Non-Rayleigh ultrasonic characterization of tissue scattering microstructure via a multibandwidth probing technique

Recent studies on the statistics of the envelope of the ultrasound echo signal from a random scattering medium suggest that the statistical moments of the signal may carry quantitative information about the scattering microstructure. A mathematical model for the backscattered signal is developed borrowing from linear systems theory and assuming narrow bandwidth conditions. Several microstructures, including sponges of different pore size as well as pig liver, human breast tissue, and human skeletal muscle, are probed experimentally with multiple bandwidth pulses with center frequency matched to the transducer center frequency. Variations of the second normalized intensity moment with the cell volume are considered and exploited experimentally for structure characterization. The concept of effective cell volume and its relationship to the system point spread function is established. The influence of the imaging system point spread function on the statistical moments is considered. To estimate an effective scatterer number and scatterer number density for every sample, higher order and fractional moments are calculated and fitted to theoretical Non- Rayleigh distributions: K, Generalized K, and Rice. Information on interscatterer spacing is obtained from the autocorrelation of the second normalized intensity moment. To analyze the sample structure, phantoms were created from histology sections and the same experimental and analysis procedures were followed. The concept of effective cell surface and its relationship to the system point spread function is established. The experimental results indicate that non-Rayleigh statistical analysis of speckle prove to be useful in characterizing both normal, and abnormal tissue

A New Application for Displaying and Fusing Multimodal Data Sets

A recently developed, freely available, application specifically designed for the visualization of multimodal data sets is presented. The application allows multiple 3D data sets such as CT (x-ray computer tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), and SPECT (single photon emission tomography) of the same subject to be viewed simultaneously. This is done by maintaining synchronization of the spatial location viewed within all modalities, and by providing fused views of the data where multiple data sets are displayed as a single volume. Different options for the fused views are provided by plug-ins. Plug-ins typically used include color-overlays and interlacing, but more complex plug-ins such as those based on different color spaces, and component analysis techniques are also supported. Corrections for resolution differences and user preference of contrast and brightness are made. Pre-defined and custom color tables can be used to enhance the viewing experience. In addition to these essential capabilities, multiple options are provided for mapping 16-bit data sets onto an 8-bit display, including windowing, automatically and dynamically defined tone transfer functions, and histogram based techniques. The 3D data sets can be viewed not only as a stack of images, but also as the preferred three orthogonal cross sections through the volume. More advanced volumetric displays of both individual data sets and fused views are also provided. This includes the common MIP (maximum intensity projection) both with and without depth correction for both individual data sets and multimodal data sets created using a fusion plug-in

Shortness of breath after AV ablation: case of left phrenic nerve palsy

Phrenic nerve palsy has been recognized as a complication of catheter ablation with a prevalence of 0.11–0.48% after atrial fibrillation ablation, independent of the type of ablation catheter or energy source, likely due to the anatomical relationship of the nerves. This report describes a case of new onset of shortness of breath (SOB) due to left diaphragm paralysis following transcatheter radiofrequency ablation in a patient with underlying chronic obstructive pulmonary disease

Design of a Multiple Component Geometric Breast Phantom

The quality and realism of simulated images is currently limited by the quality of the digital phantoms used for the simulations. The transition from simple raster based phantoms to more detailed geometric (mesh) based phantoms has the potential to increase the usefulness of the simulated data. A preliminary breast phantom which contains 12 distinct tissue classes along with the tissue properties necessary for the simulation of dynamic positron emission tomography scans was created (activity and attenuation). The phantom contains multiple components which can be separately manipulated, utilizing geometric transformations, to represent populations or a single individual being imaged in multiple positions. A new relational descriptive language is presented which conveys the relationships between individual mesh components. This language, which defines how the individual mesh components are composed into the phantom, aids in phantom development by enabling the addition and removal of components without modification of the other components, and simplifying the definition of complex interfaces. Results obtained when testing the phantom using the SimSET PET/SPECT simulator are very encouraging

Simulation of High-Resolution Magnetic Resonance Images on the IBM Blue Gene/L Supercomputer Using SIMRI

Medical imaging system simulators are tools that provide a means to evaluate system architecture and create artificial image sets that are appropriate for specific applications. We have modified SIMRI, a Bloch equation-based magnetic resonance image simulator, in order to successfully generate high-resolution 3D MR images of the Montreal brain phantom using Blue Gene/L systems. Results show that redistribution of the workload allows an anatomically accurate 2563 voxel spin-echo simulation in less than 5 hours when executed on an 8192-node partition of a Blue Gene/L system