Ashley S, Brooks S G, Gehani A A, Kester R C, Rees M R
Cardiac Research unit, Killingbeck Hospital, Leeds, England.
Angiology. 1990 Jun;41(6):453-62. doi: 10.1177/000331979004100606.
Laser angioplasty may offer percutaneous recanalization of occluded vessels where conventional guidewire and balloon techniques fail. Metal laser thermal angioplasty probes may, however, cause excessive thermal damage due to high tip temperatures (greater than 400.C). Therefore, contact probes made from artificial sapphire crystal designed for general laser surgery are currently being evaluated for use in laser angioplasty with continuous wave Nd-YAG energy. The sapphire modifies the laser energy in various ways, and this paper examines the physical characteristics of five types of rounded sapphire probe (SMTR, MTR, MTRL, OS, LT) and how these properties are affected by clinical usage. The laser beam profile emitted by these probes demonstrates a focal spot 1-2 mm in front of the tip. However, the forward transmission of Nd-YAG energy through the sapphires varied (SMTR, 85%; MTR, 83%; MTRL, 75%; OS, 54%; LT, 69%). Probe heating occurs owing to energy absorption within the sapphire. The surface temperature of the sapphires was measured in air by infrared thermography and the hottest region within the probes localized by an isothermographic technique. At energy settings used clinically (20 J, 10 watts for 2 s) the SMTR, MTR, and MTRL probes exhibited higher temperature rises (94-112.C) than the OS and LT probes (30.C), and heating was localized to the front surface of the former probes. Peak sapphire temperatures remained lower than those of metal probes even at higher energies. After clinical use, the MTR probe demonstrated reduced transmission, beam defocusing, and increased heating, due to surface pitting. Thus, recanalization with sapphire probes occurs by a combination of photothermal and contact thermal effects that are localized to the probe tip and may reduce the degree of thermal injury associated with metal probes. Understanding these basic properties is important to the application and development of contact probes for laser recanalization.
对于传统导丝和球囊技术无法打通的闭塞血管，激光血管成形术或许能实现经皮再通。然而，金属激光热血管成形术探头可能因尖端温度过高（超过400℃）而导致过度热损伤。因此，目前正在评估用于一般激光手术的人工蓝宝石晶体制成的接触式探头在连续波Nd-YAG能量激光血管成形术中的应用。蓝宝石以多种方式改变激光能量，本文研究了五种圆形蓝宝石探头（SMTR、MTR、MTRL、OS、LT）的物理特性以及这些特性如何受到临床使用的影响。这些探头发射的激光束轮廓显示在尖端前方1-2毫米处有一个焦点。然而，Nd-YAG能量通过蓝宝石的向前传输各不相同（SMTR为85%；MTR为83%；MTRL为75%；OS为54%；LT为69%）。探头发热是由于蓝宝石内部的能量吸收。通过红外热成像在空气中测量蓝宝石的表面温度，并通过等温成像技术确定探头内最热区域的位置。在临床使用的能量设置下（20焦耳，10瓦，持续2秒），SMTR、MTR和MTRL探头的温度上升幅度（94-112℃）高于OS和LT探头（30℃），且发热集中在前一种探头的前表面。即使在更高能量下，蓝宝石的峰值温度仍低于金属探头。临床使用后，由于表面出现麻点，MTR探头的传输减少、光束散焦且发热增加。因此，蓝宝石探头的再通是通过光热和接触热效应的结合实现的，这些效应集中在探头尖端，可能会降低与金属探头相关的热损伤程度。了解这些基本特性对于激光再通接触式探头的应用和开发至关重要。
