John E. Dean

Design aspects of a scrolling color LCoS display

Abstract The Philips scrolling color liquid crystal on silicon (LCoS) architecture is a very attractive approach towards affordable large area displays. The color sequential nature coupled with high resolution brings demands on speed and bandwidth. Design requirements and solutions tailored to address scrolling color LCoS demands are presented. We have implemented high quality displays based on silicon backplanes employing a mixed digital–analog construction, high speed FPGA based drive electronics, a thin nematic liquid crystal cell, and a scanning stripe optical engine. Despite challenging demands we have found many opportunities to exploit available technologies in our system designs.

Real-time photoacoustic data acquisition with Philips iU22 ultrasound scanner

A one of a kind photoacoustic system has been built around a Philips iU22 ultrasound scanner. The modified channel board architecture allows access to the raw per-channel photoacoustic data, while keeping all of the imaging capabilities of an actual commercial ultrasound scanner. A captured photoacoustic data frame is Fourier beamformed to generate a single laser shot photoacoustic image. In addition to the photoacoustic data, the system supplies the beamformed ultrasound data, providing a truly dual-modality imaging capability. A tunable OPO laser system (700-900nm), pumped by an Nd:YAG solid state laser, is used as an illumination source with 5ns long pulses. An FPGA-based electronic board synchronizes the iU22 start of frame with the laser firing, currently permitting photoacoustic imaging at a rate of 10 Hz (laser repetition rate limit). At that imaging frame rate the photoacoustic system, consisting of a PC modified with 32 Gbytes of acquisition memory and an FPGA array, is able to store several minutes of continuously captured data, enabling monitoring and off-line analysis of dynamic photoacoustic events and/or fast scanning for performing pseudo-3D imaging. The system can use all of the standard iU22 array transducers both for photoacoustic imaging, and in all of the ultrasound imaging modes.

58.1: Single-Panel LCOS Color Projector with LED Light Sources

We report a full color projection display based on a single LCOS panel using LED light sources. We have demonstrated that light output limitation due to polarization conversion can be substantially overcome by the small working F/# of the LCOS panel and LED compatibility with polarization recycling without increasing source etendue. We are presenting key technology developments in light collection optics and driving strategies for an LCOS based projection HDTV. Our demonstrator with currently available LEDs produces more than 40 screen lumens.

In vivo photoacoustic and ultrasonic mapping of rat sentinel lymph nodes with a modified commercial ultrasound imaging system

Sentinel lymph node biopsy (SLNB) has become the standard method for axillary staging in breast cancer patients, relying on invasive identification of sentinel lymph nodes (SLNs) following injection of blue dye and radioactive tracers. While SLNB achieves a low false negative rate (5-10%), it is an invasive procedure requiring ionizing radiation. As an alternative to SLNB, ultrasound-guided fine needle aspiration biopsy has been tested clinically. However, ultrasound alone is unable to accurately identify which lymph nodes are sentinel. Therefore, a non-ionizing and noninvasive detection method for accurate SLN mapping is needed. In this study, we successfully imaged methylene blue dye accumulation in vivo in rat axillary lymph nodes using a Phillips iU22 ultrasound imaging system adapted for photoacoustic imaging with an Nd:YAG pumped, tunable dye laser. Photoacoustic images of rat SLNs clearly identify methylene blue dye accumulation within minutes following intradermal dye injection and co-registered photoacoustic/ultrasound images illustrate lymph node position relative to surrounding anatomy. To investigate clinical translation, the imaging depth was extended up to 2.5 cm by adding chicken breast tissue on top of the rat skin surface. These results raise confidence that photoacoustic imaging can be used clinically for accurate, noninvasive SLN mapping.