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P Schmalbrock

Publications and source records attributed to P Schmalbrock.

At least 19 recordsLinked to original sources
PubMed2002

Temporal bone dissection simulation--an update.

We report on our continued development of a virtual simulation for temporal bone dissection that provides stereoscopic display, haptic feedback, and aural simulation into a straightforward, comprehensive learning environment. The multimodal interface provides a seamless simulation for non-deterministic drilling and cutting of bone in the surgical context, as well as an intuitive interface for the intelligent tutor for learning regional anatomy. We present novel methodologies for integrating multimodal and multiresolution data sets, including extension to functional and structural segmentation. We will present our initial efforts to validate this environment. Through continued iterations, it is our hope that the system will provide a valuable tool for training future otologic surgeons as well as an environment for the quantitative evaluation of surgical skill.

Aged↗
PubMed2001

Texture detection of simulated microcalcification susceptibility effects in magnetic resonance imaging of breasts.

The presence, size, structure and clustering characteristics of microcalcifications can indicate breast cancer. The magnetic susceptibility of microcalcifications differs from soft biological tissues, leading to directional blurring effects that can be detected by statistical image processing methods. A study of the ability of statistical texture analysis to detect simulated localized blurring in magnetic resonance imaging (MRI) of dense breast is presented. This method can detect localized blurring with sensitivity of 88.89% to 94.44%, specificity of 99.72% to 100%, positive predictive value of 73.91% to 100% and negative predictive value of 99.91% to 99.95%. J. Magn. Reson. Imaging 2001;13:876-881.

Artifacts↗
PubMed2001

T1 measurements in cell cultures: a new tool for characterizing contrast agents at 1.5T.

The objective of this work was to assess the feasibility and accuracy of T1 and relaxivity measurements in cell cultures using 1.5T magnetic resonance imaging (MRI) with the long-term goal to develop a tool for evaluation of novel paramagnetic agents in a realistic macromolecular environment. This initial study was carried out using MCF-7 cells treated with independently determined concentrations of Gd-DTPA. Two cell culture systems were evaluated: cell pellets and single layers of cells grown on microporous inserts. High-resolution T1 measurements of cell cultures were acquired with two dimensional Inversion Recovery Fast Spin Echo (2D-IR-FSE), three dimensional Inversion Recovery Fast Spin Echo (3D-IR-FSE), and 3D-SPGR sequences. The T1 and relaxivity accuracy of these sequences was confirmed with aqueous Gd-DTPA samples of known concentration. Relaxivities of 1.71 +/- 0.15 [mM(-1)second(-1)] and 1.55 +/- 0.50 [mM(-1)second(-1)] were measured in the cell pellets and cell monolayers, respectively, and were different from the value of 4.3 [mM(-1)second(-1)] for Gd-DTPA in water. Both cell pellets and monolayers are suitable for initial assessment of novel MR contrast agents.

Breast Neoplasms↗
PubMed2001

Comparison of autopsy, X-ray, and M.R.I. findings following a low speed impact to the shoulder.

The objectives of the study was to generate data useful to engineers improving crash test dummies and to physicians in anticipating low speed lateral impact injuries to the shoulder. Constant impact mass, distance and variable speeds were used to generate impact forces. Twelve unembalmed human cadavers were studied within 48 hours of death. Pre-test and Post-test physical, X-Ray, and Magnetic Resonance examinations were completed. X-Ray best identified bone injury, Magnetic Resonance intratendinous and intramuscular pathology and autopsy joint instability. Low speed (3.5-7.0 m/sec) impacts under these testing conditions frequently produce soft tissue and bone injuries. Sternoclavicular and acromioclavicular joint instabilities were found in 83% of the cadavers. The most frequent bone fractures were in the distal clavicle of 42% and labral or rotator cuff tears in 13% of the cadavers.

Accidents, Traffic↗
PubMed2000

Comparison of three-dimensional fast spin echo and gradient echo sequences for high-resolution temporal bone imaging.

T2-weighted high-resolution gradient and fast spin echo sequences are widely used as an alternative or adjunct to contrast-enhanced T1-weighted temporal bone imaging. However, to date no systematic comparison has been presented. The purpose of this work is to identify optimal acquisition parameters and to compare volume gradient and fast spin echo techniques. Signal intensities and scan efficiency were computed for gradient echo segment-interleaved motion-compensated acquisition into steady state (SIMCAST), standard fast spin echo (FSE), and fast recovery fast spin echo (FR-FSE). Computations were compared with inner ear images acquired with cubic voxel sizes of 0.35-0.40 mm(3)in 5-8 minutes. Given otherwise identical conditions, the FR-FSE sequence produces images with improved SNR in shorter scan times than standard FSE. For FR-FSE, the scan efficiency is optimal for specific pairs of TR and echo train length, eg, 400 ms/8, 735 ms/16, and 2,050 ms/48. FR-FSE images with large TR and echo trains, while achieving better SNR, are severely compromised by blurring. Imaging with echo train lengths of 16-24 and TR of 800-1,200 ms is a good compromise, and FR-FSE signal-to-noise ratio (SNR) and scan efficiency become comparable to SIMCAST. In vivo image quality is excellent with both FR-FSE and SIMCAST, but SIMCAST images have slightly higher SNR and are significantly more crisp. J. Magn. Reson. Imaging 2000;12:814-825.

Adult↗
PubMed2000

Tumor growth and audiometric change in vestibular schwannomas managed conservatively.

OBJECTIVE: To prospectively define the correlation between changes in tumor volume and audiometric function in vestibular schwannomas managed conservatively. STUDY DESIGN: Prospective longitudinal study. METHODS: Twenty-one patients (age range, 15-84 y; mean age, 63.3 y) with newly diagnosed vestibular schwannomas were enrolled between 1994 and 1999 in a protocol at The Ohio State University Hospital (Columbus, OH) to evaluate the correlation between tumor volume and audiometric change during a period of observation. Patients were evaluated yearly by clinical examination, a standardized internal auditory canal magnetic resonance imaging scan with gadolinium contrast for volumetric analysis, and audiometric function testing. Demographic data, historical features, neurofibromatosis type 2 (NF2) status, initial testing results, and serial testing results were recorded. RESULTS: An increase in tumor volume occurred in 14 of the 21 patients (66%). The pattern of volumetric change was found to be extremely variable. Multiple regression analysis revealed significant correlations of changes in tumor volume with changes in pure-tone average and speech discrimination score (P < .0001 and P = .0021, respectively). Change in tumor volume had greater effect on pure-tone average and speech discrimination score in patients initially with class D audiometric function when compared with those initially in class A (P = .0083 and P = .0245, respectively). The presence of NF2 had an independent protective effect against deterioration of the pure-tone average when compared with patients without NF2 (P = .0125). CONCLUSIONS: This study demonstrated a significant correlation between a change in volume and auditory deterioration in vestibular schwannomas being managed with a trial of observation. A given change in tumor volume appeared to have a greater effect on pure-tone average and speech discrimination score as initial auditory classification declined.

Adolescent↗
PubMed2000

Interactive medical data on demand: a high-performance imaged-based approach across heterogeneous environments.

Medical data in image format continues to increase in both size and complexity. We have integrated advanced techniques in visualization, networked computing, and interface design to improve methods for accessing medical data comprising high-resolution images for reconstructions into three-dimensional volumetric representations. We present two approaches to handle the range of low to high-end client platforms, support visualization functionality, and provide the ability to manipulate very large data over heterogeneous computing and networking environments. We present examples of its use for clinical, research, and educational purposes and discuss future extensions.

Computer Communication Networks↗
PubMed2000

Virtual temporal bone dissection simulation.

We have developed a working prototype system for the virtual simulation of temporal bone dissection. The system offers a paradigm from traditional practices by integrating technological advances to provide a safer and more cost effective way to learn fundamental techniques used in temporal bone surgeries. We present our methods to provide a real-time interactive volumetric system that obviates the need for physical materials in initial training, and provides a more accessible way for residents to practice and to increase exposure to pathological variance. Finally, we discuss ways to extend this work to more advanced resident training, presurgical planning, and surgical documentation.

Aged↗
PubMed1999

Assessment of internal auditory canal tumors: a comparison of contrast-enhanced T1-weighted and steady-state T2-weighted gradient-echo MR imaging.

BACKGROUND AND PURPOSE: Although contrast-enhanced T1-weighted MR imaging is the standard of reference for diagnosing tumor in the cerebellopontine angle, high-resolution T2-weighted imaging may show more details of the seventh and eighth cranial nerve branches, resulting in more accurate tumor volume measurements. The purpose of this study was to compare two MR sequences for their ability to delineate internal auditory canal tumors. METHODS: Twenty-seven ears in 21 patients with 16 confirmed schwannomas were studied with the 3D T2-weighted prototype segment-interleaved motion-compensated acquisition in steady state (SIMCAST) and the T1-weighted contrast-enhanced spoiled gradient-echo (SPGR) techniques. Twenty-eight axial sections were acquired using parameters of 17/3.3 (TR/TE), a 40 degrees flip angle, a 20 x 15-cm or 22 x 16-cm field of view (FOV), a 512 x 256 matrix, and a 0.4- or 1.2-mm section thickness for the SIMCAST technique, and 30/4.2, a 30 degrees flip angle, a 20 x 20-cm FOV, a 512 x 288 matrix, and a 1.5-mm section thickness for the SPGR technique. Tumor appearance and depiction of surrounding anatomy, including the cranial nerves, were evaluated. Tumor volumes were measured by manual tracing. RESULTS: Both sequences clearly identified tumors that ranged in size from 0.06 to 3.0 cm3. Measurements on both sequences agreed, on average, within 14%. The information from both sequences was complementary. SIMCAST usually delineated the CSF spaces better, whereas SPGR more clearly showed the tumor/brain boundary. CONCLUSION: SIMCAST and SPGR are suitable for tumor detection and volume measurements. SPGR has somewhat better contrast, but SIMCAST excels at depicting the surrounding anatomy and tumor involvement of the seventh and eighth cranial nerves.

Adolescent↗
PubMed1998

Development of the force-feedback model for an epidural needle insertion simulator.

The Ohio Supercomputer Center and the Department of Anesthesiology at the OSU Medical Center have developed a computer-based simulation system for use in training anesthesiology residents in the technique of placing a needle for an epidural block. Although the simulator has been well regarded, the fidelity of the haptic feedback is limited because it is based on subjective expert-user evaluation and not on objective model-based or data-based empirical methods. Only a single degree of freedom for force-feedback is required. However, the simulation must be able to accurately portray the force required to puncture each layer of tissue in order to feel realistic. The purpose of the research described in this paper was to devise a methodology for creating empirically based realistic force-feedback models for the epidural needle insertion procedure using MRI data and biomechanical data from materials testing.

Anesthesia, Epidural↗
PubMed1998

High-resolution MR imaging of the auditory pathway.

MR imaging is a valuable tool in the evaluation of the auditory pathway. The current techniques in high-resolution MR imaging of the temporal bone are presented followed by a review of normal anatomy. Several diseases involving the middle ear, inner ear, internal auditory canal, and cerebellopontine angle are then presented. A radiologic-pathologic approach is used to illustrate the nature of these diseases and their appearance on MR imaging.

Auditory Diseases, Central↗
PubMed1998

Endolymphatic sac occlusion for the enlarged vestibular aqueduct syndrome.

OBJECTIVE: To test the efficacy of occlusion of the enlarged vestibular aqueduct to treat the progressive sensorineural hearing loss associated with the enlarged vestibular aqueduct (EVA) syndrome. STUDY DESIGN: Prospective controlled study. SETTING: Tertiary care referral center. PATIENTS: Sixteen consecutive patients (29 affected ears) with progressive sensorineural hearing loss and vestibular aqueducts >1.5 mm in diameter without other inner ear anomalies participated in this study. INTERVENTION: In 10 patients with progressive hearing loss, the EVA was occluded in the ear with worse hearing by placing a fascia graft between the posterior fossa dura overlying the endolymphatic sac and intraosseous duct and the posterior semicircular canal without opening the endolymphatic sac. In the operative ears, serial postoperative audiograms were compared with the contralateral ear in patients with bilateral EVA and with the other nonoperated control ears. MAIN OUTCOME MEASURES: The rate of decline of pure-tone average and speech discrimination before surgery in the operated ear was compared with the rate of decline postoperatively in the same ear. The rates of decline in the nonoperated contralateral ear from the same patient and the nonoperated control ears from other patients were also used for comparison with the postoperative rate of decline in the operated ears. RESULTS: There was no statistically significant change in the rate of hearing loss in patients undergoing occlusion of the EVA. CONCLUSIONS: Extraluminal soft-tissue occlusion of the EVA appears to be a safe procedure but has not yet been shown to be significantly effective in altering the sensorineural hearing loss accompanying the EVA syndrome. Further surgical intervention does not appear warranted until such time that longitudinal follow-up shows sufficient evidence of efficacy of the procedure.

Adolescent↗
PubMed1997

Introduction of fast MR imaging in the assessment of hepatic steatosis.

We determined the utility of fast gradient echo techniques (modified Dixon method) in the assessment of hepatic fat content. Fast spoiled gradient echo was performed on bovine liver/corn oil homogenates with known fat fractions (FFE) to assess the accuracy of fat quantitation (FFMRI). The pulse sequence was manipulated via alterations in TE (echo time), TR (repetition time), and alpha (flip angle). In vivo studies were then performed using breath-holding maneuvers on normal adult volunteers and subjects at risk to develop hepatic steatosis, with cystic fibrosis or morbid obesity. At out-of-phase, TE, TR, and alpha were 2.1 ms, 7.3 ms, and 30-50 degrees and in-phase TE, TR, and alpha were 4.2 ms, 9.3 ms, and 30-50 degrees; FFMRI correlated well with FFE. An elevated fat fraction was observed in a high percentage of subjects with cystic fibrosis and morbid obesity. Fast gradient echo techniques were used successfully in the assessment of hepatic steatosis. The reduced acquisition times permitted in vivo analysis on adults and children using breath hold maneuvers.

Adipose Tissue↗
PubMed1997

Visualization of compression neuropathies through volume deformation.

This paper describes an interdisciplinary effort to simulate and visualize the mechanisms involved in compression neuropathies, specifically tissue deformation occurring during vaginal delivery. These neuropathies often evolve into chronic pelvic pain. We present our methodologies of using high resolution magnetic resonance acquisitions from submillimeter pulse sequences to develop interactive computer simulations based on physically plausible volume models to drive 3D simulations of childbirth. This effort will elucidate tissue movements and mechanics involved in pain disorders and better explain the etiology of these disorders.

Computer Simulation↗
PubMed1997

A volumetric approach to virtual simulation of functional endoscopic sinus surgery.

Advanced display technologies have made the virtual exploration of relatively complex models feasible in many applications. Unfortunately, only a few human interfaces allow natural interaction with the environment. Moreover, in surgical applications, such realistic interaction requires real-time rendering of volumetric data-placing an overwhelming performance burden on the system. We report on a collaboration of an interdisciplinary group developing a virtual reality system that provides intuitive interaction with volume data by employing real-time volume rendering and force feedback (haptic) sensations. We describe our rendering methods and the haptic devices and explain its utility of this system in the real-world application of Endoscopic Sinus Surgery (ESS) simulation.

Computer Simulation↗
PubMed1997

High-resolution MR of the intraparotid facial nerve and parotid duct.

PURPOSE: To describe a high-resolution MR imaging technique that depicts the complex anatomy of the region of the parotid gland, focusing on the intraparotid components of the facial nerve and parotid duct. METHODS: High-resolution T1-weighted images of the parotid gland were acquired with a prototype three-dimensional Fourier transform gradient-echo sequence that permits a very short echo time (4.2 milliseconds) by using a modified phase-encoded time-reduced acquisition scheme. The sequences were obtained at 1.5 T with a head and neck coil. Postprocessed multiplanar, curved and volumetric images were obtained. The most clinically useful images were acquired at parameters of 40/4.2 (TR/TEeff) a flip of 30 degrees, a field of view of 18 to 20 cm, a matrix of 512 x 288 or 512 x 256, an axial plane, 60 images, no gaps, and a section thickness of 1.5 mm. Eighteen healthy subjects were examined. The position of the facial nerve within the parotid gland was determined by identifying the facial nerve in the stylomastoid foramen and then following it on sequential sections through the parotid gland. Curved reformations were used to confirm the visibility of the nerve. A similar technique was used for the parotid duct. RESULTS: The image contrast obtained was similar to that of standard spin-echo T1-weighted images. The parotid gland showed intermediate signal intensity while the fat spaces showed high signal intensity. The vessels had variable signal intensity depending on saturation. The cerebrospinal fluid, nerves, muscles, and ducts had lower signal intensity. In all 18 subjects, the facial nerve from the brain stem to the parotid gland, and the parotid duct from the mouth to the hilus of the gland were seen bilaterally. The proximal intraparotid facial nerve to the level of the retromandibular vein was seen in 72% of the subjects and the main intraparotid ducts were seen in 66% of the subjects. CONCLUSION: High-resolution MR imaging offers simultaneous display of most of the important structures in the region of the parotid gland, including the intraparotid duct and facial nerve.

Adult↗
PubMed1996

Submillimeter magnetic resonance imaging of the temporal bone in Meniere's disease.

The pathoetiology of Meniere's disease remains elusive. Histopathologic and imaging studies have implicated congenital or developmental abnormality of the endolymphatic duct as a likely predisposing factor to the development of endolymphatic hydrops and clinical Meniere's disease. Recently, improved high-resolution magnetic resonance imaging (MRI) protocols have allowed better demonstration of the soft tissues of the endolymphatic duct and sac. This study is a prospective evaluation of the ability of submillimeter MRI to detect the endolymphatic duct in Meniere's disease patients and control subjects. In addition, the development of the temporal bone in the region of the endolymphatic sac and duct is evaluated by measurements of the distance from the posterior semicircular canal to the subarachnoid space and the distance from the vestibule to the subarachnoid space. Visualization of the endolymphatic duct was found to be significantly less frequent in the Meniere's disease patients (29%) than in the control subjects (91%). Temporal bone measurements in the region of the endolymphatic duct showed patients with Meniere's disease to have smaller dimensions than control subjects.

Adult↗