Biomedical subjects

Robert J Witte

Publications and source records attributed to Robert J Witte.

13 recordsLinked to original sources

PubMed2007

Scalar localization of the electrode array after cochlear implantation: a cadaveric validation study comparing 64-slice multidetector computed tomography with microcomputed tomography.

HYPOTHESIS: Improved resolution available with 64-slice multidetector computed tomography (MDCT) could potentially be used clinically to localize the cochlear implant (CI) electrode array within the basal turn. BACKGROUND: In CI surgery, the electrode array should be inserted into and remain within the scala tympani to avoid injury to Reissner's membrane and the scala media. Correlating the position of the electrode in the basal turn with surgical technique and implant design could be helpful in improving outcomes. METHODS: After a standard left mastoid exposure of the round window niche through the facial recess performed on a cadaver head, an electrode array from a Nucleus Softip Contour CI was fully inserted through a cochleostomy. The head was then scanned axially on a 64-slice MDCT with 0.4-mm slice thickness and reconstructed into the oblique axial, oblique coronal, and oblique sagittal planes of the cochlea. The temporal bone was then harvested and imaged on a microcomputed tomographic scanner using 20-microm slice thickness. Identical reconstructions were made and compared with the 64-slice images to confirm exact location of the electrode array. RESULTS: The 64-slice MDCT accurately localized the electrode array to the scala tympani. This was best demonstrated in the oblique sagittal plane, identifying the electrode array in the posterior inferior portion of the basal turn, posterior to the spiral lamina. CONCLUSION: This ex vivo validation study suggests that 64-slice MDCT has the potential to allow accurate localization of the CI electrode array within the basal turn of the cochlea.

Cadaver↗

PubMed2006

Clinical-pathologic study of biomarkers in FTDP-17 (PPND family with N279K tau mutation).

The objective of this clinical-pathologic study was to identify biomarkers for a pallidopontonigral degeneration (PPND) kindred of frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) harboring the N279K tau mutation. Five affected subjects, one at-risk who later became symptomatic, and one at-risk asymptomatic mutation carrier, had abnormal (18)fluorodeoxyglucose PET demonstrating asymmetric temporal lobe hypometabolism. All except the asymptomatic mutation carrier had abnormal brain MRI. Parkinsonism, myoclonus, anosmia, insomnia, speech, and autonomic dysfunction were identified. Autopsy of six affected subjects showed frontotemporal degeneration with extensive tauopathy. Further studies of FTDP-17 patients are needed to replicate these findings.

Adult↗

PubMed2006

Clinicopathological and imaging correlates of progressive aphasia and apraxia of speech.

Apraxia of speech (AOS) is a motor speech disorder characterized by slow speaking rate, abnormal prosody and distorted sound substitutions, additions, repetitions and prolongations, sometimes accompanied by groping, and trial and error articulatory movements. Although AOS is frequently subsumed under the heading of aphasia, and indeed most often co-occurs with aphasia, it can be the predominant or even the sole manifestation of a degenerative neurological disease. In this study we determine whether the clinical classifications of aphasia and AOS correlated with pathological diagnoses and specific biochemical and anatomical structural abnormalities. Seventeen cases with initial diagnoses of a degenerative aphasia or AOS were re-classified independently by two speech-language pathologists--blinded to pathological and biochemical findings--into one of five operationally defined categories of aphasia and AOS. Pathological diagnoses in the 17 cases were progressive supranuclear palsy in 6, corticobasal degeneration in 5, frontotemporal lobar degeneration with ubiquitin-only-immunoreactive changes in 5 and Pick's disease in 1. Magnetic resonance imaging analysis using voxel-based morphometry (VBM), and single photon emission tomography were completed, blinded to the clinical diagnoses, and clinicoimaging and clinicopathological associations were then sought. Interjudge clinical classification reliability was 87% (kappa = 0.8) for all evaluations. Eleven cases had evidence of AOS, of which all (100%) had a pathological diagnosis characterized by underlying tau biochemistry, while five of the other six cases without AOS did not have tau biochemistry (P = 0.001). A majority of the 17 cases had more than one yearly evaluation, demonstrating the evolution of the speech and language syndromes, as well as motor signs. VBM revealed the premotor and supplemental motor cortices to be the main cortical regions associated with AOS, while the anterior peri-sylvian region was associated with non-fluent aphasia. Refining the classification of the degenerative aphasias and AOS may be necessary to improve our understanding of the relationships among behavioural, pathological and imaging correlations.

Aged↗

PubMed2005

Imaging microscopy of the middle and inner ear: Part II: MR microscopy.

Anatomic definition of the membranous labyrinth in the clinical setting remains limited despite significant technological advances in magnetic resonance imaging (MRI). Recent developments in ultra-high resolution imaging for use in the research laboratory on small animals and pathologic specimens have given rise to the field of imaging microscopy. We have delineated for the first time the labyrinthine structures in a human temporal bone cadaver specimen using these novel techniques. This approach to the study of the middle and inner ear avoids tissue destruction inherent in histological preparations using standard light microscopy techniques. Part I of this series focused on bony middle and inner ear anatomy with MicrCT. In Part II, we present high-resolution MicroMR images to highlight the utility of this technique in teaching radiologists and otolaryngologists clinically relevant anatomy focusing on the membranous labyrinth. This anatomy can be further enhanced using 3D volume-rendered images. It is hoped that familiarity with these ex vivo anatomic techniques will encourage further developments in the field of high-resolution clinical imaging for patients with temporal bone pathologies.

Anatomy, Cross-Sectional↗

PubMed2005

MRI correlates of alien leg-like phenomenon in corticobasal degeneration.

We describe the clinical and neuroradiologic correlates in two patients with the clinical picture of CBD and alien leg phenomena. The MRI brain scan in both had unique focal abnormalities in the corresponding leg area of the homunculus that may be the substrate for the alien limb features.

Aged↗

PubMed2004

Imaging microscopy of the middle and inner ear: Part I: CT microscopy.

Anatomic definition of the middle ear and bony labyrinth in the clinical setting remains limited despite significant technological advances in computed tomography (CT). Recent developments in ultra-high resolution imaging for use in the research laboratory on small animals and pathologic specimens have given rise to the field of imaging microscopy. We have taken advantage of this technique to image a human temporal bone cadaver specimen to delineate middle ear and labyrinthine structures, only seen previously using standard light microscopy. This approach to the study of the inner ear avoids tissue destruction inherent in histological preparations. We present high-resolution MicroCT images of the middle ear and bony labyrinth to highlight the utility of this technique in teaching radiologists and otolaryngologists clinically relevant temporal bone anatomy. This study is not meant to function as a complete anatomic atlas of the temporal bone. We have selected several structures that are routinely delineated on clinical scanners to highlight the utility of imaging microscopy in displaying critical anatomic relationships in three orthogonal planes. These anatomic relationships can be further enhanced using 3D volume rendering.

Cadaver↗

PubMed2004

3-T imaging of the cochlear nerve and labyrinth in cochlear-implant candidates: 3D fast recovery fast spin-echo versus 3D constructive interference in the steady state techniques.

BACKGROUND AND PURPOSE: High-resolution imaging of the internal auditory canal and labyrinth at 1.5 T is often performed by using three-dimensional (3D) fast spin-echo or T2* techniques. We evaluated both techniques at 3 T in the preoperative assessment of patients being considered for cochlear implants. METHODS: Sagittal 3D fast recovery fast spin-echo (FRFSE) and 3D constructive interference in the steady state (CISS) images were acquired in eight patients at 3.0 T by using dual surface coils. Contrast-to-noise ratios (CNRs) for the intracanalicular nerve and CSF were measured in the internal auditory canal. Two neuroradiologists reviewed the images to determine whether the techniques provided images of diagnostic quality. RESULTS: CNRs for 3D CISS were twice those obtained with 3D FRFSE. Both techniques provided images of diagnostic quality, though spurious signal intensity loss at the apex of the superior semicircular canals was encountered on 3D FRFSE images in four of eight patients. CONCLUSION: Both 3D FRFSE and 3D CISS provide high-resolution images of the internal auditory canal and labyrinth at 3.0 T. We predict that the superior CNRs obtained with 3D CISS will prove advantageous as we move to smaller fields of view at higher field strength.

Artifacts↗

PubMed2004

Giant cell reparative granuloma of the nasal cavity.

We report an unusual case of giant cell reparative granuloma (GCRG) arising in the nasal cavity of a 7-year-old girl. GCRG is an uncommon benign lesion that is most commonly found in the mandible and maxilla. The MR imaging and CT findings of this lesion, as well as GCRGs in other craniofacial bones and extragnathic sites, will be reviewed. Although rare, the imaging characteristics of GCRGs should be recognized, and this entity should be suggested when the clinical information, CT, and MR features suggest a fibrous-osseous lesion in the nasal cavity.

Biopsy↗

PubMed2002

Hybrid phased array for improved internal auditory canal imaging at 3.0-T MR.

PURPOSE: To develop and evaluate a hybrid phased array for internal auditory canal (IAC) imaging at 3.0 T. MATERIALS AND METHODS: A hybrid phased array was designed and built as two circular surface receive-only coils combined with a volume transmit-receive birdcage head coil for simultaneous image acquisition. Phantom and volunteer images were obtained to assess the coil performance. RESULTS: The phantom data show that significant signal-to-noise ratio (SNR) improvement was achieved in the region corresponding to the inner ear, i.e., by a factor of 2.5 compared to the standard head coil data. Volunteer IAC image quality was deemed superior as compared to images acquired at 3.0 T using a standard head coil. CONCLUSION: This hybrid array combined with three-dimensional fast spin-echo (FSE) acquisition resulted in improved high spatial resolution IAC imaging.

Ear, Inner↗

PubMed2002

Magnetic resonance imaging and deep brain stimulation.

OBJECTIVE: To determine whether cranial magnetic resonance imaging (MRI) is associated with deep brain stimulation (DBS) lead displacement or program interference. METHODS: In vitro and in vivo studies were performed with the Itrel II implantable pulse generator (IPG) (Model 7424; Medtronic, Minneapolis, MN), Medtronic 3387 and 3389 leads, and a 1.5-T GE Horizon LX scanner (General Electric, Milwaukee, WI). In the in vivo study, two MRI volumetric data sets were compared for each of five patients undergoing staged, bilateral, DBS electrode placement in the thalamic or subthalamic nucleus. The data sets were acquired shortly after the initial implantation and during stereotactic planning for the second implantation (1-8 mo between acquisitions). An additional thalamotomy-treated patient was included as a control patient. Volumetric data were analyzed in a blinded manner, using AnalyzeAVW 3.0 software (Biomedical Imaging Resource, Mayo Clinic, Rochester, MN), to determine lead movement. In the in vitro study, the IPG and leads were positioned in the magnetic field in various configurations and were systematically assessed for movement. RESULTS: In vivo, the majority of measured deviations (88%) were within the standard error of measurement (1.4 mm). The maximal measured deviation was 3 mm (2% occurrence). Excellent tremor control with stimulation was demonstrated, which did not change after MRI. In vitro, the DBS leads demonstrated no deflection when introduced into the magnetic field. Similarly, no changes in IPG battery strength, lead impedance, or program settings were observed. CONCLUSION: MRI was not associated with significant DBS electrode movement or changes in clinical responses. Other IPG models and components and MRI scanners should be evaluated, to develop specific guidelines for MRI among individuals with implanted DBS systems.

Electric Stimulation Therapy↗

PubMedDate not supplied

Retinal detachment: imaging of surgical treatments and complications.

Rhegmatogenous retinal detachment occurs in 5%-7% of the population with a peak prevalence between 40 and 80 years of age. The objects of treatment are to create a chorioretinal scar at the site of the retinal tear and to mechanically appose the detached sensory retina to the underlying retinal pigment epithelium. This apposition is achieved by means of scleral buckling or intraocular tamponade. In scleral buckling, the eye wall is indented under the retinal tear with a silicone buckling element. In intraocular tamponade, the eye is filled with a bubble of air, gas, or silicone oil. In patients treated with these techniques, neuroimaging commonly demonstrates incidental orbital findings. Familiarity with these techniques is essential if the radiologist is to differentiate normal postoperative findings from ocular disease. Furthermore, the ability to recognize the appearance of uncomplicated ocular surgery is a prerequisite for aiding the surgeon in diagnosis of postoperative complications.

Humans↗

PubMedDate not supplied

Pediatric and adult cochlear implantation.

The frequency of cochlear implantation has increased tremendously over the past decade. Cochlear implantation is often performed as an outpatient procedure and is considered an acceptable treatment for severe to profound sensorineural hearing loss in patients who are refractory to conventional hearing augmentation. Imaging plays an important part in the work-up of cochlear implant candidates, and an understanding of imaging evaluation procedures is essential. The radiologist must be familiar with imaging findings that contraindicate implantation (absence of the cochlea or cochlear nerve) and with those that could significantly alter surgery (facial nerve dehiscence, cochlear ossification). It is also imperative to be familiar with the growing number of imaging options (particularly magnetic resonance [MR] imaging pulse sequences) to optimize evaluation of cochlear implant candidates. Imaging choices will be substantially influenced by the manufacturer of the computed tomographic scanner or MR imager. Radiologists will assume an expanding role in evaluating affected patients as the frequency of cochlear implantation continues to increase.

Adult↗

PubMedDate not supplied

Middle and inner ear: improved depiction with multiplanar reconstruction of volumetric CT data.

Many anatomic structures of the middle and inner ear are not optimally depicted at computed tomography (CT) with image reconstruction in the standard axial and coronal planes. Recent advances in multidetector CT, including the development of scanners with 32 detector rows, allow the acquisition of isotropic voxels that can be reconstructed in any plane of section. This technique gives radiologists the opportunity to visualize the anatomic structures of the middle and inner ear (the ossicular chain, stapedial footplate-oval window complex, round window, cochlea, vestibular aqueduct, and bones of the superior semicircular canal and facial nerve canal) in greater detail and may help increase the accuracy of CT for the diagnosis of diseases of the middle and inner ear.

Ear Diseases↗