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Cochlear Implants and Auditory Brainstem Implants
Published in R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne, Scott-Brown's Essential Otorhinolaryngology, 2022
Rajeev Mathew, Deborah Vickers, Patrick Axon, Manohar Bance
Complications of CI surgery include standard complications of mastoid surgery (see Chapter 10). In addition, patients must be warned of the risk of device failure and of meningitis. For the latter reason, patients should have the 23-valent polysaccharide pneumococcal vaccination (given after the age of 2) in addition to the childhood meningitis immunisation programme. Intraoperative cerebrospinal fluid (CSF) leak can occur when making the cochleostomy or RW opening in patients with inner ear malformations but can be managed by raising the head of the bed and inserting the electrode with a soft tissue seal around it; lumbar drainage is rarely required. Occasionally the electrode cannot be inserted fully due to cochlear fibrosis/ossification, e.g. due to meningitis or otosclerosis. In some cases, it is necessary to drill out the basal turn of the cochlea or even insert a split electrode for which an additional channel is drilled into the middle turn of the cochlea. Tip folds over of the electrode in the cochlea and facial nerve stimulation from the CI are complications that can usually be managed by altering the stimulation settings for the CI. Some patients also experience chronic pain following surgery, which rarely necessitates device explantation. There is a risk of magnet displacement with MRI and the make of implant should always be checked and appropriate precautions taken prior to such imaging.
Principles behind Magnetic Resonance Imaging (MRI)
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Magnetic resonance imaging (MRI) is a well-established medical imaging technique, traditionally associated with excellent soft-tissue contrast properties. Current clinical MRI systems provide not only morphological information throughout the body, but also a number of advanced techniques related to tissue and organ function, physiology, and microstructure.
Magnetic Resonance Imaging Physics
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
The risks of having an MRI scan are quite different compared to other imaging modalities that use ionising radiation. MRI scans are generally perceived to be safer than scans involving X-rays, but this is only true if MRI is carried out with strict safety control measures in place. It is important for Clinical Scientists to be aware of new scientific publications related to MRI safety and adjust local rules and procedures in accordance to the latest scientific and regulatory information.
Radiation impacts on toxicity of cobalt–chromium (CoCr) implant debris
Published in Nanotoxicology, 2023
Kevin L. Trout, Sanghamitra Majumdar, Anil K. Patri, Tariq Fahmi
Patients with metal implants often undergo routine surveillance to ensure successful surgical placement and to monitor for complications. Noninvasive imaging approaches include magnetic resonance imaging (MRI), ultrasound, and radiological imaging (Mushtaq et al. 2019). Metal implants pose unique imaging challenges, as certain metals may torque or heat due to interaction with MRI magnetic fields (Winter et al. 2021; Shellock 2002) or cause artifacts that need to be mitigated with techniques, such as metal artifact reduction sequence (MARS) (Jungmann et al. 2017). Radiological imaging procedures may include conventional X-rays, computed tomography (CT), fluoroscopy, or nuclear medicine options, such as bone scintigraphy (Mushtaq et al. 2019). Higher radiation energies tend to be used with metal implants to reduce artifact due to beam hardening, which can result in increased radiation dose (Kataoka et al. 2010). In addition, studies have shown that metal implants can amplify radiation exposure to surrounding tissue (Song et al. 2019; Reft et al. 2003; Rosengren et al. 1993). While continued implant surveillance may improve patient outcomes, recurrent exposure to ionizing radiation increases the risk of adverse deterministic or stochastic health effects, such as widespread cellular damage or cancer. These are a result of genetic damage caused by direct absorption of radiation energy, indirect damage caused by free radicals, or other bystander effects (Council 2006; Desouky, Ding, and Zhou 2015).
MRI-guided endovascular intervention: current methods and future potential
Published in Expert Review of Medical Devices, 2022
Bridget F. Kilbride, Kazim H. Narsinh, Caroline D. Jordan, Kerstin Mueller, Teri Moore, Alastair J. Martin, Mark W. Wilson, Steven W. Hetts
Safety protocols have been established for interventional MRI procedures [59], but they must be revisited with the introduction of new technology. Training is essential to incorporate proper safety checks into the workflow of the surrounding area and the MRI suite. Personnel entering the MRI suite should be checked for metallic materials. Prior to entering the MRI suite, the patient must be checked for potentially dangerous metallic materials, such as EKG electrodes or pacemakers. Equipment entering the MRI suite, such as anesthesia pumps, ventilators, and gas tanks, must be at least MRI-conditional and clearly marked as such in accordance with ASTM standards [60,61]. If equipment is not safe to enter the MRI suite, tubing and wires may be routed through RF-shielded wall conduits to the patient, introducing additional layers of complexity to interventional MRI procedures.
Changes of prominent vessel sign and susceptibility vessel sign in acute ischemic stroke patients with and without successful recanalization: a study based on susceptibility weighted images
Published in Neurological Research, 2022
Zhiye Li, Xiaoyan Bai, Peiyi Gao, Yan Lin, Yi Ju, Binbin Sui
MRI was conducted at our institution on a 3.0 T scanner (Ingenia, Philips Healthcare, Best, the Netherlands) with a 32-channel head coil. The MR protocol included sagittal and axial T1-weighted imaging, axial T2-weighted and T2-weighted fluid attenuation inversion recovery (FLAIR), and three-dimensional (3D) time-of-flight MR angiography (3D TOF MRA). A single-shot echo-planar imaging DWI sequence was used with the following parameters: repetition time/echo time (TR/TE) = 2342.00/65.97 ms, b = 1000 s/mm2, slice thickness = 5 mm, slice number = 23, field of view = 228 mm, and matrix = 144 x 144. A related apparent diffusion coefficient (ADC) map was generated. SWI images were based on heavily T2* images which were acquired by multiecho FFE sequence. The parameters for 3D SWI sequences were as follows: TR/TE = 30.04/6.03 ms, flip angle = 15 degrees, slice thickness = 2.50 mm with a 1.25 mm slice gap, 47 sections per slab, matrix = 432 x 432, and FOV = 230 mm. Minimal intensity projection (mIP) images were reconstructed with a thickness of 3 mm. Follow-up MRI included the same protocol for all patients at 24 hours (±6 hours) after recanalization treatment.