Theramal, mechanical, optical, and morphologic changes in bovine nucleus pulposus induced by Nd:YAG (lambda = 1.32 microm) laser irradiation.
Theramal, mechanical, optical, and morphologic changes in bovine nucleus pulposus induced by Nd:YAG (lambda = 1.32 microm) laser irradiation.
复制标题
Nd:YAG（λ = 1.32 微米）激光照射引起的牛髓核的热、机械、光学和形态变化。
DOI：
10.1002/lsm.1046
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Wong,BJ
中科院分区：
文献类型：
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作者：
Choi,JY;Tanenbaum,BS;Milner,TE;Dao,XV;Nelson,JS;Sobol,EN;Wong,BJ
背景和目的探讨激光减压手术中光热加热对椎间盘突出的生物物理效应。研究设计/材料和方法用Nd：YAG激光（λ = 1.32μm，曝光时间100秒，9-31W/cm2，光斑直径4.8mm）照射离体牛髓核标本，组织热、机械和光学发生变化分别通过红外辐射测量、组织张力测量和氦氖探针激光器的漫反射来监测特性。通过记录激光照射前后的形状变化和称重样本来监测形态变化和质量减少。结果在功率密度低于 20 W/cm2 时，在照射过程中，视频中一致观察到水蒸发和样本体积减少（收缩）。相反，超过 20 W/cm2 时，样品基质内会形成蒸汽泡，随后破裂（释放出加热的蒸汽）。当辐射表面温度接近约 60 至 70°C（组织变性阈值）时，组织张力开始增加，这与标本长度减少的观察结果一致。组织张力的这种变化的开始也反映在漫反射率的特征改变中。随着激光照射的停止，观察到组织张力持续增加，这与标本长度和体积的变化一致。较高的激光功率会导致更快的加热速率，从而加速张力变化。当辐照度为 9-31 W/cm2 时，样品质量减少量分别从初始质量的 19% 增加到 72%。与风干样本（24 小时）相比，经过辐照的样本在盐水中浸泡（48 小时）后没有恢复到原来的形状和大小。结论这些观察结果表明，光热加热会导致不可逆的基质改变，导致形状变化和体积减小（在视频中观察到，并通过组织张力的增加证明），发生在大约 65°C 的温度下。由于高激光功率会导致气泡形成和样品撕裂，因此必须控制加热过程。漫反射测量提供了一种非接触式、高灵敏度的方法来动态监测核张力的变化。激光外科。医学。 28:248–254, 2001。© 2001 Wiley-Liss, Inc.
Background and ObjectiveTo examine the biophysical effects of photothermal heating on herniated intervertebral discs during laser decompression surgery.Study Design/Materials and MethodsEx vivo bovine nucleus pulposus specimens were irradiated with a Nd: YAG laser (λ = 1.32 μm, 100 seconds exposure time, 9–31 W/cm2, 4.8 mm spot diameter), whereas changes in tissue thermal, mechanical, and optical properties were monitored by using, respectively, infrared radiometry, tissue tension measurements, and diffuse reflectance from a HeNe probe laser. Morphologic changes and mass reduction were monitored by recording shape changes on video and weighing specimens before and after laser exposure.ResultsAt power densities below 20 W/cm2, evaporation of water and specimen volume reduction (shrinking) were consistently observed on video during irradiation. In contrast, above 20 W/cm2, vapor bubbles formed within the specimen matrix and subsequently ruptured (releasing heated vapors). When radiometric surface temperature approaches approximately 60 to 70°C (denaturation threshold for tissue), tissue tension begins to increase, which is consistent with observations of specimen length reduction. The onset of this change in tissue tension is also reflected in characteristic alterations in diffuse reflectance. With cessation of laser irradiation, a sustained increase in tissue tension is observed, which is consistent with changes in specimen length and volume. Higher laser power results in a faster heating rate and subsequently an accelerated tension change. Specimen mass reduction increased with irradiance from 19 to 72% of the initial mass for 9–31 W/cm2, respectively. Irradiated specimens did not return to their original shape after immersion in saline (48 hours) in contrast to air‐dried specimens (24 hours), which returned to their original shape and size.ConclusionThese observations suggest that photothermal heating results in irreversible matrix alteration causing shape change and volume reduction (observed on video and evidenced by the increase in tissue tension) taking place at approximately 65°C. Inasmuch as high laser power results in vapor bubble formation and specimen tearing, the heating process must be controlled. Diffuse reflectance measurements provide a noncontact, highly sensitive means to monitor dynamically changes in tension of nucleus purposus. Lasers Surg. Med. 28:248–254, 2001. © 2001 Wiley‐Liss, Inc.