We previously reported the potential of using vascular reactivity during respiratory challenges as a marker to predict the response of breast tumor to chemotherapy in a rat model by using a continuous wave near-infrared spectroscopy. However, it cannot visualize how the vascular reactivity from tumor vessel can predict the tumor response to its treatment. In this study, we utilized a spectral domain optical coherence tomography (SD-OCT) system to visualize vascular reactivity of both tumor and normal vasculature during respiratory challenges in a mouse model. We adapted intensity based Doppler variance algorithm to draw angiogram from the ear of mouse (8-week-old Balb/c nu/nu). Animals were anesthetized using 1.5% isoflurane, and the body temperature was maintained by a heating pad. Inhalational gas was switched from air (10min) to 100% oxygen (10min), and a pulse oximeter was used to monitor arterial oxygen saturation and heart rate. OCT angiograms were acquired 5 min after the onset of each gas. The vasoconstriction effect of hyperoxic gas on vasculature was shown by subtracting an en-face image acquired during 100% oxygen from the image acquired during air inhalation. The quantitative change in the vessel diameter was measured from the en-face OCT images of the individual blood vessels. The percentage of blood vessel diameter reduction varied from 1% to 12% depending on arterial, capillary, or venous blood vessel. The vascular reactivity change during breast tumor progression and post chemotherapy will be monitored by OCT angiography.
KEYWORDS: Optical coherence tomography, Image processing, Data processing, Parallel computing, Data acquisition, Signal processing, Doppler tomography, Digital signal processing, Graphics processing units, Neodymium
We demonstrate a real-time display of processed OCT images using multi-thread parallel computing with
a quad-core CPU of a personal computer. The data of each A-line are treated as one vector to maximize
the data translation rate between the cores of the CPU and RAM stored image data. A display rate of 29.9
frames/sec for processed OCT data (4096 FFT-size x 500 A-scans) is achieved in our system using a
wavelength swept source with 52-kHz swept frequency. The data processing times of the OCT image and
a Doppler OCT image with a 4-time average are 23.8 msec and 91.4 msec.
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