激光技术在医学领域中的新应用及我国的发展概况

1　在医学领域中的新应用1 960年美国科学家制造出世界第一台红宝石激光器 ,翌年立即用于临床治疗。激光技术在 40余年来取得了巨大成就。在医学领域内 ,激光技术已广泛应用于诊断、治疗及基础理论研究。由于激光器具有切割、凝固、气化、打孔、截骨等功能 ,目前已广泛应用于眼科、耳鼻喉科、皮肤科、普外科、神经外科和肿瘤科等。医用激光器作为手术治疗的器械 ,已充分显示了它无与伦比的优越性。近年在医学领域中的应用更是举世瞩目 ,拓展了临床应用 ,主要表现在以下一些范围中。1 .激光葡萄糖测定　美国 Spect Rt公司用激光无痛地在皮肤…     

激光技术在医学域领中的最新应用

1960年美国科学家制造出世界第一台红宝石激光器,翌年立即用于医疗。激光技术在40年来取得了巨大成就。在医学领域内,激光技术已广泛应用于诊断、治疗及基础理论研究。由于激光器具有切割、凝固、气化、打孔、截骨等功能,目前已广泛应用于眼科、耳鼻喉科、皮肤科、普外科、神经外科和肿瘤科等。医用激光器作为手术治疗的器械,已充分显示了它无与伦比的优越性。近年在医学领域中的应用更是举世瞩目,下面介绍几种激光技术最新应用情况。     

凑型准分子激光器的发展及其在医学中的应用

由于在绝缘材料和气体放电技术方面的进展,处于紫外波段的准分子激光器已经在工业、科学研究,特别是医学等领域成为主要应用工具。在本文中,我们将介绍新颖紧凑型准分子激光器在医学中的应用。此外,在文章中对紧凑型准分子激光器所采用的关键技术,诸如固态开关、电晕预电离和金属,陶瓷腔等技术进行了详细的讨论。     

凑型准分子激光器的发展及其在医学中的应用

由于在绝缘材料和气体放电技术方面的进展,处于紫外波段的准分子激光器已经在工业、科学研究,特别是医学等领域成为主要应用工具.在本文中,我们将介绍新颖紧凑型准分子激光器在医学中的应用.此外,在文章中对紧凑型准分子激光器所采用的关键技术,诸如固态开关、电晕预电离和金属/陶瓷腔等技术进行了详细的讨论.     

激光技术在医学发展中的地位

本文叙述了激光技术促进医学发展的几个方面：激光为分析细胞学提供了技术基础;激光推动现代分子生物学的发展;Ｘ激光将革新体视和显微成象技术;激光已成为解决临床治疗难题的有力武器。     

PCR技术及其在畜牧业中的应用

本文综述了PCR技术的来源、原理以及PCR技术的研究进展,此外还着重叙述了PCR技术在畜牧业中的应用及其展望,指出PCR技术在畜牧业中正发挥着越来越重要的作用。     

K T P 绿激光在医学临床中的应用

激光自被应用于医学,临床以来,科学家对其进行了多方面研究,并根据其特性,分别应用于医学诊断与治疗。随着科学技术的发展,在医学领域中应用的激光种类也越来越多,特别是KTP绿激光的多学科应用。为医学临床提供了新的治疗方法。本文就激光的特性、KTP绿激光的发展及医学,临床应用做一简要概述。     

氮分子激光对雄性小家鼠生殖细胞染色体畸变率的影响

激光是六十年代出现的一门新兴技术。它 具有能量高度集中、光色单一、方向性好等特 点。激光在农作物育种上的应用已有不少报 道^[1],并证明有一定的诱变作用。．在遗传效应 的研究方面,也先后在各种农作物上观察到激 光照射后能提高染色体畸变频率^[2]。在医学临 床上,利用激光治疗各种疾病,并进一步开展了 激光对生物和医学方面的基础理论研究^[3,4]。另 一方面,随着激光在工、农、医及国防方面应用 的不断发展,越来越多的人接触激光器。因此, 不同程度地受到激光照射,激光对人的眼睛、皮 肤和中枢神经系统的损伤已有不少报道^[5]。至 于激光照射其它器官,特别是生殖器官的作用 如何,目前还很少报道。由于激光对生殖细胞 的改应可能导致遗传效应,因此,具有特殊的重 要性。我们以染色体畸变为指标,研究了激光 对雄性小家鼠生殖细胞染色体畸变率的影响。     

微束激光转基因技术研究进展

本文叙述了激光微速穿刺法导入外源ＤＮＡ的基本原理及其有关影响因素等。利用该转化方法,现已成功地获得了多种动植物细胞外源基因的转化。实验证明,激光微束穿刺转化技术简便有效、重复性好、靶体选择性强,对靶体无损伤等优点。随着转化技术自动化水平的提高。光镊技术的渗透和结合,激光微束转化技术将会得到更广泛的应用     

激光陷阱及基在生物医学领域中的应用

激光陷阱及基在生物医学领域中的应用奇云,杜润才,王华（安徽省淮南职业医学专科学校,２３２００１）一、激光陷阶的光学理论激光具有动量,因此可对原子和其它中性粒子产生作用力。如果有具有某一特殊频率激光照射一个原子,该原子将会连续不断地吸收并发射光子。在原...     

Critical evaluation of indications for the holmium:YAG laser and the neodymium:YAG laser in orthopedic surgery based on an in vitro study]

This is an in vitro study of the biophysical effects of holmium:YAG and neodymium-YAG lasers that was prompted by the poor clinical results obtained with lumbar percutaneous laser discus decompression (PLDD). In the absence of adequate cooling, ablation of tissue with the holmium:YAG laser causes thermal damage to the surrounding tissues. Utilizing the immediate colour-independent laser coupling effect, the holmium:YAG laser removes soft and hard tissue immediately. The low tissue penetrating power (max. 0.32 mm), together with the use of irrigation, avoids thermal problems, and this laser type with its high pulse energy and frequency is to be recommended for arthroscopic surgery. In contrast, the effects of the neodymium:YAG laser are highly dependent on tissue colour. Using this laser on light-coloured tissue only diffuse warming but no ablation of soft tissue was often seen. The depth of tissue penetration seen in our study was 0.58 mm, but is greatly dependent on the duration of application, and is much larger with long application times. In conclusion, we believe that the neodymium:YAG laser is more suitable for percutaneous intradiscal procedures than the holmium:YAG laser. For arthroscopic surgery, the holmium:YAG laser will be the better choice. The effect of each type of laser depends not only on its physical properties, but also on tissue properties (light or dark-coloured, thermal conductivity) and duration of application.     

A comparative study of thermal effects of 3 types of laser in eye: 3D simulation with bioheat equation

The application of laser in ophthalmology and eye surgery is so widespread that hardly can anyone deny its importance. On the other hand, since the human eye is an organ susceptible to external factors such as heat waves, laser radiation rapidly increases the temperature of the eye and therefore the study of temperature distribution inside the eye under laser irradiation is crucial; but the use of experimental and invasive methods for measuring the temperature inside the eye is typically high-risk and hazardous. In this paper, using the three-dimensional finite element method, the distribution of heat transfer inside the eye under transient condition was studied through three different lasers named Nd:Yag, Nd:Yap and ArF. Considering the metabolic heat and blood perfusion rate in various regions of the eye, numerical solution of space–time dependant Pennes bioheat transfer equation has been applied in this study. Lambert–Beer's law has been used to model the absorption of laser energy inside the eye tissues. It should also be mentioned that the effect of the ambient temperature, tear evaporation rate, laser power and the pupil diameter on the temperature distribution have been studied. Also, temperature distribution inside the eye after applying each laser and temperature variations of six optional regions as functions of time have been investigated. The results show that these radiations cause temperature rise in various regions, which will in turn causes serious damages to the eye tissues. Investigating the temperature distribution inside the eye under the laser irradiation can be a useful tool to study and predict the thermal effects of laser radiation on the human eye and evaluate the risk involved in performing laser surgery.     

Measuring physical traits of primates remotely: the use of parallel lasers

Physical traits, such as body size, and processes like growth can be used as indices of primate health and can add to our understanding of life history and behavior. Accurately measuring physical traits in the wild can be challenging because capture is difficult, disrupts animals, and may cause injury. To measure physical traits of arboreal primates remotely, we adapted a parallel laser technique that has been used with terrestrial and marine mammals. Two parallel lasers separated by a known distance (4 cm) and mounted onto a digital camera are projected onto an animal. When a photograph is taken, the laser projections on the target provide a scale bar. We validated the technique for measuring the physical traits of identifiable red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda. First, we photographed the tails of monkeys with laser projections and compared these with measurements previously obtained when the animals were captured. Second, we manually measured the distance between two markers placed on tree branches at similar heights to those used by monkeys, and compared them with the measurements obtained through digital photographs of the markers with parallel laser projections. The mean tail length of the monkeys via manual measurements was 63.3+/-4.4 cm, and via remote measurements was 63.0+/-4.1 cm. The mean distance between the markers on tree branches via manual measurements was 13.8+/-3.59 cm, and via remote measurements was 13.9+/-3.58 cm. The mean error using parallel lasers was 1.7% in both cases. Although the needed precision will depend on the question asked, our results suggest that sufficiently precise measurements of physical traits or substrates of arboreal primates can be obtained remotely using parallel lasers.     

Automatic verification of SSD and generation of respiratory signal with lasers in radiotherapy: A preliminary study

PurposeSource to surface distance (SSD) plays a very important role in external beam radiotherapy treatment verification. In this study, a simple technique has been developed to verify the SSD automatically with lasers. The study also suggests a methodology for determining the respiratory signal with lasers.MethodsTwo lasers, red and green are mounted on the collimator head of a Clinac 2300 C/D linac along with a camera to determine the SSD. A software (SSDLas) was developed to estimate the SSD automatically from the images captured by a 12-megapixel camera. To determine the SSD to a patient surface, the external body contour of the central axis transverse computed tomography (CT) cut is imported into the software. Another important aspect in radiotherapy is the generation of respiratory signal. The changes in the lasers separation as the patient breathes are converted to produce a respiratory signal. Multiple frames of laser images were acquired from the camera mounted on the collimator head and each frame was analyzed with SSDLas to generate the respiratory signal.ResultsThe SSD as observed with the ODI on the machine and SSD measured by the SSDlas software was found to be within the tolerance limit. The methodology described for generating the respiratory signals will be useful for the treatment of mobile tumors such as lung, liver, breast, pancreas etc.ConclusionThe technique described for determining the SSD and the generation of respiratory signals using lasers is cost effective and simple to implement.     

激光辐照微生物的研究概况

应用激光辐照微生物的研究非常广泛。本文概述了激光辐照微生物的刺激效应的一些最新进展,同时,也就其可能机制进行了探讨。此外,还提出了在激光辐照微生物研究中的几个问题,旨在促进对激光诱变效应机制的深入和全面的了解,并进一步扩大其在生产实践中的应用。     

生物组织激光消融阈值的光谱特性

在一个宽光谱范围内研究不同激光作用下生物组织的消融,对理解激光与组织间相互作用及开发激光在外科的新应用有着极其重要的意义。其中消融阈值及其与激光波长的函数依赖关系是激光外科研究的重点。阐述了消融阈值的物理描述,并对消融阈值的波长依赖关系进行了初步探讨。     

A simplified physical model of pressure wave dynamics and acoustic wave generation induced by laser absorption in the retina

Shock waves have been proposed in the literature as a mechanism for retinal damage induced by ultra-short laser pulses. For a spherical absorber, we derive a set of linear equations describing the propagation of pressure waves. We show that the formation of shock fronts is due to the form of the absorber rather than the inclusion of nonlinear terms in the equations. The analytical technique used avoids the need for a Laplace transform approach and is easily applied to other absorber profiles. Our analysis suggests that the ’soft’ nature of the membrane surrounding retinal melanosomes precludes shock waves as a mechanism for the retinal damage induced by ultra-short pulse lasers. The quantitative estimates of the pressure gradients induced by laser absorption which are made possible by this work, together with detailed meso-scale or molecular modelling, will allow alternative damage mechanisms to be identified.     

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies

The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 10⁷. Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH₂F₂, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO₂ pump laser, and strength.     

Design and testing of low intensity laser biostimulator

Background

The non-invasive nature of laser biostimulation has made lasers an attractive alternative in Medical Acupuncture at the last 25 years. However, there is still an uncertainty as to whether they work or their effect is just placebo. Although a plethora of scientific papers published about the topic showing positive clinical results, there is still a lack of objective scientific proofs about the biostimulation effect of lasers in Medical Acupuncture. The objective of this work was to design and build a low cost portable laser device for stimulation of acupuncture points, considered here as small localized biosources (SLB), without stimulating any sensory nerves via shock or heat and to find out a suitable method for objectively evaluating its stimulating effect. The design is aimed for studying SLB potentials provoked by laser stimulus, in search for objective proofs of the biostimulation effect of lasers used in Medical Acupuncture.

Methods

The proposed biostimulator features two operational modes: program mode and stimulation mode and two output polarization modes: linearly and circularly polarized laser emission. In program mode, different user-defined stimulation protocols can be created and memorized. The laser output can be either continuous or pulse modulated. Each stimulation session consists of a pre-defined number of successive continuous or square pulse modulated sequences of laser emission. The variable parameters of the laser output are: average output power, pulse width, pulse period, and continuous or pulsed sequence duration and repetition period. In stimulation mode the stimulus is automatically applied according to the pre-programmed protocol. The laser source is 30 mW AlGaInP laser diode with an emission wavelength of 685 nm, driven by a highly integrated driver. The optical system designed for beam collimation and polarization change uses single collimating lens with large numerical aperture, linear polarizer and a quarter-wave retardation plate. The proposed method for testing the device efficiency employs a biofeedback from the subject by recording the biopotentials evoked by the laser stimulus at related distant SLB sites. Therefore measuring of SLB biopotentials caused by the stimulus would indicate that a biopotential has been evoked at the irradiated site and has propagated to the measurement sites, rather than being caused by local changes of the electrical skin conductivity.

Results

A prototype device was built according to the proposed design using relatively inexpensive and commercially available components. The laser output can be pulse modulated from 0.1 to 1000 Hz with a duty factor from 10 to 90 %. The average output power density can be adjusted in the range 24 - 480 mW/cm2, where the total irradiation is limited to 2 Joule per stimulation session. The device is controlled by an 8-bit RISC Flash microcontroller with internal RAM and EEPROM memory, which allows for a wide range of different stimulation protocols to be implemented and memorized. The integrated laser diode driver with its onboard light power control loop provides safe and consistent laser modulation. The prototype was tested on the right Tri-Heater (TH) acupuncture meridian according to the proposed method. Laser evoked potentials were recorded from most of the easily accessible SLB along the meridian under study. They appear like periodical spikes with a repetition rate from 0.05 to 10 Hz and amplitude range 0.1 - 1 mV.

Conclusion

The prototype's specifications were found to be better or comparable to those of other existing devices. It features low component count, small size and low power consumption. Because of the low power levels used the possibility of sensory nerve stimulation via the phenomenon of shock or heat is excluded. Thus senseless optical stimulation is achieved. The optical system presented offers simple and cost effective way for beam collimation and polarization change. The novel method proposed for testing the device efficiency allows for objectively recording of SLB potentials evoked by laser stimulus. Based on the biopotential records obtained with this method, a scientifically based conclusion can be drawn about the effectiveness of the commercially available devices for low-level laser therapy used in Medical Acupuncture. The prototype tests showed that with the biostimulator presented, SLB could be effectively stimulated at low power levels. However more studies are needed to derive a general conclusion about the SLB biostimulation mechanism of lasers and their most effective power and optical settings.     

Investigation of thermal distribution for pulsed laser radiation in cancer treatment with nanoparticle-mediated hyperthermia

In this paper, we have simulated the efficacy of gold/gold sulfide (GGS) nanoshells in NIR laser hyperthermia to achieve effective targeting for tumor photothermal therapy. The problem statement takes into account the heat transfer with the blood perfusion through capillaries, and pulsed laser irradiation during the hyperthermia. Although previous researchers have used short laser pulses (nanosecond and less), in order to prevent heat leakage to the neighbor tissues, we have examined the effect of millisecond pulses, as the extent of the target volume to which hyperthermia is induced is usually larger and also the lasers with this specification are more available. A tumor with surrounding tissue was simulated in COMSOL software (a finite element analysis, solver and simulation software) and also in a phantom made of agarose and intralipid. The tumor was irradiated by 10, 20 and 30 laser pulses with durations of 15, 50 and 200 ms and fluences of 20, 40 and 60 J/cm². Experimental tests performed on a phantom prove the ability of the applied numerical model to capture the temperature distribution in the target tissue. We have shown that our simulation permits prediction of treatment outcome from computation of thermal distribution within the tumor during laser hyperthermia using GGS nanoshells and millisecond pulsed laser irradiation. The advantage of this simulation is its simplicity as well as its accuracy. Although, to develop the model completely for a given organ and application, all the parameters should be estimated based on a real vasculature of the organ, physiological conditions, and expected variation in those physiological conditions for that application in the organ.