Showing papers by "Michael W. Vannier published in 2002"

Validation of medical image processing in image-guided therapy

Abstract: Do we need an abstract ?.

White paper: validation of medical image processing in image-guided therapy

Abstract: Clinical use of image-guided therapy (IGT) systems has grown, creating the need for a common and rigorous validation methodology, as reported in recent workshops and conferences. [1,2,3,4] One key characteristic of IGT systems is that they employ medical image processing methods (e.g. segmentation, registration, visualization, calibration). As a result of this intrinsic structure, validation of IGT systems should include both individual validation of these components, validation of the overall system and a study of how uncertainties propagate through the entire image guided therapy process. Significant progress has been made on IGT system validation recently. Today almost all peer-reviewed publications reporting on the development of new medical image processing methods include a validation section, but this was not always true in the past.

3D volume rendering using multislice CT for dental implants.

Abstract: Objectives: To determine the precision and accuracy of three-dimensional (3D) volume rendering spiral multislice computed tomography (CT)-based linear measurements of the mental foramen for dental implants, in vitro, and their precision, in vivo. Methods: Five cadaver heads were imaged by multislice spiral CT (Toshiba Aquilion) with 0.5 mm thick axial slices (0.5 mm/0.5 s of table feed) at 0.5 mm interval reconstructions. The image data sets were transferred to a networked computer workstation. Using computer graphics the data were analysed with a 3D volume rendering technique using Vitrea 1 software. Two oral and maxillofacial radiologists, independently, made electronic linear measurements from the superior border of the mental foramen to the crest of the alveolar process. The soft tissues were removed and physical measurements made using a 3 Space TM (Polhemus, Colchester, VT, USA) electromagnetic digitizer with a personal computer running Windows 1 98. The same linear measurements of 15 patients using the same imaging methodology were performed and the precision was analysed. Results: The findings showed no statistically significant inter- or intra-observer diAerences in vitro and in vivo, or between imaging and physical measurements in vitro (P40.05). Conclusions: 3D multislice spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using volume rendering is suitable for implant planning. Dentomaxillofacial Radiology (2002) 31, 218‐223. doi:10.1038/sj.dmfr.4600701

The Pattern of Alveolar Crest Height Change in Healthy Postmenopausal Women After 3 Years of Hormone/Estrogen Replacement Therapy

Abstract: Background: The loss of ovarian function at menopause is associated with loss of postcranial and oral bone. Hormone/estrogen replacement therapy (HRT/ERT) has a positive effect on both postcranial and oral bone. The objective of the study was to determine if the positive effect of HRT/ERT on alveolar crest height (ACH) is generalized or site specific. Methods: The sample consisted of 49 women who completed a 3-year, HRT/ERT prospective study. Cemento-enamel junction distances (ACH) were measured on digitized images of bitewing radiographs. Lumbar spine and proximal femur bone mineral densities (BMDs) were determined with dual-energy x-ray absorptiometric scans. Measurements were made at baseline and at the end of year 3. For the 3-year study period, mean change in ACH was determined for each patient. In addition, the sites with the greatest, second and third greatest ACH changes were determined for each patient. Correlations between changes in ACH (as determined by the various methods) and postcranial BMD...

Blind deblurring of spiral CT images - Comparative studies on edge-to-noise ratios

Abstract: A recently developed blind deblurring algorithm based on the edge-to-noise ratio has been applied to improve the quality of spiral CTimages. Since the discrepancy measure used to quantify the edge and noise effects is not symmetric, there are several ways to formulate the edge-to-noise ratio. This article is to investigate the performance of those ratios with phantom and patient data. In the phantom study, it is shown that all the ratios share similar properties, validating the blind deblurring algorithm. The image fidelity improvement varies from 29% to 33% for different ratios, according to the root mean square error (RMSE) criterion; the optimal iteration number determined for each ratio varies from 25 to 35. Those ratios that are associated with most satisfactory performance are singled out for the image fidelity improvement of about 33% in the numerical simulation. After automatic blind deblurring with the selected ratios, the spatial resolution of CT is substantially refined in all the cases tested.

Medical image archives — present and future

Abstract: Repositories, data warehouses, public archives, and multimedia databases, especially those containing images, are important for clinical practice, education, and research in medicine. Imaging modalities, such as digital radiography, computed tomography, ultrasonography, nuclear medicine, digital angiography and magnetic resonance imaging produce large amounts of data that are managed, archived, and reported using picture archiving and communications systems (PACS) in an integrated healthcare enterprise (IHE) infrastructure. The technology and applications of PACS and IHE are well understood and widely available worldwide.

CARS 2002 Computer Assisted Radiology and Surgery

Abstract: Nerve rehabilitation in cases of facial paralysis is an important issue in plastic and reconstructive surgery. However, surgeons need to know which muscles of the mimic musculature are most suited for reinnervation to achieve an optimal rehabilitation of a patient's physiognomy. We present results of our work on the simulation of anatomy based, muscle driven facial mimics on basis of an elaborate volumetric facial tissue model and a physics based tissue modelling approach, that could meet the demands for such a surgery planning task.

Imaging Apoptosis in Rheumatoid Arthritis

Abstract: Quantitative imaging of apoptosis using 99mTc-labeled annexin V in rheumatoid arthritis challenges our conventional thinking on how disease progression or remission should be monitored and reported. Until now, we imaged collagen vascular diseases using radiographs to study bone morphology and using

Multirow detector CT technology: Present and future

Abstract: Multirow CT detectors coupled with 2, 4, 8 and 16 or more simultaneous data acquisition channels are now used in clinical imaging. Furthermore, multirow CT detectors are used with conventional or flat-panel image intensifiers mounted on c-arms that allow 3D CT scanning in rotational angiography or orthopedic interventions. These multirow, multichannel CT systems provide increased speed that translates into the ability to scan larger segments of anatomy more quickly. The principal drawback of multislice/multidector/multichannel CT scanners are increased computational burden, faster data rates, more voluminous data sets, and most importantly, the requirement to use cone beam rather than slice-by-slice reconstruction algorithms. The future of multichannel CT in clinical applications demands improved radiation dose efficiency, isotropic imaging, tailored cone beam reconstruction algorithms, and post-processing visualization of volume image data.

Image-guided magnetic surgery

Abstract: Catheters, magnetic seeds, untethered endoscopes, and slurries of ferromagnetic particles may be moved, guided, and/or steered in living tissue by the shaped field of a repositionable external magnet for minimally invasive surgical procedures. A magnetic surgery system (MSS) consists of a control processor, a pointing device, a magnet assembly generating a magnetic field, a display, and a 3D medical imaging system. Biplane fluoroscopic images of the patient in which the magnetic delivery vehicle is implanted are shown on a screen, each image representing a projection in space of the operating region. The pointing device is operated to move a cursor from a projection of a present location of the magnetic delivery vehicle to a projection of a desired future location. When the locations are completely specified, the currents applied to multiple magnets in the MSS produce a magnetic field and move or orient the magnetic delivery vehicle. Multiple superconducting magnetic coils are activated simultaneously to move a magnetic object to precisely specified locations within the body under command of a physician-operator observing the motion with live fluoroscopic imaging fused with a more detailed preoperative image. A workstation contains the preoperative images and the fluoroscopic images, as well as the means to effect changes in the coil currents and position the magnetic object motion as desired. The control method operates the coils in pairs on opposite sides of the body to minimize the necessary current changes, thus avoiding the quenching of the superconducting coils. Combinations of these pairs can execute motion of the magnetic object in any direction in an impulsive manner and with high precision. The display provides real-time imaging of the implanted magnetic object in comparison to the desired path as the object is moved. This system has applications in neurosurgery, cardiac electrophysiology mapping and ablation, brachytherapy, and endoscopy that are currently under development. The technical features of an MSS and examples of its applications will be presented.

An improved fMRI analysis for detecting motor cortex activity near brain tumors

Abstract: Functional magnetic resonance images (fMRI) typically represent a correlation of the hemodynamic response in a region of the brain that is associated with a stimulus or task; and is used to elucidate areas of neural activity. An inadequate model of the hemodynamic response function (HRF) may prevent the detection of regional brain activity, particularly in brain regions distorted by tumor or other pathology. Thus, idealized HRFs may not provide good models of hemodynamic response in brain regions near a tumor, and subject-specific and/or region-specific HRFs are needed.