Temporal bone imaging: comparison of flat panel volume CT and multisection CT

Improved radiological imaging of congenital aural atresia using flat-panel volume CT

BACKGROUND

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers a high-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy.

AIM OF THE WORK

Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for a more accurate diagnosis and treatment of congenital aural atresia.

MATERIAL AND METHODS

Seven patients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering.

RESULTS

Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. A significant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D.

DISCUSSION

The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

[Improved radiological imaging of congenital aural atresia using flat-panel volume CT. German version]

BACKGROUND

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers a high-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy.

AIM OF THE WORK

Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for a more accurate diagnosis and treatment of congenital aural atresia.

MATERIAL AND METHODS

Seven patients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering.

RESULTS

Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. A significant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D.

DISCUSSION

The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Photon Counting Versus Energy-integrated Detector CT in Detection of Superior Semicircular Canal Dehiscence

BACKGROUND

Superior semicircular canal dehiscence (SSCD), an osseous defect overlying the SSC, is associated with a constellation of audiovestibular symptoms. This study sought to compare conventional energy-integrated detector (EID) computed tomography (CT) to photon-counting detector (PCD)-CT in the detection of SSCD.

MATERIAL AND METHODS

Included patients were prospectively recruited to undergo a temporal bone CT on both EID-CT and PCD-CT scanners. Two blinded neuroradiologists reviewed both sets of images for 1) the presence or absence of SSCD (graded as present, absent, or indeterminate), and 2) the width of the bone overlying the SSC (if present). Any discrepancies in the presence or absence of SSCD were agreed upon by consensus.

RESULTS

In the study 31 patients were evaluated, for a total of 60 individual temporal bones (2 were excluded). Regarding SSCD presence or absence, there was substantial agreement between EID-CT and PCD-CT (k = 0.76; 95% confidence interval, CI 0.54-0.97); however, SSCD was present in only 9 (15.0%) temporal bones on PCD-CT, while EID-CT examinations were interpreted as being positive in 14 (23.3%) temporal bones. This yielded a false positive rate of 8.3% on EID-CT. The bone overlying the SSC was thinner on EID-CT images (0.66 mm; SD = 0.64) than on PCD-CT images (0.72 mm; SD = 0.66) (p < 0.001).

CONCLUSION

The EID-CT examinations tend to overcall the presence of SSCD compared to PCD-CT and also underestimate the thickness of bone overlying the SSC.

An exploratory study of imaging diagnostic clues for overhanging facial nerve in ultra-high-resolution CT

PURPOSE

Overhanging facial nerve (FN) may be challenging in imaging diagnosis. The purpose of the study is to investigate the imaging clues for overhanging FN near the oval window on ultra-high-resolution computed tomography (U-HRCT) images.

METHODS

Between October 2020 and August 2021, images of 325 ears (276 patients) were included in the analysis obtained by an experimental U-HRCT scanner. On standard reformatted images, the morphology of FN was evaluated and its position was quantitatively measured using the following indices: protrusion ratio (PR), protruding angle (A), position of FN (P-FN), distance between FN and stapes (D-S), and distance between FN and anterior and posterior crura of stapes (D-AC and D-PC). According to the FN morphology in imaging, images were divided into overhanging FN group and non-overhanging FN group. Binary univariate logistic regression analysis was used to identify the imaging indices independently associated with overhanging FN.

RESULTS

Overhanging FN was found in 66 ears (20.3%), which manifested as downwards protrusion of either local segment (61 ears, 61/66) or the entire course near the oval window (5 ears, 5/66). D-AC [odds ratio: 0.063, 95% CI 0.012-0.334, P = 0.001) and D-PC (odds ratio: 0.008, 95% CI 0.001-0.050, P = 0.000) were identified as independent predictors of FN overhang (area under the curve: 0.828 and 0.865, respectively).

CONCLUSION

Abnormal morphology of the lower margin of FN, D-AC and D-PC on U-HRCT images provide valuable diagnostic clues for FN overhang.

Assessment of subjective image quality, contrast to noise ratio and modulation transfer function in the middle ear using a novel full body cone beam computed tomography device

BACKGROUND

Multi slice computed tomography (MSCT) is the most common used method in middle ear imaging. However, MSCT lacks the ability to distinguish the ossicular chain microstructures in detail resulting in poorer diagnostic outcomes. Novel cone beam computed tomography (CBCT) devices' image resolution is, on the other hand, better than MSCT resolution. The aim of this study was to optimize imaging parameters of a novel full body CBCT device to obtain optimal contrast to noise ratio (CNR) with low effective dose, and to optimize its clinical usability.

METHODS

Imaging of five anonymous excised human cadaver temporal bones, the acquisition of the effective doses and the CNR measurements were performed for images acquired on using Planmed XFI® full body CBCT device (Planmed Oy, Helsinki, Finland) with a voxel size of 75 µm. All images acquired from the specimens using 10 different imaging protocols varying from their tube current exposure time product (mAs) and tube voltage (kVp) were analyzed for eight anatomical landmarks and evaluated by three evaluators.

RESULTS

With the exception of protocol with 90 kVp 100 mAs, all other protocols used are competent to image the finest structures. With a moderate effective dose (86.5 µSv), protocol with 90 kV 450 mAs was chosen the best protocol used in this study. A significant correlation between CNR and clinical image quality of the protocols was observed in linear regression model. Using the optimized imaging parameters, we were able to distinguish even the most delicate middle ear structures in 2D images and produce accurate 3D reconstructions.

CONCLUSIONS

In this ex vivo experiment, the new Planmed XFI® full body CBCT device produced excellent 2D resolution and easily created 3D reconstructions in middle ear imaging with moderate effective doses. This device would be suitable for middle ear diagnostics and for e.g., preoperative planning. Furthermore, the results of this study can be used to optimize the effective dose by selecting appropriate exposure parameters depending on the diagnostic task.

New Navigation Approaches for Endoscopic Lateral Skull Base Surgery

Image-guided navigation is well established for surgery of the brain and anterior skull base. Although navigation workstations have been used widely by neurosurgeons and rhinologists for decades, utilization in the lateral skull base (LSB) has been less due to stricter requirements for overall accuracy less than 1 mm in this region. Endoscopic approaches to the LSB facilitate minimally invasive surgeries with less morbidity, yet there are risks of injury to critical structures. With improvements in technology over the years, image-guided navigation for endoscopic LSB surgery can reduce operative time, optimize exposure for surgical corridors, and increase safety in difficult cases.

Highly precise navigation at the lateral skull base by the combination of flat-panel volume CT and electromagnetic navigation

This study aimed to evaluate the feasibility and accuracy of electromagnetic navigation at the lateral skull base in combination with flat panel volume computed tomography (fpVCT) datasets. A mastoidectomy and a posterior tympanotomy were performed on 10 samples of fresh frozen temporal bones. For registration, four self-drilling titanium screws were applied as fiducial markers. Multi-slice computed tomography (MSCT; 600 µm), conventional flat panel volume computed tomography (fpVCT; 466 µm), micro-fpVCT (197 µm) and secondary reconstructed fpVCT (100 µM) scans were performed and data were loaded into the navigation system. The resulting fiducial registration error (FRE) was analysed, and control of the navigation accuracy was performed. The registration process was very quick and reliable with the screws as fiducials. Compared to using the MSCT data, the micro-fpVCT data led to significantly lower FRE values, whereas conventional fpVCT and secondary reconstructed fpVCT data had no advantage in terms of accuracy. For all imaging modalities, there was no relevant visual deviation when targeting defined anatomical points with a navigation probe. fpVCT data are very well suited for electromagnetic navigation at the lateral skull base. The use of titanium screws as fiducial markers turned out to be ideal for comparing different imaging methods. A further evaluation of this approach by a clinical trial is required.

Computed Tomography-Based Measurements of the Cochlear Duct: Implications for Cochlear Implant Pitch Tuning

OBJECTIVES

To determine the sources of variability for cochlear duct length (CDL) measurements for the purposes of fine-tuning cochlear implants (CI) and to propose a set of standardized landmarks for computed tomography (CT) pitch mapping.

DESIGN

This was a retrospective cohort study involving 21 CI users at a tertiary referral center. The intervention involved flat-panel CT image acquisition and secondary reconstructions of CIs in vivo. The main outcome measures were CDL measurements, CI electrode localization measurements, and frequency calculations.

RESULTS

Direct CT-based measurements of CI and intracochlear landmarks are methodologically valid, with a percentage of error of 1.0% ± 0.9%. Round window (RW) position markers (anterior edge, center, or posterior edge) and bony canal wall localization markers (medial edge, duct center, or lateral edge) significantly impact CDL calculations [F(2, 78) = 9.9, p < 0.001 and F(2, 78) = 1806, p < 0.001, respectively]. These pitch distortions could be as large as 11 semitones. When using predefined anatomical landmarks, there was still a difference between researchers [F(2, 78) = 12.5; p < 0.001], but the average variability of electrode location was reduced to differences of 1.6 semitones (from 11 semitones.

CONCLUSIONS

A lack of standardization regarding RW and bony canal wall landmarks results in great CDL measurement variability and distorted pitch map calculations. We propose using the posterior edge of the RW and lateral bony wall as standardized anatomical parameters for CDL calculations in CI users to improve pitch map calculations. More accurate and precise pitch maps may improve CI-associated pitch outcomes.

Virtual Quality Control in Middle Ear Surgery: Is Image-guided Tympanoscopy a Valuable Tool for Depicting Borderline Situations?

HYPOTHESIS

Before modern imaging was introduced, revision surgery was the only way to evaluate possible reasons for inadequate improvement in hearing after ossicular replacement during reconstructive middle ear surgery.

BACKGROUND

The aim of this study was to evaluate freely navigable virtual tympanoscopy using different computed tomographic modalities. We compared cone-beam computed tomography (CBCT), flat panel computed tomography (FPCT), and conventional computed tomography in helical mode (CTH), volume mode (CTV), and ultra high resolution mode (CTD).

METHODS

Four temporal bone specimens were reconstructed with partial or total ossicular replacement prostheses. The best functional results for prosthetic coupling were achieved under the control of laser Doppler vibrometry (LDV). Afterward, a progressive step-by-step decoupling of the prostheses was carried out. Different prosthesis positions were evaluated by LDV as well as different computed tomographic modalities with 3D reconstruction of each dataset.

RESULTS

Anatomical structures were better depicted and the best position and coupling of inserted prostheses were achieved using CBCT. All imaging techniques could be used to control the position of middle ear prostheses, but CBCT provided the highest resolution and the best image quality in both 2D and 3D reformations and in 3D-animated video representation.

CONCLUSION

Compared with several other imaging modalities, CBCT was best at depicting miscellaneous coupling problems. Noninvasive detection of coupling problems caused by minimal loss of contact between prostheses and middle ear ossicles will influence the clinical outcome. This early detection will help to determine whether revision surgery is needed.

Intratympanic application of triamcinolone in sudden hearing loss-radiologic anatomy in cone beam CT and its' correlation to clinical outcome

PURPOSE

To evaluate temporal bone cone-beam CT in patients with idiopathic sudden sensorineural hearing loss (ISSNHL) being treated with primary and secondary intratympanic (IT) triamcinolone and to possibly correlate these results to the clinical outcome.

METHODS

Retrospective analysis of patients treated with IT triamcinolone for ISSNHL at our department in 2018. Pre- and post-therapeutic audiologic examinations included four-tone average (FTA) at 0.5, 1, 2 and 3 kHz. Using a clinical questionnaire, pre-therapeutic CBCT scans were re-evaluated looking at items, which might interfere with adequate drug diffusion into the inner ear (e.g. bony overhangs or secondary membranes at the round or oval window).

RESULTS

Thirty-one patients were included. Twenty-four (77%; group A) had experienced ineffective systemic steroid therapy before and seven (23%; group B) received primary IT injections. Four group A-patients (21%) and two group B-patients (33%) showed a post-therapeutic FTA improvement of more than 15 dB HL. Bony overhangs at the round window niche (RWN) were present in seven cases (26%), a secondary membrane at the RWN in four (15%) and soft tissue in eight (30%) cases, respectively.

CONCLUSION

Most patients present radiological findings in CBCT imaging, which might interfere with drug diffusion through the RW membrane. Interestingly, soft or bony tissue obstructing the RWN or the OWN was found in 50% of patients, who showed improvement of hearing. We conclude that radiologic 'tiny' findings are either clinically irrelevant or improvement in hearing is independent from intratympanic drug delivery.

Image quality of flat-panel computed tomography using 2 different acquisition times versus multidetector computed tomography in whole-head temporal bone specimen

PURPOSE

Imaging of temporal bone and skull base acquire high resolution due to the small anatomic structures with high clinical relevance. The purpose of this study was to compare image quality of the temporal bone in standard 20 s protocol flat-panel computed tomography (FPCT) with the new time- and dose improved 10 s protocol as well as with 128 slice multidetector computed tomography (MDCT). The aim was to evaluate the new time- and dose improved 10 s protocol.

METHODS

10 whole-skull preparations-20 temporal bones-were scanned with either 128 slice MDCT CT (SOMATOM Definition AS + , Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10 s or 20 s protocol.

RESULTS

We show here that overall FPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the temporal bone compared to 128 slice MDCT. Especially the shorter, dose saving 10 s protocol of the FPCT is still superior to 128 slice MDCT. The 20 s FPCT protocol was only significantly superior in identification of the cochlear apical turn and can thereby be used specifically in clinical cases with pathologies in this area.

CONCLUSIONS

The 10 s FPCT protocol yields a significantly better image quality than MDCT in imaging finer structures of the temporal bone.

Comparison of a Photon-Counting-Detector CT with an Energy-Integrating-Detector CT for Temporal Bone Imaging: A Cadaveric Study

BACKGROUND AND PURPOSE

Evaluating abnormalities of the temporal bone requires high-spatial-resolution CT imaging. Our aim was to assess the performance of photon-counting-detector ultra-high-resolution acquisitions for temporal bone imaging and compare the results with those of energy-integrating-detector ultra-high-resolution acquisitions.

MATERIALS AND METHODS

Phantom studies were conducted to quantify spatial resolution of the ultra-high-resolution mode on a prototype photon-counting-detector CT scanner and an energy-integrating-detector CT scanner that uses a comb filter. Ten cadaveric temporal bones were scanned on both systems with the radiation dose matched to that of the clinical examinations. Images were reconstructed using a sharp kernel, 0.6-mm (minimum) thickness for energy-integrating-detector CT, and 0.6- and 0.25-mm (minimum) thicknesses for photon-counting-detector CT. Image noise was measured and compared using adjusted 1-way ANOVA. Images were reviewed blindly by 3 neuroradiologists to assess the incudomallear joint, stapes footplate, modiolus, and overall image quality. The ranking results for each specimen and protocol were compared using the Friedman test. The Krippendorff α was used for interreader agreement.

RESULTS

Photon-counting-detector CT showed an increase of in-plane resolution compared with energy-integrating-detector CT. At the same thickness (0.6 mm), images from photon-counting-detector CT had significantly lower (P < .001) image noise compared with energy-integrating-detector CT. Readers preferred the photon-counting-detector CT images to the energy-integrating-detector images for all 3 temporal bone structures. A moderate interreader agreement was observed with the Krippendorff α = 0.50. For overall image quality, photon-counting-detector CT image sets were ranked significantly higher than images from energy-integrating-detector CT (P < .001).

CONCLUSIONS

This study demonstrated substantially better delineation of fine anatomy for the temporal bones scanned with the ultra-high-resolution mode of photon-counting-detector CT compared with the ultra-high-resolution mode of a commercial energy-integrating-detector CT scanner.

Flat Panel Angiography in the Cross-Sectional Imaging of the Temporal Bone: Assessment of Image Quality and Radiation Dose Compared with a 64-Section Multisection CT Scanner

BACKGROUND AND PURPOSE

Cross-sectional imaging of the temporal bone is challenging because of the complexity and small dimensions of the anatomic structures. We evaluated the role of flat panel angiography in the cross-sectional imaging of the temporal bone by comparing its image quality and radiation dose with a 64-section multisection CT scanner.

MATERIALS AND METHODS

We retrospectively collected 29 multisection CT and 29 flat panel angiography images of normal whole-head temporal bones. Image quality was assessed by 2 neuroradiologists, who rated the visualization of 30 anatomic structures with a 3-point ordinal scale. The radiation dose was assessed with an anthropomorphic phantom.

RESULTS

Flat panel angiography showed better image quality than multisection CT in depicting the anterior and posterior crura of the stapes, the footplate of the stapes, the stapedius muscle, and the anterior ligament of the malleus (P < .05). In contrast, multisection CT showed better image quality than flat panel angiography in assessing the tympanic membrane, the bone marrow of the malleus and incus, the tendon of the tensor tympani, the interscalar septum, and the modiolus of the cochlea (P < .05). Flat panel angiography had a significantly higher overall image quality rating than multisection CT (P = .035). A reduction of the effective dose of approximately 40% was demonstrated for flat panel angiography compared with multisection CT.

CONCLUSIONS

Flat panel angiography shows strengths and weaknesses compared with multisection CT. It is more susceptible to artifacts, but due to the higher spatial resolution, it shows equal or higher image quality in assessing some bony structures of diagnostic interest. The lower radiation dose is an additional advantage of flat panel angiography.

Comparison of digital volume tomography and high-resolution computed tomography in detecting superior semicircular canal dehiscence--a temporal bone study

CONCLUSION

In detecting a thin bony coverage of a superior semicircular canal (SSC), digital volume tomography (DVT) scans in Poeschl projection seem to be superior to high-resolution computed tomography (CT) scans. Still, a definite diagnosis of SSC dehiscence (SSCD) is not possible with any radiologic imaging technique.

OBJECTIVE

To compare CT and DVT to find out whether DVT is equal, better or worse in showing a thin bony layer on top of an SCC.

METHODS

In 11 human temporal bone specimens, the SSC was microscopically blue-lined leaving a thin bony coverage on top of it. All specimens were assessed with both high-resolution CT and DVT. After reconstructing the images in Stenvers and Poeschl projections, all images were evaluated by five independent examiners experienced in radiologic imaging of the temporal bone using a four-point ordinal scale, from 1 (distinct dehiscence) to 4 (distinct coverage).

RESULTS

The mean score for all CT scans was 2.58 compared with 3.22 for DVT scans (p = 0.000). Poeschl projection showed a mean score of 3.25 compared with 2.55 for Stenvers projection (p = 0.000). The best imaging modality was found to be DVT scans in Poeschl projections, with a mean score of 3.60.

Determining compliance of ear CT scan with interaoperative findings in deaf children with cochlear implantation

INTRODUCTION

Defecated or impaired hair cell function of the cochlea causes deafness. Cochlear implantation allows transmission of sound information through central auditory pathways using direct electric stimulation of auditory nerve dendrites. Using radiologic imaging, including CT scan is very helpful in selection of candidates and evaluation after implantation. The purpose of this study is to determine compliance of CT findings in deaf children undergoing cochlear implantation compared with the intra-operative findings.

METHOD

In a periodical-descriptive study, 100 patients (56 male and 44 female), 6 months to 6 years of age, who were candidates for cochlear implantation at Baqiyatallah Hospital in Tehran between January 2010 and October 2011, were studied. After getting informed consent form the parents of patients, demographic data was recorded. CT scan and surgical data were double blindly collected in the designed questionnaire which was approved by three radiologists and three ENT specialists. Finally, surgical and radiological data were compared and t-test and chi-square test was used.

RESULTS

Atic status in 89 patients (89%) was statistically significant between radiology and surgery (P=0.06). Positive Predictive Value and Negative Predictive Value were respectively 100 and 92.8. Middle ear space was same in 85 patients (85%) in the two methods (P=0.01) (NVP=63.4). Pyramid status was similar in radiology and surgery results in 67 patients (67%) (P=0.000) and PPV and NPV were 100 and 63.4 respectively. Jugular bulb was similar in 73 patients (73%) (P=0.00). There was no significant difference between other modalities.

CONCLUSION

In most cases examined in this study, compliance between the surgical and radiological findings was above 80%. In some cases, CT scan could give confidence to the surgeon, but in atic, middle ear space, pyramid and jugular bulb there might be insufficient reliance to CT findings and there would be need to more accurate observation during surgery.

Differences of radiological artefacts in cochlear implantation in temporal bone and complete head

OBJECTIVES

Accurate radiological evaluation of cochlear implants is essential for improvement of devices and techniques and also for assessing the position of the electrodes within the cochlea. Radiological study of implants has focused on isolated temporal bones. Previous studies showed relevant sizes of artefacts (dimensions of the radiological image compared with the actual dimensions of the electrode) in visualization of cochlear implants in computed tomography and cone beam computed tomography (CBCT). In this study, we aimed to obtain CBCT images of cochlear electrodes in isolated temporal bones and in whole heads and to assess the differences in image quality between the two.

METHODS

Cochlear electrodes were implanted in three complete human heads. Radiological examinations were performed using a single CBCT scanner with varying x-ray tube currents, voltages, and rotation angles. The temporal bones were then removed and the same radiological examinations were repeated, with and without the receiver coils. Artefacts from a basal electrode (electrode 9) and an apical electrode (electrode 2) were calculated. These were compared with each other by measuring the diameter of the image of the electrode (electrode inclusive of imaging artefacts) and with the real electrode diameters from the manufacturer's data. Additionally, the radiological diameters (inclusive of artefact) of the electrodes were compared to the cross-sectional diameters of the basal and apical coils of the cochlea at the locations of these two electrodes.

RESULTS

In comparison to the real electrode diameters, radiological artefact proportions of 51-58% for electrode 9 and 56-61% for electrode 2 were calculated. The differences between whole head images (group 1) and temporal bone images with and without the receiver coil (groups 2 and 3) were highly significant for each protocol (P < 0.001).

DISCUSSION AND CONCLUSION

These results indicate that it is not possible reliably to determine the exact intracochlear positions of electrodes using CBCT. Imaging of isolated temporal bones produced significantly greater artefacts than imaging of the whole head. Evaluations of image quality based only on results for isolated temporal bones are not transferable to clinical situations, and should be assessed critically.

Primary blast lung injury prevalence and fatal injuries from explosions: insights from postmortem computed tomographic analysis of 121 improvised explosive device fatalities

BACKGROUND

Primary blast lung injury (PBLI) is an acknowledged cause of death in explosive blast casualties. In contrast to vehicle occupants following an in-vehicle explosion, the injury profile, including PBLI incidence, for mounted personnel following an external explosion has yet to be as well defined.

METHODS

This retrospective study identified 146 cases of UK military personnel killed by improvised explosive devices (IEDs) between November 2007 and July 2010. With the permission of Her Majesty's Coroners, relevant postmortem computed tomography imaging was analyzed. PBLI was diagnosed by postmortem computed tomography. Injury, demographic, and relevant incident data were collected via the UK Joint Theatre Trauma Registry.

RESULTS

Autopsy results were not available for 1 of 146 cases. Of the remaining 145 IED fatalities, 24 had catastrophic injuries (disruptions), making further study impossible, leaving 121 cases; 79 were dismounted (DM), and 42 were mounted (M). PBLI was noted in 58 cases, 33 (79%) of 42 M fatalities and 25 (32%) of 79 DM fatalities (p < 0.0001). Rates of associated thoracic trauma were also significantly greater in the M group (p < 0.006 for all). Fatal head (53% vs. 23%) and thoracic trauma (23% vs. 8%) were both more common in the M group, while fatal lower extremity trauma (7% vs. 48%) was more commonly seen in DM casualties (p < 0.0001 for all).

CONCLUSION

Following IED strikes, mounted fatalities are primarily caused by head and chest injuries. Lower extremity trauma is the leading cause of death in dismounted fatalities. Mounted fatalities have a high incidence of PBLI, suggesting significant exposure to primary blast. This has not been reported previously. Further work is required to determine the incidence and clinical significance of this severe lung injury in explosive blast survivors. In addition, specific characteristics of the vehicles should be considered.

Visualisation of the Bonebridge by means of CT and CBCT

Background

With the Bonebridge, a new bone-anchored hearing aid has been available since March 2012. The objective of the study was to analyse the visualisation of the implant itself as well as its impact on the representation of the bony structures of the petrosal bone in CT, MRI and cone beam CT (CBCT).

Methods

The Bonebridge was implanted unilaterally in two completely prepared human heads. The radiological imaging by means of CBCT, 64-slice CT, 1.5-T and 3.0-T MRI was conducted both preoperatively and postoperatively. The images were subsequently evaluated from both the ENT medical and nd radiological perspectives.

Results

As anticipated, no visualisation of the implant or of the petrosal bones could be realised on MRI because of the interactive technology and the magnet artefact. In contrast, an excellent evaluability of the implant itself as well as of the surrounding neurovascular structures (sinus sigmoideus, skull base, middle ear, inner ear, inner auditory canal) was exhibited in both the CT and in the CBCT.

Conclusion

The Bonebridge can be excellently imaged with the radiological imaging technologies of CT and CBCT. In the process, CBCT shows discrete advantages in comparison with CT. No relevant restrictions in image quality in the evaluation of the bony structures of the petrosal bones could be seen.

[Intracochlear electrode position: evaluation after deep insertion using cone beam computed tomography]

INTRODUCTION

Due to the increasing number of cochlear implantations (CI), postoperative radiological verification of the electrode position, e.g., with respect to quality control, plays a central role. The aim of this study was to evaluate the intracochlear position of deep inserted electrodes by cone beam computed tomography (CBCT).

MATERIALS AND METHODS

CBCT data sets (Accu-I-tomo, Morita, Kyoto, Japan) of 22 patients (28 ears operated between 2008 and 2011) were retrospectively analyzed. All patients underwent a CI (round window approach) with deep insertion of the electrode (Flex soft or standard electrode from MedEl©). CBCT data were analyzed for intracochlear position of the electrode (scala vestibuli, scala tympani, malposition between the scalae) and the certainty of this evaluation.

RESULTS

All ears could be evaluated with the status certain or relatively certain in the basal turn of the cochlea. Thereby, the electrode array was inserted into the scala tympani in 93% (n = 26). Primary insertion into the scala vestibuli and the scala media was observed in 3.5% of the ears, respectively. In the apical part of the cochlea, only 32% (n = 9 ears) could be evaluated with relative certainty. The remaining 68% of cases could not be evaluated. Of the 32% interpretable cases in the apical part of the cochlea, 25% (n = 7) were inserted into the scala tympani, 3.5% (n = 1) into the scala vestibuli, and 3.5% (n = 1) were malpositioned between the scalae.

CONCLUSION

The exact evaluation of the intracochlear position of the electrode by CBCT is only possible in the basal turn of the cochlea. In deep insertion, determination of the position in the medial and apical parts of the cochlea by CBCT is still not possible. Furthermore, the round window approach allows reliable implantation into the scala tympani.

Device setting modifications for 3D flatpanel imaging in skull base surgery

To evaluate the image quality and clinical implementation after setting modification of a three-dimensional isocentric C-arm fluoroscopic image intensifier system combined with a digital flatpanel detector as a new tool for sinus and petrous bone surgery. Image acquisition was performed using two cadaveric heads. Experimental design was oriented to the clinically sensible intraoperative setup. Different tube currents and orbital movements of the C-arm system were evaluated for image quality by three otolaryngological surgeons using predetermined landmarks. Modification of the X-ray intensity did not attain statistically significant values compared to the X-ray-intensity predetermined by producer (12.0-18.5 mA, p > 0.05) for either sinus or for petrous bone scans. Elliptical orbital movement resulted in significantly superior image quality than data sets acquired by circular orbital movement (3.194 vs. 2.809, p < 0.0001). New C-arm systems with 3D-capabiltity offer a promising tool for intraoperative near real-time image guidance. Image quality of the skull base can be improved significantly with optimized system settings.

Artifacts of the electrode in cochlea implantation and limits in analysis of deep insertion in cone beam tomography (CBT)

Until now more than 250,000 cochlea implantations have been performed worldwide. The surgical procedure is well standardized. A discussion about the kind of postoperative radiological control has started since cone beam tomography (CBT) has been established in ENT and hearing preservation operations have come more into the focus. Further research has been concentrated on the role of CBT and the insertion of the basal turn. The aim of this study was to look for the possibilities of CBT and deep insertion. The second aim was to analyze the artifacts of cochlea implants in CBT. Three human cadaver ears were implanted with a flex soft electrode of MedEl© in a standard operation procedure with round window insertion and a full insertion. Afterwards 72 CBT sets per ear were performed with different X-ray-tube currents (2-10 mA), voltages (72-90 kV), and exposure times (9 and 17 s). On each data set, the radiological diameter of the electrode 9 (basal), electrode 2 (apical), the diameter of the cable next to the electrodes 9 and 2, and the associated diameter of the cochlea next to the electrodes 9 and 2 were evaluated. Additionally, a comparison to the real diameter was done. The mean radiological diameters of the measure point at electrode 9 were: electrode = 1.19 mm; cable = 0.65 mm; cochlea = 1.77 mm. Results for measure point at electrode 2 were: electrode = 0.98 mm; cable = 0.48 mm; cochlea = 1.21 mm. The real diameters were at electrode 9 in lateral view 0.58 mm and in top view 0.63 mm and at electrode 2 in lateral view 0.36 mm and in top view 0.50 mm. Differences between the diameters of the electrode 9 and 2 were highly significant. Interestingly, the real diameter of the electrode is half in comparison to the radiological one. Also in comparison to the diameter of the cable and the associated electrode is nearly half. Nearly 50% artifact exists on radiologic evaluation of the diameter of the electrode. Varying the X-ray adjustments did not lead to optimized results. The difficulties in evaluating a cochlea electrode with CBT could be shown. The high rate of artifacts (50%) makes it extremely difficult to predict the inserted scale, especially when evaluating the intracochlear position in the medial and apical turn of the cochlea. In conclusion, until now CBT allows a relatively safe evaluation of the electrode in the basal turn, whereas in deep insertion it is not really a useful tool to answer the question of insertion trauma, implanted scale, or scale displacements.

Evaluation of portable CT scanners for otologic image-guided surgery

PURPOSE

Portable CT scanners are beneficial for diagnosis in the intensive care unit, emergency room, and operating room. Portable fixed-base versus translating-base CT systems were evaluated for otologic image-guided surgical (IGS) applications based on geometric accuracy and utility for percutaneous cochlear implantation.

METHODS

Five cadaveric skulls were fitted with fiducial markers and scanned using both a translating-base, 8-slice CT scanner (CereTom(®)) and a fixed-base, flat-panel, volume CT (fpVCT) scanner (Xoran xCAT(®)). Images were analyzed for: (a) subjective quality (i.e., noise), (b) consistency of attenuation measurements (Hounsfield units) across similar tissue, and (c) geometric accuracy of fiducial marker positions. The utility of these scanners in clinical IGS cases was tested.

RESULTS

Five cadaveric specimens were scanned using each of the scanners. The translating-base, 8-slice CT scanner had spatially consistent Hounsfield units, and the image quality was subjectively good. However, because of movement variations during scanning, the geometric accuracy of fiducial marker positions was low. The fixed-base, fpVCT system had high spatial resolution, but the images were noisy and had spatially inconsistent attenuation measurements, while the geometric representation of the fiducial markers was highly accurate.

CONCLUSION

Two types of portable CT scanners were evaluated for otologic IGS. The translating-base, 8-slice CT scanner provided better image quality than a fixed-base, fpVCT scanner. However, the inherent error in three-dimensional spatial relationships by the translating-based system makes it suboptimal for otologic IGS use.

The value of digital volume tomography in assessing the position of cochlear implant arrays in temporal bone specimens

OBJECTIVES

Radiological evaluation of the position of cochlear implant (CI) devices is an upcoming method for quality control after CI surgery. First, results of imaging of the middle and inner ear with digital volume tomography (DVT) show considerable advantages such as exceptional image quality, thin slice thickness, and low radiation dose. The aim of this study was to evaluate whether DVT is an appropriate method for postoperative imaging of CI patients and to identify the exact position of the implant array within the cochlear by multiple measurements.

DESIGN

Thirteen formalin-fixed temporal bone specimens were implanted with a CI array and scanned in DVT. To determine the exact electrode position, these specimens were ground and stained for microscopic measurements. The measurements on grindings acted as a referee and were compared with the measurements in DVT scans. The statistical analysis between the two measurement protocols was performed using the Bland-Altman method.

RESULTS

Best achievable agreement between DVT scans and histological reference was shown. Mean differences between DVT and grindings from -1.55 to -65.40 microm were calculated. All means are within the region of accuracy. General positioning of the implant into the cochlea could be verified in all specimens. The exact position of the implanted array within the cochlear scalae could be recognized correctly in 11 of 13 cases in DVT. It was possible to identify shiftings between the tympanic and vestibular scalae in all cases.

CONCLUSION

DVT seems to be a convenient technique for postoperative position control after cochlear implantation.