Zhang Yi, Cao Yingchun, Cheng Ji-Xin
Opt Lett. 2019 Aug 1;44(15):3841-3844. doi: 10.1364/OL.44.003841.
Intravascular photoacoustic imaging can potentially improve the identification of lipid-laden atherosclerotic plaque. Most intravascular photoacoustic endoscopes use multimode fibers, which do not allow tight focusing of photons. Recent experiments on pulse propagation in multimode graded-index fibers have shown a nonlinear improvement in beam quality. Here, we harness this nonlinear phenomenon for fiber-delivery of nanosecond laser pulses. We built a photoacoustic catheter 1.4 mm outer diameter, offering a lateral resolution as fine as 30 μm within a depth range of 2.5 mm. Such resolution is one order of magnitude better than current multimode fiber-based intravascular photoacoustic catheters. At the same time, the delivered pulse energy can reach as high as 20 μJ, which is two orders of magnitude higher than that of an optical resolution photoacoustic endoscope built with a single mode fiber. These improvements are expected to promote the biomedical application of photoacoustic endoscopes which require both high resolution and high pulse energy.
血管内光声成像有可能改善富含脂质的动脉粥样硬化斑块的识别。大多数血管内光声内窥镜使用多模光纤，这使得光子无法紧密聚焦。最近关于脉冲在多模渐变折射率光纤中传播的实验表明，光束质量有非线性改善。在此，我们利用这种非线性现象实现纳秒激光脉冲的光纤传输。我们制造了一种外径为1.4毫米的光声导管，在2.5毫米的深度范围内提供低至30微米的横向分辨率。这种分辨率比目前基于多模光纤的血管内光声导管好一个数量级。同时，传输的脉冲能量可高达20微焦，这比用单模光纤构建的光学分辨率光声内窥镜高两个数量级。这些改进有望推动对高分辨率和高脉冲能量均有要求的光声内窥镜在生物医学领域的应用。
