Benoit M. Dawant

Vanderbilt University, Nashville, Michigan, United States

Are you Benoit M. Dawant?

Claim your profile

Publications (301)347.84 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Identification of error in non-rigid registration is a critical problem in the medical image processing community. We recently proposed an algorithm that we call "Assessing Quality Using Image Registration Circuits" (AQUIRC) to identify non-rigid registration errors and have tested its performance using simulated cases. In this article, we extend our previous work to assess AQUIRC's ability to detect local non-rigid registration errors and validate it quantitatively at specific clinical landmarks, namely the Anterior Commissure (AC) and the Posterior Commissure (PC). To test our approach on a representative range of error we utilize 5 different registration methods and use 100 target images and 9 atlas images. Our results show that AQUIRC's measure of registration quality correlates with the true target registration error (TRE) at these selected landmarks with an R² = 0.542. To compare our method to a more conventional approach, we compute Local Normalized Correlation Coefficient (LNCC) and show that AQUIRC performs similarly. However, a multi-linear regression performed with both AQUIRC's measure and LNCC shows a higher correlation with TRE than correlations obtained with either measure alone, thus showing the complementarity of these quality measures. We conclude the article by showing that the AQUIRC algorithm can be used to reduce registration errors for all five algorithms.
    IEEE transactions on medical imaging. 07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Deep brain stimulation, which is used to treat various neurological disorders, involves implanting a permanent electrode into precise targets deep in the brain. Reaching these targets safely is difficult because surgeons have to plan trajectories that avoid critical structures and reach targets within specific angles. A number of systems have been proposed to assist surgeons in this task. These typically involve formulating constraints as cost terms, weighting them by surgical importance, and searching for optimal trajectories, in which constraints and their weights reflect local practice. Assessing the performance of such systems is challenging because of the lack of ground truth and clear consensus on an optimal approach among surgeons. Due to difficulties in coordinating inter-institution evaluation studies, these have been performed so far at the sites at which the systems are developed. Whether or not a scheme developed at one site can also be used at another is thus unknown. In this article, we conduct a study that involves four surgeons at three institutions to determine whether or not constraints and their associated weights can be used across institutions. Through a series of experiments, we show that a single set of weights performs well for all surgeons in our group. Out of 60 trajectories, our trajectories were accepted by a majority of neurosurgeons in 95% of the cases and the average acceptance rate was 90%. This study suggests, albeit on a limited number of surgeons, that the same system can be used to provide assistance across multiple sites and surgeons.
    IEEE transactions on bio-medical engineering 05/2014; · 2.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hypothesis: Three surgical approaches, cochleostomy (C), round window (RW), and extended round window (ERW) and two electrodes types, lateral wall (LW) and perimodiolar (PM), account for the vast majority of cochlear implantations. The goal of this study was to analyze the relationship between surgical approach and electrode type with final intracochlear position of the electrode array and subsequent hearing outcomes.Study Design: Comparative longitudinal study.Methods: One hundred postlingually implanted adult patients were enrolled in the study. From the post-operative scan, intracochlear electrode location was determined by using rigid registration, transformed back to the pre-operative CT. Likelihood ratio chi-square statistics were used to evaluate for differences in electrode placement with respect to surgical approach (C, RW, ERW) and type of electrode (LW, PM).Results: Electrode placement completely within the ST was more common for LW than PM designs (89% vs 58%, p < 0.001). RW and ERW approaches were associated with lower rates of electrode placement outside the ST than for the cochleostomy approach (9%, 16% and 63%, respectively, p < 0.001). This pattern held true regardless of whether the implant was LW or PM. When examining electrode placement and hearing outcome, those with electrode residing completely within the ST had better CNC word scores than patients with any number of electrodes located outside the ST (p=0.045).Conclusion: These data suggest that RW and ERW approaches and LW electrodes are associated with an increased likelihood of successful ST placement. Furthermore, electrode position entirely within the ST confers superior audiological outcomes.
    The Laryngoscope 04/2014; · 1.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this case report, we present a novel, minimally invasive image-guided approach to drainage of a petrous apex lesion. A 34-year-old man diagnosed with a petrous apex lesion consistent with cholesterol granuloma. The granuloma was large and caused mild compression of the brainstem with associated neurologic symptoms and seizure-like activity. Based on the anatomic location of the lesion, it was determined that the treatment plan would be to surgically drain the lesion via 2 linear paths-one after an infralabyrinthine approach and the other a subarcuate approach. Customized microstereotactic frames that mount on bone-implanted markers and constrain the drill along the desired path were used to accurately drill these desired paths and avoid damage to surrounding critical structures. After a simple mastoidectomy, the petrous apex was successfully reached without damage to vital adjacent structures by drilling the 2 linear channels using 2 custom microstereotactic frames. Viscous brown liquid and debris was recovered by irrigating through one of the channels and suctioning through the other. Drainage of the petrous apex was successfully performed via 2 linear channels without any complications. Custom microstereotactic frames were used to accurately drill those linear channels. Postoperative CT ensured no complications. Postoperative course of the patient was remarkable with normal hearing and normal facial nerve function. We presented a successful implementation of an image-guided approach to drain petrous apex.
    Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 04/2014; 35(4):649-55. · 1.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A cochlear implant (CI) is a device that restores hearing using an electrode array that is surgically placed in the cochlea. After implantation, the CI is programmed to attempt to optimize hearing outcome. Currently, we are testing an image-guided CI programming (IGCIP) technique we recently developed that relies on knowledge of relative position of intracochlear anatomy to implanted electrodes. IGCIP is enabled by a number of algorithms we developed that permit determining the positions of electrodes relative to intra-cochlear anatomy using a pre- and a post-implantation CT. One issue with this technique is that it cannot be used for many subjects for whom a pre-implantation CT was not acquired. Pre-implantation CT has been necessary because it is difficult to localize the intra-cochlear structures in post-implantation CTs alone due to the image artifacts that obscure the cochlea. In this work, we present an algorithm for automatically segmenting intra-cochlear anatomy in post-implantation CTs. Our approach is to first identify the labyrinth and then use its position as a landmark to localize the intra-cochlea anatomy. Specifically, we identify the labyrinth by first approximately estimating its position by mapping a labyrinth surface of another subject that is selected from a library of such surfaces and then refining this estimate by a standard shape model-based segmentation method. We tested our approach on 10 ears and achieved overall mean and maximum errors of 0.209 and 0.98 mm, respectively. This result suggests that our approach is accurate enough for developing IGCIP strategies based solely on post-implantation CTs.
    Proceedings - Society of Photo-Optical Instrumentation Engineers 03/2014; 9034:90342V.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A cochlear implant (CI) is a neural prosthetic device that restores hearing by directly stimulating the auditory nerve using an electrode array that is implanted in the cochlea. In CI surgery, the surgeon accesses the cochlea and makes an opening where he/she inserts the electrode array blind to internal structures of the cochlea. Because of this, the final position of the electrode array relative to intra-cochlear anatomy is generally unknown. We have recently developed an approach for determining electrode array position relative to intra-cochlear anatomy using a pre- and a post-implantation CT. The approach is to segment the intra-cochlear anatomy in the pre-implantation CT, localize the electrodes in the post-implantation CT, and register the two CTs to determine relative electrode array position information. Currently, we are using this approach to develop a CI programming technique that uses patient-specific spatial information to create patient-customized sound processing strategies. However, this technique cannot be used for many CI users because it requires a pre-implantation CT that is not always acquired prior to implantation. In this study, we propose a method for automatic segmentation of intra-cochlear anatomy in post-implantation CT of unilateral recipients, thus eliminating the need for pre-implantation CTs in this population. The method is to segment the intra-cochlear anatomy in the implanted ear using information extracted from the normal contralateral ear and to exploit the intra-subject symmetry in cochlear anatomy across ears. To validate our method, we performed experiments on 30 ears for which both a pre- and a post-implantation CT are available. The mean and the maximum segmentation errors are 0.224 and 0.734mm, respectively. These results indicate that our automatic segmentation method is accurate enough for developing patient-customized CI sound processing strategies for unilateral CI recipients using a post-implantation CT alone.
    Medical image analysis 02/2014; 18(3):605-615. · 3.09 Impact Factor
  • Yuan Liu, Pierre-Francois D'Haese, Benoit M. Dawant
    [Show abstract] [Hide abstract]
    ABSTRACT: Deep brain stimulation, which is used to treat various neurological disorders, involves implanting a permanent electrode into precise targets deep in the brain. Accurate pre-operative localization of the targets is difficult to achieve, as these are typically located in homogenous regions with poor contrast. Population-based statistical atlases are often used to assist with this process. These atlases are created by acquiring the location of efficacious target points in many subjects and projecting these onto reference image volumes using non-rigid registration algorithms. The registration algorithm used in the normalization process may bias the atlases and it is thus important to study how different deformable registration methods may affect the process. In this paper, we have qualitatively and quantitatively compared six well-known deformable registration methods using various metrics designed to measure the centroid, spread, and shape of the statistical maps. This study is conducted on a large-scale dataset which includes 100 patient volumes and three additional volumes used as references, resulting in a total of 1800 deformable registrations. Results show that statistical atlases constructed by different deformable registration methods share comparable centroids and spreads with marginal differences in their shape. Among the six methods being studied, Diffeomorphic Demons performs the most differently with centroids being furthest apart and largest spreads, but differences between mean spread values are not found to be significant.
    SPIE; 02/2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Minimally invasive image-guided cochlear implantation (CI) involves accessing the cochlea via a linear path from the lateral skull to the cochlea avoiding vital structures including the facial nerve. Herein, we describe and demonstrate the feasibility of the technique for pediatric patients. Prospective. Children's Hospital. Thirteen pediatric patients (1.5 to 8 years) undergoing traditional CI participated in this Institutional Review Board-approved study. Three fiducial markers were bone-implanted surrounding the ear, and a CT scan was acquired. The CT scan was processed to identify the marker locations and critical structures of the temporal bone. A safe linear path was determined to target the cochlea avoiding damage to vital structures. A custom microstereotactic frame was fabricated that would mount on the fiducial markers and constrain a tool to the desired trajectory. After traditional mastoidectomy and prior to cochleostomy, the custom microstereotactic frame was mounted on the bone-implanted markers to confirm that the achieved trajectory was safe and accurately accessed the cochlea. For all the 13 patients, it was possible to determine a safe trajectory to the cochlea. Custom microstereotactic frames were validated successfully on 9 patients. Two of these patients had inner ear malformations, and this technique helped the surgeon confirm ideal location for cochleostomy. For patients with normal anatomy, the mean and standard deviation of the closest distance of the trajectory to facial nerve and chorda tympani were 1.1 ± 0.3 mm and 1.2 ± 0.5 mm, respectively. Minimally invasive image-guided CI is feasible for pediatric patients.
    Otolaryngology Head and Neck Surgery 01/2014; · 1.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We hypothesize that surface landmarks surrounding the round window typically used to guide electrode placement during cochlear implantation (CI) exhibit substantial variability with respect to intracochlear anatomy. Recent publications suggest that both atraumatic electrode insertion and electrode location within the scala tympani can affect auditory performance after CI. However, current techniques for electrode insertion rely on surface landmarks alone for navigation, without actual visualization of intracochlear structures other than what can be seen through a surgically created cochleostomy. In this study, we quantify how well the position of intracochlear anatomy is predicted by surface landmarks surrounding the round window. Structures representing middle ear surface and intracochlear anatomy were reconstructed in μCT scans of 10 temporal bone specimens. These structures were then reoriented into a normalized coordinate system to facilitate measurement of inter-subject anatomical shape variations. Only minor intersubject variations were detected for intracochlear anatomy (maximum deviation, 0.71 mm; standard deviation, 0.21 mm), with greatest differences existing near the hook and apex. Larger intersubject variations in intracochlear structures were detected when considered relative to surface landmarks surrounding the round window (maximum deviation, 0.83 mm; standard deviation, 0.54 mm). The cochlea and its scala exhibit considerable variability in relation to middle ear surface landmarks. While support for more precise, atraumatic CI electrode insertion techniques is growing in the otologic community, landmark guided insertion techniques have limited precision. Refining the CI insertion process may require the development of image-guidance systems for use in otologic surgery.
    Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 12/2013; 34(9):1675-1680. · 1.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: Minimally-invasive image-guided approach to cochlear implantation (CI) involves drilling a narrow, linear tunnel to the cochlea. Reported herein is the first clinical implementation of this approach. Study Design: Prospective, cohort study. Methods: On preoperative CT, a safe linear trajectory through the facial recess targeting the scala tympani was planned. Intraoperatively, fiducial markers were bone-implanted, a second CT was acquired, and the trajectory was transferred from preoperative to intraoperative CT. A customized microstereotactic frame was rapidly designed and constructed to constrain a surgical drill along the desired trajectory. Following sterilization, the frame was employed to drill the tunnel to the middle ear. After lifting a tympanomeatal flap and performing a cochleostomy, the electrode array was threaded through the drilled tunnel and into the cochlea. Results: Eight of nine patients were successfully implanted using the proposed approach with six insertions completely within scala tympani. Traditional mastoidectomy was performed on one patient following difficulty threading the electrode array via the narrow tunnel. Other difficulties encountered included use of the back-up implant when an electrode was dislodged during threading via the tunnel, tip fold-over, and facial nerve paresis (House-Brackmann II/VII at 12 months) secondary to heat during drilling. Average time of intervention was 182±36 minutes. Conclusion: Minimally-invasive, image-guided CI is clinically achievable. Further clinical study is necessary to address technological difficulties during drilling and insertion and to assess potential benefits including decreased time of intervention, standardization of surgical intervention, and decreased tissue dissection potentially leading to shorter recovery and earlier implant activation.
    The Laryngoscope 11/2013; · 1.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Population-based studies indicate that between 5 and 9 percent of US children exhibit significant deficits in mathematical reasoning, yet little is understood about the brain morphological features related to mathematical performances. In this work, deformation-based morphometry (DBM) analyses have been performed on magnetic resonance images of the brains of 79 third graders to investigate whether there is a correlation between brain morphological features and mathematical proficiency. Group comparison was also performed between Math Difficulties (MD-worst math performers) and Normal Controls (NC), where each subgroup consists of 20 age and gender matched subjects. DBM analysis is based on the analysis of the deformation fields generated by non-rigid registration algorithms, which warp the individual volumes to a common space. To evaluate the effect of registration algorithms on DBM results, five nonrigid registration algorithms have been used: (1) the Adaptive Bases Algorithm (ABA); (2) the Image Registration Toolkit (IRTK); (3) the FSL Nonlinear Image Registration Tool; (4) the Automatic Registration Tool (ART); and (5) the normalization algorithm available in SPM8. The deformation field magnitude (DFM) was used to measure the displacement at each voxel, and the Jacobian determinant (JAC) was used to quantify local volumetric changes. Results show there are no statistically significant volumetric differences between the NC and the MD groups using JAC. However, DBM analysis using DFM found statistically significant anatomical variations between the two groups around the left occipital-temporal cortex, left orbital-frontal cortex, and right insular cortex. Regions of agreement between at least two algorithms based on voxel-wise analysis were used to define Regions of Interest (ROIs) to perform an ROI-based correlation analysis on all 79 volumes. Correlations between average DFM values and standard mathematical scores over these regions were found to be significant. We also found that the choice of registration algorithm has an impact on DBM-based results, so we recommend using more than one algorithm when conducting DBM studies. To the best of our knowledge, this is the first study that uses DBM to investigate brain anatomical features related to mathematical performance in a relatively large population of children.
    Magnetic Resonance Imaging 10/2013; · 2.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Image segmentation has become a vital and often rate-limiting step in modern radiotherapy treatment planning. In recent years, the pace and scope of algorithm development, and even introduction into the clinic, have far exceeded evaluative studies. In this work we build upon our previous evaluation of a registration driven segmentation algorithm in the context of 8 expert raters and 20 patients who underwent radiotherapy for large space-occupying tumours in the brain. In this work we tested four hypotheses concerning the impact of manual segmentation editing in a randomized single-blinded study. We tested these hypotheses on the normal structures of the brainstem, optic chiasm, eyes and optic nerves using the Dice similarity coefficient, volume, and signed Euclidean distance error to evaluate the impact of editing on inter-rater variance and accuracy. Accuracy analyses relied on two simulated ground truth estimation methods: simultaneous truth and performance level estimation and a novel implementation of probability maps. The experts were presented with automatic, their own, and their peers' segmentations from our previous study to edit. We found, independent of source, editing reduced inter-rater variance while maintaining or improving accuracy and improving efficiency with at least 60% reduction in contouring time. In areas where raters performed poorly contouring from scratch, editing of the automatic segmentations reduced the prevalence of total anatomical miss from approximately 16% to 8% of the total slices contained within the ground truth estimations. These findings suggest that contour editing could be useful for consensus building such as in developing delineation standards, and that both automated methods and even perhaps less sophisticated atlases could improve efficiency, inter-rater variance, and accuracy.
    Physics in Medicine and Biology 05/2013; 58(12):4071-4097. · 2.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: INTRODUCTION: Postoperative programming in deep brain stimulation (DBS) therapy for movement disorders can be challenging and time consuming. Providing the neurologist with tools to visualize the electrode location relative to the patient's anatomy along with models of tissue activation and statistical data can therefore be very helpful. In this study, we evaluate the consistency between neurologists in interpreting and using such information provided by our DBS programming assistance software. METHODS: Five neurologists experienced in DBS programming were each given a dataset of 29 leads implanted in 17 patients. For each patient, probabilistic maps of stimulation response, anatomical images, models of tissue activation volumes, and electrode positions were presented inside a software framework called CRAnialVault Explorer (CRAVE) developed in house. Consistency between neurologists in optimal contact selection using the software was measured. RESULTS: With only the efficacy map, the average consistency among the five neurologists with respect to the mode and mean of their selections was 97% and 95%, respectively, while these numbers were 93% and 89%, respectively, when both efficacy and an adverse effect map were used simultaneously. Fleiss' kappa statistic also showed very strong agreement among the neurologists (0.87 when using one map and 0.72 when using two maps). CONCLUSION: Our five neurologists demonstrated high consistency in interpreting information provided by the CRAVE interactive visualization software for DBS postoperative programming assistance. Three of our five neurologists had no prior experience with the software, which suggests that the software has a short learning curve and contact selection is not dependent on familiarity with the program tools.
    Neuromodulation 05/2013; · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: Validation of a novel minimally invasive, image-guided approach to implant electrodes from three FDA-approved manufacturers-Medel, Cochlear, and Advanced Bionics-in the cochlea via a linear tunnel from the lateral cranium through the facial recess to the cochlea. METHODS: Custom microstereotactic frames that mount on bone-implanted fiducial markers and constrain the drill along the desired path were utilized on seven cadaver specimens. A linear tunnel was drilled from the lateral skull to the cochlea followed by a marginal, round window cochleostomy and insertion of the electrode array into the cochlea through the drilled tunnel. Post-insertion CT scan and histological analysis were used to analyze the results. RESULTS: All specimens ([Formula: see text]) were successfully implanted without visible injury to the facial nerve. The Medel electrodes ([Formula: see text]) had minimal intracochlear trauma with 8, 8, and 10 (out of 12) electrodes intracochlear. The Cochlear lateral wall electrodes (straight research arrays) ([Formula: see text]) had minimal trauma with 20 and 21 of 22 electrodes intracochlear. The Advanced Bionics electrodes ([Formula: see text]) were inserted using their insertion tool; one had minimal insertion trauma and 14 of 16 electrodes intracochlear, while the other had violation of the basilar membrane just deep to the cochleostomy following which it remained in scala vestibuli with 13 of 16 electrodes intracochlear. CONCLUSIONS: Minimally invasive, image-guided cochlear implantation is possible using electrodes from the three FDA-approved manufacturers. Lateral wall electrodes were associated with less intracochlear trauma suggesting that they may be better suited for this surgical technique.
    International Journal of Computer Assisted Radiology and Surgery 04/2013; · 1.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nonlinear partial volume (NLPV) effects can be significant for objects with large attenuation differences and fine detail structures near the spatial resolution limits of a tomographic system. This is particularly true for small metal devices like cochlear implants. While traditional model-based approaches might alleviate these artifacts through very fine sampling of the image volume and subsampling of rays to each detector element, such solutions can be extremely burdensome in terms of memory and computational requirements. The work presented in this paper leverages the model-based approach called “known-component reconstruction” (KCR) where prior knowledge of a surgical device is integrated into the estimation. In KCR, the parameterization of the object separates the volume into an unknown background anatomy and a known component with unknown registration. Thus, one can model projections of an implant at very high spatial resolution while limiting the spatial resolution of the anatomy - in effect, modeling NLPV effects where they are most significant. We present modifications of the KCR approach that can be used to largely eliminate NLPV artifacts, and demonstrate the efficacy of the modified technique (with improved image quality and accurate implant position estimates) for the cochlear implant imaging scenario.
    SPIE Medical Imaging 2013, Lake Buena Vista, Florida, USA; 03/2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last 20 years, cochlear implants (CIs) have become what is arguably the most successful neural prosthesis to date. Despite this success, a significant number of CI recipients experience marginal hearing restoration, and, even among the best performers, restoration to normal fidelity is rare. In this article, we present image processing techniques that can be used to detect, for the first time, the positions of implanted CI electrodes and the nerves they stimulate for individual CI users. These techniques permit development of new, customized CI stimulation strategies. We present one such strategy and show that it leads to significant hearing improvement in an experiment conducted with 11 CI recipients. These results indicate that image-guidance can be used to improve hearing outcomes for many existing CI recipients without requiring additional surgical procedures.
    IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 03/2013; · 2.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is widely believed that major factors in achieving atraumatic insertion of the electrode array into the cochlea in cochlear implant (CI) surgery include amount of tissue resection, selection of the entry point, and angle of insertion. Our group is interested in developing an image guidance (IG) system for electrode insertion if IG can improve outcomes. Thus, in this work we conducted the first study evaluating whether IG could aid atraumatic electrode insertion. To do this, we measured the performance of experienced surgeons when tasked to perform cochleostomy resection and to select CI insertion trajectories in virtual 3D surgical field-of-view simulation software. This software, which simulates views through the surgical microscope, was designed to allow a user to manually perform cochleostomy resection and to select a preferred insertion trajectory in one of two modes: (a) where the traditional approach is simulated and sub-surface anatomy is not visible; and (b) where an IG approach is simulated and the surgical view is augmented with rendering of subsurface intra-cochlear structures. We used this software to compare two surgeons' performance in selecting insertion trajectories with and without IG. Our results show that when using virtual IG, both surgeons could choose insertion trajectories with less variability, select higher quality insertion trajectories, and create the cochleostomy with substantially less tissue resection. These results suggest that IG could indeed aid performance of atraumatic cochlear implantation techniques.
    Proc SPIE 03/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A cochlear implant (CI) is a neural prosthetic device that restores hearing by directly stimulating the auditory nerve with an electrode array. In CI surgery, the surgeon threads the electrode array into the cochlea, blind to internal structures. We have recently developed algorithms for determining the position of CI electrodes relative to intra-cochlear anatomy using pre- and post-implantation CT. We are currently using this approach to develop a CI programming assistance system that uses knowledge of electrode position to determine a patient-customized CI sound processing strategy. However, this approach cannot be used for the majority of CI users because the cochlea is obscured by image artifacts produced by CI electrodes and acquisition of pre-implantation CT is not universal. In this study we propose an approach that extends our techniques so that intra-cochlear anatomy can be segmented for CI users for which pre-implantation CT was not acquired. The approach achieves automatic segmentation of intra-cochlear anatomy in post-implantation CT by exploiting intra-subject symmetry in cochlear anatomy across ears. We validated our approach on a dataset of 10 ears in which both pre- and post-implantation CTs were available. Our approach results in mean and maximum segmentation errors of 0.27 and 0.62 mm, respectively. This result suggests that our automatic segmentation approach is accurate enough for developing customized CI sound processing strategies for unilateral CI patients based solely on postimplantation CT scans.
    Proc SPIE 03/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the past 15 years, rapid improvements in imaging technology and methodology have had a tremendous impact on how we study the human brain. During deep brain stimulation surgeries, detailed anatomical images can be combined with physiological data obtained by microelectrode recordings and microstimulations to address questions relating to the location of specific motor or sensorial functions. The main advantage of techniques such as microelectrode recordings and microstimulations over brain imaging is their ability to localize patient physiological activity with a high degree of spatial resolution. Aggregating data acquired from large populations permits to build what are commonly referred to as statistical atlases. Data points from statistical atlases can be combined to produce probabilistic maps. A crucial step in this process is the intersubject spatial normalization that is required to relate a position in one subject's brain to a position in another subject's brain. In this paper, we study the impact of spatial normalization techniques on building statistical atlases. We find that the Talairach or anterior-posterior commissure coordinate system commonly used in the medical literature produces atlases that are more dispersed than those obtained with normalization methods that rely on nonlinear volumetric image registration. We also find that the maps produced using nonlinear techniques correlate with their expected anatomic positions.
    Stereotactic and Functional Neurosurgery 02/2013; 91(3):148-152. · 1.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVES: To report a novel modification of the cochlear drill-out procedure that uses customized microstereotactic frames as drill guides. PATIENT(S): A 34-year-old man with an 18-year history of profound bilateral hearing loss and completely ossified cochleae that underwent a previous unsuccessful conventional cochlear drill-out procedure in the contralateral ear. INTERVENTIONS: Image-guided cochlear implantation using customized microstereotactic frames to drill linear basal and apical cochlear tunnels. MAIN OUTCOME MEASURES: Transfacial recess cochlear drill-out procedure with full electrode insertion. RESULTS: Two linear paths were drilled using customized microstereotactic frames targeting the proximal and distal basal turn followed by a full split array insertion. Postoperative imaging confirmed 2 cochlear tunnels straddling the modiolus with adequate clearance of the facial nerve and internal carotid artery. The patient received auditory benefit with device use and did not experience any surgical complication. CONCLUSION: Successful cochlear implantation in the setting of total scalar obliteration poses a significant challenge. Image guidance technology may assist in navigating the ossified cochlea facilitating safe and precise cochlear tunnel drilling.
    Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 01/2013; · 1.44 Impact Factor

Publication Stats

5k Citations
347.84 Total Impact Points


  • 1970–2014
    • Vanderbilt University
      • • Department of Electrical Engineering and Computer Science
      • • Vanderbilt University Institute of Imaging Science (VUIIS)
      • • Department of Biomedical Engineering
      Nashville, Michigan, United States
  • 2013
    • University of Alabama at Birmingham
      • Department of Radiation Oncology
      Birmingham, Alabama, United States
    • University of Vermont
      Burlington, Vermont, United States
  • 2006
    • Boston College, USA
      Boston, Massachusetts, United States
  • 2005
    • California College San Diego
      San Diego, California, United States
    • Catholic University of Louvain
      • Department of Electrical Engineering
      Louvain-la-Neuve, WAL, Belgium
  • 2003
    • National Eye Institute
      Maryland, United States
  • 2002
    • Western New England College
      Springfield, Missouri, United States
  • 1996
    • Wake Forest University
      Winston-Salem, North Carolina, United States
  • 1988–1989
    • University of Houston
      • Department of Electrical & Computer Engineering
      Houston, Texas, United States