Daniel deLahunta Vasilios Morikis Dr. Hyle Park

Overview of OCT  High resolution, live imaging  Subsurface features  No preparation  Used in many fields Retinal imaging Gastrointestinal imaging Skin imaging

Basic Working of OCT system  Tissue sample is place under light source  Light is reflected back out  Information about the tissue structure is encoded in the reflected light  Signal gets weaker with depth  Resolution is on the order of micrometers with up to several millimeters of imaging depth

Ultrasound

Optical coherence tomography  OCT uses an interferometer to detect the much shorter time delays between light signals  Interference fringes form when the reference and sample arm lengths are equal to within the coherence length of the light source  A depth profile (A-line) is obtained by detection of the interference pattern generated by light returning from the sample and reference arms as the length of the reference arm is scanned.

Optical coherence tomography  The intensity of interference patterns tells the reflectivity throughout the tissue  A 2D image (or 3D volume) is formed by scanning the beam laterally across the sample.

Polarization-sensitive OCT  Image of knuckle

Summer Projects  Analyze data from previous system Determine degree of inflammation in rat nerve after crush Improve predicted value of myelin thickness  Building of two new OCT systems Set-up and calibration of reference and sample arms

Rat Nerve Inflammation  Images previously taken  Rat nerves were crushed and then imaged 1, 7, 14, 21, and 28 days after  Purpose was to determine degree to which the myelin regrows after injury Useful for multiple sclerosis, blunt peripheral nerve trauma  Day 1 data was unusable at the time due to large amount of inflammation

Determining Amount of Inflammation  Use ImageJ  Convert images to binary  Create new image with white background and black where nerve is  Combine the two images  Inflammation is highlighted  Determine area of inflammation and total area

Inflammation results control crush site

Initial Data  Myelin measurements from intensity sensitive system  PS-OCT Slope from polarization sensitive system

Incorporation of Day 1  Still large amount of scatter in data  Repeat inflammation process with other days

Days 7,14, 21, and 28

Other Options  Compared control and crush site data by dividing crush site from control  Compared control and crush site data by subtracting crush site from control

Building of New Systems Old 800New 800New 1310 TechniqueIntensityPolarization Center wavelength800 nm 1310 nm Depth scan rate30,000/sec144,000/sec45,000/sec Lateral resolution6.5 μm2.5 μm6 μm Vertical resolution2 μm1.5 μm3 μm

Contributions  Galvanometer and control box  800 nm sample arm  Calibrated reference arm for both systems

Acknowlegdements  Dr. Hyle Park, Shahid, Yan, Erica, Christian, and the rest of the BIONIL research group  NSF, BRITE program, and Jun Wang