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Abstract 7‐Tesla (T) magnetic resonance imaging may allow for higher resolution images but may produce greater acoustic noise than 1.5‐ and 3‐T scanners. We sought to characterize the intensity of acoustic noise from 7‐ versus 3‐T scanners. A‐weighted sound pressure levels from 5 types of pulse sequences used for brain and inner ear imaging in 3‐ and 7‐T scanners were measured. Time‐averaged sound level and maximum sound levels generated for each sequence were compared. Time‐averaged sound levels exceeded 95 dB and reached maximums above 105 dB on the majority of 3‐ and 7‐T scans. The mean time‐averaged sound level and maximum sound level across pulse sequences were greater in 7‐ than 3‐T (105.6 vs 91.4, P = .01; 114.0 vs. 96.5 dB, P

Background: In-vivo MR-based high-resolution volumetric quantification methods of the endolymphatic hydrops (ELH) are highly dependent on a reliable segmentation of the inner ear's total fluid space (TFS). This study aimed to develop a novel open-source inner ear TFS segmentation approach using a dedicated deep learning (DL) model. Methods: The model was based on a V-Net architecture (IE-Vnet) and a multivariate (MR scans: T1, T2, FLAIR, SPACE) training dataset (D1, 179 consecutive patients with peripheral vestibulocochlear syndromes). Ground-truth TFS masks were generated in a semi-manual, atlas-assisted approach. IE-Vnet model segmentation performance, generalizability, and robustness to domain shift were evaluated on four heterogenous test datasets (D2-D5, n = 4 × 20 ears). Results: The IE-Vnet model predicted TFS masks with consistently high congruence to the ground-truth in all test datasets (Dice overlap coefficient: 0.9 ± 0.02, Hausdorff maximum surface distance: 0.93 ± 0.71 mm, mean surface distance: 0.022 ± 0.005 mm) without significant difference concerning side (two-sided Wilcoxon signed-rank test, p >0.05), or dataset (Kruskal-Wallis test, p >0.05; post-hoc Mann-Whitney U, FDR-corrected, all p >0.2). Prediction took 0.2 s, and was 2,000 times faster than a state-of-the-art atlas-based segmentation method. Conclusion: IE-Vnet TFS segmentation demonstrated high accuracy, robustness toward domain shift, and rapid prediction times. Its output works seamlessly with a previously published open-source pipeline for automatic ELS segmentation. IE-Vnet could serve as a core tool for high-volume trans-institutional studies of the inner ear. Code and pre-trained models are available free and open-source under https://github.com/pydsgz/IEVNet. [ABSTRACT FROM AUTHOR]

In congenital vestibular disorders (CVDs), children develop an abnormal inner ear before birth and face postnatal challenges to maintain posture, balance, walking, eye-hand coordination, eye tracking, or reading. Only limited information on inner ear pathology is acquired from clinical imaging of the temporal bone or studying histological slides of the temporal bone. A more comprehensive and precise assessment and determination of the underlying mechanisms necessitate analyses of the disorders at the cellular level, which can be achieved using animal models. Two main criteria for a suitable animal model are first, a pathology that mirrors the human disorder, and second, a reproducible experimental outcome leading to statistical power. With over 40 genes that affect inner ear development, the phenotypic abnormalities resulting from congenital vestibular disorders (CVDs) are highly variable. Nonetheless, there is a large subset of CVDs that form a common phenotype of a sac-like inner ear with the semicircular canals missing or dysplastic, and discrete abnormalities in the vestibular sensory organs. We have focused the review on this subset, but to advance research on CVDs we have added other CVDs not forming a sac-like inner ear. We have included examples of animal models used to study these CVDs. Presently, little is known about the central pathology resulting from CVDs at the cellular level in the central vestibular neural network, except for preliminary studies on a chick model that show significant loss of second-order, vestibular reflex projection neurons. [ABSTRACT FROM AUTHOR]

In congenital vestibular disorders (CVDs), children develop an abnormal inner ear before birth and face postnatal challenges to maintain posture, balance, walking, eye-hand coordination, eye tracking, or reading. Only limited information on inner ear pathology is acquired from clinical imaging of the temporal bone or studying histological slides of the temporal bone. A more comprehensive and precise assessment and determination of the underlying mechanisms necessitate analyses of the disorders at the cellular level, which can be achieved using animal models. Two main criteria for a suitable animal model are first, a pathology that mirrors the human disorder, and second, a reproducible experimental outcome leading to statistical power. With over 40 genes that affect inner ear development, the phenotypic abnormalities resulting from congenital vestibular disorders (CVDs) are highly variable. Nonetheless, there is a large subset of CVDs that form a common phenotype of a sac-like inner ear with the semicircular canals missing or dysplastic, and discrete abnormalities in the vestibular sensory organs. We have focused the review on this subset, but to advance research on CVDs we have added other CVDs not forming a sac-like inner ear. We have included examples of animal models used to study these CVDs. Presently, little is known about the central pathology resulting from CVDs at the cellular level in the central vestibular neural network, except for preliminary studies on a chick model that show significant loss of second-order, vestibular reflex projection neurons.

BACKGROUND: For the imaging of ossicular chains, muscles, bony labyrinths, ligaments and other structures, conventional thin-slice CT scans are difficult to achieve the most ideal results. OBJECTIVE: To evaluate the image quality and radiation dose of High Resolution (HR) precise tomographic reconstruction algorithm in thin-layer CT scan of the middle and inner ears. METHODS: Thin-layer scanning of the inner ear was performed in 21 volunteers. All scanned images were reconstructed by two reconstruction algorithms. The study group was reconstructed by 0.275 mm HR precision tomography, and the control group was reconstructed by 0.55 mm conventional thin layer. The images were processed by multiplanar reconstruction technology, and the display rates of anterior malleolar ligament, posterior anvil ligament, superior malleolar ligament and lateral malleolar ligament were calculated, and the image display effects of ossicular chain, muscle, labyrinthine and ligament were scored subjectively. The volume CT dose index volume and dose length product were recorded, and the effective dose was calculated. The study protocol was implemented in line with the ethic requirements of the First Affiliated Hospital of Jinzhou Medical University, and all the subjects were fully informed of the study procedures. RESULTS AND CONCLUSION: All anatomical structures could be seen in axial and coronal images of HR precision tomography reconstruction and conventional thin-layer reconstruction (P > 0.05). In axial and coronal images, the display quality of the middle and inner ear structure in the study group was significantly better than that in the control group (P < 0.05). The effective dose of precision tomography in middle and inner ear was (1.19±0.26) mGy. To conclude, precision tomography has higher image resolution, by which we can observe the structures of the middle and inner ears more clearly. [ABSTRACT FROM AUTHOR]

In-vivo non-invasive verification of endolymphatic hydrops (ELH) by means of intravenous delayed gadolinium (Gd) enhanced magnetic resonance imaging of the inner ear (iMRI) is rapidly developing into a standard clinical tool to investigate peripheral vestibulo-cochlear syndromes. In this context, methodological comparative studies providing standardization and comparability between labs seem even more important, but so far very few are available. One hundred eight participants [75 patients with Meniere's disease (MD; 55.2 ± 14.9 years) and 33 vestibular healthy controls (HC; 46.4 ± 15.6 years)] were examined. The aim was to understand (i) how variations in acquisition protocols influence endolymphatic space (ELS) MR-signals; (ii) how ELS quantification methods correlate to each other or clinical data; and finally, (iii) how ELS extent influences MR-signals. Diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, head-impulse test, audiometry, and iMRI. Data analysis provided semi-quantitative (SQ) visual grading and automatic algorithmic quantitative segmentation of ELS area [2D, mm2] and volume [3D, mm3] using deep learning-based segmentation and volumetric local thresholding. Within the range of 0.1–0.2 mmol/kg Gd dosage and a 4 h ± 30 min time delay, SQ grading and 2D- or 3D-quantifications were independent of signal intensity (SI) and signal-to-noise ratio (SNR; FWE corrected, p < 0.05). The ELS quantification methods used were highly reproducible across raters or thresholds and correlated strongly (0.3–0.8). However, 3D-quantifications showed the least variability. Asymmetry indices and normalized ELH proved the most useful for predicting quantitative clinical data. ELH size influenced SI (cochlear basal turn p < 0.001), but not SNR. SI could not predict the presence of ELH. In conclusion, (1) Gd dosage of 0.1–0.2 mmol/kg after 4 h ± 30 min time delay suffices for ELS quantification. (2) A consensus is needed on a clinical SQ grading classification including a standardized level of evaluation reconstructed to anatomical fixpoints. (3) 3D-quantification methods of the ELS are best suited for correlations with clinical variables and should include both ears and ELS values reported relative or normalized to size. (4) The presence of ELH increases signal intensity in the basal cochlear turn weakly, but cannot predict the presence of ELH.

In-vivo non-invasive verification of endolymphatic hydrops (ELH) by means of intravenous delayed gadolinium (Gd) enhanced magnetic resonance imaging of the inner ear (iMRI) is rapidly developing into a standard clinical tool to investigate peripheral vestibulo-cochlear syndromes. In this context, methodological comparative studies providing standardization and comparability between labs seem even more important, but so far very few are available. One hundred eight participants [75 patients with Meniere's disease (MD; 55.2 ± 14.9 years) and 33 vestibular healthy controls (HC; 46.4 ± 15.6 years)] were examined. The aim was to understand (i) how variations in acquisition protocols influence endolymphatic space (ELS) MR-signals; (ii) how ELS quantification methods correlate to each other or clinical data; and finally, (iii) how ELS extent influences MR-signals. Diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, head-impulse test, audiometry, and iMRI. Data analysis provided semi-quantitative (SQ) visual grading and automatic algorithmic quantitative segmentation of ELS area [2D, mm2] and volume [3D, mm3] using deep learning-based segmentation and volumetric local thresholding. Within the range of 0.1–0.2 mmol/kg Gd dosage and a 4 h ± 30 min time delay, SQ grading and 2D- or 3D-quantifications were independent of signal intensity (SI) and signal-to-noise ratio (SNR; FWE corrected, p < 0.05). The ELS quantification methods used were highly reproducible across raters or thresholds and correlated strongly (0.3–0.8). However, 3D-quantifications showed the least variability. Asymmetry indices and normalized ELH proved the most useful for predicting quantitative clinical data. ELH size influenced SI (cochlear basal turn p < 0.001), but not SNR. SI could not predict the presence of ELH. In conclusion, (1) Gd dosage of 0.1–0.2 mmol/kg after 4 h ± 30 min time delay suffices for ELS quantification. (2) A consensus is needed on a clinical SQ grading classification including a standardized level of evaluation reconstructed to anatomical fixpoints. (3) 3D-quantification methods of the ELS are best suited for correlations with clinical variables and should include both ears and ELS values reported relative or normalized to size. (4) The presence of ELH increases signal intensity in the basal cochlear turn weakly, but cannot predict the presence of ELH. [ABSTRACT FROM AUTHOR]

7-Tesla (T) magnetic resonance imaging may allow for higher resolution images but may produce greater acoustic noise than 1.5- and 3-T scanners. We sought to characterize the intensity of acoustic noise from 7- versus 3-T scanners. A-weighted sound pressure levels from 5 types of pulse sequences used for brain and inner ear imaging in 3- and 7-T scanners were measured. Time-averaged sound level and maximum sound levels generated for each sequence were compared. Time-averaged sound levels exceeded 95 dB and reached maximums above 105 dB on the majority of 3- and 7-T scans. The mean time-averaged sound level and maximum sound level across pulse sequences were greater in 7- than 3-T (105.6 vs 91.4, P  = .01; 114.0 vs. 96.5 dB, P  < .01). 7- and 3-T magnetic resonance imaging scanners produce high levels of acoustic noise that exceed acceptable safety limits, emphasizing the need for active and passive noise protection., Competing Interests: The authors declare that there is no conflict of interest., (© 2023 The Authors. OTO Open published by Wiley Periodicals LLC on behalf of American Academy of Otolaryngology–Head and Neck Surgery Foundation.)

The development of inner ear gene carriers and delivery systems has enabled genetic defects to be repaired and hearing to be restored in mouse models. Today, promising advances in translational therapies provide confidence that targeted molecular therapy for inner ear diseases will be developed. Unfortunately, the currently available non-invasive modalities, such as Computerized Tomography scan or Magnetic Resonance Imaging provide insufficient resolution to identify most pathologies of the human inner ear, even when the current generation of contrast agents is utilized. The development of targeted contrast agents may play a critical role in determining the cause of, and treatment for, sensorineural hearing loss. Such agents should be able to pass through the cochlea barriers, possess minimal cytotoxicity, and easily conjugate to a targeting agent, without distorting the anatomic details. This review focuses on a series of contrast agents which may fit these criteria for potential clinical application. [ABSTRACT FROM AUTHOR]

Purpose: To assess the z-axis resolution improvement and dose reduction potential achieved using a z-axis deconvolution technique with iterative reconstruction (IR) relative to filtered backprojection (FBP) images created with the use of a z-axis comb filter. Methods: Each of three phantoms were scanned with two different acquisition modes: (1) an ultrahigh resolution (UHR) scan mode that uses a comb filter in the fan angle direction to increase in-plane spatial resolution and (2) a z-axis ultrahigh spatial resolution (zUHR) scan mode that uses comb filters in both the fan and cone angle directions to improve both in-plane and z-axis spatial resolution. All other scanning parameters were identical. First, the ACR CT Accreditation phantom, rotated by 90° so that the high-contrast spatial resolution targets were parallel to the coronal plane, was scanned to assess limiting spatial resolution and image noise. Second, section sensitivity profiles (SSPs) were measured using a copper foil embedded in an acrylic cylinder and the full-width-at-half-maximum (FWHM) and full-width-at-tenth-maximum (FWTM) of the SSPs were calculated. Third, an anthropomorphic head phantom containing a human skull was scanned to assess clinical acceptability for imaging of the temporal bone. For each scan, FBP images were reconstructed for the zUHR scan using the narrowest image thickness available. For the CT accreditation phantom, zUHR images were also reconstructed using an IR algorithm (SAFIRE, Siemens Healthcare, Forchheim, Germany) to assess the influence of the IR algorithm on image noise. A z-axis deconvolution technique combined with the IR algorithm was used to reconstruct images at the narrowest image thickness possible from the UHR scan data. Images of the ACR and head phantoms were reformatted into the coronal plane. The head phantom images were evaluated by a neuroradiologist to assess acceptability for use in patients undergoing clinically indicated CT imaging of the temporal bone. Results: The limiting spatial resolution was 12 lp/cm for the FBP-zUHR images and the IR-UHR images, although visual assessment indicated a slight improvement for the IR-UHR images. Image noise was 213.0, 181.8, and 153.5 for the FBP-zUHR, IR-zUHR, and IR-UHR images, respectively. While the FWHM was essentially the same for the FBP-zUHR and IR-UHR images, the FWTM of the IR-UHR images was almost 50% smaller compared to the FBP-zUHR images (0.83 vs 1.25 mm, respectively). Images of the anthropomorphic head phantom were judged to be of higher quality for the IR-UHR images compared to the FBP-zUHR images. Conclusions: With use of a z-axis deconvolution technique, z-axis spatial resolution was improved for scans acquired using a comb filter only in the fan angle direction relative to FBP images acquired with a comb filter in both the fan and cone angle directions. By avoiding use of the comb filter in the cone angle direction and use of an IR algorithm, image noise was substantially reduced for the same scanner output (CTDIvol). Thus, overall image quality (spatial resolution and image noise) can be maintained relative to the FBP-zUHR technique at a lower radiation dose. [ABSTRACT FROM AUTHOR]

Imaging of the temporal bone is under continous developement. In the recent decades the technical advances of magnetic resonance imaging and computed tomography have contributed to improved imaging quality in assessment of the temporal bone. Dedicated imaging protocols have been developed and are routinely employed in most institutions. However, imaging interpretation remains challenging, since the temporal bone is an anatomically highly complex region and most diseases of the inner ear occur with low incidence, so that even radiologists experienced in the field may be confronted with such entities for the first time. The current review gives an overview about symptoms and imaging appearance of malformations and acquired lesion of the inner ear. [ABSTRACT FROM AUTHOR]

Objectives/Hypothesis Fistulae of the otic capsule occur in approximately 10% of cholesteatoma cases. Preoperative imaging of this complication is valuable in limiting intraoperative morbidity. Three-dimensional virtual endoscopic imaging provides a new method for analysis of conventional computed tomography (CT) imaging data. The purpose of the study was to examine the feasibility and efficacy of this technique in detecting labyrinthine fistulae caused by cholesteatoma. Study Design Retrospective case study. Methods Fifteen patients with surgically confirmed lateral semicircular canal fistula and preoperative CT scan were included. Scans meeting inclusion criteria were imported into a software program for production of virtual endoscopic images. Dehiscent and normal lateral semicircular canals were navigated while varying threshold values for surrounding bone. Changes in threshold values produce the effect of thickening or thinning the bone enveloping the semicircular canal. Threshold parameters that produced easy circumnavigation ('open') and intact inner surface of the lateral canal ('closed') were recorded. Results The fistula group demonstrated a significantly lower 'closed' threshold level and, consequently, a greater range of navigation between 'open' and 'closed' thresholds. Intrasubject absolute differences in threshold values between normal and abnormal ears appeared to be the most accurate method for detecting a fistula. The suggested imaging parameters displayed an overall sensitivity for fistula detection of 67% with a specificity of 93%. Conclusions The three-dimensional virtual endoscopic algorithm shows promise as a method for confirmation of otic capsule dehiscences. Sensitivity for detection is suboptimal but can be improved by alterations in image acquisition parameters. [ABSTRACT FROM AUTHOR]

Objective: To observe the imaging characteristics of guinea pig cochlear structure using 9.4 Tesla magnetic resonance imaging system at different time intervals of contrast agent distribution in the inner ear. Methods: Form May 2015 to October 2015, five albino guinea pigs were injected with Gd-DTPA via the right internal jugular vein (3 ml/kg). Inner ears were scanned with 9.4T MRI. At the 10 th, 30 th, 60 th, 90 th and 120 th minutes post-Gd-DTPA, we took inner ear images to detect changes of endolymph and perilymph. Using Image J software, we acquired MRI gray value through the first, second, third and apical turn of cochlear at different time points. Analysis by one-way ANOVA was taken to analyze the resultsusing GraphPad Prism 5 software. Results: Only outlines of the cochlea and vestibule were visible before Gd-DTPA injection and there was no clear distinction between endolymph and perilymph. Cochlea vestibule on T1 weighted images was enhanced at the 10 th (the first turn of cochlear 8 203±819) after injection, and then imaging of each part of cochlea, including cochlea, vestibule, semicircular canal and even endolymph and perilymph, can be distinguished clearly, because they enhanced gradually at the 30 th(10 489±819), 60 th(13 965±591), and at 90 th(18 050±1 250) after injection. While at the 120 th(18 952±1 185) minute, imaging was not significantly enhanced than at the 90 th minute. The speed and volume of contrast agent spreaded into the various parts of the inner ear were different, and changes with distribution of contrast agent in each part of the inner ear showed a rising process in a certain period of time. The distribution of contrast agent in the inner ear had concentration gradient via basal turn higher and apical turn lower. Conclusions: Endolymph of inner ear can be distinguished from the perilymph using a 9.4T MRI system with Gd-DTPA, and the best observation timer was 90 minutes after intravenous injection of contrast agent. In summary, our study provides the clearly visualized imaging evidence of the changes of the lymphatic fluid, which may be useful for diagnosis of inner ear diseases such as Meniere's Disease.

The development of inner ear gene carriers and delivery systems has enabled genetic defects to be repaired and hearing to be restored in mouse models. Today, promising advances in translational therapies provide confidence that targeted molecular therapy for inner ear diseases will be developed. Unfortunately, the currently available non-invasive modalities, such as Computerized Tomography scan or Magnetic Resonance Imaging provide insufficient resolution to identify most pathologies of the human inner ear, even when the current generation of contrast agents is utilized. The development of targeted contrast agents may play a critical role in determining the cause of, and treatment for, sensorineural hearing loss. Such agents should be able to pass through the cochlea barriers, possess minimal cytotoxicity, and easily conjugate to a targeting agent, without distorting the anatomic details. This review focuses on a series of contrast agents which may fit these criteria for potential clinical application., (Copyright © 2017 Elsevier Inc. All rights reserved.)

During the last decade, there have been major improvements in imaging modalities and the development of molecular imaging in general. However detailed inner ear imaging still provides very limited information to physicians. This is unsatisfactory as sensorineural hearing loss is the main cause of permanent hearing loss in adults and at least 134 genetic mutations that result in congenital hearing loss have been identified. We are still unable, in most cases where gross anatomical changes are not observed, to determine the exact cause of hearing loss at a cellular or molecular level in patients using non-invasive techniques. This limitation in inner ear diagnostic modalities is a major obstacle behind the delay in discovering treatments for many of the causes of sensorineural hearing loss. This paper initially investigated the use of targeted gold nanoparticles as contrast agents for inner ear imaging. These nanoparticles have many useful characteristics such as being easy to target and possessing minimal cytotoxicity. We were able to detect the nanoparticles diffusing in the hair cells using confocal microscopy. Regrettably, despite their many admirable characteristics, the gold nanoparticles were unable to significantly enhance CT imaging of the inner ear. Consequently, we investigated liposomal iodine as a potential solution for the unsatisfactory CT contrast obtained with the gold nanoparticles. Fortunately, significant enhancement of the micro-CT image was observed with either Lugol's solution or liposomal iodine, with Lugol's solution enabling fine inner ear structures to be detected.