Figure 2 from Hedjoudje et al
Method for generating MSCT (A and B) and FPCT (C and D) MPR. Two planes are generated. The first plane is approximately tangential to the thin segments of the superior and horizontal SCCs at their junctions with their ampullae and includes the 6 electrode contacts of the forked array inserted into the superior and horizontal ampullae. The second plane is in the posterior plane of the SCC and includes the 3 electrode contacts of the linear array implanted in the posterior canal and the tip of braided platinum/iridium wire inserted into the common crus. Section thickness was set to 2 mm to include all electrode contacts on 1 image for both planes. Window width and contrast level were adjusted as needed to optimize the visibility of electrode contacts. A 3D representation of the vestibular lumen and vestibular nerve is added in transparency (E and F) to help visualize the anatomy.

Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51–66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n = 2) or flat panel CT (n = 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9° (range, −57.5° to 45°), and the median reference electrode insertion length was 42 mm (range, −21−66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.


Jeffrey Ross

• Mayo Clinic, Phoenix

Dr. Jeffrey S. Ross is a Professor of Radiology at the Mayo Clinic College of Medicine, and practices neuroradiology at the Mayo Clinic in Phoenix, Arizona. His publications include over 100 peer-reviewed articles, nearly 60 non-refereed articles, 33 book chapters, and 10 books. He was an AJNR Senior Editor from 2006-2015, is a member of the editorial board for 3 other journals, and a manuscript reviewer for 10 journals. He became Editor-in-Chief of the AJNR in July 2015. He received the Gold Medal Award from the ASSR in 2013.

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