Y. Huang, W. Sun, L. Yan, A. Nitkowski, A. Weinroth, N. Tansu, C. Zhou
Keywords: optical coherence tomography, photonic device, biomedical imaging
Summary:Label-free and non-destructive imaging technologies with micron-scale resolutions are greatly desirable for biomedical applications. Optical coherence tomography (OCT) is an emerging biomedical imaging technology that enables micron scale, cross sectional, and three-dimensional (3D) imaging of biological tissues non-invasively. OCT functions as a type of “optical biopsy,” imaging tissue microstructure with resolutions approaching that of standard histopathology by microscopy, but without the need to remove and process tissue specimens. OCT is analogous to ultrasound imaging, except that light instead of sound is used in OCT to provide 10–100 times better resolution compared to ultrasound. To date, OCT has been used in a wide range of clinical applications in humans, including ophthalmology, cardiology, endoscopy, oncology, dermatology, and dentistry. In 2013, it was estimated that over 32 million ophthalmic OCT procedures were performed world-wide for the diagnosis of eye diseases, corresponding to about one ophthalmic OCT procedure performed in each second. High definition 3D scan of the patient’s eye is greatly desired by ophthalmologists as it provides a way to reliably co-register volumetric images in the human retina in order to track disease progression. Current commercial ophthalmic OCT systems, however, take about 3-10 seconds to finish a single 3D scan. This often results in severe motion artifacts, which make the images unusable to track disease progression. Our group developed a space-division multiplexing OCT (SDM-OCT) technology that achieved over an order of magnitude speed improvement compared to current state-of-the-art commercial OCT systems. This technique allows parallel imaging from multiple sample locations and therefore improves OCT axial scan rate by a factor equal to the number of beams used simultaneously. In our first lab prototype, we achieved an effective 800,000 A-scans/s imaging speed and were able to acquire 3D scan of a fruit fly larva in less than 0.4 second. Our first prototype SDM-OCT system was developed based on fiber optics. However, the process to make the fiber optical assembly was time consuming and prone to errors. It is also challenging to achieve very precise control of optical delays between different channels. Recently, we developed an integrated photonic chip for SDM-OCT. Custom optical delays and spacing between each output beam of the chip can be independently chosen to fit specific imaging applications. The delays and spacing are defined lithographically during the fabrication process and are precise to within sub-micron tolerances. With the SDM-OCT technology, high definition 3D scans of the eye can be acquired within a fraction of a second, instead of 3-10 seconds. This will significantly reduce motion artifacts, minimize procedure time, and improve procedure yields, diagnosis accuracy, and patient comfort. Furthermore, this technology can be inexpensively implemented in the next generation OCT devices (i.e. new customers), as well as retrofit into existing OCT devices (i.e. a huge existing customer base). The SDM-OCT technology can also be used for other biomedical, industrial and academic applications. This technology will represent a significant competitive advantage for the OCT device company in the highly competitive, nearly $1B OCT device market.