Lab: Diffuse Optical Spectroscopy
Purpose: The objectives of this lab are: 1) to perform an instrumentation analysis of a diffuse optical spectroscopy set-up useful for quantitative clinical assessment of tissue dysplasia, and 2) to gain hands-on experience in aspects of instrument design, implementation, and signal processing by taking measurements, graphing data, and converting sensor data into numbers useful for biomedical purposes.
Materials:
• One fiberoptic bronchoscope (BF 3C30, Olympus)
• One 150W endoscope cold light source (CLK-3, Olympus)
• One photodiode (S120B, 400-1000nm, ThorLabs)
• Tissue phantoms
• Real tissue (chicken, human)
Procedure, Day 1:
1) While waiting, read the paper by Zonios et al., about a diffuse optical spectroscopy (DOS) application toward early diagnosis of cancer. The whole paper is a little beyond thescope of this course, but focus on the sections 2, 3, and 4. The most important equations are Equations 3 and 4.
Question 1: how does their DOS system attempt to diagnose pre-cancer (polyp)? What differences are shown between normal tissue and polyp in Figures 4-6?
Question 2: write down one aspect of the instrument design of their DOS system.
Question 3: write down one fact about tissue or hemoglobin optical properties that you did not know before.
2) When called up to perform the optical measurements:
a. Write down the wavelengths you are assigned
b. Write down optical power output from the photodiode sensor.
c. Perform measurements on the various tissues and phantoms that the TA will present.
3) Once all are finished, designate one person as “master of the excel spreadsheet”
4) Pool together all your data. Send to instructor to place on Blackboard.
Then, on your own:
5) Subtract the background (if any).
6) Normalize to the reflectance standard.
7) List the absorption peaks for oxy-hemoglobin (HbO2) and deoxyhemoglobin (Hb). Hint: The values are in the paper, and are in units of nm.
8) In your background-subtracted, normalized diffuse reflectance spectra, are there any peaks (or valleys) corresponding to hemoglobin?
9) Is the lamp output the same intensity over all wavelengths?
10) What is the sampling rate in spectral wavelength and error in the power measurements? How might these values affect a final determination of tissue hemoglobin content or scattering properties?