CBCT artefact-burden of zirconia-based as compared to titanium implants for different beam energies: an analytical approach.

Beam hardening artefacts induced by highly-dense material (e.g. metal) is a common quality issue in maxillofacial Cone Beam Computed Tomography (CBCT-) images. This experimental and analytical study investigated attenuation patterns of two typical dental implant materials: zirconia-ceramic and pure titanium. By application of different x-ray beam energies (60, 70, 80, 90 [kVp]) energy-dependent attenuation of these materials is assessed and the resulting artefact induction in the resulting CBCT-images evaluated. A zirconia (Y-TZP-) implant ([Formula: see text]: 4.1 mm) and a pure titanium rod ([Formula: see text]: 4.0 mm) were exposed in a commercial CBCT (3D Accuitomo 170). The raw two-dimensional (2D) projection radiographs the CBCT utilizes for three-dimensional reconstruction applied for acquisition of attenuation profiles through the circular central slice of the implant-phantom images. Distances the x-rays traverse through the implant-phantoms at this location were computed. Using this information and the linear attenuation coefficient, transmission and attenuation was computed for each material and beam energy. These data were related to beam hardening artefacts that were assessed in the axial reconstructions of the implants' CBCT images. Transmission of titanium for all peak kilovoltages (kVp) was higher and approximately 200% that of Y-TZP at 60 kVp versus 530% at 90 kVp. At 4 mm diameter transmission for Y-TZP was only approximately 5 % for all four beam-energies. In agreement with this finding, beam hardening artefacts for Y-TZP could not be reduced using higher energies, whereas for titanium they decreased with increasing energy. For the energy spectrum used in this study (60-90 kVp), beam hardening caused by titanium can be reduced using higher energies while this is not the case for zirconia-ceramic (Y-TZP)

Prompt Gamma-ray 3D-Imaging for Cultural Heritage Purposes

The development of new, and the enhancement of existing element-sensitive imaging methods utilizing neutrons of different energy regions was the aim of the European ANCIENT CHARM project. During the present work the setup for Prompt Gamma-ray Activation Analysis (PGAA) at the research reactor FRM 2 in Garching near Munich was modified to enable the spatial mapping of elemental abundances in the analysed samples. Because the PGAA setup at FRM 2 was under construction at the beginning of the project first tests and the development of calibration and measurement procedures for the new imaging method were done by the PGAA group at the Budapest Research Reactor in cooperation with the Institute for Nuclear Physics of the University of Cologne. Due to the higher neutron flux at the PGAA setup at FRM 2 the equipment was transferred from the Budapest Research Reactor to FRM 2 after the PGAA setup at FRM 2 started its regular operation. After further optimizations and the characterization of the setup, measurements were started on replicas of real archaeological objects before several measurements on real objects were performed and analysed. Several measurement configurations were applied. Additional to 2D and 3D imaging measurements a new application for the measurement of thin surface layers in the order of a few 100 micro-meters was developed. For the quantitative analysis of elemental distributions the exact knowledge of the neutron flux at each measured position in the analysed sample has to be known. Based on the well-established cold Neutron Tomography (NT) method a method and software have been developed, which enables the calculation of the neutron flux inside samples with the map of attenuation properties obtained through NT. A new data acquisition system was developed for the regular operation of the PGAA setup at FRM 2, which supports traditional bulk PGAA measurements as well as measurements in the new imaging configuration. The high automation of the system allows a significantly more efficient use of the available measurement time than it was the case before. The new software �HDTV� for the analysis of gamma-ray spectra, which is currently under active development at the Institute for Nuclear Physics of the University of Cologne, was extended by some functionality for the analysis of PGAA spectra. It is a proposed modern successor of the currently used software �TV� and allows the semiautomatic analysis of multiple, similar spectra, what is essential for the new imaging PGA method

Airway responses and inflammation in subjects with asthma after four days of repeated high-single-dose allergen challenge

Background: Both standard and low-dose allergen provocations are an established tool in asthma research to improve our understanding of the pathophysiological mechanism of allergic asthma. However, clinical symptoms are less likely to be induced. Therefore, we designed a protocol for repetitive high-dose bronchial allergen challenges to generate clinical symptoms and airway inflammation. Methods: A total of 27 patients aged 18 to 40 years with positive skin-prick tests and mild asthma underwent repetitive high-dose allergen challenges with household dust mites for four consecutive days. Pulmonary function and exhaled NO were measured at every visit. Induced sputum was analysed before and after the allergen challenges for cell counts, ECP, IL-5, INF-γ, IL-8, and the transcription factor Foxp3. Results: We found a significant decrease in pulmonary function, an increased use of salbutamol and the development of a late asthmatic response and bronchial hyperresponsiveness, as well as a significant induction of eNO, eosinophils, and Th-2 cytokines. Repeated provocation was feasible in the majority of patients. Two subjects had severe adverse events requiring prednisolone to cope with nocturnal asthma symptoms. Conclusions: Repeated high-dose bronchial allergen challenges resulted in severe asthma symptoms and marked Th-2-mediated allergic airway inflammation. The high-dose challenge model is suitable only in an attenuated form in diseased volunteers for proof-of-concept studies and in clinical settings to reduce the risk of severe asthma exacerbations. Trial registration: ClinicalTrials.govNCT0067720

Vertical head rotation as major source of differences between time-separated digital cephalometric radiographs of patients acquired in one cephalostat X-ray device.

BACKGROUND The purpose of the retrospective study was to analyze the reliability and repeatability of specific landmark-positions used in cephalometry to determine the major sources of absolute landmark position differences for repeated, time-separated (time-point I and II) digital cephalometric radiographs (CEPH) of the same patients. METHODS 100 pairs of CPEHs from the database of a sample of adult patients (18 to 28 years) were analyzed by one calibrated observer and three landmark points (Sella: S, Nasion: N, Subspinale: A) were digitally marked using ImageJ-software. The coordinates of these points entered the evaluation using displacement vectors as primary endpoints between the coordinates of the landmarks in the two images as well as SNA-angles and the angle ω of SN relative to the floor. RESULTS Displacement vectors between CEPHI and CEPHII were rather large (N: 7.95 ± 4.85 mm, S: 5.34 ± 3.50 mm, A: 4.81 ± 3.95 mm. SNA was rather stable between the two sequential radiographs (mean difference: 0.002° ± 1.85°). and did not correlate with age of the patient (SNAI: spearman-Rho: 0.0239, p = 0.8134; SNAII : spearman-Rho: 0.0244, p = 0.8096). Although the vertical angle ω did not differ between CEPHI and CEPHII (mean difference: 0.4° ± 4.7°, pwilcoxon = 0.8155), it showed a quadratic relationship (pF-statistic: < 2.2e-16) with the length of the displacement vector N. CONCLUSION The significantly varying location of the reference points S, N and A between time-separated CEPHs of one patient can largely be explained by different angulation (head rotation within the sagittal plane) of the Frankfurt plane to the floor (horizontal plane)

Correlation of objective image quality and working length measurements in different CBCT machines: An ex vivo study

To investigate potential correlations between objective CBCT image parameters and accuracy in endodontic working length determination ex vivo. Contrast-to-noise ratio (CNR) and spatial resolution (SR) as fundamental objective image parameters were examined using specific phantoms in seven different CBCT machines. Seven experienced observers were instructed and calibrated. The order of the CBCTs was randomized for each observer and observation. To assess intra-operator reproducibility, the procedure was repeated within six weeks with a randomized order of CBCT images. Multivariate analysis (MANOVA) did not reveal any influence of the combined image quality factors CNR and SR on measurement accuracy. Inter-operator reproducibility as assessed between the two observations was poor, with a mean intra-class correlation (ICC) of 0.48 (95%-CI 0.38, 0.59) for observation No. 1. and 0.40 (95%-CI 0.30, 0.51) for observation No. 2. Intra-operator reproducibility pooled over all observers between both observations was only moderate, with a mean ICC of 0.58 (95%-CI 0.52 to 0.64). Within the limitations of the study, objective image quality measures and exposure parameters seem not to have a significant influence on accuracy in determining endodontic root canal lengths in CBCT scans. The main factor of variance is the observer

CBCTs in a Swiss university dental clinic: a retrospective evaluation over 5 years with emphasis on radiation protection criteria.

OBJECTIVES To retrospectively evaluate all cone-beam computed tomography (CBCT) scans acquired from 2017 to 2022 in a Swiss university dental clinic with particular emphasis on radiation protection aspects. MATERIAL AND METHODS Radiological databases at the dental clinic of the University of Bern, Switzerland, were explored using a self-developed search algorithm. Data of all acquired CBCT from 01.01.2017 to 27.06.2022 were screened. Exposure parameters (exposure time, exposure angle, milliampere (mA), kilovoltage (kV), field of view (FOV) size), dose area product (DAP), age, and sex of the patient were recorded anonymously. The collected data were analyzed mainly descriptively. Correlations measured the statistical relationships between the variables. RESULTS A total of 10,348 CBCT datasets were analyzed. Patient age ranged from 5 to 96 years (mean: 49.4 years, SD: 21.6 years). The number of CBCTs in patients under 25 years was around 20% each year. In total, 10,313 (99.7%) CBCTs were acquired in small to medium FOV (FOV up to 10 cm of height), and 35 (0.3%) in large FOV (height > 10 cm). DAPs of small FOVs were 518.3 ± 233.2 mGycm2 (mean ± SD), of medium FOV 1233 ± 502.2 mGycm2, and of large FOV 2189 ± 368.7 mGycm2. DAP (ρ = 0.4048, p < 0.0001) and kV (ρ = 0.0210, p = 0.0327) correlated positively with age. Reduced scan angle correlated with young age (rpb 0.2729, p < 0.001). mA did not correlate with age (p = 0.3685). CONCLUSIONS This study demonstrates that certain well-known radiation protection aspects as the reduction of FOV, mA, kV, and scan angle were only partly considered. CLINICAL RELEVANCE Known radiation protection aspects, especially in young patients, should be fully applied in regular clinical practice

Motion Correction for Separate Mandibular and Cranial Movements in Cone Beam CT Reconstructions.

BACKGROUND Patient motions are a repeatedly reported phenomenon in oral and maxillofacial cone beam CT scans, leading to reconstructions of limited usability. In certain cases, independent movements of the mandible induce unpredictable motion patterns. Previous motion correction methods are not able to handle such complex cases of patient movements. PURPOSE Our goal was to design a combined motion estimation and motion correction approach for separate cranial and mandibular motions, solely based on the 2D projection images from a single scan. METHODS Our iterative three-step motion correction algorithm models the two articulated motions as independent rigid motions. First of all, we segment cranium and mandible in the projection images using a deep neural network. Next, we compute a 3D reconstruction with the poses of the object's trajectories fixed. Third, we improve all poses by minimizing the projection error while keeping the reconstruction fixed. Step two and three are repeated alternately. RESULTS We find that our marker-free approach delivers reconstructions of up to 85% higher quality, with respect to the projection error, and can improve on already existing techniques, which model only a single rigid motion. We show results of both synthetic and real data created in different scenarios. The reconstruction of motion parameters in a real environment was evaluated on acquisitions of a skull mounted on a hexapod, creating a realistic, easily reproducible motion profile. CONCLUSIONS The proposed algorithm consistently enhances the visual quality of motion impaired CBCT scans, thus eliminating the need for a re-scan in certain cases, considerably lowering radiation dosage for the patient. It can flexibly be used with differently sized regions of interest and is even applicable to local tomography. This article is protected by copyright. All rights reserved

Localization of group II and III metabotropic glutamate receptors at pre- and postsynaptic sites of inner hair cell ribbon synapses

Glutamate is the major excitatory neurotransmitter in the CNS binding to a variety of glutamate receptors. Metabotropic glutamate receptors (mGluR1 to mGluR8) can act excitatory or inhibitory, depending on associated signal cascades. Expression and localization of inhibitory acting mGluRs at inner hair cells (IHCs) in the cochlea are largely unknown. Here, we analyzed expression of mGluR2, mGluR3, mGluR4, mGluR6, mGluR7, and mGluR8 and investigated their localization with respect to the presynaptic ribbon of IHC synapses. We detected transcripts for mGluR2, mGluR3, and mGluR4 as well as for mGluR7a, mGluR7b, mGluR8a, and mGluR8b splice variants. Using receptor-specific antibodies in cochlear wholemounts, we found expression of mGluR2, mGluR4, and mGluR8b close to presynaptic ribbons. Super resolution and confocal microscopy in combination with 3-dimensional reconstructions indicated a postsynaptic localization of mGluR2 that overlaps with postsynaptic density protein 95 on dendrites of afferent type I spiral ganglion neurons. In contrast, mGluR4 and mGluR8b were expressed at the presynapse close to IHC ribbons. In summary, we localized in detail 3 mGluR types at IHC ribbon synapses, providing a fundament for new therapeutical strategies that could protect the cochlea against noxious stimuli and excitotoxicity

Effectiveness of Telemedicine and Teledentistry after the COVID-19 Pandemic.

Telemedicine has become increasingly important worldwide over the last two decades. As a new field, it became known especially during the COVID-19 pandemic; this review presents fields of activity with special attention to opportunities and risks. Numerous areas of application offer the possibility for broad use in the medical and dental care landscape in diagnostics, therapy, rehabilitation, and decision advice across a spatial distance. Technical and semantic standards are required, and profiles and guidelines are increasingly defined and organized. Medical/dental consultations have been established in various regions around the world as a response to pandemic challenges and have made video and online emergency consultations possible. Telemedicine applications are already regularly used in medical/dental emergencies, regardless of the pandemic situation, both for transport by train and by plane, from which patients benefit. However, legal hurdles are often still unresolved, but infrastructure challenges both for provider, user hard- and software also complicate deployment. Problems are particularly prevalent in the absence of necessary internet coverage or among socially disadvantaged and vulnerable groups who cannot afford expensive equipment or do not know how to use the technology. Broad access must be enabled, and hardware and software interfaces and updates must be regularly checked and updated. Telemedicine might also improve access to and delivery of oral and general health care support both for rural and urban areas with low costs. Even though dentistry and many medical specialties are still performed clinically by means of practical/manual examination, there are areas of diagnostics where telemedicine applications can provide good support. Therefore, as conclusions, access, and delivery of telemedicine applications in dentistry and medicine should be expanded and improved to provide access to all population groups