Most applications of lasers in medicine are based on the producing of a controlled thermal damage into a preferably tissue location. Laser safety deals with non controlled damage (thermal or other) that could be randomly produced into a non preferable tissue locations. This kind of damage is not allowed and the laser safety material is designed to provide the user with a knowledge and with sufficient safety instructions and means to prevent such damage. Following the laser safety instructions is especially important for the medical applications because in these applications the laser beam is brought in a close proximity to the patient's body and non-desired damage can be easily produced. Most medical lasers are classified as Class 4 laser products, the highest hazard class. Direct laser beam of class 4 is capable to produce skin burns and to ignite flammable materials, and even its scattered beam may produce severe eye damage. The paper presents the nature of the skin and eye damage for different spectral range, and the state of the art rules in preventing such damage. The safety means that should be implemented in, and around, the laser clinique and in the laser surgery room will also be highlighted.

It is said that clinicians today learn less and less about more and more until they end up knowing nothing about everything, whereas researchers learn more and more about less and less until they end up knowing everything about nothing. This is a phenomenon which is slowly creeping into the field of clinical applications and basic research in laser surgery and laser therapy. This trend is definitely to be discouraged, as it will effectively narrow the scope of both clinicians and researchers at a time when the scope needs to be expanded just as appropriate applications in laser surgery, and bona fide applications for laser therapy are also expanding. "Publish, or be damned" is a well-known dictum in the heady halls of academe. Unfortunately, for many of the papers which are submitted on laser applications but which do not reach the pages of the target journal, and indeed for some papers which are published elsewhere by journals which should know a little better, or should at least have done their homework, the saying should perhaps be amended to; "Publish and be damned," meaning that the paper actually do more harm than good to the cause of lasers in medical science.

The summons from a medical congress or symposium chairman, chairwoman or president to be a session moderator or to deliver an invited lecture, or the offer to participate in a free paper session are events which can turn the most seasoned clinician and researcher into something which lies on the bed of the ocean and shivers, namely, a nervous wreck. However, proper planning and the following of a few simple rules can eliminate the mental trauma for the presenter often wrongly associated with having to give an oral presentation, and indeed obviate the sometimes much more serious trauma inflicted upon the hapless audience by an ill-prepared presentation and a hapless presenter, not to mention a mutinous moderator. The first point is that an oral presentation is not a scientific paper, and therefore while it may follow in general the usual divisions of a written article, it should not be a pictorial representation of a piece of rigid scientific writing. Secondly, presenters are almost always given a time limit for their presentation. It is the height of bad manners and total ignorance to exceed this time limit, as the presenter is often one of a series.

Laser surgery is a standard operating procedure for many specialists. These innovative technologies have dramatically reduced the risk/benefit ratios of health care. These reductions have led to marked growths in health care utilization resulting in the spiraling increases in health care costs. With innovative technologies, the question regarding health care delivery has changed from "can it be done?" to "should it be done?" Physicians do not currently have enough the information necessary to answer this question.

The connection of such key technologies as laser and sensor technology opens a broad field of applications especially in medicine. The development of sensor-controlled medical laser systems represents a quantum leap in precision and safety in medical practice. This makes the treatment or surgery more gentle and safer for both physician and patient. This paper presents the possibilities and the potential of sensor-based laser procedures in medical practice. It starts with medical laser technology and sensor systems that are already used in medical diagnostics and therapy. A concrete example from laser surgery illustrates the advantages of laser ablation for an osteotomy of the mandible and a sensor and control concept for tissue-specific bone ablation. An Er:YAG laser system was combined with a process control and qualified for layer-specific ablation of hard tissue. Layer-specific ablation of tissue is especially important when, as in the laser osteotomy of the mandible (lower jaw), vulnerable structures, as e.g. nerves (mandibular nerve), run underneath the to-be-ablated tissue that may not be damaged. The closed loop control system developed for laser osteotomy is based on the evaluation of process emissions that occur during the laser ablation and are recorded with several sensors. Thereby optical and acoustic process emissons are used for achieving switching-off criteria for the laser system before damaging the nerve. Tests were performed on dissected bone specimens from the rabbit's femur and minipig's jaw. After laser application the bone specimens were evaluated macroscopically, radiologically, histologically and by micro computed tomography.

Photodynamic therapy (PDT) involves the use of a photoactive drug (photosensitizer) and light. Upon absorption of light, the photosensitizer initiates oxygen-mediated chemical reactions that lead to the direct or indirect production of species such as singlet oxygen that cause cell death. The reaction of the cytotoxic species with subcellular organelles and molecules such as proteins and DNA lead to apoptosis or necrosis of the cells hosting the photosensitizer. Preferential accumulation of photosensitizer in cancer cells means that, as an anti-cancer treatment, this has the potential to kill selectively the tumor cells while leaving healthy cells undamaged. Photodynamic mechanisms proceed from the first excited singlet state (S1) via either Type I or Type II mechanism. A Type I reaction involves the photosensitizer losing an electron to form a radical cation, typically reacting with oxygen to form superoxide and hydroxyl radicals. In a Type II reaction, the sensitizer relaxes into the first excited triplet state (T1) which interacts with oxygen to form singlet oxygen. The species produced are very reactive and can cause cell death by either apoptosis or necrosis. Cells membranes are a primary site of action. Functional impairment of mitochondria is also observed.

Oncological research and cancer treatment are more common in human medicine than in veterinary medicine. Nevertheless the latest decennium chemotherapy, radiotherapy and surgery also figure largely in the cancer treatment of pets. For this matter, the present study tried to explore the applicability of Photodynamic Therapy (PDT) as a proper and advantageous alternative for those treatments. PDT using topical 5-aminolaevulinic acid (5-ALA) cream was applied on superficial squamous cell carcinomas (SCC) at the nasal planum of two cats. Five hours after the cream was applied, the photosensitizing agent was removed and the sensitized area was irradiated with a red Light Emitting Diode (LED) contrivance with a wavelength of 660 nm. LED irradiation was administrated during 20 minutes, at a power output of 80 mW, with an energy density outcome of 38 J/cm². The day after ths irradiation, the tumor area became erythematous and somewhat oedematous. After two days a scab occurred. Long-term post treatment observation showed complete removal of the malign cells related with regain of normal skin structure after three weeks. Follow-up period of one year for the first case and of two months for the second case revealed no recurrence. These promising results indicate that PDT is a possible alternative method to treat superficial skin tumors. Especially when taking into account that chemotherapy and radiotherapy are time-consuming treatments and that surgery (complete removal of the nasal planum) is not an esthetical solution.

Specifically, these methods reassess shielding calculations in X-ray areas with respect to the methodology of the calculation of the barrier thickness and the number of sources consider in the area. Thus, they generate an overall solution for the cases met at the medical radiation structural design. This report provides an extension of an existing method for the calculation of the barrier thickness required to reduce the three types of radiation exposure emitted from the source, the primary, secondary and leakage radiation, to a specified weekly design limit (MPD). Because each of these three types of radiation are of different beam quality, having different shielding requirements, NCRP 49 has provided means to calculate the necessary protective barrier thickness for each type of radiation individually. However, this report (NCRP 49) provides little guidance for the contribution of each of the three types of radiation to the barrier thickness requirement. The medical physicist have to estimate which components of the field are most important to be shielded and how they are to combine, if more than one component is significant to generate a single shielding requirement. In questionable situations, multiple half-value layers (HVLs) of material recommended to be added; by the general "add one half value layer (HVL)" approximation of NCRP 49.

In the stent theory for the medical applications, especially in coronary heart disease, the metallic stent of high quality demands the ability for precision micromaterial processing. It possesses an inherent advantage of adequate radio opacity. This paper describes the current status as well as fabrication of such metallic stent of length 20 mm and dia. 2.1 mm with an annular tube thickness of 0.2 mm, by using the short pulse Nd-YAG laser. Fine structures with slit width of 0.1 mm and pitch better than 0.2 mm are created with sharpness and low roughness in the cut surface. Some features of the reduced heat affected zone and dross removal process of the cut surfaces are also discussed.

Background Vascular lesions still present a major problem, and the search for a good treatment continues. The use of inappropriate treatment methods, can occasionally cause unwanted side effects. Even when the method used is appropriate, the result can be disappointing. It is important to choose an appropriate laser, and where laser treatment is not effective, we must select the most appropriate conventional treatment or combination of treatments. My treatment program is as follows; a 532 nm diode laser is the first choice for telangiectasias; the flashlamp-pumped dye laser for port wine stains and strawberry marks; and the Nd:YAG laser with a cooling device for 1 - 3 mm leg veins of the reticular and web type. For leg veins over 3 mm, surgery is required. The diode pumped 532 nm laser is excellent for superficial telangiectasias. Good effects with the pulsed dye laser are limited to vessels in the upper layers of the dermis, thus the penetration depth of the laser must thus be optimized combined with epidermal cooling. We must always avoid side effects in laser treatment of vascular lesions. Development of new wavelengths and adaptation of existing wavelengths are currently being investigated.

The use of pulsed dye laser for the treatment of Capillary Vascular Malformations (CVMs) only leads to complete clearing of the abnormality in a minority of cases. In order to examine the characteristics of a CVM, which determine its response to laser treatment, we have used videomicroscopy. By using a videomicroscope to determine the vessels diameters within a CVM in-vivo it is hoped that treatment parameters can be chosen which would be most appropriate to achieve the best response. To increase the clarity of our images and reduce reflection we carried out a videomicrographic examination using both normal white light and green filtered light on 24 sites on 18 patients. For the deeply placed reticular vessels we found no difference between the results obtained with the two techniques. However, for the superficial papillary vessels we found a statistically significant (p < 0.01) increase in the recordings taken with the green filtered lens. We attribute this difference to the reduction in reflection seen with the green filter. We have also developed a depth measuring videomicroscope, which allows the calculation of vessel depth as well as vessel diameter.

In this study, a two layer (TL) solid solder was developed with a fixed thickness to minimize the difference in temperature across the solder (ΔT) and to weld at low temperature. Solder strips comprising two layers (65% albumin, 35% water) were welded onto rectangular sections of dog small intestine by a diode laser (λ = 808 nm). The laser delivered a power of 170 ± 10 mW through an optical fiber (spot size approximately 1 mm) for 100 seconds. A solder layer incorporated also a dye (carbon black, 0.25%) to absorb the laser radiation. A thermocouple and an infrared thermometer system recorded the temperatures at the tissue interface and at the external solder surface, during welding. The repaired tissue was tested for tensile strength by a calibrated tensiometer. The TL strips were able to minimize ΔT (12 ± 4°C) and control the temperature at tissue-interface. The strips fused on tissue at 55≤T≤62°C had higher tensile strength than the strips soldered at 51≤T<55°C (19.1 ± 6.6 versus 13.1 ± 6.4 gmf). The solid solder could efficiently weld at 60°C as it became insoluble and formed stable bonds with tissue. Fluid albumin solders, by contrast, requires temperatures ≥70°C for tissue repair, which cause more irreversible thermal damage.

The purpose of this study was to investigate the efficacy of LLLT in the treatment of trigger points (TrPs) that are associated with rotator cuff tendonitis. A double-blind randomized controlled trail was conducted. Sixty patients were randomly allocated to one of two groups: sham or laser therapy. The laser (Excel, Omega Universal Technologies Ltd, London, UK) parameters used were a wavelength of 820 nm, a power output of 100 mW, a frequency of 5000 Hz (modulated) and energy density of 32 J/cm². The two groups received a course of 12 treatment sessions for four weeks (3 sessions per week). Pain, functional activities (as measured using the Shoulder Pain and Disability Index, SPADI), pressure pain threshold (PPT) and range of motion (ROM) were assessed pre and post treatment, with a three month follow-up assessment. Significant improvements in pain (p < 0.001) were observed for the laser group (6 cm median improvement on a 10 cm VAS) compared to the sham group (2 cm median improvement) immediately post treatment. The improvements in the laser group continued post treatment with a 7 cm median improvement observed at three month follow-up. Similar between group differences were observed for ROM (p < 0.01), functional activities (p ≤ 0.001) and PPT (p ≤ 0.05). The findings of the current study suggested that LLLT is effective in treating patients with TrPs associated with rotator cuff tendonitis, when using the parameters described. However, the mechanism of its action is not yet clear, and will require further investigation.

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to quantify bone morphology during post-injury ossification in rate tibiae and characterize the differences induced by laser photostimulation compared with the naturally-occurring regenerative process. SEM and AFM images of the cortical bone at the recovery stages of 8 and 15 days after the injury are discussed.

In the last time the study of the effects of LLLR on the blood is considered to be a subject of great importance in elucidating the mechanisms of action between LLLR and biologic tissues. Different methods of therapy by blood irradiation have been developed and used in clinical purposes with benefic effects. This study investigates some in vitro effects of LLLR on some selected rheologic indices of human blood. After establishing whether or not damaging effects could appear due to laser irradiation of the blood, we tried to find a new method for rejuvenating the blood preserved in MacoPharma-type bags. Blood samples were obtained from adult regular donors (volunteers). HeNe laser and laser diodes were used as radiation source, in a wide range of wavelengths, power densities, doses and other parameters of irradiation protocol. In the first series of experiments we established that LLLR does not alter the fresh blood from healthy donors, for doses between 0 and 10 J/cm³ and power densities between 30 and 180 mW/cm³. In the second series of experiments we established that LLLR does have, in some specific conditions, a revitalizing effect on the erythrocytes in preserved blood. We concluded that laser irradiation of the preserved blood, following a selected protocol of irradiation, could be used as a new method to improve the performances of preservation: prolonging the period of storage and blood rejuvenation before transfusion.

The effects of laser on the immune system have not been extensively characterized. Low power laser sources, such as GaAlAs laser have been found to produce photo biological effects with evidence of interference with immunological functions. We have investigated the effects of GaAlAs laser irradiation on the immune response due to Mycobacterium bovis BCG infection in mice. BALB/C mice were exposed on the abdomen skin to GaAlAs laser radiation (810 nm) for 3 consequent days (Days = -2, -1, 0) before infection with 1 x 10⁶ live units of Mycobacterium bovis Bacillus Calmette-Guerin (BCG) in the footpad. 21 days later groups of mice were tested for a delayed type hypersensitivity (DTH) response to the purified protein derivative (PPD) of tubercle bacilli and the course of infection was monitored by measuring the size of the infected footpad. In the mice treated by laser, the DTH response to PPD was significantly suppressed (P-value<0.045) compared to unirradiated mice, when tested 21 days after BCG infection. When laser irradiated 13 days after BCG infection (Days: +13, +14, +15) BALB/C mice did not show a significant decrease in their DTH response to PPD indicating that the laser-induced suppression of BCG occurs only at the induction stage of the immune response. Thus mice exposed to the laser radiation before BCG infection showed an impaired DTH response to Mycobacterium, whereas mice exposed to the laser irradiation after BCG did not. These studies demonstrate that a systemic effect of laser irradiation can suppress the development and expression of immunity to pathogenic bacteria in mice. This suppression could be at the induction stage of the immune response (DTH) but not the elicitation stage. Also it seems that laser radiation, potentially, could have side effects for the immune system, on the basis of suppression effects it has shown on DTH response.

The effectiveness and applicability of a variety of light sources, in the treatment of wounds has thoroughly been investigated, in vitro as well as in vivo. The current commercial availability of Light Emitting Diode (LED) sources therefore also invites research to explore the effect of low power infrared, red and green light on wound healing, e.g. by means of fibroblast proliferation. Therefore a controlled and randomized study on cultured embryonic chicken fibroblasts was conducted. The fibroblasts were irradiated during three consecutive days, at several wavelengths (950 nm, 660 nm and 570 nm) and a respective power output of 160 mW, 80 mW or 10 mW. Treatment duration varied from 1 minute to 3 minutes to obtain a surface energy density of 0.9 J/cm² (infrared and red light) or 0.2 J/cm² (green light). Statistical analysis revealed that LED irradiation for all three wavelengths induced a higher rate of proliferation in comparison of the control group. This difference was statistically significant (p < .001). With regard to the amount of proliferation the green probe yielded a significantly higher number of cells, than the red (p < .001) an the infrared probe (p < .001). Furthermore, the red probe provided a higher increase (p < .001) than the IR probe. LED irradiation results in an increased fibroblast proliferation in vitro. This outcome postulates beneficial stimulatory effects of LED at the applied wavelength, energy density and power output on wound healing in vivo. Further investigation is necessary to examine this hypothesis.

In hepatocytes, proliferation of tetraploid and binuclear cells and an increase in cytosolic and mitochondrial protein synthesis are caused by He-Ne laser irradiation. To gain some insight into the mechanism of photomodulation of cellular and subcellular activities in isolated hepatocytes, intracellular mediators of cell photostimulation were investigated in intact cells and isolated mitochondria. Irradiation of isolated hepatocytes and isolated rat liver mitochondria was carried out with He-Ne laser (wavelength: 632.8 nm; fluence: 0.24 J cm^-2; fluence rate: 12 mW cm^-2). Changes in cytosolic [(Ca²⁺)c] and mitochondrial [(Ca²⁺)m] calcium concentration, and in mitochondrial (Δψ_m) and plasma (Δψ_c) membrane potential were, monitored using either colorimetric or fluorescent probes. C-fos expression was studied by Northern and immunoblotting analysis. As a result of irradiation, an increase in (Ca²⁺)c and a calcium-dependent increase in Δψ_c were found. The increase in (Ca²⁺)c, in turn, caused an increase in c-fos expression. Finally, an increase in (Ca²⁺)m, probably owing to the increase in Δψ_m, was found. Increase in (Ca²⁺)c, leading to activation of gene expression, and a general activation of mitochondrial metabolism, could play a major role in the mechanism of photostimulation of cellular activities by He-Ne laser.

Many oral manifestations of HIV infection can be used as markers for degree of immunosupression. These manifestations may be treated with antibiotics, analgesics, and antineoplastics, which may interact and interfere with antiviral agents used to treat the disease, and possibly exacerbate it. Dentists will see more HIV-infected patients as medical research transforms this disease into a chronic illness. Lasers have been shown to be effective instruments in palliation of oral manifestations of HIV infection. The use of lasers to palliate the painful symptoms of three oral manifestations of HIV infection is described. The advantages and benefits to both patient and dentist will be discussed. The paper does not address the use of lasers as a modality to treat or cure HIV infection -- only to palliate some of its symptoms.

Despite insightful studies of various researchers, vitreous physiophathology is still only partially explored as a field of study for modern ophthalmology. There is much to be learned about the mechanisms that maintain the integrity of vitreo-retinal interface and, more deeply, about the biochemical relationship between retinal pigment epithelium and Bruchs membrane; an imbalance between the physical and biological homeostasis at these levels may determine the onset of vitreo-retinal interface disease. Despite the unclear relationship between internal limiting membrane (ILM) and hyaloid, and between pathogenesis and effect of vitreous detachment, surgical techniques are being developed that promise a resolution of most diseases associated with vitreous and retinal anomalies. Optical coherence tomography (OCT) is the main diagnostic technique supporting this advances. The authors, after briefly introducing vitreous physiology and pathology, will discuss the main indications to this type of surgery, which is guided by OCT.

Around 12,000 deaths from glioblastoma occurs within the European Community annually. At present, the best available treatment for malignant brain tumors results in a median survival of patients of 15 months despite surgery, radiotherapy, and chemotherapy. The purpose of this paper is to review our results of radiosensitized treatment of malignant brain tumors.

The purpose of this study was to investigate the beneficial and adverse local effects of PDT associated with chemoimmunotherapy on rats bearing Walker ascites tumor cells. Experiments were performed on five batches of Wistar inbred rats with ascites tumor cells receiving intraperitoneally PDT (Photofrin II and 18 hrs later HeNe laser irradiation); Cyclophosphamide (CY); interleukin-2 (IL-2) or associated therapy (PDT+CY+IL-2). The control batch consisted of untreated rats (HBSS). The following results were noticed: (a) sole administration of PDT, IL-2 or CY reduced tumor growth, gave survival rates between 28.4 and 56.5% and cure rates ranging from 12.4 to 33.3%; (b) combined therapy (PDT+CY+IL-2) decreased tumor growth, increased survival rates (88.5%) and cure rates were 73.1% forty-two days post-transplantation. Summing up, in this study we noticed that PDT associated with chemoimmunotherapy reduced mortality as well as tumor volumes and increased cure rates in rats with ascites tumor cells. This approach points to the need for further evaluation in patients with peritoneal malignancies.

An acoustic multimode fiber optic sensors for medical diagnostics based upon the shutter principle has been elaborated with semiconductor laser diode as light source. The construction and the method of component preparation are described. Other type of stethoscope is electrical one. Both stethoscopes are four channels. The kinetics and dynamic vibrations and sounds of the human body can be detected, acquired and then processing by personal computer for medical diagnostics.