Thermal and Acoustic Stabilization Of Volatile Phase-Change Contrast Agents Via Layer-By-Layer Assembly.

Objective: Phase-change contrast agents (PCCAs) are perfluorocarbon nanodroplets (NDs) that have been widely studied for ultrasound imaging in vitro, pre-clinical studies, and most recently incorporated a variant of PCCAs, namely a microbubble-conjugated microdroplet emulsion, into the first clinical studies. Their properties also make them attractive candidates for a variety of diagnostic and therapeutic applications including drug-delivery, diagnosis and treatment of cancerous and inflammatory diseases, as well as tumor-growth tracking. However, control over the thermal and acoustic stability of PCCAs both in vivo and in vitro has remained a challenge for expanding the potential utility of these agents in novel clinical applications.

Dispersion correction in the advanced volume holographic filter.

Thick volume Bragg gratings (VBG) have been used for wavefront selectivity in various applications such as data storage, endoscopy, or astronomic observation. However, a single thick grating is also selective in wavelength, severely limiting the spectral throughput of the system. Recently, our group introduced a two element Advanced Volume Holographic Filter (AVHF) where the first, dispersive Bragg grating is coupled to a thick VBG such that it dramatically improves the spectral bandwidth, and ultimately enhances the signal to noise ratio of polychromatic sources.

Bandwidth optimization for the Advanced Volume Holographic Filter.

The high angular and spectral selectivity of volume holograms have been used in fields like astronomy, spectroscopy, microscopy, and optical communications to perform spatial filtering and wavefront selection. In particular, imaging systems that utilize volume holograms to perform range-based wavefront selection have allowed for the potential to have full 24-hour observational custody of artificial satellites by enabling daytime observations. We previously introduced the Advanced Volume Holographic Filter (AVHF) which demonstrated a significant system bandwidth improvement while maintaining high angular selectivity.

Advanced volume holographic filter to improve the SNR of polychromatic sources in a noisy environment.

We present a new type of filter that improves the SNR of systems where polychromatic signal and noise are located at different distances within the same line of sight. The filter is based on holographic technology that allows for the discrimination of wavefronts by range. In using a combination of two holographic elements, a pre-disperser and a thick volume hologram, we were able to significantly increase the spectral bandwidth of the filter, from 9nm without the pre-disperser to 70nm with both holographic elements.