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Zhuoyan Li, Jin H. Shen, John A. Kozub, Ratna Prasad, Pengcheng Lu, Karen M. Joos; A Miniature B-scan Forward-imaging OCT Probe to Guide Real-time Laser Ablation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3120.
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To determine whether a miniature B-scan forward-imaging OCT probe can be combined with a laser to guide real-time incisions of gelatin and ocular tissues.
A miniature 25-gauge B-scan forward-imaging OCT probe was developed. It was combined with a 250 μm hollow-glass waveguide that was capped with a calcium fluoride window to permit delivery of 6.1 μm laser energy. The laser beam was aimed so that it was coplanar with the OCT scanning probe. The Raman-shifted alexandrite laser system delivered 6.1 μm at 10 Hz with an output energy of 0.5-0.6 mJ/pulse. To demonstrate real-time imaging of tissue ablation with the combined forward-scanning OCT probe and mid-infrared laser, a gelatin mixture (10% by weight), and porcine retinas and corneas were prepared. A preset number of pulses was delivered to the respective tissues with real-time imaging by the miniature B-scan forward-imaging probe attached to an 840 nm spectral domain OCT system (Bioptigen Inc, Durham, NC). The ablation studies were observed and recorded in real-time. The corneas and retinas were prepared for histological analysis.
The combined miniature forward-imaging OCT probe and mid-infrared laser successfully imaged the tissue ablation in real-time for gelatin, and porcine corneas and retinas. Using the Bioptigen OCT imaging software, the crater sizes were measured. A constant number of 60 pulses at 0.5 mJ was applied to the gelatin resulting in mean depth of 119 ± 14 μm for each hole. For the corneal tissue, there was a significant correlation between pulse number and depth of the lased hole (Pearson correlation coefficient = 0.82; P = 0.0002). Histological analysis of the cornea and retina tissues showed discrete holes with minimal thermal damage.
A combined miniature OCT probe and laser can monitor real-time laser tissue ablation. The incision depth is measurable with the OCT probe. The novel instrument has the potential of effectively guiding surgeries by simultaneously imaging and ablating tissue.
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