| 1. |
- Berglin, Cecilia Engmér, et al.
(författare)
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Magnetic Resonance Imaging of the Middle and Inner Ear After Intratympanic Injection of a Gadolinium-Containing Gel
- 2014
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Ingår i: Otology and Neurotology. - 1531-7129 .- 1537-4505. ; 35:3, s. 526-532
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:To investigate the distribution and elimination of a gadolinium containing high viscosity formulation of sodium hyaluronan (HYA gel) after injection to the middle ear.MATERIALS AND METHODS:The T1 contrast agent gadolinium-diethylenetriamine pentaacetic acid-bis methylamine (Gd-DTPA-BMA) was added to HYA gel and delivered to the middle ear of 13 albino guinea pigs by 3 different ways of injection. Magnetic resonance imaging was performed with a 4.7 T MRI system using a T1-weighted 3-dimentional rapid acquisition with relaxation enhancement sequence.RESULTS:An injection technique where the Gd-DTPA-BMA-containing HYA gel was delivered to the middle ear through a percutaneous injection through the auditory bulla after a small incision had been made in the tympanic membrane gave the best filling of the middle ear, covering the cochlea and the region of the round window niche for 24 hours in a majority of the ears studied. Ears injected without an incision in the tympanic membrane showed an immediate uptake of Gd-DTPA-BMA in the inner ear as a sign of rupture of the round window membrane.CONCLUSION:A percutaneous injection of a HYA gel into the tympanic bulla is distributed in a predictable way and gives a good filling of the middle ear cavity. The HYA gel remains in close vicinity to the RWM for more than 24 hours. Injection should be performed after an incision of the tympanic membrane has been made to prevent rupture of the round window membrane.
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| 2. |
- Counter, S. Allen, et al.
(författare)
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Assessment of the Brainstem- Mediated Stapedius Muscle Reflex in Andean Children Living at High Altitudes
- 2017
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Ingår i: High Altitude Medicine & Biology. - : MARY ANN LIEBERT, INC. - 1527-0297 .- 1557-8682. ; 18:1, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the physiological thresholds, amplitude growth, and contraction duration of the acoustic stapedius reflex (ASR) in Andean children aged 2-17 years living at altitudes of 2850m (Altitude I Group) and 3973m (Altitude II Group) as part of a general medical assessment of the health status of the children. The brainstem-mediated ASR reveals the integrity of the neuronal components of the auditory reflex arc, including the cochlea receptors, eight cranial nerves, and brainstem neural projections to the cochlear nuclei, bilateral superior olivary nuclei, facial nerve nuclei, and facial nerve and its stapedius branch. Uncrossed (ipsilateral) and crossed (contralateral) ASR thresholds (ASRT), ASR amplitude growth (ASRG) function, and ASR muscle contraction duration (decay/ fatigue) (ASRD) were measured noninvasively with 500, 1000 Hz and broadband (bandwidth = 125-4000 Hz) noise stimulus activators using a middle ear immittance system. Oxygen saturation (SaO(2)) level and heart rate were measured in a subsample of the study group. Statistical analyses revealed that the Altitude I and Altitude II groups had ASRT, ASRG function, and ASRD rates comparable to children at sea level and that the two groups were not significantly different for any of the ASR measures. No significant association was found between SaO(2) or heart rate and ASRT, growth, and muscle fatigue rate. In conclusion, the assessment of the ASR in children in the high-altitude groups revealed normal function. Furthermore, the results indicate no adverse oto-physiological effects of altitude on the brainstem-mediated ASR at elevations between 2850 and 4000m and suggest normal middle ear and auditory brainstem function.
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| 3. |
- Counter, S Allen, et al.
(författare)
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Experimental Fusion of Contrast Enhanced High-Field Magnetic Resonance Imaging and High-Resolution Micro-Computed Tomography in Imaging the Mouse Inner Ear
- 2015
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Ingår i: The Open Neuroimaging Journal. - : Bentham Science Publishers Ltd.. - 1874-4400. ; 9, s. 7-12
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Imaging cochlear, vestibular, and 8th cranial nerve abnormalities remains a challenge. In this study, the membranous and osseous labyrinths of the wild type mouse inner ear were examined using volumetric data from ultra high-field magnetic resonance imaging (MRI) with gadolinium contrast at 9.4 Tesla and high-resolution micro-computed tomography (µCT) to visualize the scalae and vestibular apparatus, and to establish imaging protocols and parameters for comparative analysis of the normal and mutant mouse inner ear.METHODS: For in vivo MRI acquisition, animals were placed in a Milleped coil situated in the isocenter of a horizontal 9.4 T Varian magnet. For µCT examination, cone beam scans were performed ex vivo following MRI using the µCT component of a nanoScan PET/CT in vivo scanner.RESULTS: The fusion of Gd enhanced high field MRI and high-resolution µCT scans revealed the dynamic membranous labyrinth of the perilymphatic fluid filled scala tympani and scala vestibule of the cochlea, and semicircular canals of the vestibular apparatus, within the µCT visualized contours of the contiguous osseous labyrinth. The ex vivo µCT segmentation revealed the surface contours and structural morphology of each cochlea turn and the semicircular canals in 3 planes.CONCLUSIONS: The fusion of ultra high-field MRI and high-resolution µCT imaging techniques were complementary, and provided high-resolution dynamic and static visualization of the complex morphological features of the normal mouse inner ear structures, which may offer a valuable approach for the investigation of cochlear and vestibular abnormalities that are associated with birth defects related to genetic inner ear disorders in humans.
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| 4. |
- Counter, S. Allen, et al.
(författare)
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Middle Ear Function and Pathophysiology in Andean Children Living at High Altitudes
- 2017
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 18:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- The extent of altitude-related middle ear disorders in children native to high altitudes is unclear. This study examined middle ear pathophysiology in two groups of children living in high-altitude Ecuadorian Andean communities by investigating middle ear pressure (MEP), tympanic membrane compliance (TMC), and ear canal volume (ECV) using tympanometry, and by otological examination. Altitude I Group lived at 2850m, and Altitude II Group resided at around 4000m. The two high-altitude groups were compared with a reference group of children residing at sea level. Mean MEP was -3.6daPa (SD: 39.2), 3.5daPa (SD: 28.7), and 1.3daPa (SD: 13.6) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The MEP was not significantly different among the three groups. Mean TMC was 0.63cm3 (SD: 0.51), 0.60cm3 (SD: 0.43), and 0.60cm3 (SD: 0.24) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The TMC was not significantly different among the three groups. Mean ECV was 1.1 (SD: 0.26), 1.2 (SD: 0.26), and 1.0 (SD: 0.23) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The difference in ECV between Altitude I Group and Altitude II Group was significant (p=0.043), as was the difference between Altitude II Group and the Sea Level Group (p=0.001). ECV did not differ significantly between Altitude I Group and the Sea Level Group. Otological examination revealed a low incidence of ear canal and middle ear pathology. In conclusion, tympanometric and otological findings did not reveal a high incidence of middle ear pathophysiology in children living at altitudes as high as around 4000m.
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| 5. |
- Counter, S Allen, et al.
(författare)
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MRI evidence of endolymphatic impermeability to the gadolinium molecule in the in vivo mouse inner ear at 9.4 tesla
- 2013
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Ingår i: The Open Neuroimaging Journal. - : Bentham Science Publishers Ltd.. - 1874-4400. ; 7, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:Previous in vivo experimental magnetic resonance imaging (MRI) investigations of the mammalian inner ear at 4.7 Tesla have indicated that intravenously injected gadolinium (Gd) penetrates the perilymphatic labyrinth, but not the endolymphatic membranous labyrinth. In the present study, high field MRI at 9.4T was used to visualize the in vivo mouse vestibulo-cochlea system, and to determine whether the endolymphatic system is permeable to a Gd complex.METHODS:A 9.4 T Varian magnet equipped with a 12 cm inner diameter gradient system with maximum gradient strength of 600 mT/m, a millipede coil (Varian design) and a Gd contrast agent were used for image acquisition in the normal C57 BL-6 mouse.RESULTS:High-resolution 2D and 3D images of the mouse cochlea were acquired within 80 minutes following intravenous injection of Gd. Gd initially permeated the perilymphatic scala tympani and scala vestibuli, and permitted visualization of both cochlear turns from base to apex. The superior, inferior and lateral semicircular canals were subsequently visualized in 3 planes. The membranous endolymphatic labyrinth was impermeable to intravenously injected Gd, and thus showed no apparent uptake of Gd at 9.4T.CONCLUSION:The 9.4T field strength MRI permitted acquisition of high resolution images of anatomical and physiological features of the normal, wild type mouse perilymphatic inner ear in vivo, and provided further evidence that the endolymphatic system is impermeable to intravenously injected Gd.
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| 6. |
- Counter, S. Allen, et al.
(författare)
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Ultra-high-field (9.4 T) MRI Analysis of Contrast Agent Transport Across the Blood-Perilymph Barrier and Intrastrial Fluid-Blood Barrier in the Mouse Inner Ear
- 2017
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Ingår i: Otology and Neurotology. - 1531-7129 .- 1537-4505. ; 38:7, s. 1052-1059
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Effective paramagnetic contrast agent for the penetration of the perilymphatic spaces of the scala tympani, scala vestibuli, and scala media of the mouse inner ear can be determined using intravenous injection of various gadolinium (Gd) complexes and ultra-high-field magnetic resonance imaging (MRI) at 9.4 Tesla.Background: A number of contrast agents have been explored in experimental high-field MRI to determine the most effective Gd complex for ideal signal-to-noise ratio and maximal visualization of the in vivo mammalian inner ear in analyzing the temporal and spatial parameters involved in drug penetration of the blood-perilymph barrier and intrastrial fluid-blood barrier in the mouse model using MRI.Methods: Gadoteric acid (Dotarem), Gadobutrol (Gadovist), Gadodiamide (Omniscan), Gadopent acid (Magnevist), and Mangafodipir (Teslascan) were administered intravenously using the tail vein of 60 Balb/C mice. High-resolution T1 images of drug penetration were acquired with a horizontal 9.4 T Agilent magnet after intravenously injection. Signal intensity was used as a metric of temporal and spatial parameters of drug delivery and penetration of the perilymphatic and endolymphatic spaces.Results: ANOVA analysis of the area under the curve of intensity enhancement in perilymph revealed a significant difference (p < 0.05) in the scalae uptake using different contrast agents (F (3,25) = 3.54, p = 0.029). The Gadoteric acid complex Dotarem was found to be the most effective Gd compound in terms of rapid, morphological enhancement for analysis of the temporal, and spatial distribution in the perilymphatic space of the inner ear.Conclusion: Gadoteric acid (Dotarem) demonstrated efficacy as a contrast agent for enhanced visualization of the perilymphatic spaces of the inner ear labyrinthine in the mouse, including the scala tympani and scala vestibuli of the cochlea, and the semicircular canals of the vestibular apparatus. These findings may inform the clinical application of Gd compounds in patients with inner ear fluid disorders and vertigo.
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