Donald Joseph Buckley

Combination of digital mammography with semi-automated 3D breast ultrasound

This paper describes work aimed at combining 3D ultrasound with full-field digital mammography via a semi-automatic prototype ultrasound scanning mechanism attached to the digital mammography system gantry. Initial efforts to obtain high x-ray and ultrasound image quality through a compression paddle are proving successful. Registration between the x-ray mammogram and ultrasound image volumes is quite promising when the breast is stably compressed. This prototype system takes advantage of many synergies between the co-registered digital mammography and pulse-echo ultrasound image data used for breast cancer detection and diagnosis. In addition, innovative combinations of advanced US and X-ray applications are being implemented and tested along with the basic modes. The basic and advanced applications are those that should provide relatively independent information about the breast tissues. Advanced applications include x-ray tomosynthesis, for 3D delineation of mammographic structures, and non-linear elasticity and 3D color flow imaging by ultrasound, for mechanical and physiological information unavailable from conventional, non-contrast x-ray and ultrasound imaging.

Influence of substrate elasticity on droplet impact dynamics.

Droplet impact dynamics is vital to the understanding of several phase-change and heat-transfer phenomena. This work examines the role of substrate elasticity on the spreading and retraction behavior of water droplets impacting flat and textured superhydrophobic substrates. Experiments reveal that droplet retraction on flat surfaces decreases with decreasing substrate elasticity. This trend is confirmed through a careful measurement of droplet impact dynamics on multiple PDMS surfaces with varying elastic moduli and comparison with impact dynamics on hard silicon surfaces. These findings reveal that surfaces tend to become more wettable upon droplet impact as the elastic modulus is decreased. First-order analyses are developed to explain this reduced retraction in terms of increased viscoelastic dissipation on soft substrates. Interestingly, superhydrophobic surfaces display substrate-elasticity-invariant impact dynamics. These findings are critical when designing polymeric surfaces for fluid-surface interaction applications.

Fusion of digital mammography with breast ultrasound: a phantom study

The objective of this work was to acquire co-registered digital tomosynthesis mammograms and 3-D breast ultrasound images of breast phantoms. A prototype mammography compression paddle was built for this application and installed on an x-ray tomosynthesis prototype system (GE). Following x-ray exposure, an automated two-dimensional ultrasound probe mover assembly is precisely positioned above the compression plate, and an attached high-frequency ultrasound transducer is scanned over the acoustically coupled phantom or localized region of interest within the phantom through computerized control. The co-ordinate system of one of the two data sets is then transformed into that of the other, and matching regions of interest on either image set can be simultaneously viewed on the x-ray and ultrasound images thus enhancing qualitative visualization, localization and characterization of regions of interest. The potentials of structured noise reduction, cyst versus solid mass differentiation and full 3-D visualization of multi-modality registered data sets in a single automated combined examination are realized for the first time. Elements of system design and required image correction algorithms will be described and phantom studies with this prototype, automated system on an anthropomorphic breast phantom will be presented.

A 10 Fr ultrasound catheter with integrated micromotor for 4D intracardiac echocardiography

We developed prototype catheters for real-time three-dimensional intracardiac echo (4D ICE) imaging. The catheter tips contained a low profile 64-element, 6.2 MHz phased array transducer and integrated micromotor, allowing oscillation of the transducer in the elevation direction. The tips were integrated with two-way deflectable 10 Fr catheters and used in in-vivo animal testing at multiple facilities. The 4D ICE catheters were capable of imaging a 90° azimuth by up to 180° elevation field of view. Volume rates ranged from 1 vol/sec (180° elevation) to approximately 10 vol/sec (45° elevation). We successfully imaged electrophysiology catheters, atrial septal puncture procedures, and detailed cardiac anatomy. The elevation oscillation enabled 3D visualization of devices and anatomy providing new clinical information and perspective not possible with current 2D imaging catheters.

Utilization of carbon fibers in thermal management of microelectronics

Power dissipation is expected to increase exponentially to 150-250 W per chip over the next decade. To manage this large heat output, it is necessary to minimize the thermal resistance between the chip and a heat dissipation unit that the device is attached to. It is therefore important to further improve the thermal performance of thermal interface materials (TIMs), which can be achieved through 1) improvement of the bulk thermal conductivity of TIMs; and/or 2) reduction of interfacial thermal resistances between the TIM and the device and/or TIM and the heat dissipation unit. The latter improvement may be obtained by enhanced physical properties of TIMs (e.g., viscosity or wetting ability) and/or surface modification of the heat dissipation unit or the inactive side of the device. Researchers have tried to take advantage of the high 1D thermal conductivities of graphite fibers, and more recently of carbon nanotubes (CNT), to reduce the thermal resistance between the chip and the heat dissipation unit. The efforts can be classified into three categories: 1) Forming pre-aligned graphite fiber or CNT films that have high bulk thermal conductivities in the heat transport direction, and applying such films as TIMs; 2) incorporating randomly oriented graphite fibers or CNT into silicone or epoxy matrices in the presence or absence of a second filler to improve bulk thermal conductivities, and applying the thus-formed blend as thermal greases, or adhesives or gels; and 3) growing CNT or graphite fibers from the heat sink/spreader surface and/or silicon backside and assembling them together with a TIM a to increase the bulk heat transport property and reduce the interfacial resistances, In this paper, we will present results for each of the three approaches, and discuss the challenges facing each one.

Vertical birefringence characterization for optical polymer films

This paper introduces a technique for precisely measuring the vertical birefringence of an optical polymer film. Analytical equations are derived to relate the phase retardation to the optical film birefringence. In the measurement, we first measure the in-plane birefringence of the film and locate the principal axes of refractive index ellipsoid. The film is then rotated with its normal at an angle to the incident light wave vector. The vertical birefringence is calculated from the retardations measured at several angles. Using the procedure, the vertical birefringence can be measured to a precision of 0.2 ×10-3.

Vertical Birefringence Measurement for Optical Polymer Films

This paper introduces technique for measuring vertical birefringence. We locate the in-plane axes of a film and rotate the film around the axes. Data show that VBR can be measured to a precision of 0.2*10-3.