Biomedical subjects

M W Vannier

Publications and source records attributed to M W Vannier.

At least 37 records · Page 2Linked to original sources

PubMed2000

Measurement of the volume of oral tumors by three-dimensional spiral computed tomography.

OBJECTIVE: To determine the precision and accuracy of in vitro measurements of the volume of oral tumors with three-dimensional (3D) spiral computed tomography (CT) and their precision in vivo. METHODS: Two simulated tumors made of modelling compound mixed with contrast medium were positioned medial to the mandibles of five cadaver heads and examined with subsecond spiral CT. Two observers delineated the simulated tumors twice in axial, coronal and sagittal views and then measured the volume from multiplanar reconstructed images. The software tools automatically displayed the simulated tumors in 3D-reconstructed images with the volumetric measurements. The simulated tumors were removed and their volume measured by water displacement. The volume of 15 oral tumors associated with the mandible were measured in vivo with the same imaging methods and the precision analysed. RESULTS: There were no statistically significant differences between or within observers or between imaging and physical measurements in vitro, nor between inter- and intra-observer measurements in vivo (P > 0.05). CONCLUSION: Volumetric measurements from 3D-reconstructed CT are reliable and accurate in vitro and reliable in vivo. The method is potentially useful for the management of oral neoplasms.

Aged↗

PubMed2000

The validation of 3D spiral CT-based measurements of simulated maxillofacial neoplasms.

OBJECTIVE: The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible. STUDY DESIGN: Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers. RESULTS: There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm. CONCLUSIONS: Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.

Aged↗

PubMed2000

Mandibular bone density and fractal dimension in rabbits with induced osteoporosis.

OBJECTIVE: Our goal in this investigation was to examine the mandibular bone density and radiographic textural changes and the relationship between mandibular and spinal bone mineral density in an osteoporotic rabbit model. STUDY DESIGN: Three adult female New Zealand white rabbits in each of 4 groups received daily injections of cortisone acetate at a dosage of 0.0 (control), 3.0, 7.5, or 15.0 mg/kg for 4 weeks. The rabbits were then killed, and the mandible and spine of each animal were removed. Digital radiographs (70 kVp, 10 mA, 8 impulses) of the hemimandibles and spines were made. Lateral and anteroposterior bone densities of the lumbar spine (L2) were calculated, and average mandibular interdental bone density, fractal dimension, and gradient values were calculated. RESULTS: Correlation analysis revealed that cumulative steroid dose was strongly related to mandibular bone density (r = -0.80, P <.01), moderately related to mandibular fractal dimension (r = -0.61, P <. 05), and moderately related to anteroposterior lumbar spine density (r = -0.64, P <.05). Moderate correlations were found between mandibular interdental bone density and spinal density (r = 0.56, P <.05), but mandibular fractal dimension was not related to spinal density. CONCLUSIONS: In osteoporotic female rabbits, mandibular bone mineral density decreases in relation to spinal density and cumulative steroid dose. Mandibular fractal dimension decreases with cumulative steroid dose but is not significantly related to either mandibular density or spinal density.

Absorptiometry, Photon↗

PubMed2000

Digital X-ray stereophotogrammetry for cochlear implantation.

Multielectrode, intracochlear implant systems are effective treatment for profound sensorineural hearing loss. In some cases, these systems do not perform well, which may be partially due to variations in implant location within the cochlea. Determination of each electrode's position in a patient's inner ear provides an in vivo basis for both the cochlear modeling of electrical fields and the future design of electrode arrays that deliver electrical stimulation to surviving auditory neurons, and may improve speech processor programming for better speech recognition. We developed an X-ray stereophotogrammetric approach to localize implanted electrodes in three dimensions. Stereophotogrammetry of implanted electrodes is formulated in weak perspective geometry, with knowledge of a three-dimensional (3-D) reference structure and electrode positions in each of two digital stereo-images. The localization error is theoretically, numerically, and experimentally quantified. Both numerical and experimental results demonstrate the feasibility of the technique.

Biomedical Engineering↗

PubMed2000

Three-dimensional geometric modeling of the cochlea using helico-spiral approximation.

In this paper, the three-dimensional geometry of the human cochlea is modeled by the helico-spiral seashell model. The 3-D helico-spiral model, the generalized representation of the Archimedian spiral model, provides a framework for measuring cochlear features based on consistent estimation of model parameters. Nonlinear least square minimization based algorithms are developed for the identification of rotation, center and intrinsic parameters of the helico-spiral representation. Two algorithms are designed for the rotation axis aligned to the modiolar axis: one is more susceptible in the presence of noise, while the other allows applicability to two-dimensional data sets. The estimated center and intrinsic parameters allow the calculation of length, height and angular positions needed for frequency mapping of multichannel cochlear implant electrodes. Model performance is evaluated with numerically synthesized curves with different levels of added random noise, histologic data and real human cochlear spiral computed tomography data.

Algorithms↗

PubMed2000

Three-dimensional modeling and visualization of the cochlea on the Internet.

Three-dimensional (3-D) modeling and visualization of the cochlea using the World Wide Web (WWW) is an effective way of sharing anatomic information for cochlear implantation over the Internet, particularly for morphometry-based research and resident training in otolaryngology and neuroradiology. In this paper, 3-D modeling, visualization, and animation techniques are integrated in an interactive and platform-independent manner and implemented over the WWW. Cohen's template shape with mean cross-sectional areas of the human cochlea is extended into a 3-D geometrical model. Also, spiral computer tomography data of a patient's cochlea is digitally segmented and geometrically represented. The cochlear electrode array is synthesized according to its specification. Then, cochlear implantation is animated with both idealized and real cochlear models. Insertion length, angular position, and characteristic frequency of individual electrodes are estimated online during the virtual insertion. The optimization of the processing parameters is done to demonstrate the feasibility of this technology for clinical applications.

Cochlea↗

PubMed2000

Localization of cochlear implant electrodes in radiographs.

Multielectrode cochlear implantation is the most effective treatment for profound sensorineural hearing loss. In vivo three-dimensional 3-D localization of cochlear implant electrodes is important for modeling of the electrical field in the cochlea, design of electrode arrays, and may improve speech processor programming for better speech recognition. The prerequisite for 3-D localization of the electrodes is their 2-D localization in x-ray radiographs. In this paper, we develop a practical method to localize the electrodes with high efficiency, accuracy, and reproducibility. In this method, a priori knowledge of the electrodes and their approximate positions are utilized, an intelligent thresholding and segmentation mechanism is embedded, and the electrode center is computed as the weighted geometric center of segmented electrode pixels. Experiments with physical phantoms and human data demonstrate the feasibility and utility of this method. The PC-based program developed for this project is disseminated on the Web.

Cochlear Implants↗

PubMed2000

Quantitative 3D maxillary arch evaluation of two different infant managements for unilateral cleft lip and palate.

OBJECTIVE: A two-institution retrospective study was undertaken to determine whether two different prepalatoplasty protocols quantitatively affect maxillary arch morphology in infants with complete unilateral cleft lip and palate (UCLP). DESIGN: Serial maxillary dental casts, obtained at regular intervals through the first 18 months of life from preintervention until palatoplasty were evaluated quantitatively using computer-assisted three-dimensional digitization and analysis for three populations: institution 1 (protocol 1), institution 2 (protocol 2), and unaffected individuals (neither cleft nor treatment). Sequential UCLP patients from institution 1 were matched for age and initial alveolar cleft width, sex and cleft side having been demonstrated to be nonsignificant, with UCLP patients from institution 2 and to unaffected individuals for age for the analysis. SETTING: Both treatment institutions are well-established regional interdisciplinary cleft centers. Institution 1 is located in a tertiary, academic children's hospital in a metropolis within a primarily agrarian region of the Midwest; institution 2 is a freestanding private clinic located in a small city within a primarily agrarian region of an eastern state; the unaffected population is a historic archive acquired in the 1930s. Data acquisition (model digitization) and computer processing were performed at institution 1. PATIENTS: Eighty-five casts of 28 infants from institution 1, 106 casts of 31 infants from institution 2, and 68 casts of 29 unaffected infants were analyzed. All infants had alginate impressions taken prior to intervention and at several additional 6-month intervals after that, consistent with each institution's treatment protocol. INTERVENTIONS: At institution 1, patients with UCLP underwent lip adhesion and placement of a passive alveolar molding plate at 7 weeks of age, definitive cheiloplasty at 7 months of age, and one-stage palatoplasty at 14 months of age. At institution 2, patients with UCLP underwent definitive cheiloplasty at 3 months of age, had no maxillary orthopedics, and had vomer flap hard palate repair at 12 months of age and soft palate repair at 18 months of age. MAIN OUTCOME MEASURES: The outcome measures included directly digitized (cleft segment and hemialveolar ridge lengths) and derived (alveolar base width, alveolar cleft gap, maxillary frenum-alveolar base perpendicular angle, and rates of change over time of digitized cleft segment and hemialveolar ridge lengths) features. The data were assessed by comparing simple linear regression lines and an unpaired, two-tailed t test. RESULTS: Prior to initiating therapy, there were no statistically significant differences between the two populations with clefts. However, both populations with clefts differed significantly from unaffected individuals (p < .001), with increased maxillary base widths and larger perpendicular/frenum angles. At the time of palatoplasty, the two populations with clefts had statistically significant differences between them in the maxillary base width (p < .01) and the cleft gap distance (p < .05). The base width of institution 1 did not differ significantly from that of widths of unaffected children, and that of institution 2 was significantly less, although the latter had already received first-stage palate repair. Alveolar segment growth rates were similar for the greater and lesser segments, respectively, and the left side hemialveolus of both groups. The growth rate for the noncleft side hemialveolus of institution 2 exceeded (p < .05) that of both institution 1 and unaffected patients. CONCLUSION: Two different regimens for the initial management of UCLP can significantly affect maxillary alveolar arch growth with respect to the treatment used and in comparison with unaffected controls.

Age Factors↗

PubMed2000

Alveolar bone height and postcranial bone mineral density: negative effects of cigarette smoking and parity.

BACKGROUND: Our objective was to test the association between cemento-enamel junction, alveolar-crest distance (CEJ-AC, as measured on digitized vertical bite-wing radiographs) and postcranial bone mineral density (BMD) relative to clinical, dietary, and demographic variables. METHODS: Data were collected in a cross-sectional study of 134 postmenopausal women. CEJ-AC distances were determined from digitized vertical bite-wing radiographs. Lumbar spine and proximal femur BMDs were determined from dual-energy x-ray absorptiometric scans. Correlation analysis and Student t tests were used to identify those variables most associated with CEJ-AC distance. The selected variables were modeled with a backward stepwise regression analysis, with CEJ-AC distance as the dependent variable. RESULTS: Parity (number of pregnancies to term), cigarette smoking, and the interaction of lateral spine BMD with cigarette smoking were independent predictors of CEJ-AC distance (P < or =0.05). Statistical models containing these variables accounted for 19% of the variation in CEJ-AC distances. CONCLUSIONS: CEJ-AC distance in postmenopausal women is the result of a complicated interaction of many effects, including but not limited to, parity, cigarette smoking, and skeletal BMD.

Absorptiometry, Photon↗

PubMed2000

Evaluation of 3D imaging.

Interactive computer-based simulation is gaining acceptance for craniofacial surgical planning. Subjective visualization without objective measurement capability, however, severely limits the value of simulation since spatial accuracy must be maintained. This study investigated the error sources involved in one method of surgical simulation evaluation. Linear and angular measurement errors were found to be within +/- 1 mm and 1 degree. Surface match of scanned objects was slightly less accurate, with errors up to 3 voxels and 4 degrees, and Boolean subtraction methods were 93 to 99% accurate. Once validated, these testing methods were applied to objectively compare craniofacial surgical simulations to post-operative outcomes, and verified that the form of simulation used in this study yields accurate depictions of surgical outcome. However, to fully evaluate surgical simulation, future work is still required to test the new methods in sufficient numbers of patients to achieve statistically significant results. Once completely validated, simulation cannot only be used in pre-operative surgical planning, but also as a post-operative descriptor of surgical and traumatic physical changes. Validated image comparison methods can also show discrepancy of surgical outcome to surgical plan, thus allowing evaluation of surgical technique.

Adult↗

PubMed1999

Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro.

PURPOSE: This study evaluated the measurement accuracy of three-dimensional (3D) volumetric images from spiral computed tomography (CT) in vitro. MATERIALS AND METHODS: The study sample consisted of nine cadaver heads that were submitted to an impact force by a special device to promote blunt traumatic craniofacial fractures. The heads were subsequently scanned by a spiral CT scanner (Toshiba Xpress S/X). The archived CT data were transferred to networked computer workstations (Sun Microsystems with Cemax VIP version 1.4 software) to generate 3D volumetric images. The visualization software was used to make interactive linear measurements on the 3D images. Measurements were made on the images twice by two observers, based on conventional craniofacial anatomic landmarks. The soft tissues were subsequently removed, and the same measurements were repeated on the cadaver heads with an electromagnetic digitizer (3 Space, Polhemus, Colchester, VT). RESULTS: The results showed no statistically significant differences between the 3D-CT and the physical measurements, with P>.05 for all measurements. The mean difference between the image and real measurements was less than 2 mm in all instances. CONCLUSIONS: It is concluded that measurement of the skull and facial bone landmarks by 3D reconstruction is quantitatively accurate for surgical planning and treatment evaluation of craniofacial fractures.

Aged↗

PubMed1999

Virtual arthroscopy of the visible human female temporomandibular joint.

PURPOSE: This study was designed to obtain views of the temporomandibular joint (TMJ) by means of computed arthroscopic simulation (virtual arthroscopy) using three-dimensional (3D) processing. MATERIAL AND METHODS: Volume renderings of the TMJ from very thin cryosection slices of the Visible Human Female were taken off the Internet. Analyze(AVW) software (Biomedical Imaging Resource, Mayo Foundation, Rochester, MN) on a Silicon Graphics 02 workstation (Mountain View, CA) was then used to obtain 3D images and allow the navigation "fly-through" of the simulated joint. RESULTS: Good virtual arthroscopic views of the upper and lower joint spaces of both TMJs were obtained by fly-through simulation from the lateral and endaural sides. It was possible to observe the presence of a partial defect in the articular disc and an osteophyte on the condyle. Virtual arthroscopy provided visualization of regions not accessible to real arthroscopy. CONCLUSION: These results indicate that virtual arthroscopy will be a new technique to investigate the TMJ of the patient with TMJ disorders in the near future.

Arthroscopy↗

PubMed1999

Navigation in diagnosis and therapy.

Image-guided navigation for surgery and other therapeutic interventions has grown in importance in recent years. During image-guided navigation a target is detected, localized and characterized for diagnosis and therapy. Thus, images are used to select, plan, guide and evaluate therapy, thereby reducing invasiveness and improving outcomes. A shift from traditional open surgery to less-invasive image-guided surgery will continue to impact the surgical marketplace. Increases in the speed and capacity of computers and computer networks have enabled image-guided interventions. Key elements in image navigation systems are pre-operative 3D imaging (or real-time image acquisition), a graphical display and interactive input devices, such as surgical instruments with light emitting diodes (LEDs). CT and MRI, 3D imaging devices, are commonplace today and 3D images are useful in complex interventions such as radiation oncology and surgery. For example, integrated surgical imaging workstations can be used for frameless stereotaxy during neurosurgical interventions. In addition, imaging systems are being expanded to include decision aids in diagnosis and treatment. Electronic atlases, such as Voxel Man or others derived from the Visible Human Project, combine a set of image data with non-image knowledge such as anatomic labels. Robot assistants and magnetic guidance technology are being developed for minimally invasive surgery and other therapeutic interventions. Major progress is expected at the interface between the disciplines of radiology and surgery where imaging, intervention and informatics converge.

Diagnosis, Computer-Assisted↗

PubMed1999

Straightening the colon with curved cross sections: an approach to CT colonography.

RATIONALE AND OBJECTIVES: The purpose of this study was to straighten digitally and consistently the colon with curved cross sections and to compare the results with planar cross-section-based processing for computed tomographic (CT) colonography. MATERIALS AND METHODS: In electric field-based straightening, curved cross sections are formed along electric force lines because of electric charges digitally distributed along the colon central path. Four straightening experiments were conducted on CT scans of a colonoscopy phantom. Representative images were studied for polyp detectability and feature distortion. Two further trials involved patient data to demonstrate the clinical feasibility of this method. RESULTS: In colon straightening with planar sections, a polyp was counted multiple times in both phantom and patient studies where the polyps were in central path turns with substantial curvature. Furthermore, opposite the central path turns, the colon walls were undersampled with planar sections. Straightening with curved sections produced consistent mappings. Image distortion was present in straightening with curved sections, but the conspicuity of polyps was maintained. In the soft-straightening process, trilinear interpolation greatly suppressed the surface- or volume-rendering noise associated with nearest neighbor interpolation. CONCLUSION: Straightening with curved sections outperforms straightening with planar sections in terms of polyp detectability. This approach eliminates the navigation difficulties of current CT colonography and may have clinical use.

Colon↗

PubMed1999

2-D and 3-D reconstructions of spiral computed tomography in localization of the inferior alveolar canal for dental implants.

OBJECTIVE: The purpose of this study was to compare and validate the accuracy of measurements on 2-dimensional and 3-dimensional reconstructions from spiral computed tomography in localization of the inferior alveolar canal. STUDY DESIGN: Four edentulous human cadaver heads with intact mandibles were imaged in a spiral computed tomography scanner. The data were transferred to a networked computer workstation to generate 2-dimensional orthoradially reformatted and 3-dimensional volumetric images. Linear measurements of the images were made from the superior border of the inferior alveolar canal to the alveolar crest. The specimens were then dissected at corresponding locations, and physical measurements were made. RESULTS: There were no statistically significant differences between the 2-dimensional computed tomography measurements and the physical measurements or between the 3-dimensional computed tomography measurements and the physical measurements. However, we did find a statistically significant difference between the 2-dimensional and 3-dimensional computed tomography measurements. CONCLUSIONS: 2-dimensional and 3-dimensional computed tomography images allow accurate measurements for localization of the inferior alveolar canal.

Adult↗

PubMed1999

Accurate linear measurements in the anterior maxilla using orthoradially reformatted spiral computed tomography.

OBJECTIVES: To validate measurement accuracy in proximity to the incisive canal from two-dimensional (2D) reformatted spiral computed tomography (CT). MATERIALS AND METHODS: Eight cadaver heads were examined with spiral CT with 1 mm thick axial slices and 1 mm.s-1 table feed. The data was transferred to a networked computer workstation to generate 2D orthoradially reformatted images. The length of the incisive canal and width of the alveolar crest were measured independently by two oral and maxillofacial radiologists. The soft tissues in the region of the incisive foramen were removed and physical measurements made using an electromagnetic digitizer. RESULTS: There was no statistically significant difference between measurements on orthoradial 2DCT images and physical measurements (P > 0.05). CONCLUSIONS: Accurate measurements for dental implant placement in proximity to the incisive canal can be made from reformatted spiral CT images.

Aged↗

PubMed1999

The effect of pitch in multislice spiral/helical CT.

The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of detector arrays, the detector collimation, and the table increment per x-ray source rotation. The pitch in multislice spiral CT is defined as the ratio of the table increment over the detector collimation in this study. In parallel to the current framework for studying longitudinal image resolution, the central fan-beam rays of direct and opposite directions are considered, assuming a narrow cone-beam angle. Generally speaking, sampling in the Radon domain by the direct and opposite central rays is nonuniform along the longitudinal axis. Using a recently developed methodology for quantifying the sensitivity of signal reconstruction from nonuniformly sampled finite points, the effect of pitch on raw data interpolation is analyzed in multislice spiral CT. Unlike single-slice spiral CT, in which image quality decreases monotonically as the pitch increases, the sensitivity of raw data interpolation in multislice spiral CT increases in an alternating way as the pitch increases, suggesting that image quality does not decrease monotonically in this case. The most favorable pitch can be found from the sensitivity-pitch plot for any given set of multislice spiral CT parameters. An example for four-slice spiral CT is provided. The study on the effect of pitch using the sensitivity analysis approach reveals the fundamental characteristics of raw data interpolation in multislice spiral CT, and gives insights into interaction between pitch and image quality. These results may be valuable for design of multislice spiral CT scanners and imaging protocol optimization in clinical applications.

Image Processing, Computer-Assisted↗

PubMed1999

Techniques of CT colonography (virtual colonoscopy).

Colorectal cancer is a leading cause of death in older adults, which usually involves a long-term progressive change of normal mucosa into adenomatous polyps and then cancer. The detection and treatment of this disease in an early stage can lead to a cure in most cases by simply removing the polyp. Computed tomographic colonography (CTC), also referred to as virtual colonoscopy (VC), is a recent advance that gives an intraluminal visualization of the colon that is similar to endoscopy. VC requires fast 3D display (at least 10 frames/sec) of the colon's mucosal surface on a computer screen. Spiral/helical computer tomography is used to gather 3D volume data prior to display. CTC has been demonstrated to be promising for colorectal cancer screening. Studies on unraveling of the colon are underway to map the convoluted tubular structure into a straightened and flattened image volume for global visualization. In this article, we review the current status of CTC with an emphasis on image processing and visualization algorithms. Clinical assessment results of existing techniques are summarized. Practical issues and future perspectives are also discussed.

Colonic Neoplasms↗