Development of optical techniques for imaging biological tissues
The use of optical techniques for biomedical imaging has received considerable attention because of its potential to provide high resolution imaging without the need of ionizing radiation and the associated risks. Optical Coherence Tomography is one such technique that uses low coherence light source and a fiber optic Michelson interferometer to perform high-resolution, cross-sectional imaging of biological microstructures. We have developed different variants of the Optical Coherence Tomography (OCT) setups including time domain real time OCT (8 frames/s), Fourier Domain OCT (16 frames /s) and polarization sensitive OCT using low-coherence super-luminescent diodes with ~10µm axial and ~17 µm lateral resolutions. These setup have been used to image various biological samples like in-vivo imaging of fish eye [1,2] and brain [3], mice skin[4] and hair follicles[5], growth dynamics of tumor spheroids [6]etc.
A typical in-vivo OCT image of a Zebrafish eye is shown in figure 1. These images can be used for estimation of important ocular parameters like corneal and retinal thickness, the anterior angle of cornea with iris and gradient refractive index profile of the lens [1,2]. More images recorded using these OCT setup can be found in Image Gallery.
Fig. 1. In-vivo OCT image of a Zebrafish eye. [Appl. Phy. B., 87, 607-610 (2007)]
Polarization Sensitive Optical Coherence Tomography (PSOCT) has emerged as useful technique that provides important structural and functional information based on birefringence properties of tissues. A time domain PSOCT setup been assembled in our lab using a single detector with dual reference beams generated by a non-polarizing beam splitter in the reference arm of the interferometer. PS-OCT setup has been used to image resected human breast tissues. The retardation images show considerable difference for different pathologies of the breast tissue samples. The birefringence value for malignant sample and benign sample are estimated to be 6.0 × 10-5 and 5.1 × 10-4 respectively. These values show that the benign or fibro-adenoma breast tissue samples have an order of magnitude higher birefringence than the malignant tissue samples. The difference in the measured birefringence suggests that the PSOCT can sensitively monitor the birefringence variation in malignant and benign breast tissue.
Reference:
- Non-Invasive Ophthalmic Imaging of Adult Zebrafish (Danio rerio) using Optical Coherence Tomography.
K. Divakar Rao, Y. Verma, H. S. Patel and P. K. Gupta
Current Science 90, 1506-1510 (2006)
- Measurement of gradient refractive index profile of crystalline lens of fisheye in vivo using optical coherence tomography.
Verma, Y., Rao, K.D., Suresh, M.K., Patel, H.S., Gupta, P.K.
Appl. Phy. B., 87, 607-610 (2007)
- Real-time in vivo imaging of adult Zebrafish brain using optical coherence tomography,
Rao D., A. Alex, Verma Y., S. Thampi, Gupta P. K.
Journal of Biophotonics, 2, 288-291 (2009)
- Non-invasive assessment of healing of bacteria infected and uninfected wounds using optical coherence tomography.
Sahu K, Verma Y, Sharma M, Rao K. D, Gupta PK.
To appear in Skin Res Tech, (2010)
- Effect of helium-neon laser irradiation on hair follicle growth cycle of Swiss albino mice.
Shukla S, Sahu K, Verma Y, Rao KD, Dube A, Gupta P K.
Skin Pharmacol Physiol. 23:79-85. (2010)
- Imaging growth dynamics of tumour spheroids using optical coherence tomography.
Sharma, M., Verma, Y., Rao, K.D., Nair, R., Gupta, P.K.
Biotech. Lett., 29, 273-278 (2007)
Image Gallery:
  
OCT images of whole eye (left), cornea (middle) and retina (right) of adult Zebrafish
[Current Science 90, 1506-1510 (2006)]
 
Two-dimensional cross sectional images of the adult brain of Zebrafish (left)
and 3D iso-surface reconstructed using 2D images.
[Journal of Biophotonics, 2, 288-291 (2009)]
OCT image of a growing tumor spheroid
[Biotech. Lett., 29, 273-278 (2007)]
 
OCT images of the normal and malignant tissues of Hamster cheek pouch.
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