Poppas D P, Stewart R B, Massicotte J M, Wolga A E, Kung R T, Retik A B, Freeman M R
Department of Surgery, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Lasers Surg Med. 1996;18(4):335-44. doi: 10.1002/(SICI)1096-9101(1996)18:4<335::AID-LSM2>3.0.CO;2-T.
Laser surgical procedures involving photocoagulation of soft tissue have relied on subjective visual endpoints. The thermal damage to the denatured tissue in these procedures is highly dependent on the tissue temperatures achieved during laser irradiation. Therefore, a system capable of real time temperature monitoring and closed loop feedback was used to provide temperature controlled photocoagulation (TCPC).
STUDY DESIGN/MATERIALS AND METHODS: The TCPC system consisted of a 1.32 microns Nd:YAG laser, an infrared thermometer, and a microprocessor for data acquisition and feedback control. A porcine skin model was used. Tissue welds were completed to evaluate the photocoagulation effects at different predetermined temperatures. A quantitative measurement of tissue photocoagulation was obtained by tensile strength measurements of the laser repairs. Histology of the irradiated tissue was used to determine the extent of thermal injury associated with different photocoagulation temperatures.
The TCPC system was capable of maintaining a relatively constant temperatures (+/- 4 degrees C) during laser irradiation. The tensile strengths of acute repairs increased with temperature over the range studied (65-95 degrees C). Tensile measurements made after several days of healing showed that higher temperature (95 degrees C) welds had lower strengths than repairs completed at lower (65 degrees C or 75 degrees C) temperatures and were significantly lower at 3 days. Acute histology showed that the amount thermal damage was strongly dependent on the tissue temperature and increased both in tissue depth and lateral to the repair with temperature. The histologic results suggest that the increase in the acute repair tensile strength as the weld temperature increased was due to an increase in the depth of tissue photocoagulation. The increase in the lateral tissue injury measured histologically for higher temperature welds likely resulted in the decreased chronic tensile strengths, as a healing response to excessive thermal damage.
Tissue temperatures can be controlled during laser photocoagulation of skin. The degree of acute and chronic tissue damage is highly dependent on the temperature during welding. By controlling the tissue temperature during laser procedures, the surgical outcome can be more reliably predicted and reproduced, as compared to the conventional open loop methods. In addition, the use of a TCPC system should significantly reduce the learning curve for photothermal surgical procedures.
涉及软组织光凝的激光外科手术一直依赖主观视觉终点。在这些手术中，对变性组织的热损伤高度依赖于激光照射期间达到的组织温度。因此，使用一种能够进行实时温度监测和闭环反馈的系统来提供温度控制光凝（TCPC）。
研究设计/材料与方法：TCPC系统由一台1.32微米的Nd:YAG激光、一个红外温度计以及一个用于数据采集和反馈控制的微处理器组成。使用猪皮肤模型。完成组织焊接以评估在不同预定温度下的光凝效果。通过对激光修复处的拉伸强度测量获得组织光凝的定量测量结果。对受照射组织进行组织学检查以确定与不同光凝温度相关的热损伤程度。
TCPC系统能够在激光照射期间保持相对恒定的温度（±4摄氏度）。在所研究的温度范围（65 - 95摄氏度）内，急性修复的拉伸强度随温度升高而增加。愈合数天后进行的拉伸测量表明，较高温度（95摄氏度）的焊接强度低于在较低温度（65摄氏度或75摄氏度）下完成的修复，且在3天时显著更低。急性组织学显示，热损伤量强烈依赖于组织温度，并且随着温度升高，在组织深度和修复部位的横向都有所增加。组织学结果表明，随着焊接温度升高急性修复拉伸强度增加是由于组织光凝深度增加。对于较高温度焊接，组织学测量的横向组织损伤增加可能导致慢性拉伸强度降低，这是对过度热损伤的一种愈合反应。
在皮肤激光光凝过程中可以控制组织温度。急性和慢性组织损伤程度高度依赖于焊接期间的温度。与传统的开环方法相比，通过在激光手术过程中控制组织温度，可以更可靠地预测和重现手术结果。此外，使用TCPC系统应能显著缩短光热外科手术的学习曲线。
