Wendelin S. Hayes

Surface reconstruction and visualization of the surgical prostate model

An advanced image analysis and graphics software is developed to reconstruct and visualize previously images prostate specimens to define tumor volume and distribution and pathways of needle biopsies, thus allowing improved understanding of prostate cancer behavior and current diagnosis-staging methodology. In order to reconstruct an accurate surface model of the surgical prostate, contour interpolation and surface reconstruction are performed on extracted contours of the object of interest. Contour interpolation increases the sample rate in the stacking direction in order to reconstruct sufficiently accurate surfaces of the prostate and its internal anatomical structures. An elastic contour model is developed through computing a force field between adjacent slices to deform the start contour gradually to conform to the target contour. A new finite-element deformable surface-spine model is then developed to reconstruct the computerized prostate model from the interpolated contours. A deformable spine of the prostate model is determined from its contours, and all the surface patches are contracted to the spine through expansion/compression forces radiating form the spine while the spine itself is also confined to the surface. The surface refinement is governed by a second-order partial differential equation from Lagrangian mechanics, and the refining process is accomplished when the energy of this dynamic deformable surface-spine model reaches its minimum. Interactive visualization is achieved by using the state-of- the-art 3D graphics toolkit, OpenInventor, with graphical user interface to visualize the reconstructed 3D prostate model including all internal anatomical structures and their relationships. Finally, an image-guided prostate needle biopsy simulation is implemented to validate current biopsy strategies on tumor detection and tumor volume estimation to improve prostate needle biopsy techniques.

Hepatic cavitation : a marker of transient hepatocellular injury during biliary lithotripsy

Sonographically visible microbubbles attributable to cavitation effects have been observed in bile (within the gallbladder), in hepatic vessels, and within the liver of patients undergoing biliary lithotripsy. Cavitation effects are believed to contribute to stone fragmentation and possibly tissue injury during lithotripsy. To study the latter, the relationship between intraparenchymal hepatic cavitation and serum transaminase activity and clinical follow-up was analyzed in 81 patients undergoing 164 lithotripsy treatments. Seventy-one treatments (43%) resulted in sonographically evident microbubbles in the liver parenchyma during lithotripsy. A temporary, yet statistically significant (P<0.01) rise in SGOT and SGPT was observed within 2 hr of completion of lithotripsy compared to those patients without hepatic microbubbles. All but one patient had a return to pretreatment baseline levels of SGOT and SGPT by two weeks after lithotripsy. In this patient, persistent elevation of transaminases was attributed to the delayed passage of fragments and not to any sequelae from hepatic cavitation effects. Ultrasound immediately after, two weeks after, and 3–12 months after lithotripsy showed no hepatic structural abnormalities. Ursodiol administration at the time of treatment did not predispose to hepatic cavitation or elevation of transaminase. Detection of hepatic microbubbles during lithotripsy is a marker of hepatocellular injury. Their correlation with transaminase elevation refutes the contention that transaminasemia results solely from fragment passage after lithotripsy. Although not associated with recognizable structural damage or long-term sequelae, cavitation effects and transaminasemia reiterate that shockwaves are not entirely benign as they traverse parenchymal organs.

Digital mammography: tradeoffs between 50- and 100-micron pixel size

Improvements in mammography equipment related to a decrease in pixel size of digital mammography detectors raise questions of the possible effects of these new detectors. Mathematical modeling suggested that the benefits of moving from 100 to 50 micron detectors were slight and might not justify the cost of these new units. Experiments comparing screen film mammography, a storage phosphor 100 micron digital detector, a 50 micron digital breast spot device, 100 micron film digitization and 50 micron film digitization suggests that object conspicuity should be better for digital compared to conventional systems, but that there seemed to be minimal advantage to going from 100 to 50 microns. The 50 micron pixel system appears to provide a slight advantage in object contrast and perhaps in shape definition, but did not allow smaller objects to be detected.

A deformable surface-spine model for 3-D surface registration

A finite-element deformable surface-spine model is developed in this paper to register two surfaces by recovering the nonlinear deformation with respect to each other. The deformable surface-spine model is a dynamic model governed by Lagrangian motion equations. A 9 degree-of-freedom (dof) finite-element surface element and a 4-dof spine element are developed to iteratively solve Lagrangian equations for computing the deformation between two surfaces. The method has been applied to registration of computerized surgical prostate models. Experimental results have demonstrated that the new registration method can successfully match complex-structured surfaces by recovering the nonlinear deformation.

Effects of motion-JPEG compression on the diagnostic quality of pediatric echocardiograms

Congenital heart disease is infrequent and often is apparent in the immediate newborn period. Accurate diagnosis delivered in real-time or near-real-time is important to provide appropriate care to avoid patient morbidity and mortality. Color-flow Doppler echocardiograms are an essential part of the diagnostic assessment of the newborn, however, few hospitals have the staff to interpret these studies appropriately. Transmission of these studies to a regional center with subspecialists will allow interpretation of the studies by physicians with expertise in this subspecialty. Transmission of these studies to a regional center with subspecialists will allow interpretation of the studies by physicians to appropriately and rapidly triage neonates with high-risk congenital heart disease. To make a teleradiology service affordable in the near future, the 73 million bit per second transmission speed must be reduced to affordable bandwidths using compression. The purpose of this study is to evaluate the impact of motion JPEG on the diagnostic quality of pediatric echocardiograms.

Technology assessment for an integrated PC-based platform for three telemedicine applications

This paper investigates the design and technical efficacy of an integrated PC based platform for three different medical applications. The technical efficacy of such a telemedicine platform has not been evaluated in the literature and optimal technical requirements have not been developed. The first application, with the Department of Surgery, Division of Urology, tests the utility of a telemedicine platform including radiology images for a surgical stone disease consultation service from an off site location in West Virginia. The second application, with the Department of Internal Medicine, Division of Clinical Pharmacology, investigates the usefulness of telemedicine when used for a clinical pharmacology consultation service from an off-site location. The third application, with the Department of Pediatrics, will test telemedicine for trauma care triage service first within an off-site location in Virginia and then from there to Georgetown University Medical Center.

Digital mammography: the effects of decreased exposure

It has been stated that digital mammography will reduce the exposure required for mammography. This poster explores the effects of decreased exposure on the information present in digital mammography. In general, the digital system performed better than screen film mammography with lower exposures. With the usual exposures used for screen film mammography, performance was equal. With high exposures sufficient to result in a dark film (OD 1.5), the digital system performed better than screen film with very small test objects. Proposals have been made to decrease the tube loading required for slot scanning devices by increasing KVP. This would result in their being less object contrast due to the decreases in the absorption coefficient of calcium compared to water at higher KVP. This poster looks at the potential for correcting the loss in object contrast that would result from the use of high contrast look up tables. It was found that in the tested system, one could restore the information in one of the two test objects used (but not the other), but that the image processing methods used would result in an image that radiologists would probably find inadequate for interpretation.

A computerized simulation for prostate needle biopsy

The authors developed an image-guided biopsy simulation system that uses advanced image analysis and computer graphics techniques. First, they reconstruct three-dimensional (3-D) computerized prostate models with accurate 3-D representation of all internal anatomical structures of the prostate. The prostate needle biopsy simulation system is then implemented by an interactive 3-D visualization system with various realistic imaging probes and needles for examination and path planning. They show two specific ways such a simulation system can be used: (a) as a virtual simulation system where a surgeon can sit in front of the computer to plan better needle paths and can practice the actual biopsy procedure before he or she actually performs on a patient and (b) for validating the effectiveness of various biopsy techniques in prostate cancer detection and tumor volume estimation.

Design-based approach to ethics in computer-aided diagnosis

A design-based approach to ethical analysis examines how computer scientists, physicians and patients make and justify choices in designing, using and reacting to computer-aided diagnosis (CADx) systems. The basic hypothesis of this research is that values are embedded in CADx systems during all phases of their development, not just retrospectively imposed on them. This paper concentrates on the work of computer scientists and physicians as they attempt to resolve central technical questions in designing clinically functional CADx systems for lung cancer and breast cancer diagnosis. The work of Lo, Chan, Freedman, Lin, Wu and their colleagues provides the initial data on which this study is based. As these researchers seek to increase the rate of true positive classifications of detected abnormalities in chest radiographs and mammograms, they explore dimensions of the fundamental ethical principal of beneficence. The training of CADx systems demonstrates the key ethical dilemmas inherent in their current design.

Clinical Pharmacology Consultation from an Off‐Site Location Using Telemedicine: Report of a Pilot Study

Clinical Pharmacology & Therapeutics (1996) 59, 211–211; doi: 10.1038/sj.clpt.1996.345