Cone-beam CT versus multi-slice CT systems for postoperative imaging of cochlear implantation--a phantom study on image quality and radiation exposure using human temporal bones

Comparison of 96-kV and 120-kV cone-beam CT for the assessment of cochlear implants

BACKGROUND

To compare the diagnostic value of 120-kV with conventional 96-kV Cone-Beam CT (CBCT) of the temporal bone after cochlear implant (CI) surgery.

METHODS

This retrospective study included CBCT scans after CI surgery between 06/17 and 01/18. CBCT allowed examinations with 96-kV or 120-kV; other parameters were the same. Two radiologists independently evaluated following criteria on 5-point Likert scales: osseous spiral lamina, inner and outer cochlear wall, semi-circular canals, mastoid trabecular structure, overall image quality, metal and motion artefacts, depiction of intracochlear electrode position and visualisation of single electrode contacts. Effective radiation dose was assessed.

RESULTS

Seventy-five patients (females, n = 39 [52.0%], mean age, 55.8 ± 16.5 years) were scanned with 96-kV (n = 32, 42.7%) and 120-kV (n = 43, 57.3%) protocols including CI models from three vendors (vendor A n = 7; vendor B n = 43; vendor C n = 25). Overall image quality, depiction of anatomical structures, and electrode position were rated significantly better in 120-kV images compared to 96-kV (all p < = 0.018). Anatomical structures and electrode position were rated significantly better in 120-kV CBCT for CI models from vendor A and C, while 120-kV did not provide improved image quality in CI models from vendor B. Radiation doses were significantly higher for 120-kV scans compared to 96-kV (0.15 vs. 0.08 mSv, p < 0.001).

CONCLUSIONS

120-kV and 96-kV CBCT provide good diagnostic images for the postoperative CI evaluation. While 120-kV showed improved depiction of temporal bone and CI electrode position compared to 96-kV in most CI models, the 120-kV protocol should be chosen wisely due to a substantially higher radiation exposure.

Ultra-low-dose photon-counting CT of paranasal sinus: an in vivo comparison of radiation dose and image quality to cone-beam CT

PURPOSE

This study investigated the differences in subjective and objective image parameters as well as dose exposure of photon-counting CT (PCCT) compared to cone-beam CT (CBCT) in paranasal sinus imaging for the assessment of rhinosinusitis and sinonasal anatomy.

METHODS

This single-centre retrospective study included 100 patients, who underwent either clinically indicated PCCT or CBCT of the paranasal sinus. Two blinded experienced ENT radiologists graded image quality and delineation of specific anatomical structures on a 5-point Likert scale. In addition, contrast-to-noise ratio (CNR) and applied radiation doses were compared among both techniques.

RESULTS

Image quality and delineation of bone structures in paranasal sinus PCCT was subjectively rated superior by both readers compared to CBCT (P < .001). CNR was significantly higher for photon-counting CT (P < .001). Mean effective dose for PCCT examinations was significantly lower than for CBCT (0.038 mSv ± 0.009 vs. 0.14 mSv ± 0.011; P < .001).

CONCLUSION

In a performance comparison of PCCT and a modern CBCT scanner in paranasal sinus imaging, we demonstrated that first-use PCCT in clinical routine provides higher subjective image quality accompanied by higher CNR at close to a quarter of the dose exposure compared to CBCT.

Visualization of Different Types of Cochlear Implants in Postoperative Cone-Beam CT Imaging

RATIONALE AND OBJECTIVES

To evaluate cone-beam computed-tomography (CBCT) images of the temporal bone for radiological delineation, metal artifacts, and accuracy for localization of six different electrode arrays after cochlear device implantation.

MATERIALS AND METHODS

This retrospective study included 116 patients who underwent CBCT (120kV, 7.1mA) within 24 hours after cochlear device implantation. Exclusion criteria were anatomical abnormalities, and electrode misinsertion. Six different CI electrodes were implanted: Advanced Bionics HiFocus Mid-Scala, Cochlear Contour Advance, Cochlear Slim-Straight, Cochlear Slim-Modiolar, MED-EL Flex 24 and MED-EL Flex 28. Two radiologists rated independently presence of metal artifacts, overall image quality, as well as dedicated visualization of the osseous spiral lamina, inner and outer cochlear wall, single electrode contacts, and electrode position using 5-point-Likert scales. Inter-rater agreement was calculated by using Cohen's kappa and intraclass correlation.

RESULTS

Of 116 patients, 94 (81.0%; 56.1 ± 16.9 years; age range, 13-86 years; 49 [52.1%] females) were included in the study. Overall image quality was rated good for all electrode models without significant differences (p = 0.061). Depiction of electrode contacts was rated significantly better for Advanced Bionics HiFocus Mid-Scala, Cochlear Slim-Straight, and MED-EL Flex 24 and 28 compared to Cochlear Contour Advance and Slim-Modiolar (p < 0.001). Depiction of the osseous spiral lamina (p = 0.20), inner (p = 0.42) and outer cochlear wall (p = 0.35), metal artifacts (p = 0.18), and electrode position (p = 0.31) did not show significant differences between electrode models. Inter-rater agreement varied from substantial to almost perfect (0.70-0.93).

CONCLUSION

CBCT provides excellent visualization of all evaluated CI electrode types, in particular electrode arrays with greater spacing between contacts and contact size allow improved radiologic evaluation.

A dose-neutral image quality comparison of different CBCT and CT systems using paranasal sinus imaging protocols and phantoms

Purpose

To compare the image quality produced by equivalent low-dose and default sinus imaging protocols of a conventional dental cone-beam computed tomography (CBCT) scanner, an extremity CBCT scanner and a clinical multidetector computed tomography (MDCT) scanner.

Methods

Three different phantoms were scanned using dose–neutral ultra-low-dose and low-dose sinus imaging protocols, as well as default sinus protocols of each device. Quantified parameters of image quality included modulation transfer function (MTF) to characterize the spatial response of the imaging system, contrast-to-noise ratio, low contrast visibility, image uniformity and Hounsfield unit accuracy. MTF was calculated using the line spread and edge spread functions (LSF and ESF).

Results

The dental CBCT had superior performance over the extremity CBCT in each studied parameter at similar dose levels. The MDCT had better contrast-to-noise ratio, low contrast visibility and image uniformity than the CBCT scanners. However, the CBCT scanners had better resolution compared to the MDCT. Accuracy of HU values for different materials was on the same level between the dental CBCT and MDCT, but substantially poorer performance was observed with the extremity CBCT.

Conclusions

The studied dental CBCT scanner showed superior performance over the studied extremity CBCT scanner when using dose–neutral imaging protocols. In case a dental CBCT is not available, the given extremity CBCT is still a viable option as it provides the benefit of high resolution over a conventional MDCT.

Cone-Beam CT Compared to Multi-Slice CT for the Diagnostic Analysis of Conductive Hearing Loss: A Feasibility Study

OBJECTIVES

Multislice computed tomography (MSCT) is commonly used as a diagnostic tool for patients with a conductive hearing loss. Recent studies indicate that cone-beam computed tomography (CBCT) may be used as a low-radiation dose alternative for temporal bone imaging. This study compares image quality and radiation dose between CBCT and MSCT when assessing anatomical landmarks related to conductive hearing loss.

MATERIALS AND METHODS

Five human cadaver heads (10 ears) were imaged on the NewTom 5G CBCT and the Discovery CT750 HD MSCT. Visibility of 16 anatomical landmarks of the middle and inner ear was assessed by two observers on a 4-point Likert scale. Furthermore, effective radiation dose was compared, and contrast-to-noise ratio and spatial resolution were measured with a phantom head.

RESULTS

Image quality of CBCT was assessed as superior to MSCT. Effective radiation dose of the high-resolution CBCT protocol was 30.5% of the clinical MSCT dose. High-resolution CBCT was reported as having a higher spatial resolution and superior contrast-to-noise perception in comparison with MSCT.

CONCLUSION

High-resolution CBCT was evaluated as superior to MSCT in the assessment of structures related to conductive hearing loss. Furthermore, CBCT imaging resulted in a considerably lower effective radiation dose.

Radiohistologic Comparison Study of Temporal Bone Specimens After Cochlear Implant Electrode Array Insertion: Is Cone-Beam CT Superior to MDCT?

OBJECTIVE. The purpose of this article is to evaluate subjective image quality and diagnostic accuracy to determine cochlear implant (CI) electrode position in a temporal bone (TB) specimen on cone-beam CT (CBCT) versus MDCT. MATERIALS AND METHODS. In this retrospective study, two radiologists independently reviewed CBCT (96-kV and 120-kV settings) and MDCT images of 20 TB specimens after electrode implantation. Qualitative evaluation of bone structures of the otic capsule, inner and outer cochlear wall, osseous spiral lamina, electrode position relative to the osseous spiral lamina, visualization of single electrode contacts on the array, metal artifacts, and overall image quality was performed using a five-point scale. Intracochlear electrode position was subsequently correlated with histologic examination. RESULTS. Radiologic assessment of bone structures of the otic capsule, the cochlear wall (except the outer part), osseous spiral lamina, electrode position, visualization of single electrode contacts on the array, metal artifacts, and overall image quality were significantly higher in CBCT compared with MDCT (maximum p = .04). No significant differences were found between CBCT at 96 kV and 120 kV (minimum p = .21). The intracochlear electrode position with histologic correlation was correctly diagnosed in 100% and 97.5% of specimens on 120-kV and 96-kV CBCT, respectively, whereas 77.5% were correctly assessed using MDCT. CONCLUSION. The data suggest that CBCT shows a higher diagnostic accuracy in TB specimen imaging after CI compared with MDCT, in particular to determine the intracochlear localization of the implant.

Cone-beam CT versus Multidetector CT in Postoperative Cochlear Implant Imaging: Evaluation of Image Quality and Radiation Dose

BACKGROUND AND PURPOSE

Cone-beam CT is being increasingly used in head and neck imaging. We compared cone-beam CT with multidetector CT to assess postoperative implant placement and delineate finer anatomic structures, image quality, and radiation dose used.

MATERIALS AND METHODS

This retrospective multicenter study included 51 patients with cochlear implants and postoperative imaging via temporal bone cone-beam CT (n = 32 ears) or multidetector CT (n = 19 ears) between 2012 and 2017. We evaluated the visualization quality of single electrode contacts, the scalar position of the electrodes, cochlear walls, mastoid facial canal, metallic artifacts (using a 4-level visual score), and the ability to measure the insertion angle of the electrodes. The signal-to-noise ratio and radiation dose were also evaluated.

RESULTS

Cone-beam CT was more sensitive for visualizing the scalar position of the electrodes (P = .046), cochlear outer wall (P = .001), single electrode contacts (P < .001), and osseous spiral lamina (P = .004) and had fewer metallic artifacts (P < .001). However, there were no significant differences between both methods in visualization of the modiolus (P = .37), cochlear inner wall (P > .99), and mastoid facial canal wall (P = .07) and the ability to measure the insertion angle of the electrodes (P > .99). The conebeam CT group had significantly lower dose-length product (P < .001), but multidetector CT showed a higher signal-to-noise ratio in both bone and air (P = .22 and P = .001).

CONCLUSIONS

Cone-beam CT in patients with cochlear implants provides images with higher spatial resolution and fewer metallic artifacts than multidetector CT at a relatively lower radiation dose.

Intraoperative Impedance-Based Estimation of Cochlear Implant Electrode Array Insertion Depth

OBJECTIVE

Cochlear implant impedances are influenced by the intracochlear position of the electrodes. Herein, we present an intuitive approach to calculate tissue resistances from transimpedance recordings, ultimately enabling to estimate the insertion depth of cochlear implant electrodes.

METHODS

Electrode positions were measured in computed-tomography images of 20 subjects implanted with the same lateral wall cochlear implant model. The tissue resistances were estimated from intraoperative telemetry data using bivariate spline extrapolation from the transimpedance recordings. Using a phenomenological model, the electrode insertion depths were estimated.

RESULTS

The proposed method enabled the linear insertion depth of all electrodes to be estimated with an average error of 0.76 ± 0.53 mm.

CONCLUSION

Intraoperative telemetry recordings correlate with the linear and angular depth of electrode insertion, enabling estimations with an accuracy that can be useful for clinical applications.

SIGNIFICANCE

The proposed method can be used to objectively assess surgical outcomes during and after cochlear implantation based on non-invasive and readily available telemetry recordings.

Fluoroscopy guided electrode-array insertion for cochlear implantation with straight electrode-arrays: a valuable tool in most cases

PURPOSE

To highlight the advantages of real time fluoroscopy guided electrode-array (EA) insertion (FGI) during cochlear implants surgery.

METHODS

All surgical procedures were performed in a dedicated operating room equipped with a robotic C-arm cone beam device, allowing for intraoperative real time 2D FGI and postoperative 3D imaging. Only straight EAs were used. Patients were sorted out in three groups: ANAT, with anatomical concerns; HP, with residual hearing; NPR: patients with no particular reason for FGI. In all cases the angle of EA-insertion was measured. In the HP group pre and postoperative hearing were compared. The radiation delivered to the patient was recorded.

RESULTS

Fifty-three cochlear implantation procedures were achieved under fluoroscopy in 50 patients from November 2015 to January 2020 (HP group: n = 10; ANAT group: n = 13; NPR group: n = 27). In the ANAT group, FGI proved to be helpful in 8 cases (61.5%), successfully guiding the surgeon during EA -insertion. On average, the angle of insertion was at 424° ± 55°. In the HP group, a controlled smooth EA-insertion was carried out in all cases but one. The targeted 360° angle of insertion was always reached. Hearing preservation was possible with an eventual average drop of 30 ± 1.5 dB. In the NPR group, FGI helped control the quality of insertion in all cases and appeared very informative in five (17.8%): one EA-misrouting, three stuck EAs, and one case with hidden electrodes out of the cochlea in revision surgery. Final 3D cone beam CT scan double-checked the EA position in all adults. The radiation dose was equivalent to a bit less than four digital subtract radiographs.

CONCLUSION

The FGI is a very useful adjunct in cochlear implantation in all cases of expected surgical pitfalls, in patients with residual hearing, and even in case without preoperative particular reason, with low irradiation.

The Image Fusion Technique for Cochlear Implant Imaging: A Study of its Application for Different Electrode Arrays

OBJECTIVES

To investigate the benefits of the image fusion technique for precise postoperative assessment of intracochlear placement with six different electrode arrays.

STUDY DESIGN

Consecutive retrospective case study.

SETTINGS

Tertiary referral center.

PATIENTS

Analyses of imaging data of 30 patients implanted with six different electrode arrays.

INTERVENTIONS

Electrode reconstructions obtained from postoperative cone-beam computed tomography (CBCT) were overlaid onto preoperative magnetic resonance imaging (MRI) and/or high-resolution computed tomography (HRCT) registrations to create artefact-free images.

MAIN OUTCOME MEASURES

Each electrode's intracochlear position was analyzed with the image fusion reconstructions and compared with the results obtained by CBCT alone. The electrode location was classified according to its position in relation to the basal membrane at four different insertion angles.

RESULTS

In 40 out of 151 measurements (26.5%), the location grading obtained by CBCT alone changed after the assessment with the image fusion reconstructions. A significant association was found between deep insertions (over 360 degrees) and the effectiveness of image fusion (p = 0.019). The difference between the impact of the fusion technique for the basal turn versus the apical part was highly significant (p = 0.001). There was no significant difference between the effectiveness of the image fusion and the different electrodes.

CONCLUSIONS

By utilizing an image fusion technique, a more accurate assessment of electrode placement could be achieved for all types of electrodes. Image fusion was especially beneficial for insertions beyond 360 degrees.

The Insertion Results of a Mid-scala Electrode Assessed by MRI and CBCT Image Fusion

OBJECTIVES

To investigate the results of clinical surgical insertions with a Mid-scala array (HIFocus Mid-Scala Electrode, HFms).

STUDY DESIGN

Consecutive retrospective case study.

SETTINGS

Tertiary referral center.

PATIENTS

Analyses of imaging data of 26 consecutive patients (31 insertions) implanted with the HFms.

INTERVENTION (S)

The evaluation of insertion trauma evoked by a previously validated image fusion technique. Electrode reconstructions from postoperative cone-beam computed tomography (CBCT) were overlaid onto preoperative magnetic resonance imaging (MRI) scans to create artifact-free images.

MAIN OUTCOME MEASURES

The electrode position was quantified in relation to the basilar membrane. Trauma scaling adopted from Eshraghi was used for evaluating insertion trauma. The results of the visual assessment of the postoperative CBCT were compared to those obtained with the fusion technique.

RESULTS

Three insertions had to be excluded due to incompatibility of the imaging data with the fusion software. We found consistent peri- to mid-modiolar placement of the HFms with a mean insertion depth angle of 376°. According to the medical records, a visual examination of the postoperative CBCT indicated that there had been no scala dislocations but when assessed by the image fusion technique, five scala dislocations (17.8%) were found. Additionally, one tip fold-over was detected in the postoperative CBCT even though this was not evident in any intraoperative measurements.

CONCLUSION

HFms showed atraumatic surgical insertion results with consistent mid-modiolar placement. Image fusion enhances the accuracy of the insertion trauma assessment. Routine postoperative imaging is recommended for identifying tip fold-over as well as for quality control and documentation.

Cochlear Implantation With a Novel Long Straight Electrode: the Insertion Results Evaluated by Imaging and Histology in Human Temporal Bones

HYPOTHESIS

To evaluate the insertion results of a novel straight array (EVO) by detailed imaging and subsequent histology in human temporal bones (TB).

BACKGROUND

The main focuses of modern cochlear implant surgery are to prevent damage to the intracochlear structures and to preserve residual hearing. This is often achievable with new atraumatic electrode arrays in combination with meticulous surgical techniques.

METHODS

Twenty fresh-frozen TBs were implanted with the EVO. Pre- and postoperative cone beam computed tomography scans were reconstructed and fused for an artifact-free representation of the electrode. The array's vertical position was quantified in relation to the basilar membrane on basis of which trauma was classified (Grades 0-4). The basilar membrane location was modeled from previous histologic data. The TBs underwent subsequent histologic examination.

RESULTS

The EVOs were successfully inserted in all TBs. Atraumatic insertion (Grades 0-1) were accomplished in 14 of 20 TBs (70%). There were three apical translocations, and two basal translocations due to electrode bulging. One TB had multiple translocations. The sensitivity and specificity of imaging for detecting insertion trauma (Grades 2-4) was 87.5% and 97.3.0%, respectively.

CONCLUSION

Comparable insertion results as reported for other arrays were also found for the EVO. Insertion trauma can be mostly avoided with meticulous insertion techniques to prevent bulging and by limiting the insertion depth angle to 360 degrees. The image fusion technique is a reliable tool for evaluating electrode placement and is feasible for trauma grading.

Intraoperative Evaluation of Cochlear Implant Electrodes Using Mobile Cone-Beam Computed Tomography

OBJECTIVE

To evaluate the electrode status during cochlear implantation (CI) using mobile cone-beam CT (mCBCT).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral hospital.

PATIENTS

Fifty-seven patients (7 bilateral surgeries, 64 ears) who underwent CI and who received intraoperative mCBCT imaging.

INTERVENTION

CI and CBCT during surgery.

MAIN OUTCOME MEASURE

Electrode location and angular insertion depth determined by intraoperative mCBCT images.

RESULTS

There were six cases with cochlear malformation where intraoperative mCBCT was useful to confirm electrode location. Of 58 ears with a normal cochlear morphology, perimodiolar, straight, and mid-scalar electrodes were used in 30 (cochleostomy; 14 advance off-stylet technique cases), 27 (26 round window [RW] insertion, 1 extended round window [ERW] insertion), and 1 (RW insertion) ears, respectively. Complete scala-tympani (ST) insertion was achieved in 35 ears (14 cochleostomy, 21 RW or ERW insertion). The complete ST-insertion rate was significantly higher with RW or ERW insertion than that for cochleostomy insertion (p = 0.03), although cochleostomy insertion using the advanced off-stylet technique had a similar rate to RW or ERW insertion. The angular insertion depth values (average ± standard deviation) for perimodiolar electrodes (354.4 ± 29.44 degrees) were significantly smaller than those for Flex24 (464.8 ± 43.09 degrees) and Flex28 (518.2 ± 61.91 degrees) electrodes (p < 0.05).

CONCLUSIONS

Evaluation of CI electrodes using intraoperative mCBCT was comparable to that with fan-beam CT or c-arm-based CBCT. Considering the low radiation dose of mCBCT and its availability in any operation room, mCBCT is the better modality for evaluating cochlear implant electrode arrays.

Intraoperative Conebeam CT for Assessment of Intracochlear Positioning of Electrode Arrays in Adult Recipients of Cochlear Implants

BACKGROUND AND PURPOSE

Intraoperative conebeam CT has been introduced into the operating room and provides quick radiologic feedback. This study aimed to investigate its utility in the assessment of the positioning of the electrode array after cochlear implantation.

MATERIALS AND METHODS

This was a retrospective study of 51 patients (65 ears) with intraoperative imaging by conebeam CT (O-arm) after cochlear implantation between 2013 and 2017. Correct placement into the cochlea was immediately identified. Positioning assessments were later analyzed with OsiriX software.

RESULTS

Intraoperative imaging was quickly performed in all cases. No misplacement into the vestibule or semicircular canals was found. A foldover of the implanted array was identified in 1 patient. Secondary analysis by 2 raters showed excellent agreement on insertion depth angle (intraclass correlation = 0.96, P < .001) and length of insertion of the electrode array (intraclass correlation coefficient = 0.93, P = .04) measurements. The evaluation of the number of extracochlear electrodes was identical between the 2 raters in 78% of cases (Cohen κ = 0.55, P < .001). The scalar position was inconsistent between raters. When we compared O-arm and high-resolution CT images in 14 cases, the agreement was excellent for insertion depth angle (intraclass correlation coefficient = 0.97, P < .001) and insertion length (intraclass correlation coefficient = 0.98, P < .001), good for the number of extracochlear electrodes (Cohen κ = 0.63, P = .01), but moderate for the scalar position (Cohen κ = 0.59, P = .02).

CONCLUSIONS

Intraoperative conebeam CT using the O-arm is a safe, rapid, easy, and reliable procedure to immediately identify a misplacement or foldover of an electrode array. The insertion depth angle, insertion length, and number of electrodes inserted can be accurately assessed.

Comparison of radiation doses imparted during 128-, 256-, 384-multislice CT-scanners and cone beam computed tomography for intra- and perioperative cochlear implant assessment

PURPOSE

To examine radiation-doses imparted during multislice (MSCT) and cone-beam computed-tomography (CBCT) for perioperative examination of cochlear-implant insertion.

METHODS

Radiation-doses were assessed during standardized petrous-bone CT-protocols at different MSCT ((I) single-source CT-scanner Somatom-Definition-AS+, (II) 2nd generation of dual-source CT-scanner Somatom-Definition-Flash, (III) 3rd generation of dual-source CT-scanner Somatom-Force and at the CBCT Ziehm-Vision-RFD3D ((IV) (a) RFD-3D (Standard-modifier), (b) RFD-3D (Low-dose-modifier)). Image quality was examined by two radiologists appraising electrode-array placement, quality-control of cochlear-implant surgery and complications based on real patients' examinations (n=78).

RESULTS

In MSCT-setting following radiation-doses were assessed (CTDI_w; DLP): (I) 21.5mGy; 216mGycm; (II) 19.7mGy; 195mGycm; (III) 12.7mGy; 127mGycm; in the CBCT setting radiation doses were distributed as follows: (IV) (a) 1.9mGy; 19.4mGycm; (b) 1.2mGy; 12.9mGycm. Overall, image quality was evaluated as good for both, MSCT- and CBCT-examinations, with a good interrater reliability (r=0.81).

CONCLUSION

CBCT bears considerable dose-saving potential for the perioperative examination of cochlear-implant insertion while maintaining adequate image quality.

Possibility of differentiation of cochlear electrodes in radiological measurements of the intracochlear and chorda-facial angle position

Due to an increasing number of cochlear implantations, quality control has become more important. In addition to intraoperative biophysical measurements, radiological imaging is another possibility. An upcoming technique regarding this is Cone Beam CT (CBCT). Sixty-five data sets (35 Nucleus Contour Advance–Cochlear; 30 Flex Soft–MedEl) of postoperative imaging by CBCT (Accu-I-tomo F17, Morita, Kyoto, Japan) underwent further evaluation. Insertion angle, height of the cochlea, distance of the electrode to the medial or lateral wall, angle between chorda tympani and facial nerve and the precise position of the electrode cable in the facial-chordal angle were determined. The typical difference between the perimodiolar and lateral course of the electrodes could also be shown in radiological measurements. This demonstrates the accuracy and advantage of CBCT in visualisation of small structures with fewer metal artifacts. Furthermore, in 75% of patients, the angle of the chorda and facial nerve could be visualised. Significant differences in dependence of the electrode type for the relation of them to the facial nerve could be seen. In conclusion, CBCT achieves reliable visualisation and detailed imaging-based measurements of the intracochlear position of different cochlea electrodes. Additionally, clinically known differences can be reproduced. Even visualisation of the position of the electrode in the chorda-facial angle is possible. Therefore, CBCT is a useful tool in intra- and postoperative control of cochlear implants.

Computed Tomography Staging of Middle Ear Cholesteatoma

Background

To establish computed tomography (CT) staging of middle ear cholesteatoma and assess its impact on the selection of the surgical procedure.

Material/Methods

Prospective study was conducted on 61 consecutive patients (mean age 26.8 years) with middle ear cholesteatoma. CT scan of the temporal bone and surgery were performed in all patients. CT staging classified cholesteatoma according to its location in the tympanic cavity (T); extension into the mastoid (M); and associated complications (C). Cholesteatoma was staged as stage I (T1, T2), stage II (T3, M1, M2, C1), and stage III (C2).

Results

The overall sensitivity of CT staging of cholesteatoma compared to surgery was 88% with excellent agreement and correlation between CT findings and intra-operative findings (K=0.863, r=0.86, P=0.001). There was excellent agreement and correlation of CT staging with surgical findings for T location (K=0.811, r=0.89, P=0.001), good for M extension (K=0.734, r=0.88, P=0.001), and excellent for associated C complications (K=1.00, r=1.0, P=0.001). Atticotympanotomy was carried out in stage I (n=14), intact canal wall surgery was performed in stage II (n=38), and canal wall down surgery was done in stage III (n=5) and stage II (n=4).

Conclusions

We established CT staging of middle ear cholesteatoma that helps surgeons to select an appropriate surgery.