Design of illumination system using characterized illuminances for smartphone-based fundus camera.

Recently, smartphone-based fundus camera (SBFC) research has been actively conducted in response to the need to expand medical infrastructure in underdeveloped countries and the increased telemedicine since the COVID-19 pandemic. Compared to the conventional table-top system, SBFCs have technical challenges that make it difficult to guarantee uniform illumination and avoid back-reflection because of the design constraints of minimizing the form factor and cost. This paper proposes a novel illumination design methodology using characterized illuminance to obtain high-quality fundus images for SBFCs. Key performance indicators (KPIs), such as retinal uniformity, back-reflection suppression, and optical efficiency, were defined to evaluate the performance of the illumination system. Each KPI was calculated using optical simulation software based on Monte-Carlo ray tracing and mapped into a normalized three-dimensional coordinate, the retinal illumination performance space (RIPS). In RIPS, the KPIs are combined into a single parameter ΔRIPS, which is the quantitative difference evaluated as the Euclidean distance between the ideal and actual design point. A compact SBFC illumination system with five design variables was presented to verify the proposed methodology. The final design values at the minimum ΔRIPS were determined using the Taguchi method and response surface methodology. Finally, a working prototype was built, and fundus images were acquired by clinical testing under institutional review board approval. The fundus image had sufficient brightness and resolution to diagnose the lesion with a viewing angle of approximately 50° in one shot.

Synthesis of water well-dispersed PEGylated iron oxide nanoparticles for MR/optical lymph node imaging.

We reported the synthesis of highly water-stable iron oxide nanoparticles by a simple one-pot reaction. Non-toxic polyethylene glycol MW 600 (PEG) acted as a solvent, capping agent and reducing agent in the synthesis of iron oxide nanoparticles. As a result of the synthesis, PEGylated small-size (4.2 ± 0.39 nm average diameter and 7.2 ± 1.9 nm hydrodynamic sizes measuring by DLS) iron oxide nanoparticles (USPIO) were obtained, which show great colloidal stability in water and tolerate high salt concentration (0.75 M sodium chloride) and a wide pH range of 4 to 12. Oxidation of PEG was observed during the synthesis of iron oxide nanoparticles, which makes USPIO easy to functionalize with other molecules. Functionalization of the USPIO surface with fluorescein isothiocyanate (FITC) was conducted for investigating the possibility for multimodal imaging. Also the cytotoxicity test and lymph node imaging were performed by using the FITC labelled USPIO (FITC@USPIO). According to these results, the stable water dispersed USPIO and FITC@USPIO are expected to apply for multimodal in vivo imaging.