Configuration-based processing of phosphene pattern recognition for simulated prosthetic vision.

Visual prosthesis can elicit phosphenes by stimulating the retina, optic nerve, or visual cortex along the visual pathway. Psychophysical studies have demonstrated that visual function can be partly recovered with phosphene-based prosthetic vision. This study investigated the cognitive process of prosthetic vision through a face recognition task. Both behavioral response and the face-specific N170 component of event-related potential were analyzed in the presence of face and non-face stimuli with natural and simulated prosthetic vision. Our results showed that: (i) the accuracy of phosphene face recognition was comparable with that of the normal one when phosphene grid increased to 25 x 21 or more; (ii) shorter response time was needed for phosphene face recognition; and (iii) the N170 component was delayed and enhanced under phosphene stimuli. It was suggested that recognition of phosphene patterns employ a configuration-based holistic processing mechanism with a distinct substage unspecific to faces.

Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging.

We develop a novel dual-modal contrast agent-encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles-for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins.

Synthesizing and binding dual-mode poly (lactic-co-glycolic acid) (PLGA) nanobubbles for cancer targeting and imaging.

Accurate assessment of tumor boundaries and recognition of occult disease are important oncologic principles in cancer surgeries. However, existing imaging modalities are not optimized for intraoperative cancer imaging applications. We developed a nanobubble (NB) contrast agent for cancer targeting and dual-mode imaging using optical and ultrasound (US) modalities. The contrast agent was fabricated by encapsulating the Texas Red dye in poly (lactic-co-glycolic acid) (PLGA) NBs and conjugating NBs with cancer-targeting ligands. Both one-step and three-step cancer-targeting strategies were tested on the LS174T human colon cancer cell line. For the one-step process, NBs were conjugated with the humanized HuCC49 Delta C(H)2 antibody to target the over-expressed TAG-72 antigen. For the three-step process, cancer cells were targeted by successive application of the biotinylated HuCC49 Delta C(H)2 antibody, streptavidin, and the biotinylated NBs. Both one-step and three-step processes successfully targeted the cancer cells with high binding affinity. NB-assisted dual-mode imaging was demonstrated on a gelatin phantom that embedded multiple tumor simulators at different NB concentrations. Simultaneous fluorescence and US images were acquired for these tumor simulators and linear correlations were observed between the fluorescence/US intensities and the NB concentrations. Our research demonstrated the technical feasibility of using the dual-mode NB contrast agent for cancer targeting and simultaneous fluorescence/US imaging.

Dual-mode imaging of cutaneous tissue oxygenation and vascular function.

Accurate assessment of cutaneous tissue oxygenation and vascular function is important for appropriate detection, staging, and treatment of many health disorders such as chronic wounds. We report the development of a dual-mode imaging system for non-invasive and non-contact imaging of cutaneous tissue oxygenation and vascular function. The imaging system integrated an infrared camera, a CCD camera, a liquid crystal tunable filter and a high intensity fiber light source. A Labview interface was programmed for equipment control, synchronization, image acquisition, processing, and visualization. Multispectral images captured by the CCD camera were used to reconstruct the tissue oxygenation map. Dynamic thermographic images captured by the infrared camera were used to reconstruct the vascular function map. Cutaneous tissue oxygenation and vascular function images were co-registered through fiduciary markers. The performance characteristics of the dual-mode image system were tested in humans.