Wert überein. Zusätzlich konnte der Fehler um etwa 10% reduziert werden (Kapitel 4.1). Die zweite untersuchte Reaktion, HBr+ + CO à HCO+ + Br·, konnte ebenfalls beobachtet werden. Leider mussten an dieser Stelle die Untersuchungen am HBr-System abgebrochen werden, da das HBr die Lager der Turbomolekularpumpen korrodiert hatte, so dass die Pumpen ausfielen. Aus diesem Grund wurde das weniger aggressives Ammoniak gewählt. Mit Hilfe der dritten Reaktion, NH3+ + NH3 à NH4+ + NH2, wurden erstmals k-Werte bei c.m.-Stoßenergien von 0.06 bis 3.5 eV untersucht. Die Ergebnisse sind in Abb. 5 1 zusammengefasst (vgl. Abb. 4 14). Der exponentielle Fit der experimentell ermittelten k-Werte passt sehr gut zu den theoretischen Berechnungen nach Langevin (Gl. 4 4) und �Locked Dipole� (Gl. 4 5). Einzig bei c.m.-Stoßenergien kleiner 0.5 eV kommt es zu einer stärkeren Streuung der k-Werte. Mit Hilfe der Molekularstrahltechnik und noch besser stabilisierten Netzteilen für Polebias, Beschleunigungslinsen und rf- Amplitude, um die kinetische Energie der Ionen noch genauer kontrollieren zu können, soll in künftigen Untersuchungen versucht werden dieses Problem zu lösen. Die vierte Reaktion, NH3+ + H2CO à CH2NH+ + H2O, konnte nicht beobachtet werden, trotzdem die Wärmetönung der Reaktion mit �0.21 eV exotherm ist. Wie Rechnungen von Walch[108] ergaben, besitzt sie eine nicht vernachlässigbare zweite Reaktionsbarriere von etwa 35kcal/mol = 1.513 eV. Dies legt die Vermutung nahe, dass unter den geplanten Reaktionsbedingungen der vorliegenden Arbeit CH2NH in zu geringem Anteil gebildet wird, um es zu nachweisen zu können.In this work a new machine for the examination of ion-molecule-reactions was planned and built. The focus was the analysis of reaction constants and correspondingly cross sections at low c.m.-energies. To achieve this goal it was necessary to connect an ion-guide with a quadrupole mass spectrometer, where the ion-guide was operated in energy-conserving (adiabatic) mode. The four poles of the ion-guide, a quadrupole itself, were constructed with 15 wires each, arranged in a hyperbolic form (Chapter 3.2). The core piece of the ion-guide is the rf-generator (Chapter 3.3). It was constructed by an efficient design using two radio tubes. Frequency and amplitude were adjusted according to the needs of the experiment. Compared to semiconductors, tubes have some major advantages. On one hand they are more powerful and short- circuit-proof and on the other hand they are much cheaper. Furthermore, a rf- generator with radio tubes can be built with much less components than one with semiconductors; this considerably simplifies the tuning process and troubleshooting. The analysis of the effective c.m.-energy was more difficult than originally assumed. Multiple effects can influence the c.m.-energy: besides the acceleration energy of the ions, there is (i) the radial energy by the rf-field and (ii) the Doppler broadening because of the Maxwellian velocity distribution of the target molecules (Chapter 4.3.2). The amount of radial energy considerably depends on the point of ionisation (Fig. 4 8) and has to be redetermined with each change in the experimental setup. Since a direct measurement of the radial energy is not possible one has to rely on calculations with SIMION 3D (Fig. 4 10). The Doppler broadening always occurs when the target molecules have a Maxwellian velocity distribution. Both the Doppler broadening effect, as well as the radial energy influence have been incorporated in the calculation of errors for the c.m.-energy (Chapter 4.3.2). The second part of the present study involves the investigation of four ion- molecule reactions. With the help of these reactions (i) the functional efficiency of the machine could be proofed and (ii) initial measurements of k-values at low c.m.-energies (< 1 eV) were made. The first reaction, HBr+ + HBr à H2Br+ + Br·, was used to determine an accurate k-value at a defined c.m.-energy, and ultimately to verify the functional efficiency of the assembly. The results of this experiment are summarised in Tab. 6 1. The k-value calculated from this work is in agreement with the theory and k-value given by Zare and co-workers. In addition the error margin could be reduced by approximately 10% (Chapter 4.1). The second reaction, HBr+ + CO à HCO+ + Br·, could be also investigated. However, both this and the first reaction had to be discontinued since HBr corroded the turbo molecular pumps, which subsequently resulted in their breakdown. For this reason the less corrosive system with ammonia was selected. The third reaction, NH3+ + NH3 à NH4+ + NH2, was utilised to measure the first k-values at c.m.-energies from 0.06 eV to 3.5 eV. The results are summarised in Abb. 6 1 (comp. Fig. 4 14). The exponential fit of the experimental data correlates well with Langevin (Eq. 4 4) and Locked Dipole (Eq. 4 5) theoretical calculations. At c.m.-energies lower than 0.5 eV, a greater spreading of the k-values was observed. To overcome this problem in future investigations, the c.m.-energy control should be improved by using the molecular beam technique and better-stabilized power supplies for polebias, acceleration lenses and rf-amplitude. The fourth reaction, NH3+ + H2CO à CH2NH+ + H2O, was not observed, even though the reaction is exothermic at -0.21 eV. According to calculations from Walch[108], this reaction has a non-negligible second reaction barrier of approximately 35kcal/mol = 1.513 eV. This implies that the reaction conditions originally planned were not suitable to form CH2NH+ in quantities large enough to detect

Open Source 3D Multipurpose Measurement System with Submillimetre Fidelity and First Application in Magnetic Resonance

Abstract Magnetic resonance imaging (MRI) is the mainstay of diagnostic imaging, a versatile instrument for clinical science and the subject of intense research interest. Advancing clinical science, research and technology of MRI requires high fidelity measurements in quantity, location and time of the given physical property. To meet this goal a broad spectrum of commercial measurement systems has been made available. These instruments frequently share in common that they are costly and typically employ closed proprietary hardware and software. This shortcoming makes any adjustment for a specified application difficult if not prohibitive. Recognizing this limitation this work presents COSI Measure, an automated open source measurement system that provides submillimetre resolution, robust configuration and a large working volume to support a versatile range of applications. The submillimetre fidelity and reproducibility/backlash performance were evaluated experimentally. Magnetic field mapping of a single ring Halbach magnet, a 3.0 T and a 7.0 T MR scanner as well as temperature mapping of a radio frequency coil were successfully conducted. Due to its open source nature and versatile construction, the system can be easily modified for other applications. In a resource limited research setting, COSI Measure makes efficient use of laboratory space, financial resources and collaborative efforts