Laser therapy has been used to perform both ablation and coagulation of diseased tissue. To avoid over or under exposure, monitoring such therapies with a cost-effective method remains an issue however. We present an integrated solution based on an optical coherence tomography (OCT) system allowing simultaneous imaging, quantitative monitoring and therapy delivery in real-time.
The system exploits a double-clad fiber coupler (DCFC) to inject the OCT signal into the double-clad fiber (DCF) core and the therapy laser into the inner cladding making them co-localized. The single fiber solution permits both imaging and therapy at the same time. Furthermore, the DCFC allows the implementation of our technique in any OCT system sharing the same wavelength bandwidth.
Therapy monitoring is achieved by measuring the speckle intensity decorrelation. During coagulation, the optical properties of the tissue start to vary, thereby changing the speckle intensity pattern seen in the OCT tomograms. The proposed algorithm includes both novel motion and noise corrections, extending the usable monitoring depth. Furthermore, the code has been optimized to run during therapy providing real-time monitoring.
In a proof of concept experiment, a system was built with a 532 nm CW laser for therapy and a 1310 nm swept-source laser for OCT imaging. We present ex-vivo cross-sectional imaging and monitoring during therapy. Experimental results were validated against Monte-Carlo simulations and visual inspection.
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