This Small Business Innovation Research (SBIR) Phase I project addresses the need for high-speed real-time high-resolution cross-sectional images of the internal microstructure of living tissue. This is a fundamental need of modern medical diagnostics that only optical coherence tomography (OCT) can meet. This is particularly important for imaging of the eye, blood vessels, and cancerous non-transparent tissue. Today's systems are relatively slow at 1300 nm, and they have limited depth resolution, which are all drawbacks in identifying tissue and microstructure in real time. The objective of this project is to make a novel sensor chip that can increase the depth of imaging by 2x and increase the sensitivity by 6 dB, all while taking scans at a rate of 195 kHz, giving a real-time imaging solution. This project will implement substantial improvements in readout chip architecture to realize these goals of high speed, large data rate and improved sensitivity.
The broader impact/commercial potential of this project translates mainly in the realization of OCT equipment that will enhance the diagnostic capabilities of many medical disciplines, in particular ophthalmology, cardiology, cancer detection and dentistry. This powerful medical diagnostic tool will help enhance the quality of life of many people. The growth of the OCT market is expected to be very significant, from $200 million today to over $800 million in four years. This high-speed, high-sensitivity OCT sensor will capture a significant part of this market. Its performance is far above the competition, enabling real-time imaging, raising the expectation is that it would not only capture the projected market share, but it should also grow the overall market. Also, significantly, the success of this product will generate hundreds of high-technology jobs in the United States.
This Small Business Innovation Research Phase I project addressed the need for high speed optical coherence tomography (OCT) for real time imaging. OCT imaging is particularly important for imaging of blood vessels and non-transparent tissue (including cancerous tissue). Currently available 1300 nm-based systems are too slow for real-time imaging, and they have limited depth resolution and sensitivity. Aerius Photonics proposed to make a novel sensor chip that can increase the depth of imaging by 2X and increase the sensitivity by 6 dB, all while taking scans at a line rate of 200 kHz, which translates into a frame rate of 6 Hz for a 256x256 format image. Currently, the next-best offering is only capable of 1.5 Hz, which is too slow for real-time imaging. To achieve this objective, the readout integrated circuit chip (ROIC), a component of the sensor chip, must be substantially improved to increase the speed and size of the overall sensor. In addition, since the chip is a hybrid of the ROIC and an InGaAs detector array, another necessary improvement is to make a wide InGaAs array on a very small pitch that is capable of being bump bonded to the silicon ROIC. Aerius’ unique experience in making large detector arrays using their proprietary low dark current InGaAs (which is mated to the ROIC) and high speed ROICs give them the expertise to realize the complex sensor. The ROIC architecture will enable the development of a sensor product for the OCT market with unparalleled performance. Overall, Aerius has made substantial progress toward reaching the goal of the overall project. We designed the overall sensor. In addition, we designed and simulated the top level architecture of the ROIC and determined that a digitally enabled architecture would be the only way to achieve the speed required for this application. In addition, we designed and fabricated small pixel detectors required for the project and showed that we were able to maintain low dark current in these detectors. The dark current is important because it contributes directly to the noise of the sensor which degrades the sensitivity of the detector. These steps are the building block to making the extremely wide sensor that is proposed for Phase II of this project. If successful, the implications of this sensor affect real-time surgical decisions. With real-time feedback from this high resolution depth monitor, surgeons can use this tool to more accurately remove unwanted tissue without affecting healthy tissue. With increased removal, patients’ life expectancy and quality of life are expected to improve.
