Types of medical lasers

The knowledge about different types of lasers and their potential use in medicine is presented. A very rapid development of laser technology in the world imposes a need for up-to-date information about the characteristics of different laser instruments. Without this kind of information it would be difficult to keep in touch with the latest developments in the world's technology. Different types of lasers have different indication range in the medical practice. An inquiry into the fundamental principles of lasers physics is an important prerequisite for successful application of this technology in medicine. Laser as a surgical knife has shown certain advantages over scalpel, electrocautery and cryosurgery, as the laser surgery is a noncontact method, bloodless, precise, with better visualization, minimal postoperative edema, painless healing, without complications. Although laser cannot entirely replace conventional surgical instruments, it is still the instrument of choice for treatment of numerous pathological conditions. The carbon dioxide laser is a highly precise, bloodless light scalpel used for incising and excising tissues and sealing small blood vessels. The infrared beam at 10,600 nm wavelength is absorbed by water and tissue destruction is due to the instantaneous vaporization at relatively low temperature of 100 degrees C. The beam seals blood vessels of up to 0.5 mm in diameter and if the beam is defocused, larger vessels may be controlled. The beam also seals lymphatics, possibly reducing the spread of tumour cells by this route, and seals nerve endings: there is no incidence of neuroma formation. Carbon dioxide laser has shown a great efficiency in otorhinolaryngology, in maxillo-facial surgery and plastic surgery, in urology and gynecology. Provides true "no touch" surgery, and is used increasingly in neurosurgery for the precise atraumatic removal of tissue and for creation of precise lesions for the control of pain. The carbon dioxide laser beam cannot, at present, be transmitted via a flexible fibre, although a number of fibres are being investigated. Delivery of laser energy to microscope, colposcope or handpiece is via an articulated arm which is a hollow tube with mirrors at the articulations. The argon laser produces blue-green coherent light at a number of wavelengts but 80% of the energy is at wavelengths of 488 and 514 nm. This laser was first used in ophtalmology to treat diabetic retinopathy through, and without damage to, the clear anterior parts of the eye. The argon laser is used for blood vessel coagulation but can be used to perform slow, thermal tissue destruction at higher power levels. Argon laser is most commonly used in ophthalmology for otological micro-surgery, particularly in the treatment of otosclerosis and tympanosclerosis. Very good results have been achieved in the argon laser treatment of gastrointestinal bleeding ulcers, vascular lesions and polyps. Dermatology is another field where argon laser has shown great efficiency: hemangyomas, telangiectasias, tattoos, small benign and malignant tumours are amenable to argon laser treatment. In neurosurgery it is used to control both normal and abnormal blood vessels but at present much work on treatment of arteriovenous malformations and aneurysms is experimental. Both the argon laser energy can be transmitted via flexible fibre optic delivery system which can then be attached to an operating microscope, slit lamp, endoscope delivery fibre or handpiece. The Neodymium-YAG laser is used both for tissue destruction with good haemostasis and for the control of normal and abnormal blood vessels. This laser produces infrared coherent light at 1060 nm wavelength, which is deeply absorbed in the tissues without colour or tissue specificity. Neodymium-YAG laser is mostly used in tracheobronchial, gastrointestinal and urologic pathology in the treatment of stenoses, granulomas, benign tumours, and for reduction of malignant tumours. (ABSTRACT TRUN     

Diagnostic and biostimulating lasers

In this brief report authors present data regarding the application of diagnostic and biostimulating laser instruments in medicine. For diagnostic purposes there are several types of laser instruments and procedures available: Laser Microscopic Masonic Analyzer (LAMMA), Flow cytometry. Doppler effects of laser rays (Laser Doppler velocytometry, Laser Doppler spermokhinezymetry, Laser Doppler spectrometry), Laser fluorescent microscopy, Laser nephelometry, Transilumination by lasers (diaphanography), Laser spectroscopy, Laser holography, Laser rethinoscopy, Microirradiation by lasers. Literary data concerning favorable effects of low power laser radiation on series of diseases covering different medical specialties are cited, pointing to possibility of significant enrichment of already available arsenal of physical methods, thera-pies and rehabilitation procedures. Mechanisms of biostimulation of human tissues and organs under low power laser radiation are also presented. All these stimulatory and regulatory mechanisms of the cell metabolism are involved in the wound epitelization, reduction of edema and inflammation and reestablishement of arterial, venous and lymph microcirculation and consequently inducing better tissue nutrition. The use of laser spectroscopy for quantitative analysis of cations from a single drop of dried blood on a piece of filter paper was not realized, although individual analyses of frozen skin biopsies for calcium, arsenic and gold were accomplished. In Europe, this technique has also found its application in forensic medicine. Furthermore, laser-based methods have been used to study air pollution with carcinogens in occupational exposures and also for the detection of narcotic drugs. Laser cytofluorometry utilizes the argon laser for scanning of single stained cells and has achieved utilization in mass examination programs for Pap-smear determinations. The same technique is used in cell sorting system that is now important in monoclonal antibody determination in hybridoma technology. Other possible diagnostic applications include laser particle size measurement techniques, and laser nephelometry for determination of immunoglobulins classes and autoantibodies such as rheumatoid factors. Laser Doppler velocimetry is used to measure blood flow by means of a simple probe that rests on the lip. Biostumulating laser instruments The world famous Hungarian scientist Mester Endre, from Budapest, is one of the pioneers with the greatest experimental and clinical experience in the use of biostimulating effects of lasers. His former student, O. Ribari first used biostimulating effects of He-Na laser (390 mJ power) for the epitelization of perforated tympanic membrane and treatment of postoperative fistulas of the neck and of the mastoid. Generally speaking, biostimulating effect of low level laser treatment (LLLT) is in its anti-inflammatory, analgesic and anti-edematous effect on tissues. There is absolute increase in microcirculation, higher rates of ATP, RNA and DNA synthesis, and thus better tissue oxygenation and nutrition. There is also increase in the absorption of interstitial fluid, better tissue regeneration and stimulation of the analgesic effect. The past three decades of laser medicine and surgery have shown great progress and promise for the future.     

Lasers in dermatologic surgery

The authors review their experiences with the use of carbon-dioxide (CO2) lasers in dermatological surgery in a group of 3000 patients, with a total number of 3920 tumorous skin lesions, during a three-year period. The word LASER is an acronym for L-ight A-mplification by S-timulated E-mission of R-adiation. It must be pointed out that it is electromagnetic radiation, not X-irradiation. In regard to the spectrum laser light is between infrared and ultraviolet light, mainly in the visible spectrum, so its application does not produce new generations of iatrogenic malignancies as in the case of ionizing radiation. The laser is a new scalpel which differs from the metal surgical scalpel (also called "optical knife" and "light scalpel"). In the conclusion authors state that using (CO2) complete success was achieved in treatment of the following skin lesions: common viral warts, senile keratosis, seborrhoeic keratosis, plantar viral warts, papillomas, capillary telangiectasias of the face, hemangiomas, juvenile viral warts of the face, ingrown nails, condyloma acuminata, pendular fibromas, xanthelasmas, atheromas, pyogenic granulomas, keratoacanthomas, tattooed skin and basocellular epitheliomas.     

An exact algorithm for self-calibration of two-dimensional precision metrology stages

We describe an algorithm that can achieve exact self-calibration for high-precision two-dimensional (2-D) metrology stages. Previous attempts to solve this problem have often given nonexact or impractical solutions. Self-calibration is the procedure of calibrating a metrology stage by an artifact plate whose mark positions are not precisely known. By assuming rigidness of the artifact plate, this algorithm extracts the stage error map from comparison of three different measurement views of the plate. The algorithm employs the orthogonal Fourier series to expand the stage error map, which allows fast numerical computation. When there is no random measurement noise, this algorithm exactly calibrates the stage error at those sites sampled by the mark array. In the presence of random measurement noise, the algorithm introduces a calibration error of about the same size as the random measurement noise itself, which is the limit to be achieved by any self-calibration algorithm. The algorithm has been verified by computer simulation with and without random measurement noise. Other possible applications of this algorithm are also discussed.     

Analysis of blood flow in adnexal tumors by using color Doppler imaging and pulsed spectral analysis

Because of various contradictory reports in the literature and an increasingly urgent need for preoperative evaluation of adnexal masses before laparoscopic surgery, our aim was to disclose if examination by means of color Doppler ultrasound is useful in distinguishing benign from malignant adnexal tumors in our population. Prior to surgery, pulsed color Doppler velocimetry of the adnexal blood supply was performed in a prospective study in 80 patients with benign and 40 with malignant adnexal tumors. Vascularization was equally frequent in both groups of tumors. Blood vessels of benign tumors had a diffuse, intraseptal or intraproliferative location significantly more often and malignant tumor vessels more often exhibited a diffuse, intraseptal or intraproliferative location (p < 0.01). The mean value of RI+/-SD was 0.56+/-0.14 in benign and 0.33+/-0.13 in malignant tumors. The differences in RI between benign and malignant tumors are statistically significant (p < 0.01). In detecting malignant adnexal tumors, the sensitivity of RI < or = 0.40 is 82%, its specificity 97%, positive predictive value 94%, negative predictive value 92% and its accuracy 92%. The analysis of vascularization presence seems not to have any value in predicting the nature of adnexal tumors, and blood vessels arrangement, as well as measured RI < or = 0.40, allows us to predict the presence of malignancy with limited reliability.     

Omeprazole, azithromycin and amoxicillin or amoxicillin plus clavulanic acid in eradication of Helicobacter pylori in duodenal ulcer disease

Treatment with omeprazole (OME), azithromycin (AZI) and amoxicillin (AMO) resulted in encouraging Helicobacter pylori cure rates in pilot and control studies. The aim of this study was to establish whether OME + AZI in combination with either AMO or ACA (amoxicillin plus clavulanic acid) are effective in curing H. pylori infection. A hundred patients with active duodenal ulcer and H. pylori infection were treated with OME (day 1-10: 2 x 40 mg/day, day 11-24: 40 mg/day, day 25-42: 20 mg/day) plus AZI 500 mg/day for the first 6 days. Patients were randomly assigned to either AMO 2 x 1000 mg/day (group A, n = 50) or ACA 2 x 1250 mg/day (group B, n = 50) during the first 10 days of treatment. H. pylori status was determined by urease test and histology before and 6 weeks after completion of therapy. Ninety-five patients completed the study. H. pylori infection was eradicated in 85.4% (41/48) patients from group A (intention-to-treat (ITT) analysis: 82%) versus 91.5% (43/47) patients from group B (ITT) analysis: 86%) (NS). All ulcer had healed after 42 days of omeprazole treatment. Side effects, usually minor, were recorded in 12.5% (group A) and 14.9% (group B) of patients (NS). Therapy had to be discontinued in two patients (one in group A and one group B) only. Ten-days treatment with OME and AZI (for the first 6 days) with AMO or ACA are simple and highly effective regimens to cure H. pylori infection in patients with duodenal ulcer disease.     

The social embeddedness of decision making: opportunities and challenges

Sociologists have long recognized that economic decisions are socially embedded. Management sciences and business practices have gradually begun to incorporate this idea. With the rise of the Internet, large-scale data are available on friendships, recommendations, transactions and social interactions, which have led to a strong momentum for research in this area. The aim of this article is to inspire multidisciplinary research on the mechanisms and consequences of social embeddedness on decision making and to highlight opportunities and challenges by synthesizing findings from various fields, such as IS research, sociology, economics, marketing and other management disciplines. Key suggestions of this paper are to identify the causality between social embeddedness and decision making with small-scale experiments, and to learn more about network formation by analyzing the evolution of social networks.     

Classification of laser irradiation and safety measures

The use of lasers in medicine and especially surgery is rapidly expanding in many disciplines from clinical laboratory to the office practice and operating room. It is essential that users of this powerful tool have knowledge of their potential hazards and the measures to protect patients and personnel against injuries or undesired effects. Below, we have included information about the way lasers are classified; the development of protective standards; the current status of protection standards that apply to lasers, especially those used in medicine/surgery; the specific kinds of hazards associated with medical/surgical applications; and the measures by which hazards have been controlled. Since laser technology is still a young field, it is likely that problems unknown at present will occur and methodologies for controlling hazards will evolve. The American National Standards Committee produced the first consensus standard Z136.1 in 1973. The Standard was revised in 1976 to accommodate differences in biological effects for different wavelengths in the visible spectrum. The ANSI Standard has been revised again in 1980, and currently (1984) there are two additional standards in preparation, Z136.2 and 136.3, which treat the safe use of light-emitting diodes and the safe use of lasers in the health care environment, respectively. Most surgical and medical lasers are Class III or IV. Some lasers have a Class IV therapy level beam plus a Class I or II alignment beam. When using lasers, it is possible to generate incandescence or fluorescence in an irradiated object. This can occur even with protective eyewear, because the correlated radiations are usually of a different wavelength. Generally, this should not be a problem when beams are directed at biological material. However, hazard could be caused by lasers designed to produce fluorescence. Control of correlative radiation in a laser system is required in the federal regulations. Hazards of lasers may be grouped as those to the eye, skin and associated hazards, fire, x-rays, electrical, fumes, toxic materials, etc. Effects on tissue are governed by the following factors:--the energy or power density of the beam;--the absorption in tissue at the laser wavelength;--the time the beam is held at a given area.;--the protective effects of heat removal by thermal conduction and by circulation. Eye hazards include thermal burns or acoustical disruption (shock waves) from high-powered or high-energy beams in the visible and near infrared wavelengths. Direct beam exposure or specular or diffuse reflaction from these very high-power lasers can also cause injuries to other parts of the retina. For example, beams can directly penetrate through the sclera and cause retinal injury. Near ultraviolet (less than 400 hm) and far infrared (.3000 hm including CO2 lasers) can cause moderate to severe corneal burns. Far ultraviolet (200-315 nm), mid infrared (1400-3000 nanometers) can cause welders' flash or snow blindness and chronic exposure could cause cataract, and exposure to ultraviolet rays may be carcinogenic. For CO2 lasers, the far infrared radiation is attenuated by plastic goggles, or by glasses, or quartz. Other eyewear with special filters is used for different lasers. The whole personnel who may be exposed to direct beams, specular reflections, and many times diffuse reflections must wear protective eyewear. In all cases the surgeon and others viewing the procedure through the endoscope need glasses or suitable protective lenses installed in the endoscope. Persons who are not viewing the beam may not need to wear protective glasses with the same level of optical density. Glasses may be selected to provide protection for lasers operating in the visible wavelength to the point where the normal aversion response could protect the individual.     

The frequency of Chlamydia trachomatis infection in women with intraepithelial neoplasia of the uterine cervix

A case of a rare form of Sanfilippo disease, mucopolysaccharidosis type III D is presented. The cause of the disease is a deficit of N-acetylglycosamine-6-sulfate sulfatase. Differences in clinical course and symptoms with type A and B Sanfilippo disease are shown (later presentation of symptoms, milder course, lack of distinct psychomotor regression and differences in characteristic phenotypic traits, such as facial features, joint contracture, tall height). It is suggested that type III D mucopolysaccharidosis be taken into account in the differentiation of mental retardation syndromes with hyperactivity.