Gholami Asghar, Baradaran-Ghahfarokhi Molood, Ebrahimi Marjan, Baradaran-Ghahfarokhi Milad
Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, Iran.
Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, Iran ; Medical Student's Research Center, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
J Med Signals Sens. 2013 Oct;3(4):262-8.
In recent years, interest in medical application of lasers especially as a surgical alternative is considerably increasing due to their distinct advantages such as non-contact intervention, bacteriostasis, less traumatization, minimal invasiveness, decreased bleeding and less heat damage. The present study aimed to evaluate the temperature changes and the consequent released thermal stress in cortical bone caused by an Erbium:yttrium aluminum garnet (Er:YAG) laser (Fideliss 320A, Fotona Inc., Deggingen, Germany) during osteotomy, using mathematical computation by means of Maple software, version 9.5 (Maplesoft, a division of Waterloo Maple Inc., Canada). The results obtained here were compared with the experimental measurements using Er:YAG laser in the osteotomy clinics. A bone slab with thickness of 1 mm was simulated in Maple software. Then, an Er:YAG laser emitting 100 μs pulses at a wavelength of 2940 nm were modeled. Two different clinical settings of the Er:YAG laser with 200 mJ and 400 mJ energies, both with 100 μs exposure and 500 μs silence were studied. To investigate the temperature distribution in the cortical bone, the time-dependent heat conduction equations were defined and solved in the Maple software. Finally, by defining the heat distribution function in the Maple, thermal stress in the bone was investigated. Results of the computations showed that, on the bone irradiated area (center of the bone surface) the maximum temperature rise was 0.8°C and 1.6°C, for 200 mJ and 400 mJ Er:YAG laser exposure, respectively. The temperature rise reached to its minimum at radial distances of 1.2 cm from the point of irradiated area for 200 mJ laser while it was 1.5 cm for 400 mJ laser. For 200 mJ laser the maximum derived radial (σ rr ), axial (σ zz ) and azimuthally (σ θθ ) stress components were 0.20, 0.16 and 0.08 MPa, respectively. While, for 400 mJ laser the maximum derived σ rr , σ zz and σ θθ stress components were 0.39, 0.31 and 0.16 MPa, respectively. These results confirm that use of 100 μs Er:YAG laser pulses with 500 μs silence at 200 and 400 mJ energies minimizes thermal tissue damage for the laser osteotomies, without continued water cooling (irrigation) on the exposed area.
近年来，由于激光具有非接触干预、抑菌、创伤小、侵入性极小、出血少和热损伤小等显著优势，其在医学应用尤其是作为一种手术替代方法方面的关注度大幅上升。本研究旨在通过使用Maple软件9.5版（Maplesoft，加拿大滑铁卢Maple公司的一个部门）进行数学计算，评估铒：钇铝石榴石（Er:YAG）激光（Fideliss 320A，德国Deggingen的Fotona公司）在截骨过程中引起的皮质骨温度变化以及随之产生的热应力释放情况。将此处获得的结果与在截骨临床中使用Er:YAG激光的实验测量结果进行比较。在Maple软件中模拟了厚度为1毫米的骨板。然后，对发射波长为2940 nm、脉冲宽度为100 μs的Er:YAG激光进行建模。研究了Er:YAG激光两种不同的临床设置，能量分别为200 mJ和400 mJ，曝光时间均为100 μs，间隔时间均为500 μs。为了研究皮质骨中的温度分布，在Maple软件中定义并求解了随时间变化的热传导方程。最后，通过在Maple中定义热分布函数，研究了骨中的热应力。计算结果表明，在骨照射区域（骨表面中心），200 mJ和400 mJ的Er:YAG激光曝光时，最高温度分别升高了0.8°C和1.6°C。对于200 mJ的激光，在距照射区域点径向距离为1.2 cm处温度升高达到最小值，而对于400 mJ的激光，该距离为1.5 cm。对于200 mJ的激光，最大导出径向（σrr）、轴向（σzz）和周向（σθθ）应力分量分别为0.20、0.16和0.08 MPa。而对于400 mJ的激光，最大导出σrr、σzz和σθθ应力分量分别为0.39、0.31和0.16 MPa。这些结果证实，在200和400 mJ能量下使用脉冲宽度为100 μs、间隔时间为500 μs的Er:YAG激光脉冲，在不持续对暴露区域进行水冷（冲洗）的情况下，可将激光截骨时的热组织损伤降至最低。
