The Bone Ablation Characteristics Of Laser Radiation In Ear Surgery

【Objective】Investigations on ablation threshold and thermal damage of human mastoid bone tissue by applying medical laser systems in vitro are presented. Investigations on ablation of bovine tibia with pulse CO2 laser in vitro are presented. The ablation effects were compared with the cutting effects of traditional surgical instruments.【Methods】1.In-vitro human mastoid bone were radiated by using pulse pulse CO2 laser and Er:YAG laser under fix-point ablation. Morphologic characteristics of the bone ablation crater were observed and measured by both tissue slicing and scanning electron microscopy.2.Two main techniques have been used for studying on pulse CO2 laser ablation,which we may call respectively the fix-point and dynamic scanning. Traditional surgical instruments were established as a control group. Morphologic characteristics of the bone ablation crater were observed by both stereoscopic microscopy and scanning electron microscopy, and measured by optical coherence tomography.【Results】Relations between varieties of bone ablation crater and thermal damage extension as well as change of laser energy density were obtained, mastoid bone ablation threshold by both pulse CO2 laser and Er:YAG laser were determined. The ablation effects of two methods were compared with the cutting effects of traditional surgical instruments and analysed.【Conclusion】1. The range of ablation thresholds which by applying pulse CO2 laser radiated mastoid bone tissue in vitro is 1.98～2.60J/cm2, the depth of thermal injury is about 14 ~ 90μm.2. The range of ablation thresholds which by applying Er:YAG laser radiated mastoid bone tissue in vitro is 0.46～1.19J/cm2, the depth of thermal injury is about 8～24μm.3. The results show that both pulse CO2 laser and Er:YAG laser are effective instruments to ablate mastoid bone tissue.4. Bone ablation effect by using pulse CO2 laser is similar to cutting effect by using electric drill and electric saw.5. Results of the study provide useful light dosimetry data for clinical application, and would benefit the application of laser ablation technology in ear surgery.