scholarly journals A Miniature, Fiber-Optic Vibrometer for Measuring Unintended Acoustic Output of Active Hearing Implants during Magnetic Resonance Imaging

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6589
Author(s):  
Guy Fierens ◽  
Joris Walraevens ◽  
Ronald Peeters ◽  
Nicolas Verhaert ◽  
Christ Glorieux
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Sound Pressure ◽  
Pulse Sequences ◽  
Test Method ◽  
Signal Frequency ◽  
Resonance Imaging ◽  
Active Middle Ear Implant ◽  
Sound Pressure Levels ◽  
Mri Environment

Making use of magnetic resonance imaging (MRI) for diagnostics on patients with implanted medical devices requires caution due to mutual interactions between the device and the electromagnetic fields used by the scanner that can cause a number of adverse events. The presented study offers a novel test method to quantify the risk of unintended output of acoustically stimulating hearing implants. The design and operating principle of an all-optical, MRI safe vibrometer is outlined, followed by an experimental verification of a prototype. Results obtained in an MRI environment indicate that the system can detect peak displacements down to 8 pm for audible frequencies. Feasibility testing was performed with an active middle ear implant that was exposed to several pulse sequences in a 1.5 Tesla MRI environment. Magnetic field induced actuator vibrations, measured during scanning, turned out to be equivalent to estimated sound pressure levels between 25 and 85 dB SPL, depending on the signal frequency. These sound pressure levels are situated well below ambient sound pressure levels generated by the MRI scanning process. The presented case study therefore indicates a limited risk of audible unintended output for the examined hearing implant during MRI.

Magnetic Resonance Imaging Compatibility of a New Generation of Active Middle Ear Implant

2016 ◽  
Vol 37 (7) ◽  
pp. e222-e227 ◽  
Author(s):  
Johannes Schnabl ◽  
Astrid Wolf-Magele ◽  
Stefan Marcel Pok ◽  
Lena Hirtler ◽  
Gertraud Heinz ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Middle Ear ◽  
Resonance Imaging ◽  
Active Middle Ear Implant ◽  
Middle Ear Implant ◽  
New Generation

scholarly journals ROLE OF DIFFERENT PULSE SEQUENCES FOR BETTER CONTRAST USING MAGNETIC RESONANCE IMAGING.

2017 ◽  
Vol 5 (2) ◽  
pp. 226-232
Author(s):  
Aalia Nazir ◽  
◽  
MuhammadWaqas Akhtar ◽  
Zahida Batool. ◽  
◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Pulse Sequences ◽  
Resonance Imaging

AB1098 STRUCTURAL ELEMENTS OF THE KNEE ENTHESES ASSESSED IN HEALTHY SUBJECTS WITH ULTRA HIGH FIELD MRI (150 MICRONS).

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1838-1838
Author(s):  
D. Roche ◽  
C. Michel ◽  
P. Daudé ◽  
A. Le Troter ◽  
C. Chagnaud ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Healthy Subjects ◽  
High Field ◽  
T2 Mapping ◽  
Pulse Sequences ◽  
Structural Elements ◽  
Resonance Imaging ◽  
Ultra High Field ◽  
Mineralized Zone

Background:Fibrocartilaginous enthesis is composed of different histological zones which are commonly referred to the tendon distal extremity (a lamellar tissue with a low cell density, collagen and connective tissue), the fibrocartilaginous zone (with chondrocytes), a progressively mineralized zone and the bone. The MRI visualization of the water content of entheses is challenging given the very short relation time so that entheses has been very poorly assessed using MRI (1).Objectives:The main objective of the study was to assess the structural elements of the knee enthesis based on the quantitative T2* measurements using Ultra High Field (UHF) MRI.Methods:Twelve healthy subjects without any osteoarticular pathology were included in the study after they provided their informed consent. 3D gradient echo sequence with a 4.3 ms echo time and T2* mapping were performed. The lateral internal, external and crossed ligaments, patellar and quadricipital tendons were assessed. T2* measurements were performed specifically on the quadricipital tendon.Results:The quadricipital tendon and the bone trabeculation could be visualized on the UHF MR image. The T2* mapping analysis illustrated a large value (16.4 ± 4 ms) for the subchondral bone and much lower values for the trabecular bone (11 ± 4.5 ms) and the different zones of the keen entheses (7.7 ± 1.9 ms).Conclusion:Based on T2* measurements performed using UHF MRI, the different structural elements of the knee entheses were distinguished. This quantitative stratification could be used to assess changes in pathological conditions such as SpA and trauma.References:[1]Benjamin M, Bydder GM. Magnetic resonance imaging of entheses using ultrashort TE (UTE) pulse sequences. Journal of magnetic resonance imaging: JMRI. 2007;25(2):381-9.Disclosure of Interests:None declared

scholarly journals Dilated Virchow–Robin Spaces Mimicking a Brainstem Arteriovenous Malformation

2017 ◽  
Vol 08 (02) ◽  
pp. 291-293 ◽  
Author(s):  
Thomas J. Buell ◽  
Arjun Ramesh ◽  
Dale Ding ◽  
Daniel M. S. Raper ◽  
Ching-Jen Chen ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Arteriovenous Malformation ◽  
Arteriovenous Malformations ◽  
Pulse Sequences ◽  
Resonance Imaging ◽  
Unique Case ◽  
Cystic Neoplasms ◽  
Imaging Characteristics ◽  
Magnetic Resonance Imaging Mri

ABSTRACTVirchow–Robin spaces (VRS) are ubiquitous and commonly observed as the resolution of magnetic resonance imaging (MRI) continues to improve. The function of VRS and the etiology of their dilation is still a subject of research. Diagnosing dilated VRS (dVRS) can be challenging because they may appear similar to other pathologies such as cystic neoplasms, infectious cysts, and even arteriovenous malformations (AVMs) on certain MRI pulse sequences. We reported a unique case of brainstem dVRS mimicking an AVM. Furthermore, the extensive pontine involvement of our patient’s lesion is rarely described in neurosurgical literature. Understanding the imaging characteristics of dVRS is critical to accurately diagnose these lesions and avoid unnecessary tests and procedures.

scholarly journals Optimization of pulse sequences in ultrafast magnetic resonance imaging for the diagnosis of acute abdominal pain caused by gastrointestinal disease

2020 ◽  
Vol 9 (8) ◽  
pp. 205846012094924 ◽  
Author(s):  
Akitoshi Inoue ◽  
Akira Furukawa ◽  
Norihisa Nitta ◽  
Kai Takaki ◽  
Shinichi Ohta ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Abdominal Pain ◽  
Magnetic Resonance ◽  
Diagnostic Accuracy ◽  
Acute Abdominal Pain ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Resonance Imaging ◽  
True Fisp ◽  
Significant Difference

Background Magnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain. Purpose To investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseases Material and Methods We retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction. Results Diagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 ( P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 ( P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers ( P < 0.0083). Conclusion T2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging.

Characteristics of Incidental Pineal Cysts on Magnetic Resonance Imaging

Neurosurgery ◽  
1989 ◽  
Vol 25 (4) ◽  
pp. 636-640 ◽  
Author(s):  
Jagveer S. Sandhu ◽  
James R. McLaughlin ◽  
Camilo R. Gomez
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spin Density ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
Characteristic Appearance ◽  
Cystic Changes ◽  
Echo Pulse

Abstract Three patients with different neurological complaints were studied by magnetic resonance imaging. Coincidentally, all studies showed cystic changes within the pineal bodies. These cysts appeared hypointense on T1-weighted, spin-echo pulse sequences and hyperintense on T2-weighted images. Spin-density sequences displayed them as hypointense areas, with relaxation times similar to those of the CSF, suggesting their cystic nature. The increased use of magnetic resonance imaging may result in coincidental imaging of involutional cystic pineal changes of many individuals; their characteristic appearance will allow the differentiation between them and pineal neoplastic conditions.

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