Advanced

AJNR - American Journal of Neuroradiology

Published ahead of print on May 15, 2008
doi: 10.3174/ajnr.A1108

This Article Abstract Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Verbist, B.M. Articles by Frijns, J.H.M. Search for Related Content PubMed PubMed Citation Articles by Verbist, B.M. Articles by Frijns, J.H.M.

Evaluation of 4 Multisection CT Systems in Postoperative Imaging of a Cochlear Implant: A Human Cadaver and Phantom Study

B.M. Verbist^a, R.M.S. Joemai^a, W.M. Teeuwisse^a, W.J.H. Veldkamp^a, J. Geleijns^a and J.H.M. Frijns^b

^a Departments of Radiology, Leiden University Medical Center, Leiden, the Netherlands
^b Otolaryngology, Leiden University Medical Center, Leiden, the Netherlands

View larger version (135K): [in this window] [in a new window]   Fig 1. Scoring of the visibility of electrode contacts and anatomic structures: on a MPR perpendicular to the modiolus of an MSCT image of the implanted human cadaver temporal bone, the cochlea is divided in 4 quadrants (white crosslines). The quadrants are numbered counterclockwise, and the round window niche is located in the first quadrant (I-IV). A quantitative score from 0 to 2 was given to each electrode contact according to its visibility. Cochlear structures, such as the inner and outer wall, were scored per quadrant. The kinking of the electrode is localized in the third quadrant (arrow). b indicates basal turn of the cochlea at the level of the round window; v, vestibule, *horizontal semicircular canal (SCC); **superior SCC.

View larger version (61K): [in this window] [in a new window]   Fig 2. Photograph (A) and 1 high-resolution optical image (B) of the PMMA phantom containing a cochlear implant.

View larger version (72K): [in this window] [in a new window]   Fig 3. MSCT of the PMMA phantom: 16 electrode contacts are numbered from the tip to the base: electrode numbers 1, 5, 10, and 15 are indicated.

View larger version (83K): [in this window] [in a new window]   Fig 4. MPR CT images of the human cadaver temporal bone along the plane of the electrode array on Aquilion-64 (A), Brilliance 64 (B), LightSpeed-64 (C) (also seen in Fig 1), and Sensation-64 (D). The upper set of images is displayed with W/L 3000/800 and shows cochlear anatomic structures, such as the semicircular canals, well in all of the scanners. The lower set of images shows the chosen manually adjusted window/level setting for visualization of the electrode contacts. This illustrates that a wide range of HUs is essential for visualization of the CI.

View larger version (46K): [in this window] [in a new window]   Fig 5. Graphic presentation of the mean differences over 4 observers (y-axis) between electrode position as manually indicated and the position in the computer model (in millimeters). Values are shown per electrode contact (x-axis) for each scanner (Aquilion-64, yellow; Brilliance-64, blue; LightSpeed-64, red; Sensation-64, green). See also Table 3.

View larger version (4K): [in this window] [in a new window]   Fig 6. Clinical implications of the PSF: the dotted curves depict the pixel value of a single electrode contact through the center. Summation of these curves renders a curve (black line). When the distance between 2 electrodes is larger than FWHM, the resulting curve still shows 2 maximum values, and the electrode contacts can be separated in the image (A). If the distance between 2 electrode contacts is smaller than FWHM, the resulting curve shows a single peak; the electrode contact cannot be visualized separately (B).