Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study

Insight in to the Awareness of CBCT as an Imaging Modality in the Diagnosis and Management of ENT Disorders: A Cross Sectional Study

The advent of Cone-beam computed tomography (CBCT), has revolutionized 3D imaging in dentistry. CBCT has enormous potential to be used as an alternative imaging modality by Otolaryngologists. But their knowledge regarding CBCT is limited. The study aims to evaluate the awareness of CBCT as an imaging modality among Ear, nose and Throat (ENT) practitioners. The validated questionnaire was sent by email and the participants were asked to fill the google form through the link provided to record the responses. The participants were asked to answer 25 multiple choice questions regarding the general information and practice related to CBCT imaging. Data was evaluated according to the descriptive statistics and the Chi-square test was used to determine the test of significance. The response rate for this study was 84.4%. The mean age of the participants was 44.9 ± 11.3. 69% of the respondents were academicians,14.2% had exclusive clinical practice, and 16.8% had both clinical and academic exposure. Among the study population, 76.8% had never advised CBCT in their practice. Only 10.3% of the study participants were aware of the potential of CBCT in ENT disorders. The mean knowledge, attitude and practice scores were very low regarding the applications of CBCT. Most of the study participants advised CBCT for maxillofacial fractures (78.1%) and was statistically significant p < 0.05. The knowledge about various advantages and clinical applications of CBCT among Otolaryngologists is limited. However, continuing medical education and inclusion in the medical curriculum will increase the scope and awareness about CBCT among ENT fraternity.

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.

Contribution of the flexible incudo-malleal joint to middle-ear sound transmission under static pressure loads

The incudo-malleal joint (IMJ) in the human middle ear is a true diarthrodial joint and it has been known that the flexibility of this joint does not contribute to better middle-ear sound transmission. Previous studies have proposed that a gliding motion between the malleus and the incus at this joint prevents the transmission of large displacements of the malleus to the incus and stapes and thus contributes to the protection of the inner ear as an immediate response against large static pressure changes. However, dynamic behavior of this joint under static pressure changes has not been fully revealed. In this study, effects of the flexibility of the IMJ on middle-ear sound transmission under static pressure difference between the middle-ear cavity and the environment were investigated. Experiments were performed in human cadaveric temporal bones with static pressures in the range of +/- 2 kPa being applied to the ear canal (relative to middle-ear cavity). Vibrational motions of the umbo and the stapes footplate center in response to acoustic stimulation (0.2-8 kHz) were measured using a 3D-Laser Doppler vibrometer for (1) the natural IMJ and (2) the IMJ with experimentally-reduced flexibility. With the natural condition of the IMJ, vibrations of the umbo and the stapes footplate center under static pressure loads were attenuated at low frequencies below the middle-ear resonance frequency as observed in previous studies. After the flexibility of the IMJ was reduced, additional attenuations of vibrational motion were observed for the umbo under positive static pressures in the ear canal (EC) and the stapes footplate center under both positive and negative static EC pressures. The additional attenuation of vibration reached 4~7 dB for the umbo under positive static EC pressures and the stapes footplate center under negative EC pressures, and 7~11 dB for the stapes footplate center under positive EC pressures. The results of this study indicate an adaptive mechanism of the flexible IMJ in the human middle ear to changes of static EC pressure by reducing the attenuation of the middle-ear sound transmission. Such results are expected to be used for diagnosis of the IMJ stiffening and to be applied to design of middle-ear prostheses.

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.

Tympanoplasty - news and new perspectives

Techniques and biomaterials for reconstructive middle ear surgery are continuously and steadily developing. At the same time, clinical post-surgery results are evaluated to determine success or failure of the therapy. Routine quality assessment and assurance is of growing importance in the medical field, and therefore also in middle ear surgery. The exact definition and acquisition of outcome parameters is essential for both a comprehensive and detailed quality assurance. These parameters are not the audiological results alone, but also additional individual parameters, which influence the postoperative outcome after tympanoplasty. Selection of patients and the preoperative clinical situation, the extent of the ossicular chain destruction, the chosen reconstruction technique and material, the audiometric frequency selection and the observational interval are only some of them. If these parameters are not well documented, the value of comparative analyses between different studies is very limited. The present overview aims at describing, comparing, and evaluating some of the existing assessment and scoring systems for middle ear surgery. Additionally, new methods for an intraoperative quality assessment in ossiculoplasty and the postoperative evaluation of suboptimal hearing results with imaging techniques are available. In the area of implant development, functional elements were integrated in prostheses to enable not only good sound transmission but also compensation of occurring atmospheric pressure changes. In combination with other components for ossicular repair, they can be used in a modular manner, which so far show experimentally and clinically promising results.

Experimental Simulation of Clinical Borderline Situations in Temporal Bone Specimens After Ossiculoplasty

OBJECTIVES

One reason for insufficient hearing improvement with a distinct air-bone gap after ossiculoplasty with implantation of partial or total ossicular replacement prostheses can be the dislocation or minimal shifting of the prosthesis. The aim of this study was the simulation of common clinical borderline situations with minimal shifting of the prosthesis in temporal bone specimens after ossiculoplasty. It was furthermore the goal to identify these specific situations through imaging by cone beam computed tomography (cbCT) and direct visual inspection using the operation microscope. Additionally, the functional status was evaluated using laser-Doppler vibrometry (LDV).

DESIGN

We used a total of four temporal bone specimens for this study. A reconstruction with a partial ossicular replacement prostheses was performed in three specimens and with a total ossicular replacement prostheses in one specimen, with good initial acoustic properties. Subsequently, one specific type of prosthesis failure was simulated in each specimen, respectively, by minimally shifting, tilting, or bending the prostheses from their initial positions. These changes were introduced step-by-step until a borderline situation just short of complete acoustic decoupling was reached. Each step was examined using both LDV and cbCT and observed through the operation microscope.

RESULTS

LDV was able to quantify the mechanic function of the ossicular chain after most of the manipulation steps by demonstrating the effect of any shifting of the prosthesis on the middle ear transfer function. However, in some situations, the middle ear transfer function was better with a visually more advanced failure of the prosthesis. In addition, cbCT showed most of the steps with excellent resolution and was able to delineate changes in soft tissue (e.g., cartilage covering).

CONCLUSION

cbCT seems to be a promising imaging technique for middle ear problems. As cbCT and LDV exhibited slightly different advantages and disadvantages regarding the demonstration of borderline situations, the combination of both techniques allowed for a more precise evaluation of middle ear reconstructions. Knowledge of the specific characteristics of these methods and their possible combination might help otologists and otosurgeons to refine indications for revision surgery and improve their personal patient counseling.

Indications of cone beam CT in head and neck imaging

CONCLUSION

Cone Beam Computed Tomography (CBCT) can be widely used in imaging of bony structures of the anterior and lateral skull base. Significant differences of applied dosages result from the different protocols of the various indications.

OBJECTIVES

CBCT is increasingly being used in head and neck imaging. Until now, no precise knowledge about its dedicated usage existed.

METHODS

All CBCT of 2012 and 2013 were analysed with regard to the technical parameters, the performance, and the indication for imaging.

RESULTS

In total, 1862 patients were examined in 2012 and 2013. The top eight indications of the anterior skull were (1) chronic rhinosinusitis with disturbed nasal breathing (30.3%); (2) chronic rhinosinusitis (17.6%); (3) midfacial traumatology (13.7%); (4) disturbed nasal breathing (12.8%); (5) acute rhinosinusitis (7.9%); (6) polyposis nasi (6.3%); (7) search for focus (3.9%); and (8) persistent rhinorrhea (1.2%). For the lateral skull base, the top eight were (1) control after cochlear implantation (28.4%); (2) cholesteatoma (19.7%); (3) visualization of ear anatomy (8.7%); (4) chronic otitis media mesotympanalis (6.3%); (5) conductive hearing loss (5.1%); (6) suspected mastoiditis (4.8%); (7) pathology of external auditory canal (4.8%); and (8) otosclerosis (3.3%). Applied dosage for the anterior skull base was significantly lower than for the lateral skull base (2.90 mGy vs 5.92 mGy, p < 0.05); 2.4% and 3.6% of patients' images, respectively, had to be repeated.

Direct comparison of conventional radiography and cone-beam CT in small bone and joint trauma

OBJECTIVE

To compare the diagnostic value of cone-beam computed tomography (CBCT) and conventional radiography (CR) after acute small bone or joint trauma.

MATERIALS AND METHODS

Between March 2013 and January 2014, 231 patients with recent small bone or joint trauma underwent CR and subsequent CBCT. CR and CBCT examinations were independently assessed by two readers, blinded to the result of the other modality. The total number of fractures as well as the number of complex fractures were compared, and inter- and intraobserver agreement for CBCT was calculated. In addition, radiation doses and evaluation times for both modalities were noted and statistically compared.

RESULTS

Fracture detection on CBCT increased by 35% and 37% for reader 1 and reader 2, respectively, and identification of complex fractures increased by 236% and 185%. Interobserver agreement for CBCT was almost perfect, as was intraobserver agreement for reader 1. The intraobserver agreement for reader 2 was substantial. Radiation doses and evaluation time were significantly higher for CBCT.

CONCLUSION

CBCT detects significantly more small bone and joint fractures, in particular complex fractures, than CR. In the majority of cases, the clinical implication of the additionally detected fractures is limited, but in some patients (e.g., fracture-dislocations), the management is significantly influenced by these findings. As the radiation dose for CBCT substantially exceeds that of CR, we suggest adhering to CR as the first-line examination after small bone and joint trauma and keeping CBCT for patients with clinical-radiographic discordance or suspected complex fractures in need of further (preoperative) assessment.

[Quality control following reconstructive middle ear surgery: from bench to bedside]

BACKGROUND

The ongoing improvement of imaging quality nowadays focuses increasingly more on immediate quality evaluation of surgical measures.

METHODS

Rotational tomography (RT) has been experimentally proven to be an alternative imaging technique to computed tomography (CT) in terms of quality and postoperative localization of middle ear implants in temporal bones. Based on these results imaging parameters were determined in the form of a surgical check list in order to systematically check individual but important surgical reconstructive steps.

RESULTS

The positive benefit of RT concerning immediate and significant postoperative quality control was confirmed by a patient study. The surgical check list was successfully implemented under clinical framework requirements. Among these standardized parameters the determined angulation of inserted middle ear implants was given outstanding significance due to the predictive value concerning functional outcome.

CONCLUSION

The RT procedure has been proven to be a reliable imaging tool for postoperative quality control following reconstructive middle ear surgery.

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.

Panel 3: Recent advances in anatomy, pathology, and cell biology in relation to otitis media pathogenesis

BACKGROUND AND OBJECTIVES

The pathogenesis of otitis media (OM) involves a number of factors related to the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx. Although some issues of pathogenesis are fairly well established, others are only marginally indicated by current knowledge, and yet others remain undisclosed. The objective of this article is to provide a state-of-the-art review on recent scientific achievements in the pathogenesis of OM, as related to anatomy, pathology, and cell biology.

DATA SOURCES

PubMed, Ovid Medline, and Cochrane Library.

REVIEW METHODS

Articles published on the pathogenesis of OM and the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx between January 2007 and June 2011 were identified. Among almost 1900 abstracts, the authors selected 130 articles for full article review and inclusion in this report.

RESULTS

New knowledge on a number of issues emerged, including cell-specific expression and function of fluid transportation and innate immune system molecules, mucous cell metaplasia, mucin expression, bacterial adherence, and epithelial internalization, as well as the occurrence, composition, dynamics, and potential role of bacterial biofilm. In addition, the potential role of gastroesophageal reflux disease and cigarette smoke exposure has been explored further.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Over the past 4 years, considerable scientific progress has been made on the pathogenesis of OM, as related to issues of anatomy, pathology, and cell biology. Based on these new achievements and a sustained lack of essential knowledge, suggestions for future research are outlined.

Potential of dosage reduction in cone-beam-computed tomography (CBCT) for radiological diagnostics of the paranasal sinuses

More than 10 years ago, cone-beam-computed tomography (CBCT) was introduced in ENT radiology. Until now, the focus of research was to evaluate clinical limits of this technique. The aim of this work is the evaluation of specific dosages and the identification of potential optimization in the performance of CBCT of the paranasal sinuses. Based on different tube parameters (tube current, tube voltage, and rotation angles), images of the nose and the paranasal sinuses were taken on a phantom head with the Accu-I-tomo F17 (Morita, Kyoto, Japan). The dosages applied to the lens and parotid gland were measured with OSL dosimetry. The imaging quality was evaluated by independent observers. All datasets were reviewed according to a checklist of surgically important anatomic structures. Even for lowest radiation exposure (4 mA, 76 kV, 180°, computed tomography dosage index (CTDI) = 1.8 mGy), the imaging quality was sufficient. Of course a significant reduction of the imaging quality could be seen, so a reliable mean was set for 4 mA, 84 kV, and 180° rotation angle (CTDI = 2.4 mGy). In this combination, a reduction of 92 % in lens-dose and of 77 % of dosage at the parotid gland was observed in comparison to the maximal possible adjustments (8 mA, 90 kV, 360°, CTDI = 10.9 mGy). There is potential for optimization in CBCT. Changing the rotation angle (180° instead of 360°) leads to a dose reduction of 50 %. Furthermore from clinical point of view in case of chronic rhinosinusitis a relevant reduction of dosage is possible. Therefore, it is necessary to intensify the interdisciplinary discussion about the disease specifics required quality of imaging.

Imaging in cochlear implant patients

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.

Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT)

BACKGROUND

The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary.

PURPOSE

To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations.

MATERIAL AND METHODS

This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated.

RESULTS

In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%).

CONCLUSION

CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.

Cone-beam computed tomography: a new low dose, high resolution imaging technique of the wrist, presentation of three cases with technique

Cone-beam computed tomography (CBCT) is a relatively new technique. It generates a 3D image by emitting a pulsed cone-shaped X-ray beam. CBCT has become a very useful and widely used technique for dentomaxillofacial imaging over the last decade. It provides clear, high resolution multiplanar reconstruction images. Previously, the images could only be generated while the patient was sitting with his/her head fixed in position. With the presented new generation CBCT (NewTom 5G, QR, Verona, Italy), a more free positioning of the patient, either lying or sitting, is possible. In this way, skeletal imaging of various body parts becomes possible. In this article we present three clinical cases of CBCT imaging of the wrist, describe the background of the technique, and discuss the advantages and disadvantages of CBCT imaging.

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.

Experimental investigation of rotational tomography in reconstructed middle ears with clinical implications

A large air-bone-gap after ossiculoplasty may be due to a malpositioned or displaced prosthesis. Rotational tomography (RT) has the potential to provide high-resolution images of implants without artifacts and with less radiation dosage than CT scan. Twenty-seven temporal bone specimens underwent measurements of middle ear transfer function using Laser-Doppler-Vibrometry (LDV) before and after placement of ossicular replacement prostheses (PORPs, TORPs) made of titanium. RT was performed on all specimens. RT allowed 3-dimensional viewing of the temporal bone, accurate localization of implants within the reconstructed middle ear and determination of angles between the inserted prostheses and the tympanic membrane (TM) and/or the malleus handle (MH). Presence or absence of contact between the implant and the TM, malleus or stapes could be clearly visualized. Displaced prostheses were readily identified. The functional LDV-measurements for TORPs showed a trend favoring coupling to the malleus handle, while for PORPs, coupling to the TM was favored. For PORPs, sound transmission was worse with increasing angles between the PORP and stapes superstructure (p<0.05). Following our experimental results RT is an innovative, relevant and useful imaging technique to obtain immediate postoperative feedback after ossicular reconstruction and to precisely determine the position of middle ear implants.

Revision stapes surgery: the "lateralized piston syndrome"

OBJECTIVE

The need for revision stapes surgery has many causes, and among these, we describe a particular displacement of the piston: the "lateralized piston syndrome". The goal of this study is to define criteria and surgical management of this syndrome.

STUDY DESIGN

Retrospective study over 13 years.

SETTING

Tertiary reference center.

PATIENTS

A review of 1,289 consecutive stapes operations revealed 119 revisions (9%) from which 22 cases (18.5%) could be classified under the lateralized piston syndrome.

INTERVENTION

Revision stapedotomy.

MAIN OUTCOME MEASURES

Medical files, preoperative and postoperative audiograms, computed tomographic scans, and operative reports.

RESULTS

The 22 cases presented as a delayed conductive hearing loss in 95.5% of cases. Preoperative computed tomographic scans showed a lateralized piston out of the stapedotomy in 81% of cases and touching the tympanic membrane in 54.5% of cases. Revisions revealed a lateral displacement of the piston out of the entire oval window in 86% of cases, with closure of the stapedotomy in all cases and incus necrosis in 77% of cases. Conventional pistons were fitted in 12 cases. In case of a significantly eroded incus, total prostheses (TORPs) in 6 cases and offset pistons in 4 cases were placed. Air-bone gap (ABG) was closed to within 20 dB in 82% of cases. Air-conduction puretone audiometry improvement was 17.2 dB (standard deviation [SD], 19.2), with a mean postoperative ABG of 16.2 dB (SD, 12.7). Only 1 ear, operated with TORP, had a sensorineural deterioration of 20 dB. With offset pistons, ABG was closed to within 20 dB in 100% of cases with a mean postoperative ABG of 8.8 dB (SD, 7.2).

CONCLUSION

The lateralized piston syndrome was found in 18.5% of stapes surgery revisions. Surgical management was effective in correcting the conductive hearing loss. In the event of significant eroded incus, we observed better results with offset pistons than with TORPs.

Conebeam CT of the head and neck, part 2: clinical applications

SUMMARY

Conebeam x-ray CT (CBCT) is being increasingly used for point-of-service head and neck and dentomaxillofacial imaging. This technique provides relatively high isotropic spatial resolution of osseous structures with a reduced radiation dose compared with conventional CT scans. In this second installment in a 2-part review, the clinical applications in the dentomaxillofacial and head and neck regions will be explored, with particular emphasis on diagnostic imaging of the sinuses, temporal bone, and craniofacial structures. Several controversies surrounding the emergence of CBCT technology will also be addressed.

Cone beam computed tomography, a low-dose imaging technique in the postoperative assessment of cochlear implantation

BACKGROUND

Cone beam computed tomography (CBCT) has become an extremely useful technique for dentomaxillofacial imaging because it provides clear images of highly contrasted structures. Previous studies evaluating the applicability of this technique in otologic imaging were very encouraging but were only performed in vitro on temporal bone specimens. The intracochlear positioning of the individual electrodes after cochlear implantation by means of CBCT has not yet been shown in vivo.

OBJECTIVE

We describe a protocol for in vivo postoperative imaging of cochlear implants by CBCT. Moreover, the effective dose was measured and compared with the effective dose used on 4- and 16-slice multislice computed tomography (MSCT) by using a RANDO-phantom.

MAIN OUTCOME MEASURE

Developing a protocol for in vivo postoperative imaging of cochlear implants by CBCT.

RESULTS

CBCT provides high-resolution and almost artifact-free multiplanar reconstruction images allowing assessment of the precise intracochlear position of the electrode and visualization of each of the individual contacts. The calculated effective dose of the used CBCT and MSCT acquisitions is 80 musv for the CBCT, 3,600 musv for the 16-slice computed tomography, and 4,800 musv for the 4-slice computed tomography.

CONCLUSION

These preliminary results suggests that, for in vivo postoperative evaluation of cochlear implants, CBCT can provide at least the same information as conventional radiography, digital radiograph, and MSCT but in a more comfortable and a much more safer way.

Advances in Skull Base Imaging

Despite being introduced in the 1970s and 1980s, CT and MRI continue to be the primary imaging modalities for the temporal bone and skull base. Although the general concepts and physics remain the same, the images obtained currently are far superior. Augmenting these traditional modalities are nuclear medicine imaging techniques, functional imaging, and the fusion of different techniques. Advances in these areas are expanding our options and illuminating pathology in unique ways. As basic physiologic processes are better understood, new opportunities for novel imaging techniques should arise.