Use of Image Processing Techniques for the Analysis of Echocardiographic Images

Echocardiography is a medical imaging modality that uses ultrasound in order to obtain cross sectional views of the heart. The basic problem in the use of echocardiography is the ability to obtain a reliable set of physical parameters related to cardiac status, so that assessment of heart disease can be performed automatically. This work overviews different image processing techniques used in the analysis of two dimensional echocardiographic images. After reviewing how the echocardiographic image formation process works, an outline of the general processing steps from image acquisition to automatic detection of important features is presented. Special emphasis on cardiac image segmentation is presented. In particular, a relaxation algorithm for image segmentation is discussed. Also, echocardiographic image segmentation using temporal analysis and a new algorithm for boundary detection is described. Measurements of left ventricular area, wall thickness, and ejection fraction is also presented. Shape analysis is introduced as a tool for echocardiographic image analysis. A high level description of the left ventricular boundaries using curvature is proposed. Curvature analysis attempts to identify stable landmarks during the beating process, muscles. Tracking these landmarks aids in the detection of abnormal heart contractions. Finally the use of expert systems is proposed in the analysis of echocardiographic images

The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b

We present photometry of 13 transits of XO-3b, a massive transiting planet on an eccentric orbit. Previous data led to two inconsistent estimates of the planetary radius. Our data strongly favor the smaller radius, with increased precision: R_p = 1.217 +/- 0.073 R_Jup. A conflict remains between the mean stellar density determined from the light curve, and the stellar surface gravity determined from the shapes of spectral lines. We argue the light curve should take precedence, and revise the system parameters accordingly. The planetary radius is about 1 sigma larger than the theoretical radius for a hydrogen-helium planet of the given mass and insolation. To help in planning future observations, we provide refined transit and occultation ephemerides.Comment: To appear in ApJ [22 pages

XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary

We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a Rp=0.98+0.03/-0.01 Rjup, Mp=0.57+/-0.06 Mjup transiting extrasolar planet, XO-2b, with an orbital period of 2.615857+/-0.000005 days. XO-2 has high metallicity, [Fe/H]=0.45+/-0.02, high proper motion, mu_tot=157 mas/yr, and has a common proper motion stellar companion with 31" separation. The two stars are nearly identical twins, with very similar spectra and apparent magnitudes. Due to the high metallicity, these early K dwarf stars have a mass and radius close to solar, Ms=0.98+/-0.02 Msolar and Rs=0.97+0.02/-0.01 Rsolar. The high proper motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper<4 kpc) well confined to the Galactic disk (Zmax~100 pc). In addition, the phase space position of XO-2 is near the Hercules dynamical stream, which points to an origin of XO-2 in the metal-rich, inner Thin Disk and subsequent dynamical scattering into the solar neighborhood. We describe an efficient Markov Chain Monte Carlo algorithm for calculating the Bayesian posterior probability of the system parameters from a transit light curve.Comment: 14 pages, 10 Figures, Accepted in ApJ. Negligible changes to XO-2 system properties. Removed Chi^2 light curve analysis section, and simplified MCMC light curve analysis discussio

Gas Giants

The gas giants (Jupiter and Saturn) and icy giants (Uranus and Neptune) are fluid planets with atmospheres primarily made of hydrogen and helium. The part of their atmospheres accessible to remote sensing occupies only a small fraction of their radii (0.05%). Clouds and hazes form around the 1 bar altitude pressure level and extend vertically, according to the thermochemical models, in a layer with a thickness of 200_500 km where temperature increases with depth (usually known as the "weather layer"). Clouds made of NH3, NH4SH, H2O (in Jupiter and Saturn), with the addition of CH4 (in Uranus and Neptune), cover the planet in stratified layers that are mixed with unknown hromophore agents. Dynamical phenomena in the weather layer shape different cloud patterns that define the visible appearance of these planets. In the thermal part of the spectrum clouds act as opacity sources providing brightness contrasts. The ensemble of cloud morphologies in terms of shapes, sizes and albedos allows their use as tracers of the atmospheric motions in the weather layer (Fig. 4.1). This is the main tool employed so far to study the winds on these fourplanets

XO-6b: A transiting hot Jupiter around a fast rotating star

International audienceOrbital properties of hot Jupiters depend on the temperature and rotation rate of their host stars. These observed correlations provide some of the very few constraints on their dynamical evolution. However, almost all the objects available to such studies orbit around relatively slow rotators, with stellar rotation periods usually several times larger than the orbital periods. Because of the apparent dearth of hot Jupiters around fast rotators, the dynamical evolution of these systems is largely unconstrained. Here, we report the discovery of XO-6b, a hot Jupiter orbiting a fast rotating and bright F5 star (Teff = 6605 K, Vsini = 45 km/s, V = 10.25). This transiting hot Jupiter system is one of the very few with a stellar rotation period smaller than the planet orbital period (Prot < 1.41 d, Porb = 3.77 d), and adds to the sample of hot Jupiters around hot stars with a measured obliquity. We present the system parameters extracted from photometric follow-up and Rossiter-McLaughlin measurements. This system provides an additional constraint to dynamical and tidal models in their promising attempt of explaining the dynamical evolution of close-in giant planets, and will allow to extend the emerging picture to planets orbiting fast rotating stars

XO-6b: A transiting hot Jupiter around a fast rotating star

International audienceOrbital properties of hot Jupiters depend on the temperature and rotation rate of their host stars. These observed correlations provide some of the very few constraints on their dynamical evolution. However, almost all the objects available to such studies orbit around relatively slow rotators, with stellar rotation periods usually several times larger than the orbital periods. Because of the apparent dearth of hot Jupiters around fast rotators, the dynamical evolution of these systems is largely unconstrained. Here, we report the discovery of XO-6b, a hot Jupiter orbiting a fast rotating and bright F5 star (Teff = 6605 K, Vsini = 45 km/s, V = 10.25). This transiting hot Jupiter system is one of the very few with a stellar rotation period smaller than the planet orbital period (Prot < 1.41 d, Porb = 3.77 d), and adds to the sample of hot Jupiters around hot stars with a measured obliquity. We present the system parameters extracted from photometric follow-up and Rossiter-McLaughlin measurements. This system provides an additional constraint to dynamical and tidal models in their promising attempt of explaining the dynamical evolution of close-in giant planets, and will allow to extend the emerging picture to planets orbiting fast rotating stars

XO-7 b: A Transiting Hot Jupiter with a Massive Companion on a Wide Orbit

International audienceTransiting planets orbiting bright stars are the most favorable targets for follow-up and characterization. We report the discovery of the transiting hot Jupiter XO-7 b and of a second, massive companion on a wide orbit around a circumpolar, bright, and metal-rich G0 dwarf (V = 10.52, {T}eff}=6250+/- 100 {{K}}, [{Fe}/{{H}}]=0.432+/- 0.057 {dex}). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of 2.8641424+/- 0.0000043 days, a mass of 0.709+/- 0.034 {M}{{J}}, a radius of 1.373+/- 0.026 {R}{{J}}, a density of 0.340+/- 0.027 {{g}} {cm}}-3, and an equilibrium temperature of 1743+/- 23 {{K}}. Its large atmospheric scale height and the brightness of the host star make it well suited to atmospheric characterization. The wide-orbit companion is detected as a linear trend in radial velocities with an amplitude of ∼ 100 {{m}} {{{s}}}-1 over two years, yielding a minimum mass of 4 {M}{{J}}; it could be a planet, a brown dwarf, or a low-mass star. The hot Jupiter orbital parameters and the presence of the wide-orbit companion point toward a high-eccentricity migration for the hot Jupiter. Overall, this system will be valuable to understand the atmospheric properties and migration mechanisms of hot Jupiters and will help constrain the formation and evolution models of gas giant exoplanets