Despite the improvements in early cancer diagnosis, adequate diagnostic tools for early staging of bladder cancer tumors are lacking . MEMS-probes based on optical coherence tomography (OCT) provide cross-sectional imaging with a high-spatial resolution at a high-imaging speed, improving visualization of cancerous tissue [2-3]. Additionally, studies show that the measurement of localized attenuation coefficient allows discrimination between healthy and cancerous tissue . We have designed a new miniaturized MEMS-probe based on OCT that will optimize early diagnosis by improving functional visualization of suspicious lesions in bladder. During the optical design phase of the probe, we have studied the effect of the numerical aperture (NA) on the OCT signal attenuation. For this study, we have employed an InnerVision Santec OCT system with several numerical apertures (25mm, 40mm, 60mm, 100mm, 150mm and 200mm using achromatic lenses). The change in attenuation coefficient was studied using 15 dilutions of intralipid ranging between 6*10-5 volume% and 20 volume%. We obtained the attenuation coefficient from the OCT images at several fixed positions of the focuses using established OCT models (e.g. single scattering with known confocal point spread function (PSF)  and multiple scattering using the Extended Huygens Fresnel model ). As a result, a non-linear increase of the scattering coefficient as a function of intralipid concentration (due to dependent scattering) was obtained for all numerical apertures. For all intralipid samples, the measured attenuation coefficient decreased with a decrease in NA. Our results suggest a non-negligible influence of the NA on the measured attenuation coefficient.
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Liliana M. Peinado, Paul R. Bloemen, Mitra Almasian, Ton G. van Leeuwen, and Dirk J. Faber, "Quantification of numerical aperture-dependence of the OCT attenuation coefficient (Conference Presentation)," Proc. SPIE 9698, Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XIV, 96980Q (Presented at SPIE BiOS: February 15, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2210966.4828055416001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon