Registration of preoperative temporal bone CT-scan to otoendoscopic video for augmented-reality based on convolutional neural networks.

PURPOSE: Patient-to-image registration is a preliminary step required in surgical navigation based on preoperative images. Human intervention and fiducial markers hamper this task as they are time-consuming and introduce potential errors. We aimed to develop a fully automatic 2D registration system for augmented reality in ear surgery. METHODS: CT-scans and corresponding oto-endoscopic videos were collected from 41 patients (58 ears) undergoing ear examination (vestibular schwannoma before surgery, profound hearing loss requiring cochlear implant, suspicion of perilymphatic fistula, contralateral ears in cases of unilateral chronic otitis media). Two to four images were selected from each case. For the training phase, data from patients (75% of the dataset) and 11 cadaveric specimens were used. Tympanic membranes and malleus handles were contoured on both video images and CT-scans by expert surgeons. The algorithm used a U-Net network for detecting the contours of the tympanic membrane and the malleus on both preoperative CT-scans and endoscopic video frames. Then, contours were processed and registered through an iterative closest point algorithm. Validation was performed on 4 cases and testing on 6 cases. Registration error was measured by overlaying both images and measuring the average and Hausdorff distances. RESULTS: The proposed registration method yielded a precision compatible with ear surgery with a 2D mean overlay error of 0.65 ± 0.60 mm for the incus and 0.48 ± 0.32 mm for the round window. The average Hausdorff distance for these 2 targets was 0.98 ± 0.60 mm and 0.78 ± 0.34 mm respectively. An outlier case with higher errors (2.3 mm and 1.5 mm average Hausdorff distance for incus and round window respectively) was observed in relation to a high discrepancy between the projection angle of the reconstructed CT-scan and the video image. The maximum duration for the overall process was 18 s. CONCLUSIONS: A fully automatic 2D registration method based on a convolutional neural network and applied to ear surgery was developed. The method did not rely on any external fiducial markers nor human intervention for landmark recognition. The method was fast and its precision was compatible with ear surgery.

Image-to-Patient Registration in Computer-Assisted Surgery of Head and Neck: State-of-the-Art, Perspectives, and Challenges.

Today, image-guided systems play a significant role in improving the outcome of diagnostic and therapeutic interventions. They provide crucial anatomical information during the procedure to decrease the size and the extent of the approach, to reduce intraoperative complications, and to increase accuracy, repeatability, and safety. Image-to-patient registration is the first step in image-guided procedures. It establishes a correspondence between the patient's preoperative imaging and the intraoperative data. When it comes to the head-and-neck region, the presence of many sensitive structures such as the central nervous system or the neurosensory organs requires a millimetric precision. This review allows evaluating the characteristics and the performances of different registration methods in the head-and-neck region used in the operation room from the perspectives of accuracy, invasiveness, and processing times. Our work led to the conclusion that invasive marker-based methods are still considered as the gold standard of image-to-patient registration. The surface-based methods are recommended for faster procedures and applied on the surface tissues especially around the eyes. In the near future, computer vision technology is expected to enhance these systems by reducing human errors and cognitive load in the operating room.

Vision-Based Augmented Reality System for Middle Ear Surgery: Evaluation in Operating Room Environment.

HYPOTHESIS: Augmented reality (AR) solely based on image features is achievable in operating room conditions and its precision is compatible with otological surgery. BACKGROUND: The objective of this work was to evaluate the performance of a vision-based AR system for middle ear surgery in the operating room conditions. METHODS: Nine adult patients undergoing ossicular procedures were included in this prospective study. AR was obtained by combining real-time video from the operating microscope with the virtual image obtained from the preoperative computed tomography (CT)-scan. Initial registration between the video and the virtual CT image was achieved using manual selection of six points on the tympanic sulcus. Patient-microscope movements during the procedure were tracked using image-feature matching algorithm. The microscope was randomly moved at an approximated speed of 5 mm/s in the three axes of space and rotation for 180 seconds. The accuracy of the system was assessed by calculating the distance between each fiducial point selected on the video image and its corresponding point on the scanner. RESULTS: AR could be obtained for at least 3 minutes in seven out of nine patients. The overlay fiducial and target registration errors were 0.38 ±â€Š0.23 mm (n = 7) and 0.36 ±â€Š0.15 mm (n = 5) respectively, with a drift error of 1.2 ±â€Š0.5 µm/s. The system was stable throughout the procedure and achieved a refresh rate of 12 fps. Moderate bleeding and introduction of surgical instruments did not compromise the performance of the system. CONCLUSION: The AR system yielded sub-millimetric accuracy and remained stable throughout the experimental study despite patient-microscope movements and field of view obtrusions.

Participation of Acoustic and Electric Hearing in Perceiving Musical Sounds.

Introduction: The objective of our study was to evaluate musical perception and its relation to the quality of life in patients with bimodal binaural auditory stimulation. Materials and Methods: Nineteen adult patients with a cochlear implant (CI) for minimum 6 months, and moderate to severe contralateral hearing loss with a hearing aid (HA), and 21 normal hearing adults were included in this prospective, cross-sectional study. Pure-tone and speech audiometry, musical test evaluating sound perception characteristics and musical listening abilities, Munich questionnaire for musical habits, and the APHAB questionnaire were recoded. Performance in musical perception test with HA, CI, and HA + CI, and potential correlations between music test, audiometry and questionnaires were investigated. Results: Bimodal stimulation improved musical perception in several features (sound brightness, roughness, and clarity) in comparison to unimodal hearing, but CI did not add to HA performances in texture, polyphony or musical emotion and even appeared to interfere negatively in pitch perception with HA. Musical perception performances (sound clarity, instrument recognition) appeared to be correlated to hearing-related quality of life (APHAB RV and EC subdomains) but not with speech performances suggesting that the exploration of musical perception complements speech understanding evaluation to better describe every-day life hearing handicap. Conclusion: Testing musical sound perception provides important information on hearing performances as a complement to speech audiometry and appears to be related to hearing-related quality of life.

Use of Super Paramagnetic Iron Oxide Nanoparticles as Drug Carriers in Brain and Ear: State of the Art and Challenges.

Drug delivery and distribution in the central nervous system (CNS) and the inner ear represent a challenge for the medical and scientific world, especially because of the blood-brain and the blood-perilymph barriers. Solutions are being studied to circumvent or to facilitate drug diffusion across these structures. Using superparamagnetic iron oxide nanoparticles (SPIONs), which can be coated to change their properties and ensure biocompatibility, represents a promising tool as a drug carrier. They can act as nanocarriers and can be driven with precision by magnetic forces. The aim of this study was to systematically review the use of SPIONs in the CNS and the inner ear. A systematic PubMed search between 1999 and 2019 yielded 97 studies. In this review, we describe the applications of the SPIONS, their design, their administration, their pharmacokinetic, their toxicity and the methods used for targeted delivery of drugs into the ear and the CNS.

Bone-Anchored and Closed Skin Bonebridge Implant in Adults: Hearing Performances and Quality of Life.

INTRODUCTION: Bonebridge® is a novel active bone-anchored hearing implant. The purpose of this study was to evaluate the ease of implantation, the hearing performances, and the patient-reported benefit. MATERIALS AND METHODS: This is a prospective cross-sectional study of 24 consecutive adult patients implanted for a mixed hearing loss (13 chronic otitis media (COM) and 11 other aetiologies). Twenty-one implants were placed in the retrosigmoid position and 3 in the mastoid. Audiometry, Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire, as well as 5 implant-specific questions (analogue visual scale [AVS] 0-10 score), was administered. RESULTS: Surgery lasted 73 ± 29.7 min on average. No major complication occurred. All patients were users at the last follow-up visit (median: 9-month range: 3-25). The average prosthetic gain was similar in COM and other aetiologies (43 ± 4.8 dB and 50 ± 7.2, respectively, not significant, Wilcoxon test). Bone-conduction thresholds were not deteriorated by surgery (Kruskal-Wallis test, not significant). APHAB scores improved in all categories except aversiveness (global score 45 ± 7.0% in COM and 32 ± 10.2% in others, not significant, and Wilcoxon test). Local pain (AVS: 3.23 ± 3.2, n = 16) and manipulation difficulties (3.1 ± 3.69) were low. The device was considered aesthetic (8.3 ± 2.49). Perfectible autonomy (5.0 ± 2.8) and difficulties wearing the implant during sport or at work (5.1 ± 3.47) were the weakest points. CONCLUSIONS: BoneBridge® implant provides reproducible results for the rehabilitation of mixed hearing losses and unilateral hearing loss.

Curvilinear Multiplanar Reconstruction to Predict Useful Length and Diameter of Cochlear Lumen for Cochlear Implantation.

OBJECTIVE: Evaluate the useful length and the diameter of the cochlear lumen (CL) using routine imaging before cochlear implantation to study inter-individual variability and its impact on the insertion depth of the electrode carrier (EC). STUDY DESIGN: Prospective cross-sectional study. SETTING: Tertiary referral center. PATIENTS: Thirty-one preoperative and postimplantation temporal bone CT scans were analyzed by two investigators. INTERVENTION: Images were analyzed via orthogonal multiplanar reconstruction (Osirix) to measure the lengths of the entire CL and the basal turn. By means of curvilinear reconstruction, the CL was unfolded and the diameters of the CL and of the EC were measured every 2 mm from the round window (RW) to the apex. RESULTS: Very high-inter individual variability was found for the length of the basal turn (RSD > 1000%), the entire CL length (RSD > 800%), and the CL diameter at the RW (RSD > 600%). CL diameter was not correlated to the CL length. The inserted EC/total visible CL length ratio was 1.0 ±â€Š0.12. Reliability of the measures was acceptable for the CL length and the diameter at 16 mm from the RW (Crohnbach's alpha > 0.7, n = 31). CONCLUSION: CL length and diameter can be directly measured in a reliable manner by commercially available tools. These parameters potentially influence the EC insertion and should be assessed before cochlear implant surgery.

Video-based augmented reality combining CT-scan and instrument position data to microscope view in middle ear surgery.

The aim of the study was to develop and assess the performance of a video-based augmented reality system, combining preoperative computed tomography (CT) and real-time microscopic video, as the first crucial step to keyhole middle ear procedures through a tympanic membrane puncture. Six different artificial human temporal bones were included in this prospective study. Six stainless steel fiducial markers were glued on the periphery of the eardrum, and a high-resolution CT-scan of the temporal bone was obtained. Virtual endoscopy of the middle ear based on this CT-scan was conducted on Osirix software. Virtual endoscopy image was registered to the microscope-based video of the intact tympanic membrane based on fiducial markers and a homography transformation was applied during microscope movements. These movements were tracked using Speeded-Up Robust Features (SURF) method. Simultaneously, a micro-surgical instrument was identified and tracked using a Kalman filter. The 3D position of the instrument was extracted by solving a three-point perspective framework. For evaluation, the instrument was introduced through the tympanic membrane and ink droplets were injected on three middle ear structures. An average initial registration accuracy of 0.21 ± 0.10 mm (n = 3) was achieved with a slow propagation error during tracking (0.04 ± 0.07 mm). The estimated surgical instrument tip position error was 0.33 ± 0.22 mm. The target structures' localization accuracy was 0.52 ± 0.15 mm. The submillimetric accuracy of our system without tracker is compatible with ear surgery.

Minimally Invasive Cochlear Implantation Assisted by Intraoperative CT Scan Combined to Neuronavigation.

OBJECTIVE: The objective of this work was to study the feasibility of minimally invasive cochlear implantation under intraoperative computerized tomography-scan coupled to navigation. MATERIALS AND METHODS: Five human resin temporal bones (two adults and three children) were used. Initially, a temporal bone imaging was obtained by the intraoperative CT-scan coupled to the navigation (O-ARM). The navigation-assisted drilling began at the mastoid surface creating a conical tunnel (4-2 mm in diameter) through the facial recess and down to the round window. A cochleostomy was performed based on the navigation. A sham electrode array was inserted in the drilled tunnel and into the cochlea.Postoperative CT-scan and dissection were performed to evaluate the trajectory, and possible injury to the external auditory canal, ossicles, or facial nerve. RESULTS: The mean duration of the procedure was 24.4 ±â€Š3.79 minutes (range, 15-35). Cochleostomy was possible in all cases without injury to other structures. The sham array was inside the cochlea in all cases. The mean distance between the drilled canal and the mastoid portion of the facial nerve was 1.2 ±â€Š0.07 mm (range, 1.08-1.38). The mean tracking error was 0.6 ±â€Š0.26 mm (range, 0.20-0.72) at the entry point, 0.6 ±â€Š0.33 mm (range, 0.2-1.02) at the facial nerve and 0.4 ±â€Š0.07 mm (range, 0.36-0.51) at the cochleostomy. CONCLUSION: Cochlear implantation through a minimally invasive approach assisted by intraoperative imaging combined with navigation was feasible in operating room environment and experimental conditions.

Detection of perilymphatic fistula in labyrinthine windows by virtual endoscopy and variation of reconstruction thresholds on CT scan.

Background: Perilymphatic fistula (PLF) is a breach in a labyrinthine window. The opening might decrease the radiological density of the window.Aims/objectives: To evaluate the radiological density of the labyrinthine windows by virtual endoscopy on CT scan.Materials and methods: This prospective study included 47 adult patients with PLF and 98 control patients. Diagnosis of PLF was based on a composite radio clinical score and/or intra operative visualization of the fistula and/or resolution of the symptoms after surgery. On routine CT-scan, labyrinthine windows were examined by virtual endoscopy. The reconstruction threshold was gradually increased until a virtual opening appeared (opening threshold [OT]) and compared to the contralateral window (OT difference).Results: The OT difference was higher in patients than in controls (60.2 ± 10.36 (SEM), n = 47 versus 28.0 ± 2.29 Hounsfield units (HUs), n = 98, p < .01 unpaired t-test). A ROC analysis showed that at an OT difference of 31.5 UH had a sensitivity of 75% and a specificity of 75% for the PLF diagnosis.Conclusions: CT-scan virtual endoscopy and threshold variation provided high specificity and sensitivity in the PLF diagnosis.Significance: This post processing of radiological data appears to enhance the diagnostic value of CT scan.

Contribution of Augmented Reality to Minimally Invasive Computer-Assisted Cranial Base Surgery.

Cranial base procedures involve manipulation of small, delicate and complex structures in the fields of otology, rhinology, neurosurgery and maxillofacial surgery. Critical nerves and blood vessels are in close proximity of these structures. Augmented reality is an emerging technology that can revolutionize the cranial base procedures by providing supplementary anatomical and navigational information unified on a single display. However, the awareness and acceptance of possibilities of augmented reality systems in cranial base domain is fairly low. This article aims at evaluating the usefulness of augmented reality systems in cranial base surgeries and highlights the challenges that current technology faces and their potential solutions. A technical perspective about different strategies employed in development of an augmented realty system is also presented. The current trend suggests an increase in interest towards augmented reality systems that may lead to safer and cost-effective procedures. However, several issues need to be addressed before it can be widely integrated into routine practice.

Association of the Duration of Antibiotic Therapy With Major Surgical Site Infection in Cochlear Implantation.

Importance: Infection after cochlear implantation is a rare but serious event that can lead to meningitis. There is no consensus on prevention of infection in these patients, and each center applies its own strategy. Objective: To describe the rates of major surgical site infection for patients undergoing cochlear implantation who receive prolonged antibiotic treatment compared with those who receive a single perioperative dose of antibiotic prophylaxis. Design, Setting, and Participants: Retrospective cohort study of patients who underwent cochlear implantation between January 1, 2011, and July 8, 2015, with a postoperative follow-up of 1 to 3 years. In this multicenter study at 8 French university centers, 1180 patients (509 children and 671 adults) who underwent cochlear implantation during this period were included. Interventions: Prolonged antibiotic treatment vs single-dose antibiotic prophylaxis. Main Outcomes and Measures: Major infection and explantation. Results: Among 1180 patients (509 children [51.7% female] with a mean [SD] age of 4.6 [3.8] years and 671 adults [54.9% female] with a mean [SD] age of 54.8 [17.0] years), 12 patients (1.0%) developed a major infection, with 4 infections occurring in the prolonged antibiotic treatment group and 8 infections occurring in the antibiotic prophylaxis group (odds ratio, 2.45; 95% CI, 0.73-8.17). Children (9 of 509 [1.8%]) were more likely to develop infection than adults (3 of 671 [0.4%]). Among children, 4 infections occurred in the prolonged antibiotic group (n = 344), and 5 infections occurred in the antibiotic prophylaxis group (n = 158) (odds ratio, 2.78; 95% CI, 0.74-10.49). Among adults, 3 infections occurred in the antibiotic prophylaxis group (n = 365), whereas no infections occurred in the prolonged antibiotic treatment group (n = 290). Conclusions and Relevance: After cochlear implantation, infection was rare, was less common among those who received prolonged antibiotic treatment, and was less likely to occur in adults than in children.

Implantation of the Auditory Nerve via the Middle Ear Cavity in Rats with Partial Hearing Preservation.

The aim of this study was to evaluate the residual hearing function and cochlear morphology after auditory nerve implantation via middle ear spaces in rats. A titanium rod (1.5 mm long and 0.3 mm thick) coated with Parylene was inserted in the cochlear apex in the direction of the modiolus in 9 Wistar rats. Auditory brainstem-evoked responses to tone bursts at 2, 8, 12 and 32 kHz were recorded before surgery and on postoperative days 0, 2, 15 and 30. Eight cochleas were examined microscopically. The rod was inside the modiolus in 4, and partly or totally outside the modiolus in 4 animals. Residual hearing was present in all cases. The average threshold shift in cochleas with modiolar implant was 39 ± 11.2, 54 ± 9.7, 48 ± 20.3 and 43 ± 21.3 dB SPL on postoperative days 0, 2, 15 and 30, respectively. The transmodiolar approach allows a minimally invasive cochlear implantation and a partial hearing preservation.

Clinical evaluation of the xDP output compression strategy for cochlear implants.

Technological advances in the domain of digital signal processing adapted to cochlear implants (CI) are partially responsible for the ever-improving outcomes observed with this neural prosthesis. The goal of the present study was to evaluate audiometric outcomes with a new signal processing strategy implemented in Oticon Medical-Neurelec cochlear implant systems, the xDP strategy. The core of this approach is a preset-based back-end output compression system, modulating a multi-channel transfer function depending on the intensity and information content of input sounds. Twenty adult CI patients, matched for age and CI experience, were included in this study. Pure-tone thresholds and vocal audiometry scores were measured with their former signal processing strategy and with xDP. Speech perception was assessed using dissyllabic words presented in quiet, at different intensity levels: 40, 55, 70, and 85 dB SPL, and in a cocktail party noise at a signal-to-noise ratio of +10 dB. Results with the xDP strategy showed, as awaited, no major modification of pure-tone thresholds. A global increase of speech perception scores was observed after a 1-month habituation period, with significant improvements for speech perception in quiet for moderate (55 dB SPL), loud speech sounds (85 dB SPL), and speech-in-noise comprehension. Subjective signal quality assessment showed a preference for Crystalis(xDP) over the former strategy. These results allow the quantification of improvements provided by the xDP signal processing strategy.

Effect of corticosteroids on facial function after cerebellopontine angle tumor removal: a double-blind study versus placebo.

The aim of this study was to assess the effect of corticosteroids administered intra- and postoperatively on the occurrence of facial palsy after a cerebellopontine angle (CPA) tumor resection, and to investigate pre- and intraoperative prognostic factors. A multicenter, prospective, randomized, double-blind and versus-placebo study was conducted between 2006 and 2010. Three hundred and ten patients operated on for a CPA tumor (96% vestibular schwannomas, 4% miscellaneous) were included by five participating centers. The population was stratified into patients with small (≤15 mm CPA on axial MRI views) and large tumors. In each group, patients were randomized to receive corticosteroid (1 mg/kg/day i.v. methylprednisolone intraoperatively and at postoperative days 1-5) or placebo. Steroids did not affect the facial function at postoperative days 1, 8 and 30 in patients with small or large tumors as evaluated by House and Brackmann grading.

Navigation-guided transmodiolar approach for auditory nerve implantation via the middle ear in humans.

The aim of this study was to assess the surgical feasibility of a transmodiolar approach via the middle ear cavity for an auditory nerve implantation in humans. In the first part of the study, 6 adult human temporal bones underwent a navigator-guided transmodiolar implantation via the middle ear space after a radical mastoidectomy. In the second part, 122 temporal bone CT scans were analyzed for anatomical parameters relevant to this approach. The nerve implantation was feasible in all temporal bones in laboratory conditions, with a mean target registration error of 0.065 ± 0.0583 mm (n = 6). Evaluation of anatomical parameters on CT scans also supported the feasibility. There was a significant interindividual variation of the modiolar axis and the entry point in relation to visible anatomical landmarks, highlighting the necessity for surgical preplanning.

The effects of angiotensin II and the oxidative stress mediator 4-hydroxynonenal on human osteoblast-like cell growth: possible relevance to otosclerosis.

Otosclerosis is a complex disease characterized by an abnormal bone turnover of the otic capsule resulting in conductive hearing loss. Recent findings have shown that angiotensin II (Ang II), a major effector peptide of the renin-angiotensin system, plays an important role in the pathophysiology of otosclerosis, most likely by its proinflammatory effects on the bone cells. Because reactive oxygen species play a role both in inflammation and in the cellular signaling pathway of Ang II, the appearance of protein adducts of the "second messenger of free radicals," the aldehyde 4-hydroxynonenal (HNE), in otosclerotic bone has been analyzed. Immunohistochemical analysis of HNE-modified proteins in tissue samples of the stapedial bones performed on 15 otosclerotic patients and 6 controls revealed regular HNE-protein adducts present in the subperiosteal parts of control bone specimens, whereas irregular areas of a pronounced HNE-protein adduct presence were found within stapedial bone in cases of otosclerosis. To study possible interference by HNE and Ang II in human bone cell proliferation, differentiation, and induction of apoptosis we used an in vitro model of osteoblast-like cells. HNE interacted with Ang II in a dose-dependent manner, both by forming HNE-Ang II adducts, as revealed by immunoblotting, and by modifying its effects on cultured cells. Namely, treatment with 0.1 nM Ang II and 2.5 µM HNE stimulated proliferation, whereas treatment with 10 µM HNE or in combination with Ang II (0.1, 0.5, and 1 nM) decreased cell proliferation. Moreover, 10 µM HNE alone and with Ang II (except if 1 nM Ang II was used) increased cellular differentiation and apoptosis. HNE at 5 µM did not affect differentiation nor significantly change apoptosis. On the other hand, when cells were treated with lower concentrations of HNE and Ang II we observed a decrease in cellular differentiation (combination of 1.0 or 2.5 µM HNE with 0.1 nM Ang II) and decrease in apoptosis (0.1 and 0.5 nM Ang II). Cellular necrosis was increased with 5 and 10 µM HNE if given alone or combined with Ang II, whereas 0.5 nM Ang II and combination of 1 µ M HNE with Ang II (0.1 and 0.5 nM) reduced necrosis. These results indicate that HNE and Ang II might act mutually dependently in the regulation of bone cell growth and in the pathophysiology of otosclerosis.

Design, kinematic optimization, and evaluation of a teleoperated system for middle ear microsurgery.

Middle ear surgery involves the smallest and the most fragile bones of the human body. Since microsurgical gestures and a submillimetric precision are required in these procedures, the outcome can be potentially improved by robotic assistance. Today, there is no commercially available device in this field. Here, we describe a method to design a teleoperated assistance robotic system dedicated to the middle ear surgery. Determination of design specifications, the kinematic structure, and its optimization are detailed. The robot-surgeon interface and the command modes are provided. Finally, the system is evaluated by realistic tasks in experimental dedicated settings and in human temporal bone specimens.