Effects by Paramagnetic and Diamagnetic Materials in a 1.5-Tesla Highfield Magnetic Resonance Imaging System (MRI)

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Dieser Artikel zeigt die Ergebnisse einer experimentellen Untersuchung des Störeinflusses von paramagnetischen und diamagnetischen Materialien auf die Bildgebung in einem geschlossenen 1,5-Tesla-Hochfeld-Magnetresonanztomographen(MRT). Mit drei verschiedenen Sequenztypen (SE, GE, EPI) wurden unterschiedlich große metallische und nichtmetallische Werkstückprofile hinsichtlich der entstehenden Artefakte untersucht. Zur Darstellung der Artefakte wurde ein mit Gd-Mn-Lösung gefüllter Kunststoffbehälter (Phantom) verwendet, zu dem die zu untersuchenden Materialien während der Versuchsdurchführung in definierten Abständen parallel verschoben wurden. Die Auswertung der Schnittbilder erfolgte in transversaler und sagittaler Untersuchungsebene und ergab, daß Aluminium- und Kunststoffprofile auch bei sehr geringem Abstand zum Phantom die kleinsten Bildstörungen verursachten. Besonders starke Artefakte wurden bei den untersuchten Stahl- und Kupferprofilen festgestellt. Bei einem Vergleich der angewendeten Sequenztypen konnte nachgewiesen werden, daß besonders die SE-Sequenz, trotz der teilweise stark variierenden Materialprofile, eine geringere Artefaktanfälligkeit und somit eine höhere Stabilität in der Bildgebung im Gegensatz zur GE- und EPI-Sequenz aufwies. Diese Untersuchungen wurden im Anschluß an eine intensive Literaturstudie (Internet, Medline, Meditec) durchgeführt. Relevante Publikationsquellen gibt es bisher nur sehr wenige.This article shows the results of an experimental investigation of the interference by paramagnetic and diamagnetic materials on imaging in a closed 1.5 Tesla high field magnetic resonance imaging System(MRI). For different types of sequences (SE, GE, EPI) the effects of metal and non-metal profiles in producing artefacts were investigated. A phantom (plastictrunk) filled with Gd-Mn-solution was used for representation of the artefacts. The materials analysed were placed parallel to the phantom at predetermined distances. The images were obtained in transverse and sagittal planes and analysed with respect to the resulting artefacts.The results show that aluminium and polymer profiles produce the weakest artefacts, even when the material is positioned close to the phantom. A comparison of the sequence types shows that the SE-sequence has a low sensitivity to artefacts, despite the great profile variation in size and shape. The SE-sequence accordingly showed a higher imaging stability scompared with the GE- and EPI-sequences. Steel and copper produced the strongest artefacts. The examination was begun after an intensive study of the literature(Internet, Medline, Meditec). So far have been few publications on this subject

Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.

Peer reviewe

Charakteristik einer neu entwickelten Mammadoppelspule für die NMR Spektroskopie (1H31P) und Bildgebung

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Erstmalig wird eine Mammadoppelspule beschrieben, die für die H1-Bildgebung sowie für die H1-und 31P-Spektroskopie verwendbar ist. Diese Arbeit beschreibt die grundlegenden technischen Merkmale der Spule, das Spulendesign, das B1-Feld mit Anregung, die Feldverteilung für 1H- und 31P, die Sensitivität und die Durchführbarkeit der 31P-Spektroskopie in vivo. Der wesentliche Vorteil der für zwei Frequenzen abstimmbaren Mammadoppelspule liegt in der 1H-Bildgebung zur Tumorlokalisation und der Möglichkeit der 31P-Spektroskopie zur Kontrolle der Tumoransprechrate bei Patientinnen unter Chemotherapie. Diese Untersuchungen können ohne Umlagerung der Patientin durchgeführt werden.For the first time a double turn breast coil has been described which can be used for 1H imaging, 1H spectroscopy and 31P spectroscopy. The paper describes basic technical features of the coil, coil design, Bl field/excitation field distribution for 1H and 31P, sensitivity, and feasibility for 31P Spectroscopic in vivo studies. The main advantage of the double frequency tuneable coil is that 1H imaging for tumor localization and 31P spectroscopy for response control can be done without an additional repositioning of the patient

International investigation of breast MRI: results of a multicentre study (11 sites) concerning diagnostic parameters for contrast-enhanced MRI based on 519 histopathologically correlated lesions.

A multicentre study was undertaken to provide fundamentals for improved standardization and optimized interpretation guidelines of dynamic contrast-enhanced MRI. Only patients scheduled for biopsy of a clinical or imaging abnormality were included. They underwent standardized dynamic MRI on Siemens 1.0 (163 valid lesions > or = 5 mm) or 1.5 T (395 valid lesions > or = 5 mm) using 3D fast low-angle shot (FLASH; 87 s) before and five times after standardized bolus of 0.2 mmol Gd-DTPA/kg. One-Tesla and 1.5 T data were analysed separately using a discriminant analysis. Only histologically correlated lesions entered the statistical evaluation. Histopathology and imaging were correlated in retrospect and in open. The best results were achieved by combining up to five wash-in or wash-out parameters. Different weighting of false-negative vs false-positive calls allowed formulation of a statistically based interpretation scheme yielding optimized rules for the highest possible sensitivity (specificity 30%), for moderate (50%) or high (64-71%) specificity. The sensitivities obtained at the above specificity levels were better at 1.0 T (98, 97, or 96%) than at 1.5 T (96, 93, 86%). Using a widely available standardized MR technique definition of statistically founded interpretation rules is possible. Choice of an optimum interpretation rule may vary with the clinical question. Prospective testing remains necessary. Differences of 1.0 and 1.5 T are not statistically significant but may be due to pulse sequences

Blimp1 Prevents Methylation of Foxp3 and Loss of Regulatory T Cell Identity at Sites of Inflammation

Summary: Foxp3+ regulatory T (Treg) cells restrict immune pathology in inflamed tissues; however, an inflammatory environment presents a threat to Treg cell identity and function. Here, we establish a transcriptional signature of central nervous system (CNS) Treg cells that accumulate during experimental autoimmune encephalitis (EAE) and identify a pathway that maintains Treg cell function and identity during severe inflammation. This pathway is dependent on the transcriptional regulator Blimp1, which prevents downregulation of Foxp3 expression and “toxic” gain-of-function of Treg cells in the inflamed CNS. Blimp1 negatively regulates IL-6- and STAT3-dependent Dnmt3a expression and function restraining methylation of Treg cell-specific conserved non-coding sequence 2 (CNS2) in the Foxp3 locus. Consequently, CNS2 is heavily methylated when Blimp1 is ablated, leading to a loss of Foxp3 expression and severe disease. These findings identify a Blimp1-dependent pathway that preserves Treg cell stability in inflamed non-lymphoid tissues. : An inflammatory environment threatens the stability of Foxp3+ Treg cells. Garg et al. show that by expressing the transcriptional regulator Blimp1, Treg cells resist the IL-6-driven loss of Foxp3 in inflamed tissues. Blimp1 prevents the methylation and reduced expression of Foxp3 through inhibition of the methyltransferase Dnmt3a. Keywords: regulatory T cells, Blimp1, CNS2, epigenetic regulation, CNS, inflammation, DNA methyltransferases, Foxp3, Interleukin-