共查询到19条相似文献,搜索用时 109 毫秒
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XeCl准分子激光消融几种生物组织的实验结果 总被引:2,自引:2,他引:0
本文报道了308nmXeCl准分子激光对人牙硬组织和猪肉软组织消融的实验研究结果,在国内首次开展了XeCl准分子激光牙科应用的基础研究,为准分子激光在牙科的临床应用提供了实验依据。 相似文献
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本文从组织光学的角度 ,对激光照射血液疗法中的发展现状与存在问题进行分析 ,提出该领域应开展的若干研究内容。本文开展了激光照射血液疗法所涉及的若干组织光学研究。获得了中国人血液的吸收系数、散射系数、各项异性因子、全衰减系数等 ;研究获得了人血管的若干光学参数。通MonteCarlo模拟计算 ,以及实验测试结果 ,分别从理论与实际上分析对比了激光血管内照射时 ,光在人体血管、血液中的分布情况 ,以及不同的激光入射角 ,发散角 ,不同的血管直径等因素对激光血液照射的影响。根据对应的组织光学的研究结果 ,文中还讨论并提出… 相似文献
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光声成像和激光诱导击穿光谱技术(LIBS)是近些年在成像领域发展非常迅速的两种技术,在医学影像学方面有着巨大的潜力。当激光照射到组织时,组织表面会同时产生光声信号和等离子体,光声信号携带着生物组织内光吸收的特征信息,等离子体特征光谱也可以示踪组织内的元素信息。本文总结了两种技术的研究背景和成像原理,然后,通过对光声成像和LIBS成像模式进行分析,进一步展现了两种技术结合的可能性,并介绍了它们在病理切片成像和组织金属元素示踪等领域的应用。最后,我们对两种技术结合的双模态成像系统进行了深入的探讨和展望,以期其在医学诊断和图像领域发挥重要作用。 相似文献
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叶丽君刘鲁川 《现代生物医学进展》2011,11(5):992-994
随着科学技术的进步,激光技术正以惊人的速度向前发展。激光具有许多优异的性能,已被应用到人类生活的各个领域。伴随激光医学的进展,近来在口腔医学方面的研究已逐步开展起来,除了应用于口腔软组织处理外,激光用于牙体硬组织也得到了越来越多的关注。其中Er-YAG激光在口腔领域的实用性和安全性已得到多方面的认证。该文就激光在口腔医学特别是牙体硬组织中的应用作一综述。 相似文献
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The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation.
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The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (ArF, lambda = 193 nm) and krypton fluorine (KrF, lambda = 248 nm) excimer laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not cause material removal, the stress transients are consistent with rapid thermal expansion of the tissue. At the threshold radiant exposure for ablation, the peak stress amplitude generated by 248 nm irradiation is more than an order of magnitude larger than that produced by 193 nm irradiation. For radiant exposures where material removal is achieved, the temporal structure of the stress transient indicates that the onset of material removal occurs during irradiation. In this regime, the variation of the peak compressive stress with radiant exposure is consistent with laser-induced rapid surface vaporization. For 193 nm irradiation, ionization of the ablated material occurs at even greater radiant exposures and is accompanied by a change in the variation of peak stress with radiant exposure consistent with a plasma-mediated ablation process. These results suggest that absorption of ultraviolet laser radiation by the extracellular matrix of tissue leads to decomposition of tissue on the time scale of the laser pulse. The difference in volumetric energy density at ablation threshold between the two wavelengths indicates that the larger stresses generated by 248 nm irradiation may facilitate the onset of material removal. However, once material removal is achieved, the stress measurements demonstrate that energy not directly responsible for target decomposition contributes to increasing the specific energy of the plume (and plasma, when present), which drives the gas dynamic expansion of ablated material. This provides direct evidence that ultraviolet laser ablation of soft biological tissues is a surface-mediated process and not explosive in nature. 相似文献
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Thermodynamic response of soft biological tissues to pulsed infrared-laser irradiation. 总被引:1,自引:0,他引:1
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The physical mechanisms that achieve tissue removal through the delivery of short pulses of high-intensity infrared laser radiation, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed infrared laser irradiation was investigated by measuring and analyzing the stress transients generated by Q-sw Er:YSGG (lambda = 2.79 microns) and TEA CO2 (lambda = 10.6 microns) laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not produce material removal, the stress transients are consistent with thermal expansion of the tissue samples. The temporal structure of the stress transients generated at the threshold radiant exposure for ablation indicates that the onset of material removal is delayed with respect to irradiation. Once material removal is achieved, the magnitude of the peak compressive stress and its variation with radiant exposure are consistent with a model that considers this process as an explosive event occurring after the laser pulse. This mechanism is different from ArF- and KrF-excimer laser ablation where absorption of ultraviolet radiation by the collagenous tissue matrix leads to tissue decomposition during irradiation and results in material removal via rapid surface vaporization. It appears that under the conditions examined in this study, explosive boiling of tissue water is the process that mediates the ablation event. This study provides evidence that the dynamics and mechanism of tissue ablation processes can be altered by targeting tissue water rather than the tissue structural matrix. 相似文献
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Precise ablation of metals using tightly focused femtosecond laser pulses with intensities close to the damage threshold can
yield sub-wavelength, nanometer-sized holes or craters. These structures in metals can exhibit plasmonic effects, thereby
affecting the interactions involved. We numerically simulate light propagation inside such holes and model the ablation process.
We show that surface plasmon resonances can be excited at near-infrared and visible wavelengths. At resonance wavelengths,
significant enhancement of aspect ratio is possible. Our results show that plasmonic effects are essential for the understanding
of precision laser processing of metals, and they can be exploited to significantly enhance the performance of laser micro-
and nano-machining. 相似文献
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A comparison between laser ablation of nickel in vacuum by using 532-and 1064-nm Nd:YAG (Yttrium Aluminium Garnet) laser wavelengths,
with an intensity of 5 × 109 W/cm2, is reported. Nanosecond pulsed ablation produces high nonisotropic emission of neutrals and ionic species. For 532-nm laser
irradiation, mass quadrupole spectrometry, coupled to electrostatic ion deflection and time-of-flight measurements, allows
estimation of the energy distributions of the emitted species from plasma. For 1064-nm laser ablation, a cylindrical electrostatic
ion analyzer permits one to measure the yield and the charge state of the emitted ions and reconstruct the ion energy and
charge state distributions. Neutrals show typical Boltzmann-like distributions, while ions show Coulomb-Boltzmann-shifted
distributions depending on their charge state. Surface profiles of the ablated craters permitted study of the ablation threshold
and yields of nickel in vacuum versus the laser fluence. The plasma temperature was evaluated using experimental data. Special
regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at
nonequilibrium plasma conditions and the angular distribution of the emitted species.
Published in Russian in Fizika Plazmy, 2008, Vol. 34, No. 7, pp. 598–606.
The text was submitted by the authors in English. 相似文献
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目的 :研究 10 64nm和 53 2nm波长激光在激光能量为 14 0mJ/pulse(脉冲 )时对犬心肌切割效率。方法 :用Q开关Nd :YAG 10 64和 53 2nm波长脉冲激光分别照射犬离体和在体心肌组织 ,光学显微镜和偏振光学显微镜行组织学分析 ,观察不同条件下激光切割组织的深度和光热对组织的损伤。结果 :离体和在体实验 ,10 64nm波长激光的切割效率高于 53 2nm(p <0 .0 1)。在体和离体实验显示 10 64nm激光能量和重复率相同时 ,所致的切割效率无明显差异 (p >0 .0 5) ,血液对 10 64nm激光的切割效率影响较小。相反 ,在 53 2nm时血液对其影响较大 ,相同的激光能量和重复率 ,离体实验切割效率高于在体 (p <0 .0 1)。 10 64nm激光所致的光热和机械损伤均轻于 53 2nm激光。结论 :在切割效率方面 ,10 64nm激光比 53 2nm更适用于TMLR。 10 64nmQ开关Nd :YAG激光可通过光导纤维传输 ,是TMLR的一个有潜力的激光源 相似文献
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PurposeTo explore the relationship between ablation parameters of myopic laser surgery and measurement area of wavefront aberration (WA) with Hartmann-Shack wavefront sensor.Methods58 subjects undergone myopic laser surgeries and 74 uncorrected myopic subjects were enrolled in this experiment. The laser ablation parameters were obtained from surgical records, which included spherical error (Rx), depth, and optical zone (OZ) of ablation. The measured area of WA was tested by the WASCA, and the real pupil size was tested by Pentacam. The corneal eccentricity (E value) and curvature was also measured with the Pentacam. All the measurements were performed under mydriatic condition.ResultsFor uncorrected myopic eyes, the measured area of WA was similar with the real pupil size. But for the corrected eyes, the measured area of WA was smaller than the real pupil size with a mean difference of 0.66 ± 0.54 mm for moderate myopia (t = 6.45, p < 0.0001) and 1.76 ± 0.55 mm for high myopia (t = 18.92, p < 0.0001), but not for mild myopia. The Rx (t = -3.20, p = 0.0017), OZ (t = 64.4, p < 0.0001) and postoperative corneal E value (t = 2.52, p = 0.017) were the independent factors of measured area of WA. Measured area of WA = -0.81*Rx + 1.13*OZ + 0.49*postoperative corneal E value (r2 = 0.997).ConclusionsThe WASCA has a limitation in measuring wavefront aberration over the whole pupil area when it’s used for patients received myopic laser surgery. The measured area is smaller than the real pupil size and depends linearly on ablation depth, optical zone and corneal eccentricity. 相似文献
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The effects of rearing conditions on the functional recovery of wind-sensitive giant interneurons (GIs) after unilateral cercal ablation were investigated in the cricket, Gryllus bimaculatus. Crickets were reared in a glass vials to prohibit free walking for 14 days after unilateral cercal ablation ("14-day vial" crickets). Other crickets were reared in an apparatus called a "walking inducer" (WI) to increase the walking distance during the same 14-day period ("14-day WI" crickets). In these crickets, the response properties of GIs 8-1, 9-1, 9-2, and 9-3 to air currents from various directions were investigated. From the intensity-response curves obtained, directionality curves expressed in terms of threshold velocity and response magnitude were made independently. To understand changes in the functional recovery of GIs more thoroughly, the directional characteristics of GIs in crickets 1 day after unilateral cercal ablation ("1-day free" crickets) were also compared. Between the 1-day free and 14-day vial crickets, all the GIs showed differences in both threshold velocity and response magnitude for some stimulus directions. Between the 14-day vial and 14-day WI crickets, differences in the threshold velocities of GIs 9-1, 9-2, and 9-3, and in the response magnitudes of GIs 8-1, 9-1, and 9-3 were detected. Because the rearing condition after unilateral cercal ablation largely affects the compensatory recovery in some parameters of wind-evoked escape behavior, such as relative occurrence and escape direction, we discuss the functional differences in GIs revealed here in relation to the roles of GIs in the neural system that controls escape behavior. 相似文献
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目的:观察Q值调整非球面切削与标准化LASIK术后不同角膜直径下的角膜的非球面变化来分析Q值引导个性化切削技术的临床效果。方法:前瞻性研究。随机选取2010年至2011年来我院就诊的准分子手术患者35例68眼,分别进行标准化LASIK(S组:17例34眼)和Q值调整个体化LASIK(Q组:18例34眼)矫治。术前2组各项指标均相似,差异无统计学意义。术前屈光度数分别为标准组球镜平均值为-4.76±2.02D(-1.5D~-9.75D),柱镜平均值为-0.71±0.7D(0~-2.5D)和Q值个体化组球镜平均值为-4.78±2.21D(-1.5~-9.5D),柱镜平均值为-0.84±0.55D(0~-2.5D)两组,对比两组非球面切削与标准化LASIK术后1个月不同角膜直径下的Q值及△Q。结果:两组术前Q10、Q15、Q20、Q25、Q30平均值分别为标准组:-0.12、-0.17、-0.20、-0.25、-0.30,Q值个体化组:-0.14、-0.19、-0.22、-0.27、-0.32.。术后一个月两组的△Q(△Q=Qpost-Qpre)△Q10、△Q15、△Q20、△Q25、△Q30分别为标准组:0.58、0.88、1.08、1.10、0.85,Q值个体化组,0.39、0.75、1.03、1.10、0.84。△Q10和△Q15术前术后变化在角膜直径为3.5mm之内时的差异有统计学意义。结论:Q值调整的个体化准分子激光原位角膜磨镶术术后角膜非球面变化与标准组相比皆由术前的长椭圆型Q值向扁椭圆型变化,但Q值调整的个体化组在角膜中央区的扁椭圆变化小于标准组,尤其在角膜中央3.5mm。说明Q值调整的个体化LASIK组在角膜中央区比标准组具有优势。 相似文献
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目的:探讨右肺动脉神经节丛(RPVGP)消融对胆碱能及儿茶酚胺诱发房颤的影响。方法:20只犬麻醉开胸后,暴露RPVGP,分别在消融RPVGP前后,经股静脉静滴乙酰胆碱(ACh)及儿茶酚胺。测量房颤诱发率及两类递质诱发房颤的阈浓度。结果:RPVGP消融前,静滴Ach和异丙基肾上腺素(IPA)及肾上腺素(EPI)(1~100μmol/l)均可诱发AF,诱发率100%。Ach、IPA和EPI的诱发阈浓度分别为2.6±0.3μmol/l,3.3±0.2μmol/l,5.6±0.2μmol/l。RPVGP消融后,Ach及儿茶酚胺的AF诱发率分别降至10%及35%,且三种递质的诱发阈浓度分别提高至2.6±0.3μmol/l、22.5±2.4μmol/l和26.±2.6μmol/(lP〈0.05)。结论:消融RPVGP使乙酰胆碱和儿茶酚胺诱发房颤的阈浓度增高,并降低此二类介质的房颤诱发率。 相似文献