Zhang Jian James, Rajabhandharaks Danop, Xuan Jason Rongwei, Chia Ray W J, Hasenberg Thomas
Boston Scientific Corp, 3070 Orchard Drive, San Jose, CA, 95134, USA.
Lasers Med Sci. 2017 Jul;32(5):1017-1021. doi: 10.1007/s10103-017-2202-1. Epub 2017 Apr 12.
Calculus migration is a common problem during ureteroscopic laser lithotripsy procedure to treat urolithiasis. A conventional experimental method to characterize calculus migration utilized a hosting container (e.g., a "V" grove or a test tube). These methods, however, demonstrated large variation and poor detectability, possibly attributed to the friction between the calculus and the container on which the calculus was situated. In this study, calculus migration was investigated using a pendulum model suspended underwater to eliminate the aforementioned friction. A high-speed camera was used to study the movement of the calculus which covered zero order (displacement), first order (speed), and second order (acceleration). A commercialized, pulsed Ho:YAG laser at 2.1 μm, a 365-μm core diameter fiber, and a calculus phantom (Plaster of Paris, 10 × 10 × 10 mm) was utilized to mimic laser lithotripsy procedure. The phantom was hung on a stainless steel bar and irradiated by the laser at 0.5, 1.0, and 1.5 J energy per pulse at 10 Hz for 1 s (i.e., 5, 10, and 15 W). Movement of the phantom was recorded by a high-speed camera with a frame rate of 10,000 FPS. The video data files are analyzed by MATLAB program by processing each image frame and obtaining position data of the calculus. With a sample size of 10, the maximum displacement was 1.25 ± 0.10, 3.01 ± 0.52, and 4.37 ± 0.58 mm for 0.5, 1, and 1.5 J energy per pulse, respectively. Using the same laser power, the conventional method showed <0.5 mm total displacement. When reducing the phantom size to 5 × 5 × 5 mm (one eighth in volume), the displacement was very inconsistent. The results suggested that using the pendulum model to eliminate the friction improved sensitivity and repeatability of the experiment. A detailed investigation on calculus movement and other causes of experimental variation will be conducted as a future study.
结石移位是输尿管镜激光碎石术治疗尿路结石过程中常见的问题。一种表征结石移位的传统实验方法是使用一个容纳容器（例如，一个“V”形槽或一个试管）。然而，这些方法显示出很大的变异性和较差的可检测性，这可能归因于结石与放置结石的容器之间的摩擦。在本研究中，使用悬挂在水下的摆锤模型来研究结石移位，以消除上述摩擦。使用高速摄像机研究结石的运动，包括零阶（位移）、一阶（速度）和二阶（加速度）。利用一台商业化的波长为2.1μm的脉冲钬激光、一根芯径为365μm的光纤和一个结石模型（巴黎石膏，10×10×10mm）来模拟激光碎石术过程。将模型悬挂在一根不锈钢棒上，以10Hz的频率、0.5、1.0和1.5J的单脉冲能量对其进行1秒的激光照射（即5、10和15W）。用一台帧率为10000FPS的高速摄像机记录模型的运动。通过MATLAB程序处理每个图像帧并获取结石的位置数据，对视频数据文件进行分析。样本量为10时，单脉冲能量为0.5、1和1.5J时，最大位移分别为1.25±0.10、3.01±0.52和4.37±0.58mm。使用相同的激光功率时，传统方法显示总位移小于0.5mm。当将模型尺寸减小到5×5×5mm（体积为原来的八分之一）时，位移非常不一致。结果表明，使用摆锤模型消除摩擦提高了实验的灵敏度和可重复性。作为未来的研究，将对结石运动和实验变异的其他原因进行详细调查。
