Zusammenfassung
Lärm stellt in den entwickelten Industrieländern ein großes sozioökonomisches Problem dar. Für die Behandlung der durch die Lärmschwerhörigkeit auftretenden audiologischen Phänomene ...ist ein vertieftes Verständnis der zugrunde liegenden Schädigungsmechanismen peripherer und zentraler Anteile der Hörbahn notwendig. Die mechanische Schädigung, die Ischämie, die Exzitotoxizität sowie die auditorische Synaptopathie stellen die wesentlichen lärminduzierten Schädigungsprozesse in der Cochlea dar. Neben cochleären pathologischen Veränderungen treten jedoch auch zentralnervöse Schädigungen infolge der Lärmexposition auf. Aufgrund der Überstimulation kommt es sehr frühzeitig zum Zellverlust im Versorgungsgebiet des N. cochlearis. Der spätere Zellverlust in höheren auditorischen Kerngebieten ist im Gegensatz dazu auf die sensorische Deprivation zurückzuführen. Insgesamt wird dem strukturellen Verlust durch eine Modulation der Spontanaktivität im Sinne der Netzwerkhomöostase entgegenreguliert. Dennoch nimmt sehr wahrscheinlich die Verarbeitungsgüte durch die lärminduzierten neuroplastischen Veränderungen ab. Die Lärmschwerhörigkeit ist somit durch eine Reihe von peripheren und zentralen Veränderungen gekennzeichnet, die bisher nur teilweise einer Therapie zugänglich sind. Besonders im Hinblick auf die auditorische Synaptopathie und die zentralen Verarbeitungsdefizite werden neue therapeutische Ansätze benötigt, um audiologische Phänomene wie Tinnitus, Hyperakusis oder schlechtes Diskriminationsvermögen effektiv behandeln zu können.
Zusammenfassung
Hintergrund
Ein Lärmtrauma induziert zentralnervöse Pathologien, die zur Generierung von Hör- und Wahrnehmungsstörungen führen.
Fragestellung
Sind degenerative Prozesse in der ...zentralen Hörbahn eine direkte Auswirkung der Überstimulation oder eine Folge akustischer Deprivation?
Material und Methode
Bestimmung von Zelltodmechanismen im Mausmodell eines lärminduzierten Hörverlusts zu verschiedenen Zeitpunkten nach einfacher oder wiederholter Lärmexposition.
Ergebnisse
Eine einmalige Lärmexposition (3 h, 115 dB SPL, 5–20 kHz) induziert akute (≤1 Tag) und längerfristige (Beobachtungszeitraum 14 Tage) Degeneration insbesondere in subkortikalen Strukturen. Nach einem wiederholten Lärmtrauma treten v. a. pathologische Veränderungen im auditorischen Thalamus und Kortex auf.
Schlussfolgerung
Lärm hat direkte Auswirkungen auf basale Strukturen der zentralen Hörbahn, eine Protektion kortikaler Areale erfolgt möglicherweise aufgrund inhibitorischer neuronaler Projektionen. Degenerative Mechanismen in höheren Strukturen des vorgeschädigten Systems deuten auf eine zunehmende Beeinträchtigung komplexer Verarbeitung akustischer Informationen.
Hypothalamic neuronal thermosensitivity was investigated in brain slices of Muscovy duck embryos (28th and 33rd days of incubation) and 1-, 5-, and 10-day-old ducklings using extracellular ...recordings. Until day 5 post-hatching the hypothalamic neuronal thermosensitivity is characterized by a high cold sensitivity (up to 30%). Between days 5 and 10 post-hatching hypothalamic neuronal cold sensitivity decreases significantly from 30 to 14% while warm sensitivity increases from 5 to 14%. Temperature guardian neurons which were sensitive exclusively in a small temperature range around 36°C and 42°C (ducklings) or 38°C and 40.5°C (embryos) were found. Possibly, they might play a role in the wide band control of body temperature.
The phenotype of the HID (hystrix-like ichthyosis, deafness)/KID (keratitis, ichthyosis, deafness) syndrome is primarily characterized by skin changes. However, the connexin 26 (Cx 26) autosomal ...dominant mutation underlying this syndrome is of special neurotological interest. In the present paper, the clinical pattern, audiovestibular and neuroimaging findings and the detailed genetic analysis of 4 patients with identical HID/KID-associated mutation D50N of Cx 26 are reported. The audiological test results demonstrated profound sensorineural hearing loss in all of the patients. Neurotological testing revealed inconsistent abnormalities in dynamic posturography (sensory organization test), but the vestibular ocular reflex upon caloric irrigation was normal in all patients. Vestibular-evoked myogenic potential testing for otolith function (saccule) showed a regular response in 1 patient and pathologic responses in 3 patients, while subjective haptic vertical (utricular function) testing was normal in all of the patients. CCT showed an extended (in length), but very thin (in diameter) bony lining between the basal portion of the internal auditory canal and the vestibule in the 3 scanned patients. Our study provides evidence for functionally intact semicircular canals and normal utricular function in subjects with the autosomal dominant D50N mutation of Cx 26, in contrast to saccular function which was generally compromised and hearing loss which was profound.
The response characteristics of acoustically elicited vestibular evoked myogenic potentials (VEMPs) largely depend on the stimuli applied. A tone-burst stimulation of 500
Hz seems to be clinically ...most appropriate because those VEMPs can be elicited at the lowest stimulus intensity possible. The aim of the present paper was to describe normative data for tone-burst evoked VEMPs.
VEMPs of 64 healthy subjects were recorded ipsilaterally during air- or bone-conducted tone burst stimulation. The EMG of the tonically activated sternocleidomastoid muscle was recorded ipsilaterally by surface electrodes. Averages were taken for P1/N1-latencies and -amplitudes of male and female volunteers within 3 different age groups.
The latencies did not show any significant differences between female and male volunteers or between air- and bone-conducted stimulation. The latencies did also not show any significant difference among the 3 age groups. The limits for normal latencies (mean+2 SD) are, therefore, 20.3
ms for P1 and 28.0
ms for N1. Although the P1/N1-amplitudes were decreased with increasing age, the tonic muscle activity was not significantly different between the age groups.
The present findings strongly suggest the evaluation of VEMP latencies by using normative values obtained exactly with the same stimulus parameters.
Normative data as described in the present study are required to detect isolated saccular defects which are indicative of a vestibular disorder.
Zusammenfassung
Ziel
Der Erfolg eines Neurofeedbackverfahrens bei der Therapie von Gleichgewichtsstörungen hängt maßgeblich von der Art des Feedbacksignals und den spezifischen Trainingsparametern ...ab. Ein ideales Training sollte gezielt auf die individuellen Defizite des Patienten in Alltagssituationen abgestimmt sein. Ziel der hier vorgestellten Pilotstudie war es deshalb, die therapeutischen Möglichkeiten eines neuartigen vibrotaktilen Neurobiofeedbacksystems zu untersuchen.
Studiendesign
Auf Basis einer Schwankungsanalyse wurden die Ansprechschwellen für ein vibrotaktiles Feedbacktraining individuell berechnet (n=36). Die Reduktion der Körperschwankung sowie der Werte auf der „Vertigo Symptom Scale“ (VSS) wurde nach einem 10-tägigen Training ermittelt und mit der Placebogruppe verglichen.
Ergebnisse
Bei allen 5 Patientengruppen (gekennzeichnet durch verschiedene vestibuläre Störungen), die mit dem Verumgerät trainierten, wurde eine bessere posturale Kontrolle und ein geringerer Wert der VSS nachgewiesen (n=30) als bei der Placebokontrolle.
Fazit
Ein individualisiertes vibrotaktiles Neurofeedbacktraining mit dem Vertiguard®-System könnte den untersuchten Patientengruppen helfen, die Balance bei unterschiedlichen sensorischen Situationen zu verbessern. Künftige Studien sollten ein größeres Patientenkollektiv sowie die Langzeitwirkung untersuchen.
The objective of this paper is to measure the radiation dose and image
quality in conventional screen-film mammography and full-field digital
mammography in women referred to mammography examination. ...Participants
underwent bilateral, two-view screen-film mammography or full-field digital
mammography. The visibility of anatomical regions and overall clinical image
quality was rated by experienced radiologists. Total of 387 women and 1548
mammograms were enrolled in the study. Image quality was assessed in terms of
image quality score, whereas patient dose assessment was performed in terms
of mean glandular dose. Average mean glandular dose for cranio-caudal
projection was 1.5 mGy and 2.1 mGy in full-field digital mammography and
screen-film mammography, respectively. For medio-lateral oblique projection,
corresponding values were 2.3 and 2.1 mGy. Overall image quality criteria
scoring was 0.82 and 0.99 for screen-film and digital systems, respectively.
The scores were in the range from 0.11 to 1.0 for different anatomical
structures. Overall, full-field digital mammography was superior both in
terms of image quality and dose over the screen-film mammography. The results
have indicated that phantom dose values can assist in setting the
optimisation activities in mammography and for comparison between mammography
units. To obtain accurate diagnostic information with an acceptable radiation
dose to breast, it is necessary to periodically perform patient dose and
image quality surveys in all mammography units.
Cilj rada je procena doze za pacijenta i kvalitet slike u konvencionalnoj,
analognoj i digitalnoj mamografiji. Ispitanici su bili podvrgnuti
bilateralnom pregledu u dve projekcije, a prikazivanje anatomskih detalja i
ukupan klinicki kvalitet slike ocenjen je od strane iskusnih
posmatraca-radiologa. Ukupan broj ispitanika bio je 387, a ukupan broj
projekcija 1548. Kvalitet slike ocenjen je preko parametra ICS (image quality
score), a pacijentna doza izracunavanjem srednje glandularne doze. Srednja
vrednost doze za kranio-kaudalnu projekciju bila je u slucaju analogne i
digitalne mamografije 1.5 mGy i 2.1 mGy, respektivno. U slucaju
medio-lateralno kose projekcije, odgovarajuce vrednosti doze bile su 2.3 mGy
i 2.1 mGy. Ukupan ICS je bio 0.99 za analognu i 0.82 za digitalnu
mamografiju. Parametar ICS za pojedinacne anatomske strukture bio je u
intervalu 0.11-1.0. Pokazalo se da je digitalna mamografija superiornija u
pogledu kvaliteta slike i doze u odnosu na analognu mamografiju. Rezultati su
ukazali na cinjenicu da procena doze za standardni fantom moze biti od
znacaja za optimizaciju prakse u mamografiji kao i za poredjenje razlicitih
mamografskih jedinica. Za dobijanje tacne dijagnosticke informacije uz
razumno nisku dozu za pacijenta, neophodna je periodicna analiza kvaliteta
slike i procene pacijentne doze u svim mamografskim jedinicama.
Novel laboratory implementations of the Edge Illumination X-Ray Phase Contrast imaging (EI-XPCi) method were presented in this thesis, with the aim of facilitating its commercial translation. A ...portable system, based on compact piezoelectric motors, was developed to enable the easy transportation of the setup. Tests on the system positioning accuracy were presented, and images of standard samples were benchmarked against those obtained with the existing prototype based on stepper motors. An alternative EI implementation, which simultaneously allows the use of cheaper X-ray sources and the realisation of more compact setups, was also presented. An additional ``source mask'' introduced in a standard EI setup allows to section the large focal spot of a conventional tube into multiple sub-sources, creating a corresponding number of spatially shifted images, which need to be disentangled through dedicated algorithms. A proof-of-principle experiment provided results in agreement with simulated predictions, demonstrating the feasibility of the approach. A quantitative study on the dependence of the angular sensitivity on the source-to-detector distance (at constant system magnification, tube settings and total exposure time) was also presented. Results of a simulation based on the assumption of Poisson-distributed noise in the images (valid for photon counting detectors) were compared with experimental ones obtained by using an integrating detector. The observed discrepancies were successfully related to the additional noise sources present in an integrating detector, thus indirectly validating the simulation model. The adaptation of EI with a laser-plasma source was investigated through a proof-of-concept experiment, with the aim of realizing a system providing a synchrotron-like performance with a more compact and accessible setup. Non-ideal experimental conditions affecting the system performance were discussed, while the results of the source characterization were used to establish some basic requirements that must be satisfied to successfully implement EI with these ``new generation'' X-ray sources.
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