David C. Wang

Gradient inverse weighted smoothing scheme and the evaluation of its performance

Abstract This paper presents an image smoothing scheme for improvement of the quality of noisy pictures. It is an iterative scheme employing a 3 × 3 mask in which the weighting coefficients are the normalized gradient inverse between the center pixel and its neighbors. The smoothing operation tends to clean out noise inside a region without blurring its boundary. In order to evaluate the performance of the proposed scheme, we adopt an f statistic which is based on the analysis of variance. Simulation studies show that this method reduces the gay level scattering within a region, and keeps its mean relatively unchanged. Applications to several real world images are illustrated.

Fully Automated Common Carotid Artery and Internal Jugular Vein Identification and Tracking Using B-Mode Ultrasound

We describe a fully automated ultrasound analysis system that tracks and identifies the common carotid artery (CCA) and the internal jugular vein (IJV). Our goal is to prevent inadvertent damage to the CCA when targeting the IJV for catheterization. The automated system starts by identifying and fitting ellipses to all the regions that look like major arteries or veins throughout each B-mode ultrasound image frame. The spokes ellipse algorithm described in this paper tracks these putative vessels and calculates their characteristics, which are then weighted and summed to identify the vessels. The optimum subset of characteristics and their weights were determined from a training set of 38 subjects, whose necks were scanned with a portable 10 MHz ultrasound system at 10 frames per second. Stepwise linear discriminant analysis (LDA) narrowed the characteristics to the five that best distinguish between the CCA and IJV. A paired version of Fishers LDA was used to calculate the weights for each of the five parameters. Leave-one-out validation studies showed that the system could track and identify the CCA and IJV with 100% accuracy in this dataset.

Transgenic Knockdown of Cardiac Sodium/Glucose Cotransporter 1 (SGLT1) Attenuates PRKAG2 Cardiomyopathy, Whereas Transgenic Overexpression of Cardiac SGLT1 Causes Pathologic Hypertrophy and Dysfunction in Mice

Background The expression of a novel cardiac glucose transporter, SGLT1, is increased in glycogen storage cardiomyopathy secondary to mutations in PRKAG2. We sought to determine the role of SGLT1 in the pathogenesis of PRKAG2 cardiomyopathy and its role in cardiac structure and function. Methods and Results Transgenic mice with cardiomyocyte‐specific overexpression of human T400N mutant PRKAG2 cDNA (TGT400N) and transgenic mice with cardiomyocyte‐specific RNA interference knockdown of SGLT1 (TGSGLT1‐DOWN) were crossed to produce double‐transgenic mice (TGT400N/TGSGLT1‐DOWN). Tet‐off transgenic mice conditionally overexpressing cardiac SGLT1 in the absence of doxycycline were also constructed (TGSGLT‐ON). Relative to TGT400N mice, TGT400N/TGSGLT1‐DOWN mice exhibited decreases in cardiac SGLT1 expression (63% decrease, P<0.05), heart/body weight ratio, markers of cardiac hypertrophy, and cardiac glycogen content. TGT400N/TGSGLT1‐DOWN mice had less left ventricular dilation at age 12 weeks compared to TGT400N mice. Relative to wildtype (WT) mice, TGSGLT1‐ON mice exhibited increases in heart/body weight ratio, glycogen content, and markers of cardiac hypertrophy at ages 10 and 20 weeks. TGSGLT1‐ON mice had increased myocyte size and interstitial fibrosis, and progressive left ventricular dysfunction. When SGLT1 was suppressed after 10 weeks of overexpression (TGSGLT1‐ON/OFF), there was a reduction in cardiac hypertrophy and improvement in left ventricular failure. Conclusions Cardiac knockdown of SGLT1 in a murine model of PRKAG2 cardiomyopathy attenuates the disease phenotype, implicating SGLT1 in the pathogenesis. Overexpression of SGLT1 causes pathologic cardiac hypertrophy and left ventricular failure that is reversible. This is the first report of cardiomyocyte‐specific transgenic knockdown of a target gene.

Feedback linearizability of multi-link manipulations with one flexible link

The feedback linearization properties of a class of multilink manipulators with one flexible link are studied. This class includes the 5-bar-linkage and the elbow manipulator. It is shown that the input-output equations are feedback linearizable when the output variable is chosen appropriately. It is shown that the input-state equations are not feedback linearizable. Alternate methods of controlling these manipulators must be studied.<<ETX>>

Peripherally inserted central catheter placement with the sonic flashlight: initial clinical trial by nurses.

Objective. We describe a case series constituting the first clinical trial by intravenous (IV) team nurses using the sonic flashlight (SF) for ultrasound guidance of peripherally inserted central catheter (PICC) placement. Methods. Two IV team nurses with more than 10 years of experience with placing PICCs and 3 to 6 years of experience with ultrasound attempted to place PICCs under ultrasound guidance in patients requiring long‐term IV access. One of two methods of ultrasound guidance was used: conventional ultrasound (CUS; 60 patients) or a new device called the SF (44 patients). The number of needle punctures required to gain IV access was recorded for each patient. Results. In both methods, 87% of the cases resulted in successful venous access on the first attempt. The average number of needle sticks per patient was 1.18 for SF‐guided procedures compared with 1.20 for CUS‐guided procedures. No significant difference was found in the distribution of the number of attempts between the two methods. Anecdotal comments by the nurses indicated the comparative ease of use of the SF display, although the relatively small scale of the SF image compared with the CUS image was also noted. Conclusions. We have shown that the SF is a safe and effective device for guidance of PICC placement in the hands of experienced IV team nurses. The advantage of placing the ultrasound image at its actual location must be balanced against the relatively small scale of the SF image.

Carotid artery and jugular vein tracking and differentiation using spatiotemporal analysis

We have derived and evaluated parameters from ultrasound images of the neck to permit a computer to automatically characterize and differentiate between the carotid artery and jugular vein at image acquisition time during vascular interventions, given manually placed seed points. Our goal is to prevent inadvertent damage to the carotid artery when targeting the jugular vein for catheterization. We used a portable 10 MHz ultrasound system to acquire cross sectional B-mode ultrasound images of these great vessels at 10 fps. An expert user identified the vessels in the first frame by touching the vessels on the screen with his fingertip, and the computer automatically tracked the vessels and calculated a best-fit ellipse for each vessel in each subsequent frame. Vessel location and radii were further analyzed to produce parameters that proved useful for differentiating between the carotid artery and jugular vein. These parameters include relative location of the vessels, distension of the vessel walls, and consistent phase difference between the arterial and venous pulsations as determined by temporal Fourier analysis.

Peripherally Inserted Central Catheter Placement Using the Sonic Flashlight

The Sonic Flashlight is an ultrasound (US) device that projects real-time US images into patients with use of a semireflective/transparent mirror. The present study evaluated the feasibility of use of the Sonic Flashlight for clinical peripherally inserted central catheter placements, originally with the mirror located inside a sterile cover (n = 15), then with the mirror outside (n = 11). Successful access was obtained in all cases. Results show that this new design improved visibility, as judged subjectively firsthand and in photographs. The study demonstrated the feasibility of the Sonic Flashlight and the new design to help assure sterility without degrading visibility, allowing further clinical trials involving physicians and nurses.

Optical merger of direct vision with virtual images for scaled teleoperation

Scaled teleoperation is increasingly prevalent in medicine, as well as in other applications of robotics. Visual feedback in such systems is essential and should make maximal use of natural hand-eye coordination. This paper describes a new method of visual feedback for scaled teleoperation in which the operator manipulates the handle of a remote tool in the presence of a registered virtual image of the target in real time. The method adapts a concept already used successfully in a new medical device called the sonic flashlight, which permits direct in situ visualization of ultrasound during invasive procedures. The sonic flashlight uses a flat-panel monitor and a half-silvered mirror to merge the visual outer surface of a patient with a simultaneous ultrasound scan of the patients interior. Adapting the concept to scaled teleoperation involves removing the imaging device and the target to a remote location and adding a master-slave control device. This permits the operator to see his hands, along with what appears to be the tool, and the target, merged in a workspace that preserves natural hand-eye coordination. Three functioning prototypes are described, one based on ultrasound and two on light microscopy. The limitations and potential of the new approach are discussed.

TSAN: A package for time series analysis

Many biomedical data are in the form of time series. Analyses of these data include: (1) search for any biorhythm; (2) test of homogeneity of several time series; (3) assessment of stationarity; (4) test of normality of the time series histogram; (5) evaluation of dependence between data points. In this paper we present a subroutine package called TSAN. It is developed to accomplish these tasks. Computational methods, as well as flowcharts, for these subroutines are described. Two sample runs are demonstrated.

A novel machine interface for scaled telesurgery

We have developed a system architecture that will allow a surgeon to employ direct hand-eye coordination to conduct medical procedures in a remote microscopic environment. In this system, a scaled real-time video image of the workspace of a small robotic arm, taken from a surgical microscope camera, is visually superimposed on the natural workspace of a surgeon via a half-silvered mirror. The robot arm holds a small tool, such as a microsurgical needle holder or microsurgical forceps, and the surgeon grasps a second tool connected to a position encoder, in this case a second robot arm. The views of the local and remote environments are superimposed such that the tools in the local and remote environments are visually merged. The position encoder and small robot arm are linked such that movement of the tool by the operator produces scaled-down movement by the small robot tool. To the surgeon, it seems that his hands and the tool he or she is holding is moving and interacting with the remote environment, which is really microscopic and at a distance. Our current work focuses on using a position-controlled master-slave robot linkage of two 3 degree of freedom haptic devices, and we are pursuing the use of a 6-to-7 degree of freedom master-slave linkage to produce more realistic interaction.