Lasers in Medicine
Year:2006 | Volume:4 | Issue:4 (26)|Papers Count:13

Background and Objectives: During the last decade new bonding techniques beside sutures, staples and clips have been introduced to the modern operating room, including chemical and biological glues. But these methods do not necessarily provide a complete wound seal and adequate strength and had problems with times reactivity and infection. However the application of wavelength-specific chromophores provides a differential absorption between the dyed region and the surrounding tissue. An example of this technique is that while an extended area may be irradiated by the laser but the energy is only absorbed selectively by the dyed region. This paper describes an invitro study using a 10 CW ~ 800 nm diode laser in conjugation with an indocyanine green (ICG) dye doped with albumin protein solder to repair sheep skin specimen. The effect of temperature, power density, type of treatment, number of scan and scan velocity are studied and discussed.Material & Methods: Liquid protein solder was prepared from 25% BSA (Merck, Germany) and ICG dye (Sigma, Alderich-Germany) 0.25 mg/ml mixed in 5cc deioniozed water. The protein solder was stored in a light proof vial in a refrigerator until required. The solder was applied on the 2*20 mm2 incision by a micropipette. The laser output was focused buy a suitable optics into the rectangular image which treated the skin in static and dynamic modes. The surface temperature was measured by a digital thermometer (CHY 502A1, Taiwan) and crossed checked by a non-content laser thermometer. Mean peak temperature produced by the protein solder surface during the laser procedure, the tensile strength (s) of healed incision after 2 hours for two modes of treatments just before their point of rupture under the applied load were measured.Results: However, in practice to have an optimal condition for skin closure some parameters must be carefully studied such as number of scans (Ns) and scan velocity (Vs) in dynamic mode. The results showed that the tissue tensile strength increases by increasing both Ns and the laser power density. But also it has equally been shown that at lower Vs, hence higher temperature, a higher value of s is achieved. It is therefore imperative to consider the trade off between the scan velocity and the surface temperature for achieving the best optimum operating condition.Conclusions: Thus, it can tentatively be concluded that since the skin temperature should not exceed ~90C at any time of work, then the acceptable conditions in our experiment would correspond to I~ 47 Wcm-2, s= gr, Ns= 8, Vs=0.3mms-1.

Background and Objectives: Nowdays, Candida albicans is main etiological factor of Candidiasis especially in immunodeficient patients such as AIDS. In addition, antifungal drugs against candidiasis are ineffective and this infection maybe recurrent, therefore we studied the effect of Low Level Laser Therapy(LLLT) of Diode 685  and 830 nm on Candida albicans, In Vitro. A few amount of reliable information's in the effect of laser irradiation on fungi have been gathered, so that , The aim of this study was to examine, InVitro , are The effects of 685 and 830 nm diode laser irradiation on Candida albicans due to direct or immunomodulatory changes.Material & Methods: In these 28 months experimental and in Vitro study, we identified C.albicans using standard methods. In the next step, equal amount of C.albicans were cultured on Sabouraud Dextrose Agar with Chloramphenicol (Sc) plates .Then the plates were irradiated in 9 group included 685 nm, 25 mW; 3, 5, 10, 20 J/cm2 and 830 nm, 200 mW; 3, 5, 10, 30, 50 J/cm2. From each group 12 samples were irradiated. Also 12 plates selected as control group. Then inhibition of growth, Macroscopic and microscopic morphology, Minimum inhibitory concentrations (MIC), Pathogenesis in souries and genomic changes examined following exposureResults: The results of this study indicated that LLLT is effective on Candida albicans growth Dose dependently that the most changes were observed in ³ 10 J/cm2 685 nm and 830 nm groups. (P<0.001).Conclusions: It seems that LLLT have been effects on the C.albicans, independently, and these changes occure on the protein synthesis level and gene expressions, probably.

Background and Objectives: Tendon injuries are one of the most common injuries in musculoskeletal conditions. Low level laser therapy (LLLT) has been shown to induce wound healing especially in conditions of low microcirculation. This investigation describes the effect of low level laser therapy (LLLT) on healing of tendon injury in experimental setting.Material and Methods: The study was performed on 48 Leghorn hens. In all animals, 75% of tendon in zone II was cut and sutured and divided in 6 groups randomly. A GaAlAs laser device (50mw, 810 nm) was used for laser irradiation for six weeks in 4 groups (1J/cm2, 1.5 J/cm2, 7.5 J/cm2, 10 J/cm2). Two groups were selected as sham and control. In the end of week 6, the animals were scarified and healing of tendons was evaluated by histopathology.Results: The means of healing score in laser groups were statistically greater than the mean of healing score in sham and control group. The results in 7.5 and 10 J/cm2 was better than 1 and 1.5 J/cm2.Conclusions: Our results showed that 810 nm low level laser irradiation is effective in repairing of tendon injuries in experimental setting. It seems that LLLT could use in clinical practice for this indication. However, it is necessary to show this efficacy in randomized clinical trials.

Background and Objectives: Chest wall progression of breast carcinoma affects up to 5% of breast cancer patients and is a major source of their pain. Treatment options are limited or may not be offered to these patients. Low-dose Photofrin-induced photodynamic therapy (PDT) offers an excellent clinical response with minimal morbidity. In this paper, a new linear model is developed whose solution gives an optimal light dosage plan for photodynamic therapy which is based on the flow of photo sensitizer through blood and tissue and on its interaction with laser within the treatment time interval.Material and Methods: The arterial concentration is modeled via a differential equation that describes how photo sensitizer accumulates and degrades in blood-plasma. We use the interior-point method to solve the linear optimization problem and the suggested models are simulated with Matlab7 software.Results: This simulated model allows us to investigate how different parameters affect the success of treatment. In order to display the capabilities of our model, we used three simulated sample of tumor to determine the optimal time for light delivery to the tumor and the percentage of destruction.Conclusion: Advantage of this modeling and simulation is in optimization of PDT without need to clinical try and error methods. So we can estimate the best time for laser radiation. Results show that improving a photo sensitizer's affinity for cancerous cells will dramatically improve viability of PDT.

Background and Objectives: Delayed type hypersensivity (DTH) is the known process of chronic graft rejection. The main role in this process goes to cytokines secreted by T cells. Although many studies are done on the effect of low level lasers on DTH, but not many have focused on the mechanism of this effect. If low level lasers are able to decrease level of these cytokines, then it is possible to use them to prevent chronic graft rejection in clinic with much fewer side effects than routine immunosuppressor treatments. This study was designed to evaluate the effect of low level lasers on secretion of IL2 and TGF b in vitro.Material and Methods: we cultured 8 different samples of peripheral human blood mono nuclear cells and divided them into 4 groups. Control one was nor stimulated nor irradiated. Cells in group Control 2 were only stimulated by PHA. Group case one started receiving radiation a day prior to stimulation and group case 2, received irradiation a day after stimulation.  Both case groups were irradiated by the same laser device for 8 days. Cytokine levels were checked by ELISA technique.Results: our results showed although low level He-Ne laser can decrease amount of IL2 and TGFb, significantly in vitro, but the level will not be as the base. Our study results also suggested, starting laser irradiation prior or after the stimulation has no significant effect on amount of these cytokines.Conclusion: Our study result highly suggests the successful role of He-Ne laser on preventing chronic graft rejection. But before using them in clinic many experimental studies are required to determine the best power out put and dosage.

Appropriate application of the Nd: YAG laser has been shown to reduce bacteria associated with periodontal pockets and improves the health of the diseased periodontal pocket tissue [1&2]. The objective of this in-vivo study is to investigate the effects of the 100 micro-second pulsed width (length) Nd: YAG laser on bacteria and pocket depth associated with periodontal disease.  An Nd: YAG laser (Fidelias, FOTONA, Slovnia: 2 Watts and 10 Hz, 320 Micrometer beam diameter with a pulse duration of 100 micro-seconds) was used to irradiate the gingival pockets after the removal of calculus and appropriate root planning with hand instruments. Fifty-two teeth from six patients diagnosed with chronic periodontitis were used in this study. The samples were divided into two groups (control and experimental). All teeth were treated by normal hand instrumentation but in the experimental group the Nd: YAG laser was used to irradiate the pocket following hand instrumentation. Bacteria cultures were obtained from the gingival pockets prior to treatment, immediately after treatment, one and two months after treatment.The laser group of teeth demonstrated a significant reduction in bacteria, Probing Index (PI) and Bleeding Index (BI) compared to the control group of teeth.