Morphologic examination of the temporal bone by cone beam computed tomography: Comparison with multislice helical computed tomography

SummaryIntroductionHigh-resolution CT imaging is essential to diagnosis and follow-up of temporal bone pathology. Morphologically, CT is the reference examination. The requirement of long-term follow-up thus exposes patients to cumulative radiation doses. Limiting exposure to ionizing radiation is an increasing concern of public health authorities. The principal advantage of Cone Beam CT (CBCT) lies in a significant reduction in radiation dose. The main objective of the present study was to assess the morphologic concordance between CBCT and Multislice Helical Computed Tomography (MSCT) on 20 anatomic landmarks corresponding to regions of interest in clinical practice. The secondary objectives were to compare the two techniques qualitatively in stapes and footplate assessment and measurement of footplate thickness, and quantitatively in terms of dosimetry.Material and methodsAn experimental anatomical study was performed on 12 temporal bones from fresh human cadavers of unknown clinical history. Each underwent CBCT and MSCT.ResultsThere was no significant difference in morphologic assessment of the temporal bones on the two techniques. Exploration of the stapes, incudostapedial joint, anterior stapediovestibular joint and footplate was qualitatively more precise on CBCT, and footplate thickness showed less overestimation than on MSCT. CBCT delivered 22 times less radiation than MSCT under the present experimental conditions.ConclusionCBCT provides reliable morphologic assessment of temporal bone, thanks to higher spatial resolution than on MSCT, with significantly reduced radiation dose

Cochlear implantation feasibility in rhesus macaque monkey: anatomic and radiologic results.

International audienceBACKGROUND: Large animal models of implantable hearing devices are needed to assess innovative technologies before using them in humans. The rhesus macaque has cognitive abilities close to humans and has been used in the past but with noncommercial implants or no detailed radiologic descriptions of the surgical procedures. The aim of this study was to evaluate the feasibility of cochlear implantation in this animal model. METHODS: We present detailed radiologic data (CT scan and Cone beam computed tomography) from 7 heads of rhesus macaque monkeys coming from autopsy materials. Several comparative measurements were performed with 10 human temporal bones to emphasize similarities and differences between the macaque and the human inner ear. The radiologic analyses helped planning the surgical approach for cochlear implant insertion in the macaque. RESULTS: We managed to perform one full (720 degrees) and 3 partial insertions (190-330 degrees) of cochlear implants in 4 rhesus macaque cochleae, documented by cone beam computed tomography reconstructions. We confirm that the procedure is facilitated in this animal because the cochlea dimensions are close to humans. However, marked differences in the orientation of the external auditory canal and the basal turn must be taken into account. We suggest that the removal of the inferior wall of tympanal bone provides the optimal axis for electrode array insertion. CONCLUSION: The rhesus macaque monkey is a valid and close-to-human animal model for cochlear implants insertion. Because this species is widely used in both behavioral and physiologic studies, we expect that functional implants can be coupled with electrophysiologic recordings to study the mechanisms of auditory compensation