DOWNLOAD PDF PRINCIPLES OF COCHLEAR IMPLANT IMAGING

Transcription

1 Chapter 1 : Imaging in cochlear implant patients 7 Principles of Cochlear Implant Imaging. Andrew J. Fishman and Roy A. Holliday. Radiographic imaging plays a major role in cochlear implantation with regard to preoperative candidacy evaluation, intraoperative monitoring, postoperative evaluation, as well as research and experimental techniques. Fishman and Roy A. Holliday Radiographic imaging plays a major role in cochlear implantation with regard to preoperative candidacy evaluation, intraoperative monitoring, postoperative evaluation, as well as research and experimental techniques. At a minimum, successful cochlear implantation requires that electrical impulses be delivered to a surviving spiral ganglion cell population, and that these impulses be transmitted to a functioning auditory cortex by an existent neural connection. Accordingly, imaging the auditory pathway of the implant candidate is necessary to screen for morphological conditions that preclude or complicate the implantation process. Increasing resolution of computed tomography CT and magnetic resonance imaging MRI technology has provided the clinician with more detailed information about the integrity of the auditory pathway. As technologies evolve, a clear understanding of what information can be obtained as well as the limitations of various imaging modalities is essential to proper candidacy evaluation, and selection of the ear to be implanted in complex cases. Also important is the effect that the presence of a cochlear implant has on future imaging of the head and neck region of an implantee. In the past, the presence of a cochlear implant was considered to be a major contraindication to MRI. Analysis is performed in a stepwise approach, answering the following three questions: Are there cochleovestibular anomalies that preclude implantation? Is there evidence of luminal obstruction? Are there additional findings that may complicate the surgery or subsequent patient management? This section is not intended to review principles or techniques of image acquisition, but rather to provide a platform for discussion between the implant team and the radiologist. As a general rule, however, the more severe the deformity, the worse the hearing. Given the current technology, the minimum requirement for cochlear implantation is the presence of an implantable cavity in proximity to stimulable neural elements whose projections connect to the auditory cortex. Accordingly, the first question that must be answered is the following: Are there any cochleovestibular anomalies that preclude implantation? Embryology To fully appreciate the wide variety of possible cochleovestibular malformations, it is helpful to first review the embryogenesis of the inner ear. The development of the combined cochlear and vestibular membranous labyrinthine system begins with the formation of the otic placode as an ectodermal thickening that forms on the surface of the neural tube in the third gestational week. The otic placode invaginates from the surface and forms the otocyst in the fourth gestational week. The otocyst develops three infolds in the fifth week. The resultant pouches represent the primordial endolymphatic sac and duct, the utricle and semicircular canals, and the saccule and cochlea. Beginning in the sixth week, the cochlear duct grows from its primordial bud beginning from the basal region spiraling apically to reach its full 2. The neuroepithelial end organs continue to develop beyond this period with the organ of Corti completing its formation in the 25th week. The semicircular canals begin their formation as three small, folded evaginations on the primordial vestibular appendage. They develop as disk-like outpouchings whose centers eventually compress and fuse to ultimately form the semicircular duct structure. By the sixth week of gestational life, this compression and fusion has taken place in first the superior and then the posterior canals. The three canals continue to enlarge and complete their formation to full adult size in sequence beginning with the superior around the 20th week, and followed by the posterior and finally the lateral semicircular canals. Interestingly, the endolymphatic sac and duct are the first to appear and the last to complete their development. The osseous otic capsule eventually forms from a morphologically fully developed cartilage precursor model via 14 centers of ossification, beginning around the 15th gestational week, and is completed during the 23rd gestational week. The cartilage model and underlying membranous labyrinth continue to grow in the region of the posterior and lateral semicircular canals, while other structures, which have previously attained their final shape and size, have begun ossifying. The cochleovestibular nerves and ganglia develop in concert with the membranous labyrinth and cochleovestibular end organs. They are of neural crest origin and migrate between the epithelial layer and Page 1

2 basement membrane of the otic vesicle during the fourth gestational week. Cochlear Malformations There is much confusion in the literature regarding the nomenclature of cochlear morphologic anomalies especially regarding the term Mondini malformation. In, Carlo Mondini presented his findings on an anatomical dissection of a young deaf boy. He noted that the vestibule was not deformed but was of greater than usual size. He also noted an increase in the size of the elliptical recess though it was normal in shape. He commented that the semicircular canals appeared normal and that the positions of their openings into the vestibule were unremarkable. In observing the medial opening of the vestibular aqueduct, he commented that it was quite enlarged and was larger than the size of the common crus. The cochlea was described as possessing only 1. He also described an incompletely formed interscalar septum. The more contemporary term incomplete partition is commonly used to describe this classic anomaly and denotes this specific aspect of the deformity. Because of its relative frequency as well as its historic significance, the term Mondini malformation is commonly used to describe all forms of cochlear morphological abnormalities and not just the incomplete partition. The term Mondini dysplasia was used by Schuknecht 7 in an in-depth analysis of the histopathology and clinical features of cochlear anomalies. Schuknecht histologically described these malformations as isolated findings or in association with the Klippel-Feil, Pendred, and DiGeorge syndromes. His work detailed the clinical nature of these disorders as being unilateral or bilateral, and associated with acoustic and vestibular dysfunction that is variable in severity, static, or progressive. Phelps 8 reserves the term Mondini deformity for cochleae whose basal turns are normal and possess a deficiency of the interscalar septum of the distal 1. He differentiates these cochleae from those termed dysplastic owing to their widened basal turn being in wide communication with a dilated vestibule. According to Phelps the significance is in the clinical absence of a spontaneous cerebrospinal fluid CSF leak and meningitis in patients with his strict definition of Mondini deformity as opposed to those patients with dysplasia who did manifest these complications in a series of 20 patients studied. Since the writings of Mondini, several investigators have documented a variety of inner ear malformations. Though not the first to describe or name these malformations, Jackler et al 3 in proposed a classification system for the congenitally malformed inner ear based on the theory that a variety of deformities result from arrested development at different stages of embryogenesis. The authors clearly stated that their classification could not describe all observable abnormalities but was meant to serve as a framework upon which other describable anomalies could be added, which by their supposition would have resulted from aberrant, rather than arrested, development. Page 2

3 Chapter 2 : HiResâ Ultra 3D MRI Safety Information The Cochlear â Nucleus  Implant System contains a removable magnet, to ensure MRI compatibility, safety and comfort for Cochlear Implant recipients. Cochlear was the first to introduce this key safety feature nearly two decades ago. You are free to copy, distribute and transmit the work, provided the original author and source are credited. This article has been cited by other articles in PMC. Abstract Imaging procedures are a mainstream tool in the daily ENT workflow. Cochlear Implant patients are representing a special population with specific demands for imaging. There are different imaging techniques available for pre-operative evaluation, surgery and postoperative controls with different indications and consequences. High-resolution computed tomography and magnetic resonance imaging are mainly used in the evaluation process. New procedures, as digital volume tomography, are increasingly used intra- and postoperatively. Especially the intracochlear positioning in malformations of the inner ear, eventually added with radiological assisted navigation, can be considered a standard of modern cochlear implant surgery. In addition, digital volume tomography may serve as a quality control tool focusing on the evaluation of the intracochlear electrode position. The range of applications, indications and current results are illustrated. Introduction Electrical stimulation of the hearing nerve for auditory rehabilitation by cochlear implants is the standard therapy in congenital and acquired severe to profound deafness. Current developments are characterized by expanding indications for cochlear implant surgery, e. According to the experience of the last 25 years, imaging procedures are of utmost importance. The improvement of surgical therapy by navigation and, in future, by robotics is based on the use of imaging procedures. This survey is supposed to give an overview on currently available and necessary imaging procedures for cochlear implant patients. Basic considerations on imaging Today radiologic and magnet resonance imaging procedures are available in the daily clinical use. Procedures are selected according to the goal of the examination and can be divided into preoperative, intraoperative, and postoperative imaging procedures. Preoperative imaging High resolution computed tomography HRCT and magnetic resonance imaging are regularly used for cochlear implant preoperative evaluation for the evaluation of inner ear malformations, surgical planning, and especially the imaging of the VIIIth nerve [ 2 ], [ 3 ], [ 4 ]. In children, these imaging procedures are especially important due to the high incidence of inner ear malformations. Malformations of the inner ear can be characterized by slight changes of the morphology e. The features of surgical planning in complex malformations are discussed in the chapter Navigation. High resolution computed tomography is able to evaluate especially bony structures. An accurate analysis of the cochlear labyrinth is important for a precise surgical planning. The manufacturers of cochlear implant devices provide various electrodes like short, long, preformed, straight, perimodiolar. After analyzing the malformation, the proper electrode has to be chosen by the surgeon. In case that the analysis of the computed tomography reveals a hypoplastic cochlea Figure 1 Fig. Page 3

4 Chapter 3 : Cochlear implant Radiology Reference Article blog.quintoapp.com Cochlear's Implants are the most reliable in the industry, which is one of the reasons why Cochlear is the most chosen hearing implant company. With over, implants worldwide 3, no other company can match our record for implant reliability. Correspondence should be addressed to Philipp Mittmann ; moc. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The aim of this study was to evaluate the internal auditory canal and the labyrinth in a 1. T1 and T2 weighted sequences were conducted for each position. Excellent visibility of the internal auditory canal and the labyrinth was seen in the T2 weighted sequences with 9 cm between the magnet and the outer ear canal at every nasionâ outer ear canal angle. T1 sequences showed poorer visibility of the internal auditory canal and the labyrinth. Aftercare and visibility of intracerebral structures after cochlear implantation is becoming more important as cochlear implant indications are widened worldwide. With a distance of at least 9 cm from the outer ear canal the artifact induced by the magnet allows evaluation of the labyrinth and the internal auditory canal. Introduction Magnetic resonance imaging MRI has become a standard diagnostic procedure with different indications over all medical specialties and is part of the preoperative test battery for candidates for cochlear implant surgery. With over implantees worldwide, the probability of a MRI scan in an implanted patient for medical reasons is quite high [ 1 ]. The indication for cochlear implantation has evolved in recent decades from single-sided implantation in bilateral patients, to bilateral implantation and to patients with residual hearing and asymmetric hearing loss. This widening of the indication range has increased the probability of postoperative scanning for different medical reasons. With increasing numbers and availability of MRI scans, patients with vestibular or intracochlear schwannomas can gain from a cochlear implant. Such patients undergo either primary surgery and subsequently implantation as a single-step [ 2, 3 ] or a two-step procedure within a controlled time-frame in order to decrease the probability of tumor recurrence [ 4 ]. MRI artifacts at 3T that are induced by the cochlear implant have been reported to make it extremely difficult to realistically assess audiovestibular structures [ 5 ] with a CI magnet in place. Nevertheless Todt et al. Retrospective analyses of implantees undergoing 1. Cochlear implant manufacturers have used different approaches to enable scanning procedures at 3T. Cochlear Sydney, Australia, with a 3T-approved device [ 8 ], offers the option to remove the magnet as a solution for decreasing MRI-related artifacts. Med-El Innsbruck, Austria recently introduced a device with approval for use at 3T using a magnet that makes removal unnecessary. The aim of the present study was to observe differences in the magnet artifacts in relation to magnet position and MRI sequences under the visual assessment of the internal auditory canal and the labyrinth at 1. The study was conducted according to the principles expressed in the Declaration of Helsinki. The volunteers were scanned with T1- and T2-weighted sequences at each of these nine positions. All examinations were performed in a 1. An experienced neuroradiologist and two experienced neurotologists evaluated the internal auditory canal and labyrinth. The parameters are as follows: Results The sizes of the skulls of the three subjects were between 56 and 57 cm and did not differ significantly from each other. By comparing the different positions of the magnet, we could differentiate the labyrinth and the internal auditory canal IAC in relation to the magnet artifact when evaluating the scans. The subjects reported pressure on the side of the magnet but pain and displacement were denied. The IAC is good and the labyrinth is not visible. The IAC and the labyrinth are good visible. The IAC and the labyrinth are not visible. The IAC and the labyrinth are excellent visible. The IAC is excellent and the labyrinth is good visible. Discussion Cochlear implantation has become a standard procedure to rehabilitate patients with hearing loss worldwide. The indications are increasing and hence the number of recipients rises every year. Similar to cochlear implantation the number of MRIs is also rising in modern clinical practice. MRI scanning with any hearing implant in place is a highly relevant issue. However, this approach bears the risk of wound and implant infection or subsequently even loss of the implant. Furthermore patients are required to undergo general anaesthesia for the removal and repositioning of the Page 4

5 magnet. In the study by Wagner et al. The artifact caused by the magnet is similar to our results in the 1. Nevertheless they conclude that if the magnet is removed, MRIs at 1. With evolving indications for cochlear implantation nowadays patients after vestibular schwannoma removal are enclosed. Postoperative visualization of the IAC and the labyrinth by MRI is of great importance for follow-up in these patients [ 10 ]. MRI scanning with the magnet in place may cause problems. Demagnetization is a potential problem, especially in 3T MRIs, and depends on the position of the magnet in relation to the magnetic field of the scanner. Implant displacement has not been widely discussed in the literature [ 11 ] as most relevant studies have focused on the visualization of the IAC and the inner ear [ 5 ]. In MRI at 1. Regarding the differences between sequences, better visibility with reduced artifacts can be achieved when using T2 weighted non-3d sequences. These findings are in line with Walton et al. External positioning of the magnet on the surface of the skin with a scalp thickness of about 6 mm had no significant impact on the visibility of the important structures in comparison to an implanted magnet. Our three volunteers had skull sizes of 56 and 57 cm and had similar and comparable outcomes. Significant differences might be seen in children as they have a smaller skull size. Our study has some limitations. Only adults were included in our study. Furthermore our results are based on the evaluation of only three adults. More patients would add more weight to our results. In conclusion, with the visualization offered by MRI scans at 1. Furthermore it can be assumed that certain artifact-reduction algorithms will lead to greater tolerance limits with regard to angle and absolute distance of the implant. Disclosure The study was not funded and is part of the employment of the authors. The employer is the Unfallkrankenhaus Berlin. The funder was not involved in the manuscript writing, editing, approval, or decision to publish. Conflicts of Interest The authors declare that there are no conflicts of interest. Page 5

6 Chapter 4 : Principles of Cochlear Implant Imaging Ento Key Magnetic Resonance Imaging (MRI) scans use powerful magnets to create detailed images of the inside of a person's body. MRI safety is especially important for cochlear implant recipients, because every cochlear implant has an internal magnet that can be affected by an MRI scan. Back to Full Paper Considerations in the Cochlear Implant Process Once the decision is made to pursue a cochlear implant, there are a multitude of steps involved in the process. The first step is to contact a hospital implant center. The process usually involves medical, audiological, speech and language, education, and other support service professionals. Although each hospital center may have its own protocol, the following components of the process are typically included: Initial consult-professionals from the hospital implant center inform families of the cochlear implantation process. Topics for discussion may include pre-implantation testing and counseling, insurance coverage, the types of devices available, the surgery, programming of the external components of the device, and the training process. Audiological assessment-a current Auditory Brainstem Response ABR evaluation is necessary for young children to confirm the degree of hearing loss. For more information about understanding audiological assessment. Hearing Aid Trial-While a hearing aid trial is usually a part of the protocol, the length of the trial period may vary depending on a variety of factors. For example, a hearing aid trial may be short for young children with confirmed profound hearing levels and limited observable benefit from a hearing aid to hasten implantation in the interest of the age of the child. A hearing aid trial may be longer for an older child who has proven to be a poor hearing aid user. An implant center may be trying to determine if an older child demonstrates responsibility and motivation to wear hearing aid technology. The rationale for an increased trial sometimes backfires as a child with a profound loss may dislike and not be motivated to use his or her hearing aid as he or she obtains limited benefit from it. This same child may like a cochlear implant when he or she has increased access to sound. Similarly, a parent who is excited about obtaining a cochlear implant for the child may not devote sufficient time and energy to a hearing aid trial. Some hospitals have on-site staff trained in the specialized evaluation tools, techniques, and test standardizations for children who are deaf. Some hospital programs collaborate with support service professionals in school programs serving deaf and hard of hearing children to obtain these evaluations. No matter where the evaluations are completed, it is important that the professionals completing them are trained in, and familiar with, the tools and standards of evaluating deaf children. Medical evaluations-children are evaluated by an otolaryngologist ear, nose, and throat doctor to obtain a medical history, evaluate the structures of the ear system, and look for possible medical reasons why a child may not be a candidate for a cochlear implant. The otolaryngologist is also usually the doctor who completes the cochlear implant surgery. Family education and counseling-family members and the children themselves based on the age of the child will be counseled about what to expect related to the complex considerations related to choosing a cochlear implant. A comprehensive implant center will work closely with families and children to educate them about expectations related to the implantation process and the variable outcomes associated with implantation. Components of the habilitation process are shared so family members have a clear understanding of the training commitment that follows the surgery. Oftentimes, children participate in the habilitation process prior to surgery to become familiar with the activities and strategies that will be used after implantation. Outreach with educational programs-most children and families in the implantation process are already enrolled in an educational program. The educational professionals may bring a perspective to the candidacy process that may not otherwise be shared by the family or observed in the hospital setting. This collaboration will also facilitate development and implementation of appropriate educational goals and communication strategies for the child when he or she returns to his or her educational placement following implantation. Choices During the Implantation Process Choosing a Manufacturer There are three manufacturers of cochlear implants commonly used in the United States see links above. Some hospital implant centers offer the option of choosing an implant from any of the three companies. Some hospital implant centers may only offer one brand of cochlear implant. Some implant centers may provide a preference for one manufacturer over another, while others may Page 6

7 not. Most centers will help families compare characteristics of implants in order to make an appropriate choice. It may be helpful to speak with other families regarding their experience with a particular manufacturer as a decision is made. Possible considerations in making this decision include: For more information comparing the impact manufacturer technologies: Deciding Which Ear to Implant Single Ear Implantation If a child is going to obtain a cochlear implant in one ear, there are a variety of factors involved in making a decision about which ear to implant, including: Anatomy of the ear system-cat scans or MRIs, which indicate the condition of the cochlea and the auditory nerve, are utilized to determine the following impacting factors: If so, the insertion of the electrodes into the cochlea can be adversely impacted. Presence of ossification does not mean that cochlear implantation is not possible; however, the quality of sound may be diminished if a sufficient number of electrodes cannot be adequately inserted. If there is a difference in ossification levels between ears, this may influence which ear is chosen for implantation. Though the implant is placed within the cochlea, sound must be transmitted to the brain via the eighth nerve. If this nerve is not intact or is not present, a cochlear implant will not be possible. Some individuals who do not have an intact auditory nerve may be a candidate for a brainstem implant which places an implant beyond the auditory nerve. The auditory brainstem implant is similar in design and function to a cochlear implant, except that the electrode is placed on the first auditory relay station in the brainstem, the cochlear nucleus. Though surgery may still be possible with a malformed cochlea, the ear with a better-formed cochlea is more likely to be chosen if all other factors are equal. Electrical stimulation-if one ear is noted to respond better to the electrical stimulation of the cochlea as noted on the Promontory Stimulation Test, this may influence which ear to implant. However, this test is not completed by all hospital implant centers, and there is no definitive research as to its benefit in identifying the best ear to implant. Implantation of the better ear-if there is a difference in hearing levels between ears, some centers may choose to implant the ear with more residual hearing. This choice reasons that since this ear has more hearing and has benefited from a hearing aid, it may have better potential to benefit from the cochlear implant. If only one ear is to be implanted, this is a harder decision to make if this ear adequately benefits from a traditional hearing aid and residual hearing could then be lost. Implantation of the worse ear-if there is a difference in hearing levels between ears, some may choose to implant the worse ear. This choice reasons that the "better" ear could continue benefiting from a traditional hearing aid should the cochlear implant not be successful in that ear and there would be nothing to sacrifice in implanting this ear. Picking the ear on the right side-if there is no difference between ears and everything else is equal, some centers may lean towards implantation of the right ear. This choice reasons that since the "speech centers" of the brain are on the left side and there exists a crossover effect sound transferred from the right to the left side of the brain for processing, implantation on the right side may facilitate processing of speech and language information. Bilateral Cochlear Implantation Bilateral cochlear implants are being considered for increasing numbers of children. While it is becoming the standard of care for some, it should not be considered an automatic choice for all. Bilateral implants, through providing a binaural advantage to listening, can improve general ease in listening, speech perception in noise, and localization abilities. As it is not always possible to pick the most responsive ear with single-sided implantation, bilateral implantation always gets the "best ear. Would the child benefit from continued acoustic listening through a hearing aid in the non-implanted ear? See the module on Factors Impacting Performance Outcomes. Should bilateral implantation be completed simultaneously or sequentially? If it is sequential, when should the second implant occur? What are the implications for a child who has an older generation of a device in one ear and is receiving a newer generation of the device in the second ear? For more information on bilateral implantation: Page 7

8 Chapter 5 : Nucleus 6 Implant Information Cochlear * Recipients with MED-EL cochlear implants may be safely MRI scanned when following the specific conditions for each implant detailed in the instructions for use. HiResolution Bionic Ear System: Unilateral and bilateral recipients with this device can be safely scanned in an MR system meeting the following conditions: The external sound processor and headpiece are MR Unsafe and must be removed before entering a room containing an MR scanner. Horizontal closed bore scanners with a static magnetic field of 3. In MRI testing of unilateral and bilateral recipient conditions, respectively, the image artifact caused by the device extends from the HiRes Ultra implant approximately 5 cm using a spin echo pulse sequence in a 3. These artifacts may result in a loss of diagnostic information in the implant vicinity. The recommended minimum duration of time post implant surgery prior to undergoing an MRI scan is 2 to 4 weeks in order to allow any inflammation to subside. An MRI scan is not recommended if the patient has a fever. Horizontal closed bore scanners with a static magnetic field of 1. In MRI testing of unilateral and bilateral recipient conditions, respectively, the image artifact caused by the device extends from the HiRes Ultra implant approximately 3 cm and 4 cm using a gradient echo pulse sequence in a 1. A bandage must be applied using the bandaging protocol below. The bandaging protocol with use of the MRI Antenna Coil Cover was developed and approved to prevent magnet displacement and counteract magnet torque during a 1. Please consult with your physician if this is an issue. If discomfort persists following an MRI, please notify your physician. Please consult with your physician prior to MRI to determine if the benefits of MRI are worthwhile over other imaging techniques. The bandaging protocol recommended by Advanced Bionics is followed when the patient undergoes an MRI procedure with the magnet left in place or, The internal magnet is surgically removed and possibly replaced with the Magnet Insert Dummy before the patient undergoes an MRI procedure. The external sound processor and headpiece are removed before entering a room where an MRI scanner is located. Verify that the implant, or both implants if bilaterally implanted, are compatible for conducting an MRI before proceeding. Failure to do so can lead to device movement, device damage, magnet movement, patient discomfort, or trauma and pain to the patient. Before entering the area of an MRI scanner: Place patient in sitting position to allow access to the implant site. Place the patient headpiece with cable removed over the implant site. The magnets will hold the headpiece in place. Cut a piece of the Coach bandage that is long enough to wrap around the head once. Wrap this piece around the head, so that the bandage covers the patient headpiece. Make this wrap tight. Outline the position of the headpiece on the bandage using a marker or pen. Slip out the patient headpiece, but keep the bandage in place. Measure head size and bandage length needed for compression wrapping. Take the remaining Coach bandage roll and wrap the bandage around the head once, without stretching. Mark the location on the bandage that is one full wrap around the head. This is the head circumference. Unwrap the piece of bandage with the marked head circumference, and place it on a flat surface. Unroll the remaining bandage roll. Fold over the bandage start and crease at the marked head circumference. Cut or tear the remaining bandage where it overlaps with the bandage start. The resulting bandage piece length is twice the head circumference. Wrap this cut piece, this time very tightly, by stretching the marked line an additional half turn around the head. Chapter 6 : Magnetic Resonance Imaging Artifacts and Cochlear Implant Positioning at T In Vivo Imaging plays an important part in the work-up of cochlear implant candidates, and an understanding of imaging evaluation procedures is essential. The radiologist must be familiar with imaging findings that contraindicate implantation (absence of the cochlea or cochlear nerve) and with those that could significantly alter surgery (facial nerve. Chapter 7 : Cochlear Implants: Process Imaging procedures are a mainstream tool in the daily ENT workflow. Cochlear Implant patients are representing a Page 8

9 special population with specific demands for imaging. There are different imaging techniques available for pre-operative evaluation, surgery and postoperative controls with different. Chapter 8 : Cochlear Implants - AJNR Blog Principles of cochlear implant imaging. In: Waltzman S.B The commonly stated role of post-operative imaging in cochlear implantation is to exclude extra-cochlear. Chapter 9 : Cochlear Implants Abstract. Summary: A data acquisition protocol for postoperative imaging of cochlear implants by using multisection CT (MSCT) is described. The improved image quality of MSCT allows assessment of the precise intracochlear position of the electrode array and visualization of individual electrode contacts. Page 9