Search

Einleitung: Primärteile prothetisch oder epithetisch genutzter Magnetattachments werden auf Pfeilerzähnen und Implantaten befestigt. Bei MR-Untersuchungen sind zwei Wechselwirkungen zu erwarten: Beeinträchtigung der Bildgebung durch Artefakte und Veränderung der Flussdichte durch das Hauptfeld (B0) des MRT. Ziele dieser In-vitro-Untersuchung sind: - Die Bestimmung der Maximalausdehnung der bei 1,5 und 3 T und drei typischen MR-Sequenzen auftretenden Suszeptibilitätsartefakte. - Die Messung der Entmagnetisierung der im MRT exponierten Magnete bei unterschiedlichen Positionen zu B0. Methodik: Der maximale Radius der um drei verschiedene Minimagnet-Typen und zwei ferromagnetische Gegenanker auftretenden Signalauslöschungszonen wurde am SNR-Phantom bei den drei MR-Sequenzen SE-T1, SE-T2 und GE-T2* gemessen. In einer ersten Entmagnetisierungsstudie wurden 30 SmCo- und 60 NdFeB-Magnete und in einer Folgestudie 40 SmCo-Magnete mit erhöhter Koerzitivkraft dem Hauptfeld eines 1,5- und eines 3 T-MRT in verschiedenen Positionen im Gerätetunnel und am Geräteportal ausgesetzt. Als Äquivalent für die Haftkraft wurde die Flussdichte mit einem Teslameter gemessen. Ergebnisse: Die Auslöschungszonen zeigten keine klinisch relevanten Unterschiede bei den verschiedenen Prüfkörpern und den beiden MRT-Hauptfeldstärken. Deutliche Unterschiede traten jedoch in Abhängigkeit von den genutzten MR-Sequenzen auf: Bei den Spinecho-Sequenzen fanden sich zwar insgesamt viel kleinere, aber deutlich unsymmetrische Signallöschungszonen, deren maximaler Radius bis zu 7,4 cm betrug. Die Signallöschungen bei Gradientenecho-Sequenzen zeigten eine mehr symmetrische und großflächige Formation mit einem Maximalradius bis zu 9,7 cm. Für das Ausmaß der Demagnetisierung sind die Ausrichtung der Minimagnete im MRT-Hauptfeld (B0) und dessen Stärke entscheidend. Bei 1,5 T wurde die Flussdichte von NdFeB- und SmCo-Magneten bei Antiparallelität zu B0 deutlich reduziert, bei 3T wurden beide Magnettypen in antiparalleler Lage umgepolt. SmCo-Magnete mit erhöhter Koerzitivkraft widerstanden dem 1,5 T-Feld, wurden bei 3 T jedoch fast vollständig entmagnetisiert. Die ursprünglichen Flussdichtewerte konnten durch Remagnetisierung verlustfrei wiederhergestellt werden. Schlussfolgerung: Vor einer MRT-Untersuchung mit den hier untersuchten Sequenzen und intraoral festsitzenden ferromagnetischen Gegenankern muss geprüft werden, ob die zu untersuchenden Strukturen weit genug von der entstehenden Signallöschungszone entfernt sind. Bei intraoral oder epicranial verankerten Magnetattachments besteht bei MRT- Exposition die Gefahr einer leichten bis kompletten Demagnetisierung mit dementsprechend insuffizient werdendem Prothesenhalt. Durch Inklination oder Reklination des Patientenkopfes ist dieses Problem nicht zu umgehen. SmCo-Magnete mit erhöhter Koerzitivkraft können dagegen bei 1,5 T gefahrlos in situ verbleiben. Bei 3 T sollten alle Dentalmagnete, falls instrumentell-technisch möglich, vor MRT entfernt werden. Bei den ggf. nach MRT demagnetisierten Produkten ist eine Remagnetisierung durch den Hersteller/Vertreiber möglich., Introduction: The primary coping of prosthetic or epithetic magnetic attachments is fixed on abutment-teeth and implants. In MR-examinations two interactions are expected: Impairment of imaging due to artifacts and alteration of flux density due to the main MR-field. Objectives of this in-vitro-study are: - Determine the maximum size of susceptibility-artifacts occurring at 1.5 and 3T and three common sequences. - To measure the demagnetization of the magnets in the MRI in different positions with respect to the main field. Methods: The maximum radius of the signal loss regions around three mini magnet types and two ferromagnetic keepers was measured on the SNR phantom in the three MR sequences SE-T1, SE-T2 and GE-T2*. In an initial demagnetization study, 30 SmCo and 60 NdFeB magnets and in a follow-up study 40 SmCo magnets with increased coercivity were exposed to the main field of a 1.5 and a 3T-MRI in different positions. Flux density was measured with a teslameter. Results: The signal loss regions showed no clinically relevant differences for the various specimens and the two MRI main-field-strengths. However, significant differences occurred depending on the MR sequence used: In spin-echo-sequences, signal loss regions were much smaller but very asymmetric, with a maximum radius of up to 7.4 cm. In gradient echo sequences, signal loss regions were more symmetric and extensive, with a maximum radius of up to 9.7 cm. The extent of demagnetization depends on the orientation of the mini magnets in the MRI field and its strength. At 1.5T, flux density of antiparallel NdFeB and SmCo magnets is significantly reduced, at 3T, polarity is reversed in both magnet types. SmCo magnets with increased coercivity resisted the 1.5T field, but were almost completely demagnetized at 3T. Remagnetisation fully restored the original flux density. Conclusion: Prior to an MRI using the studied sequences on patients with fixed ferromagnetic keepers, it must be checked whether enough distance is between the structures to be examined and the resulting signal loss region. During MRI exposure, intraoral or epicranial magnetic attachments risk being demagnetised, resulting in insufficient prosthesis retention. Inclining or reclining the patient’s head does not prevent the problem. However, SmCo magnets with increased coercivity can remain in situ at 1.5T without risk. At 3T, all dental magnets should be removed before MRI, if technically possible. Manufacturers/distributors can remagnetise products demagnetised during MRI.

One of the main goals of language learners is to master all four skills of listening, speaking, reading and writing when it comes to their acquisition of the target language. However, during the process of learning English, learners inevitably face a variety of challenges related to their writing including grammatical errors, word choice, organization, idea development, and most importantly their difficulties in using collocations (Duong & Nguyen, 2021). Therefore, this study has been conducted to investigate the students’ use of English collocations in their academic essays associated with their difficulties so that appropriate pedagogical approaches and practices would be taken into consideration in order to help students improve their English collocational competences in academic writing. This descriptive study was carried out with 103 English-majored students of the High-quality program of the School of Foreign Languages at Can Tho University, Vietnam. A 5-point Likert scale survey with 18 questionnaire items was employed to examine the frequency of students' exposure to as well as their usage of English collocations, and their difficulties in using English collocations. The results of this study have shown that the most commonly used collocations in the students’ academic essays were ‘verb + noun’, and ‘adjective + noun’ lexical collocations. Additionally, the research outcomes have revealed that the types of English collocations that the students were more likely to make the most mistakes belonged to ‘verb + adverb’, and ‘adjective + noun’ lexical collocations. Article visualizations

This study was designed to evaluate the effects of astaxanthin in broodfish diets on reproductive performance, egg quality and larvae quality parameters of clownfish (Amphirion ocellaris). Five treatments were tested with 5 levels of astaxanthin (Carophyll Pink 10% CWS) of 0, 50, 100, 150 and 200 mg/kg added to the feed. Each treatment was repeated in triplicate and the supplemental feeding trials were arranged for 13 months. The results showed that there were significant differences in hatching rate of egg, malformed rate and survival rate of larvae in 3 days post-hatch (p

The golden trevally fishes (Gnathanodon specious) (2.19 ± 0.23 g) were cultured in glass tanks with density of 20 fishes/tank and they were fed supplemental diets of different MOS concentrations (0; 0.2; 0.4 and 0.6%) for 90 days. Collected data included growth rate, survival rate and some hematological characteristics of this fish. The results demonstrated that MOS supplementation did not affect growth performance, erythrocyte density and blood cell size, however the survival rate was significantly increased. On the other hand, the total number of white blood cells (BC) on the 60th day in the fish fed with MOS supplements (5.78–6.96 × 104TB/mm3) was higher than that in the control group (only 5.43 × 104TB/mm3) with the largest total leukocytes (6.96 ± 0.50 × 104TB /mm3) at 0.2% MOS (p < 0.05).

Additional file 1: Table S1. Coxiella burnetii sequences detected from tick samples. Figure S1. Comparison of Coxiella burnetii-specific primers to genome of Rickettsiella species. The comparison was performed by aligning the forward and reverse primers of C. burnetii to the genome of R. viridis (A), R. grylli (B), and R. isopodorum (C). Numbers indicate the positions on Rickettsiella genomes that had the highest similarity to the primer sequences. The distance between the forward and reverse primer positions are indicates as base pairs.