University of Rochester, The Institute of Optics, 275 Hutchinson Road, Rochester, New York 14627, USA.
J Biomed Opt. 2010 Mar-Apr;15(2):026004. doi: 10.1117/1.3368995.
Two-color nonlinear absorption imaging has been previously demonstrated with endogenous contrast of hemoglobin and melanin in turbid media using transmission-mode detection and a dual-laser technology approach. For clinical applications, it would be generally preferable to use backscattering mode detection and a simpler single-laser technology. We demonstrate that imaging in backscattering mode in turbid media using nonlinear absorption can be obtained with as little as 1-mW average power per beam with a single laser source. Images have been achieved with a detector receiving backscattered light at a 45-deg angle relative to the incoming beams' direction. We obtain images of capillary tube phantoms with resolution as high as 20 microm and penetration depth up to 0.9 mm for a 300-microm tube at SNR approximately 1 in calibrated scattering solutions. Simulation results of the backscattering and detection process using nonimaging optics are demonstrated. A Monte Carlo-based method shows that the nonlinear signal drops exponentially as the depth increases, which agrees well with our experimental results. Simulation also shows that with our current detection method, only 2% of the signal is typically collected with a 5-mm-radius detector.
双色非线性吸收成像已经在混浊介质中通过内源性对比血红蛋白和黑色素，使用透射模式检测和双激光技术得到了证明。对于临床应用，通常更倾向于使用背散射模式检测和更简单的单激光技术。我们证明，使用非线性吸收在混浊介质中进行背散射模式成像，可以使用低至每束 1mW 的平均功率和单个激光源来实现。图像是通过探测器在相对于入射光束方向成 45 度角的位置接收背散射光获得的。我们在经过校准的散射溶液中，获得了高达 20 微米分辨率和高达 0.9 毫米穿透深度的毛细管管体的图像，在信噪比约为 1 时，其管体的深度为 300 微米。我们演示了使用非成像光学的背散射和检测过程的模拟结果。基于蒙特卡罗的方法表明，非线性信号随着深度的增加呈指数衰减，这与我们的实验结果非常吻合。模拟还表明，使用我们目前的检测方法，只有 2%的信号通常可以通过 5 毫米半径的探测器收集。
