Periodic Reporting for period 2 - HandheldOCT (Handheld optical coherence tomography)
Okres sprawozdawczy: 2021-07-01 do 2022-12-31
Optical coherence tomography (OCT) is a revolutionizing in-vivo 3D imaging technique for non-invasive optical biopsy addressing medical needs in early diagnosis and effective disease management. OCT has proven its value primarily in ophthalmology but more recently also in a variety of other medical fields. However, wide adoption in health care, a requirement for effective therapy control, has not taken place mainly due to cost limitations and the non-existence of miniaturized mobile devices.
Integrated photonics is expected to leverage off many advances made in integrated electronics. Based on photonic integrated circuit technology, HandheldOCT will enable a new generation of handheld OCT systems in the 1060nm wavelength region for optimum tissue penetration with step-changes in imaging performance (4x faster imaging speed), with size (10x smaller) and cost (2-5x cheaper) beyond state-of-the-art. The monolithic integration of silicon nitride optical waveguides, Germanium photodiodes, and micro-optics combined with the hybrid integration of a novel compact all-semiconductor akinetic swept source will enable a mobile, low-cost solution of high usability. HandheldOCT is expected to contribute significantly to a widespread adoption of OCT in point-of-care diagnostics (e.g. for new-born, children, bedridden elderly, home remote diagnosis) and for diagnostic-driven therapy of major sight-threatening, mostly age-related retinal pathologies with the aim to improve patient outcome and reduce healthcare costs.
The endeavour is strongly driven by companies and research organisations with solid expertise in silicon foundry technology, miniaturized laser sources, photonic design and packaging, electronics, and medical OCT system integration. The consortium includes clinicians and the world-leading ophthalmic equipment manufacturer focusing on implementing diagnostically relevant specifications and the translational clinical proof-of-principle testing on a small patient cohort.
Integrated photonics is expected to leverage off many advances made in integrated electronics. Based on photonic integrated circuit technology, HandheldOCT will enable a new generation of handheld OCT systems in the 1060nm wavelength region for optimum tissue penetration with step-changes in imaging performance (4x faster imaging speed), with size (10x smaller) and cost (2-5x cheaper) beyond state-of-the-art. The monolithic integration of silicon nitride optical waveguides, Germanium photodiodes, and micro-optics combined with the hybrid integration of a novel compact all-semiconductor akinetic swept source will enable a mobile, low-cost solution of high usability. HandheldOCT is expected to contribute significantly to a widespread adoption of OCT in point-of-care diagnostics (e.g. for new-born, children, bedridden elderly, home remote diagnosis) and for diagnostic-driven therapy of major sight-threatening, mostly age-related retinal pathologies with the aim to improve patient outcome and reduce healthcare costs.
The endeavour is strongly driven by companies and research organisations with solid expertise in silicon foundry technology, miniaturized laser sources, photonic design and packaging, electronics, and medical OCT system integration. The consortium includes clinicians and the world-leading ophthalmic equipment manufacturer focusing on implementing diagnostically relevant specifications and the translational clinical proof-of-principle testing on a small patient cohort.
In the first 18 months of this project development and fabrication of the set of 3 SG DBR lasers for 100-nm-band wavelength swept source have been taken place. Unfortunately, this goal has not been reached due to difficulties in SG DBR laser connected with their lifetime. Thus, most work was focused on defining the problem and finding a solution to overcome it. Development of optical power amplifier (OPA) based on semiconductor chip has been successfully finished. Progress with development of optical µ-assembly is in accordance with initial Project plan.
Furthermore a technological platform for fabrication of OCTchips with passive and active optical components has been provided. In the first months of the project, IMEC provided the necessary PDK (Process Development Kit) to AIT for simulations to define the waveguide height that will be used for passive photonic integrated components. Subsequently, once the components were designed, IMEC took the charge of fabrication of the photonic chips. The first run of the project, SLR1 (Short Loop Run 1), has been completed and tested. The SLR1 was used to evaluate the SiN passive components, the data obtained from the SLR1 has been fed into the FLR1 (Full Loop Run 1) which is currently being fabricated. It will contain active components (photodetectors) and the 1st prototypes of the OCTengine.
In addition project simulations were carried out to find the optimum waveguide cross section both regarding thickness and width. In the next step, simulation routines were established for the design of the required photonic building blocks. Two CAD mask layouts (one with waveguides only for the first short loop run (SLR) and one co-integrated with photodiodes for the first full loop run (FLR)) were elaborated comprising individual photonic building blocks and first OCTengines to be used by MUW to acquire OCT images. The short loop fabrication run with the layout containing only the waveguides was finished in M12 and the supplied PICs have been evaluated since then.
The body of packaging work done so far consisted in assessing different approaches in packaging the PIC engine optically and electrically, together with corresponding tests and measurements. This involved simulating and testing four different fibre options on different edge couplers, and making the first optical test package. On 3D-printed optics side, the most suitable edge couplers were selected and micro-lenses for the sample and reference arm were simulated, developed, printed and characterized. For electrical packaging, electrical requirements were evaluated, and three different TIA options were assessed, TIA-ADC connections were also researched.
System integration so far comprised the systems concept including the opto-mechanical concept the system electronics, firm-and software and the system integration concept. The integration options with respect to sensitivity and heat load in the handheld unit have also been analyzed.
Furthermore, validation of the PICs for OCT single components, such as the passive PICs have been tested. In addition, polarizing (PZ) fibers within an OCT setup have been evaluate if this introduces imaging artefacts and the coupling losses between first passive PIC and different fiber arrays (FA) were evaluated. Preliminary OCT measurements with the passive PIC, integrated in a fiber-based OCT setup were performed. All measurements in this WP show promising results: The PZ fiber does not introduce imaging artefacts and achieves the desired polarization stability. Coupling losses could be improved by the usage of a lensed FA, which seems to be a promising option for low loss coupling between fibers and PICs.
Furthermore a technological platform for fabrication of OCTchips with passive and active optical components has been provided. In the first months of the project, IMEC provided the necessary PDK (Process Development Kit) to AIT for simulations to define the waveguide height that will be used for passive photonic integrated components. Subsequently, once the components were designed, IMEC took the charge of fabrication of the photonic chips. The first run of the project, SLR1 (Short Loop Run 1), has been completed and tested. The SLR1 was used to evaluate the SiN passive components, the data obtained from the SLR1 has been fed into the FLR1 (Full Loop Run 1) which is currently being fabricated. It will contain active components (photodetectors) and the 1st prototypes of the OCTengine.
In addition project simulations were carried out to find the optimum waveguide cross section both regarding thickness and width. In the next step, simulation routines were established for the design of the required photonic building blocks. Two CAD mask layouts (one with waveguides only for the first short loop run (SLR) and one co-integrated with photodiodes for the first full loop run (FLR)) were elaborated comprising individual photonic building blocks and first OCTengines to be used by MUW to acquire OCT images. The short loop fabrication run with the layout containing only the waveguides was finished in M12 and the supplied PICs have been evaluated since then.
The body of packaging work done so far consisted in assessing different approaches in packaging the PIC engine optically and electrically, together with corresponding tests and measurements. This involved simulating and testing four different fibre options on different edge couplers, and making the first optical test package. On 3D-printed optics side, the most suitable edge couplers were selected and micro-lenses for the sample and reference arm were simulated, developed, printed and characterized. For electrical packaging, electrical requirements were evaluated, and three different TIA options were assessed, TIA-ADC connections were also researched.
System integration so far comprised the systems concept including the opto-mechanical concept the system electronics, firm-and software and the system integration concept. The integration options with respect to sensitivity and heat load in the handheld unit have also been analyzed.
Furthermore, validation of the PICs for OCT single components, such as the passive PICs have been tested. In addition, polarizing (PZ) fibers within an OCT setup have been evaluate if this introduces imaging artefacts and the coupling losses between first passive PIC and different fiber arrays (FA) were evaluated. Preliminary OCT measurements with the passive PIC, integrated in a fiber-based OCT setup were performed. All measurements in this WP show promising results: The PZ fiber does not introduce imaging artefacts and achieves the desired polarization stability. Coupling losses could be improved by the usage of a lensed FA, which seems to be a promising option for low loss coupling between fibers and PICs.
HandheldOCT aims to develop and to bring into the market an OCT based imaging device that overcomes the limitations of the current generation of OCT devices in ophthalmology. Early diagnosis of retinal diseases that are worldwide leading causes for blindness are envisaged. Furthermore, retinal pathologies can also be considered a surrogate for other medical fields (epithelial cancers), e.g. dermatology, oral, gynaecologic or gastrointestinal cancer. Partnerships with leading innovative clinical users will enable clinical evaluation in ophthalmology within the framework of HandheldOCT.
Hence, HandheldOCT’s comprehensive approach involves all the stages needed (product development, pre-clinical studies and regulatory needs) to develop such imaging diagnostic tool:
From the product development point of view
Further research will be carried out and several technologies (based on partners’ mature technology platforms) will be integrated: SiN waveguide platform, light sources, integrated detector and Post-processing Electronics, MEMS, photonic packaging and assembly as well as biomedical signal and image processing will be included in order to deliver non-invasive, high resolution, low-cost, reliable and compact in-vivo imaging tool. The use of integrated optics will allow HandheldOCT to reduce the presently cost (~100k€) and bulkiness of current marketed devices, fostering the wider adoption of OCT based cost effective (15-25K€, 3x cheaper than commercial SOTA), high performance (> 4x faster than commercial SOTA), small footprint (5x smaller than commercial SOTA) point of care systems.
Hence, HandheldOCT’s comprehensive approach involves all the stages needed (product development, pre-clinical studies and regulatory needs) to develop such imaging diagnostic tool:
From the product development point of view
Further research will be carried out and several technologies (based on partners’ mature technology platforms) will be integrated: SiN waveguide platform, light sources, integrated detector and Post-processing Electronics, MEMS, photonic packaging and assembly as well as biomedical signal and image processing will be included in order to deliver non-invasive, high resolution, low-cost, reliable and compact in-vivo imaging tool. The use of integrated optics will allow HandheldOCT to reduce the presently cost (~100k€) and bulkiness of current marketed devices, fostering the wider adoption of OCT based cost effective (15-25K€, 3x cheaper than commercial SOTA), high performance (> 4x faster than commercial SOTA), small footprint (5x smaller than commercial SOTA) point of care systems.