Date of Graduation

5-2016

Document Type

Thesis

Degree Name

Bachelor of Science in Biomedical Engineering

Degree Level

Undergraduate

Department

Biomedical Engineering

Advisor/Mentor

Dr. Timothy Muldoon

Committee Member/Reader

Narasimhan Rajaram

Committee Member/Second Reader

Priya Puvanakrishnan

Abstract

The diffusive reflectance and spectroscopic microendoscopy (DRSME) is a multimodal imaging system that harnesses its usefulness from different light sources. One of the modalities, diffuse reflectance spectroscopy (DRS), has been used in our lab to investigate optical properties of epithelial tissues using a broadband white light as the main source. Calibration of DRS is required as it can obtain the maximum intensity and convert it to absolute reflectance. Current manual-adjusted calibration can be lengthy and often lead to inconsistent results. Therefore, a new method of calibration is introduced where additive manufacturing (or 3D printing) technology is fully utilized.

The instrumentation of DRS include a tungsten-halogen white light lamp, an optical fiber/probe, motorized switch, and a spectrometer. The probe consists of one optical fiber that is used to deliver the light and two adjacent optical fibers that are used for signal detection. These source detector separations (SDS) are located 374 and 730 microns away from the primary fiber. Based on the diffuse reflectance spectroscopy, photon that propagate deeper into the tissue will reflect further out from the origin point; and closer, for photon that cannot propagate as deep. The SDS will be able to detect the reflected signals accordingly. Therefore, during calibration, the probe’s tip must be 2.1 mm and 3.9 mm away from the reflectance standard’s surface for the 374 and 730 SDS, respectively.

The design of the 3D printed part is especially accommodated for our custom- design probe. The part was printed by the ObJet30 using a UV-crosslinked acrylics material. It was designed to allow for calibration of both 374 and 730 SDS, indicated by marks on the device.

An experiment was carried out to validate the performance of the 3D printed part by performing calibration using both methods: manual adjustment and with 3D printed device. A 20% reflectance standard was used at an integration time of 300 ms. The maxima of each spectrum and percent errors were presented. The percent errors of the device were recorded at 12.3% and 3.1% for 374 and 730 SDS, respectively. Both percent errors are consistently accounted for since intensity scales linearly with the integration time. Furthermore, the usage of this device has reduced the acquisition time which is a major step towards clinical translation.

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