A mucosite oral constitui efeito colateral dose-limitante da quimioterapia, relativamente freqüente, desconfortável e potencialmente letal. O controle terapêutico é sintomático e ainda inexiste procedimento estabelecido para prevenir a sua manifestação. O objetivo deste estudo foi verificar a eficácia do laser de baixa potência na prevenção da mucosite oral e as influências de variáveis demográficas (idade e sexo), subjetivas (xerostomia e paladar) e objetivas (história médica), em pacientes portadores de adenocarcinoma de cólon, submetidos à quimioterapia com fluorouracil (5-FU) e ácido folínico (Leucovorin®). Quarenta e oito pacientes foram incluídos no estudo. 18 homens e 30 mulheres, na faixa etária dos 37 aos 78 anos com média de idade de 62,5 anos. Os pacientes foram endereçados, seqüencial e alternadamente, para dois grupos. Vinte e cinco pacientes compuseram o grupo submetido à aplicação preventiva de laser (grupo LP) e 23 pacientes receberam aplicação placebo (grupo C). A aplicação do laser, preventivo ou placebo, foi realizada na semana de infusão da quimioterapia, uma única vez, e os pacientes foram reavaliados após sete dias. O laser utilizado foi o AlGaInP, 660nm, fluência de 3J/cm2. Os graus de mucosite foram mensurados pela escala WHO, e a xerostomia e a dor por escala visual analógica (VAS). Os pacientes que desenvolveram mucosite receberam aplicação terapêutica de laser, independentemente a que grupo pertencesse. Vinte e um pacientes cumpriram os seis ciclos programados de quimioterapia (10 C e 11 LP), e 27 pacientes completaram apenas parte do protocolo (13 C e 14 LP). Houve ocorrência similar de mucosite oral entre os grupos, cuja freqüência variou em torno de 50% em cada ciclo, com a seguinte distribuição média: 22% de mucosite grau 1, 18% de grau 2, 10% de grau 3 e nenhum grau 4. Foram registrados 95 episódios de mucosite nos 188 ciclos de quimioterapia dos 48 pacientes incluídos no estudo. Nos 126 ciclos dos 21 pacientes que cumpriram todo o protocolo ocorreram 63 episódios de mucosite. A análise estatística não mostrou diferença significativa quanto à ocorrência de mucosite entre os grupos. Os pacientes do sexo feminino, pacientes acima de 60 anos de idade e a queixa de xerostomia prévia à quimioterapia, embora tenham mostrado tendência a diferença em alguns ciclos, não mantiveram essa característica na análise integral dos resultados. Pacientes com queixa de alteração de paladar prévio à quimioterapia e história de diabetes mellitus e gastrite manifestaram quadros mais graves de mucosite que a média geral da população estudada. O efeito benéfico do laser terapêutico foi altamente significante para os pacientes que desenvolveram mucosite oral. Concluiu-se que uma única aplicação de laser de baixa potência não foi efetiva para prevenir a mucosite oral na população estudada. Pacientes portadores de diabetes, gastrite, queixa de alteração de paladar e aqueles que manifestam graus mais severos de mucosite nos ciclos iniciais da quimioterapia merecem maior atenção no seguimento em função do pior prognóstico demonstrado neste estudo. / Oral mucositis is a debilitating, dose-limited complication of chemotherapy, fairly common, debilitating and potentially lethal. Its treatment is symptomatic and there are no preventive guidelines available yet. The purpose of this study was to evaluate the efficacy of low level laser therapy (LLLT) in oral mucositis prevention and the influence of demographic (age, gender), subjective (xerostomia, taste) and objective (medical history) factors as well. Forty-eight colorectal adenocarcinoma patients submitted to fluorouracil (5-FU) and folinic acid (Leucovorin®) chemotherapy protocol were enrolled in the trial, 18 men, 30 women, ranging from 37 to 78 y.o., mean 62,5 years. Two study groups were sequentially and alternately constituted. Twenty-five patients were submitted to a preventive laser treatment (LP group) and 23 received a placebo irradiation (C group). Laser treatment, effective or placebo, was delivered one time at the beginning of the chemotherapy infusion week. Every patient was reevaluated seven days after. An AlGaInP device, 660nm, was utilized with 3J/cm2 of fluency. Oral mucositis were graded according to WHO scale. Pain and xerostomia levels were evaluated through visual analogue scale (VAS). Patients who presented oral mucositis received therapeutic laser sessions, no matter to which group they were originally driven to. Twenty-one patients undergone all six cycles of the chemotherapy protocol planned (10C, 11LP) and 27 patients accomplished only partially the chemotherapy cycles (13C, 14LP). Oral mucositis were similarly distributed between the groups studied, around 50% in every cycle: 22% of grade 1 mucositis, 18% grade 2, 10% grade 3 and none grade 4. Ninety-five oral mucositis episodes were observed in the 188 cycles followed by the 48 patients in the study group; and 63 oral mucositis episodes were registered among the 21 patients followed through 126 chemotherapy cycles. Statistical analysis showed no difference between the groups on oral mucositis manifestation. The aspects of female gender, aged over 60 and xerostomia symptoms previous to chemotherapy, showed a slight difference in some cycles but no overall statistic significance was demonstrated. Patients with taste impairment previous to chemotherapy, history of diabetes and gastritis showed more severe pictures of mucositis than the overall population studied. Laser treatment was highly effective for patients who exhibited high grade oral mucositis. We concluded that a unique LLLT irradiation was ineffective as a preventive procedure for oral mucositis in the population evaluated. In addition, patients with diabetes, gastritis, taste impairment and patients who develop severe pictures of mucositis at the beginning of chemotherapy regimens should receive more attention since they exhibited poor prognosis in this research.

>Magister Scientiae - MSc / The Physics Department at the University of the Western Cape and the Environmental Physics group at iThemba labs have been conducting radiometric studies on both land and water. In this study a 7.5 cm X 7.5 cm NaI (Tl) detector was used to study activity concentrations of primordial radionuclides in soil and sand samples. The detector and the sample were placed inside a lead castle to reduce background in the laboratory from the surroundings such as the wall and the floor. The samples were placed inside a 1 L Marinelli beaker which surrounds the detector for better relative efficiency as almost the whole sample is exposed to the detector. Additional lead bricks were placed below the detector to further reduce the background by 20%. The NaI detector is known to be prone to spectral drift caused by temperature differences inside and around the detector. The spectral drift was investigated by using a ¹³⁷Cs source to monitor the movements in the 662 keV peak. The maximum centroid shift was about 4 keV (for a period of 24 hours) which is enough to cause disturbances in spectral fitting. There was no correlation between the centroid shift and small room temperature fluctuations of 1.56 ºC. A Full Spectrum Analysis (FSA) method was used to extract the activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K from the measured data. The FSA method is different from the usual Windows Analysis (WA) as it uses the whole spectrum instead of only putting a ‘window’ around the region of interest to measure the counts around a certain energy peak. The FSA method uses standard spectra corresponding to the radionuclides being investigated, and is expected to have an advantage when low-activity samples are measured. The standard spectra are multiplied by the activity concentrations and then added to fit the measured spectrum. Accurate concentrations are then extracted using a chi-squared (χ²) minimization procedure. Eight samples were measured in the laboratory using the NaI detector and analyzed using the FSA method. The samples were measured for about 24 hours for good statistics. Microsoft Excel and MATLAB were used to calculate the activity concentrations. The ²³⁸U activity concentration values varied from 14 ± 1 Bq/kg (iThemba soil, HS6) to 256 ± 10 Bq/kg (Kloof sample). The ²³²Th activity concentration values varied from 7 ± 1 Bq/kg (Anstip beach sand) to 53 ± 3 Bq/kg (Rawsonville soil #B31). The ⁴⁰K activity concentration values varied from 60 ± 20 Bq/kg (iThemba soil, HS6) to 190 ± 20 Bq/kg (Kloof sample). The χ² values also varied from sample to sample with the lowest being 12 (Anstip beach sand) and the highest (for samples without contamination of anthropogenic nuclei) being 357 (Rawsonville soil #B28). A high χ² value usually represents incomplete gain drift corrections, improper set of fitting functions, proper inclusion of coincidence summing or the presence of anthropogenic (man made) radionuclei in the source [Hen03]. Activity concentrations of ⁴⁰K, ²³²Th and ²³⁸U were measured at four stationary points on the Kloof mine dump. The fifth stationary point was located on the Southdeep mine dump. These measurements were analysed using the FSA method and fitting by "eye" the standard spectra to the measured spectra using Microsoft Excel. These values were then compared to values obtained using an automated minimization procedure in MATLAB. There was a good correlation between these results except for ²³²Th which had higher concentrations when MATLAB was used, where 16 Bq/kg was the average value in Excel and 24 Bq/kg was the average value in MATLAB.

Most dams have a low-level outlet that consists of a closed conduit through the dam with a slide gate or valve to regulate flow. These outlets are used mainly for irrigational purposes but also for flushing the reservoir and controlling the reservoir elevation. When discharging through the low-level outlet works, negative pressures can develop on the downstream side of the gate creating a potential for cavitation damage and vibration. To minimize these effects, air vents (vented to the atmosphere) are installed on the downstream side of the gate to limit downstream pressure to something above vapor pressure (i.e., near atmospheric pressure). Previous air venting studies have been mostly limited to large dam outlet geometries, which typically feature a vertical gate in a flat-bottomed discharge tunnel. The large-dam air demand analysis has been based on the Froude number of the supercritical flow at the vena contract (located between the gate and the hydraulic jump) and the water flow rate. Small to medium-sized embankment dams typically utilize a slide gate installed on the sloped upstream face for flow control, followed by a vertical elbow connected to a sloping pipe. With this outlet geometry, there is no 1-D vena contracta flow, no classical hydraulic jump, and no representative Froude number. Additionally, no head-discharge characteristic data have been found for inclined slide gates (vented or non-vented) for small to medium-sized dams. Consequently, unless a flow measurement structure is installed in the discharge channel downstream of the dam, determining the water discharge rate based on gate opening and head on the gate, and consequently the air demand is problematic. This study focuses on quantifying air demand and air vent sizing for the small to medium-sized embankment dam low-level outlet geometries by providing: 1. Cd values as a function of gate openings and air demand; to better estimate flow rates from outlet works of similar geometries. 2. Flow conditions for varying operating conditions. 3. A new relationship for sizing air vents as a function of driving head and gate opening. 4. The magnitude of negative pressures for non-vented conduits. 5. A foundation for future studies and development of air demand research. This thesis presents the findings of this study.

When controlling the real-time system that is a robotic joint, reliability is the chief concern. Implementing controllers via embedded software imposes several limitations on the controller frequency, such as algorithm latency and supplemental processes (like networking) competing for execution time. If these obstacles prevent a controller from finishing a cycle before its period expires, stability cannot be guaranteed. A developer of embedded software controls ought to be able to prove the timeliness of the controller based on analysis and validation. Otherwise, the choice of controller frequency is arbitrary, without any guarantee of stability in worst-case scenarios. This work realized a truly distributed control system for a humanoid robot by migrating a portion of the joint controller to the low-level. While the central computer is still responsible for determining a joint torque to properly realize whole-body objectives, the low-level processor executes force control locally to produce that torque via a linear actuator. Decoupling the force controller from networking reduced its latency and variability, allowing it to execute several times between receiving desired forces. Furthermore, a real-time operating system was added on top of the existing firmware to enforce and verify timing constraints. Preemptive threading modules within the real-time kernel allow the processor to prioritize controller execution above all other activities, aiding its routine completion. The chosen RTOS provides powerful instrumentation and debugging tools to efficiently verify proper execution and quickly resolve errors. These changes allowed the controller to demonstratively operate at a greater frequency with a full guarantee that timeliness is enforced under all possible circumstances. Verification was performed on a robotic joint test stand to prepare for deployment on a full-scale humanoid robot. / Master of Science / A "control algorithm", or simply "controller", can be made to balance a humanoid robot by taking a snapshot of the robot's pose and motion to calculate how to manipulate each motor to maintain stability. This process repeats many times per second. The precise rate is a design choice termed as the controller's "frequency". While a higher frequency generally yields better performance, too great a frequency means the algorithm cannot finish before it is time to repeat, resulting in malfunction. This work implements tools for developers to observe exactly how long a controller algorithm takes to run. This helps the developer choose a frequency fast enough to maintain robot balance within the computer's capabilities.

Långa behandlingstider, recidiv och smärta är fenomen som associeras med ortodontisk behandling. Under senare år har ett flertal studier undersökt terapilaser som en metod för att förbättra ortodontisk behandling i dessa avseenden.Syftena med denna systematiska litteraturstudie var att undersöka evidensen för huruvida low-level laser therapy (LLLT) kan fungera som en effektiv metod för att (I) accelerera tandförflyttning, (II) förhindra ortodontisk recidiv eller (III) minska akut smärta vid ortodontisk behandling.Den här systematiska litteraturstudien utfördes i enlighet med riktlinjer från Statens beredning för medicinsk utvärdering, SBU. Vid litteratursökningen i februari 2013 användes databaserna PubMed/Medline samt Cochrane. En kompletterande sökning i Scitation gjordes i oktober 2013. I mars 2014 gjordes en uppdaterad sökning. Två studier där acceleration av tandförflyttning med hjälp av LLLT samt tolv studier där LLLT använts för att minska akut smärta vid ortodontisk behandling hittades. Ingen studie där LLLT använts som metod för att undvika ortodontisk recidiv matchade de givna inklusionskriterierna.Studierna visade på en trend av goda resultat vid användning av LLLT. En ökad tandförflyttningshastighet på omkring 30 % kunde ses samt att försökspersoner rapporterade en smärtreduktion på en numerisk skala, NRS eller en visuell analog skala, VAS. Stor variation kunde ses mellan studierna gällande laserstrålningens olika parametrar och det är uppenbart att det saknas konsensus gällande olika typer av laser, strålningsfrekvens samt styrka.Denna systematiska litteraturstudie föreslår att LLLT kan underlättar den ortodontiska behandlingen genom att minska både behandlingstid och smärta. Inga studier hittades gällande LLLTs inverkan på att minska recidiv. Fler väldesignade undersökningar krävs för att bestämma om low-level laser therapy är en effektiv metod för att förbättra ortodontisk behandling.Denna systematiska litteraturstudie föreslår att evidensen är låg för LLLT som metod för att accelerera ortodontisk tandförflyttning och väldigt låg för LLLT som metod för att minska akut ortodontisk smärta. Ingen studie som uppfyllde givna inklusionskriterier har gjorts gällande LLLTs förmåga att minska ortodontisk recidiv. Detta understryker behovet av forskning med hög kvalitet och större överensstämmelse i både studiedesign och laserschema för att i framtiden kunna bestämma om LLLT är en effektiv metod för att accelerera tandförflyttning, förhindra ortodontisk recidiv eller minska akut ortodontisk smärta hos barn och unga vuxna. / Extensive treatment time, relapse and pain are all phenomena associated with orthodontic treatment. Recently, several studies using laser therapy as a method to improve orthodontic treatment have been carried out to offer a solution to the above presented problems.The objectives of this systematic review were to investigate the level of evidence for low-level laser therapy as an effective method to either (I) accelerate tooth movement, (II) prevent orthodontic relapse or (III) diminish acute pain during orthodontic treatment.The present study was designed according to The Swedish Council on Technology Assessment in Health Care. The literature search was performed using PubMed, Medline electronic databases and Cochrane Controlled Clinical Trials Register up to February 2013. An additional search was carried out in Scitation in October 2013. In March 2014 an update search was done. Two studies were found regarding acceleration of tooth movement when using LLLT and twelve studies used LLLT to diminish acute pain. No study on LLLT as a method to prevent orthodontic relapse was found according to given inclusion criteria.The studies showed a trend of good results when using LLLT. Acceleration of approximately 30 % was seen when using LLLT and the subjects reported a lower pain score on numeric rate scale (NRS) or visual analogue scale (VAS) compared to control. The laser regimen was used with a wide range and it is obvious that no consensus has been reached considering different lasers, frequencies and powers.The present systematic review suggests that the quality level of evidence is low for LLLT to accelerate orthodontic tooth movement and very low for LLLT to diminish acute orthodontic pain. No study according to given inclusion criteria has been done on LLLTs ability to diminish orthodontic relapse. This emphasises the need for high quality research with consistency in study design and laser schedule to further determine if LLLT is an effective method to accelerate tooth movement, prevent orthodontic relapse or diminish acute pain during orthodontic treatment on children and young adults.

Bitstream generation has traditionally been the single part of the FPGA design flow that has not been openly reproduced. This work enables bitstream generation for "limited" resources without reverse-engineering or violating End-User License Agreement terms. Two use cases in particular have motivated this work--embedded bitstream generation and fast bitstream generation for small changes in design--both of which are not feasible with the Xilinx's bitstream generation tool. The approach is to first define a set of primitives which can implement an arbitrary digital design and create a library of micro-bitstreams of the primitives. An input design is then mapped to the set of primitives and a bitstream for the design is generated by merging the corresponding micro-bitstreams. This work uses architectural primitives. Initial support is limited to the Virtex-5 and Virtex-7 family of FPGAs from Xilinx, but it can be extended to other Xilinx architectures. Nearly all routing resources in the device, as well as the most common logic resources are supported by this work. / Master of Science

Thesis (MTech (Biomedical Technology))--Cape Technikon, Cape Town, 2004 / The need for radiobiological research was bom from the discovery that high doses of radiation could cause cancer and other health effects. However, recent developments in molecular biology uncovered the effects of low doses of radiation on different biological systems and as a result new techniques have been developed to measure these effects. The aim of this study was thus to validate biomarkers of initial DNA strand breaks, micronucleus formation, and the different pt ;ases of apoptosis as biological indicators of low-dose radiation damage. Furthermore, the difference in response of blood cells to different qualities and doses of radiation was investigated by irradiating cells with low- and high-LET radiation simultaneously. Blood from one donor was irradiated with doses between 0 and 4 Gy gamma- and neutron radiation. The alkaline single-cell gel electrophoresis (comet) assay was performed on different cell preparations directly after irradiation for the detection of initial DNA strand breaks. Radiation-induced cytogenetic damage was investigated using the cytokinesis-blocked micronucleus assay while different features of apoptosis were investigated by measuring caspase activation, enzymatic DNA fragmentation, and cellular morphology. The comet assay was sensitive enough to detect DNA strand breaks above 0.25 Gy and showed that the Iymphocyte isolation process induced some endogenous damage in cells, detected by the formation of highly damaged cells and hedgehogs in isolated cell preparations only.

Abstract Orthodontic tooth movement is a biological response to a mechanical force. One of the challenges in orthodontics is obtaining desired tooth movement during treatment. Accelerating tooth movement and decreasing demands on anchorage can reduce treatment times and overall satisfaction for patient and doctor. Low-level laser therapy (LLLT) is emerging as a technology that may decrease orthodontic treatment time. Many in vitro and in vivo studies have reported the effects of low level lasers at random time points and energy densities. None of the studies have optimized the dose required for osteoblast proliferation and differentiation. The purpose of this study was to find the optimum stimulatory dose of low level laser irradiation (LLLI) on human osteoblast cell proliferation and differentiation and to analyze our findings with reference to the Arndt-Shultz Law of applied energy. In this in vitro study a GaAlAs laser at 830nm, 20 mW with continuous exposure at various doses were used on a human osteoblast cell line. According to the Arndt-Shulz Law weak stimuli initiate vital activity, moderate stimuli enhance the cellular activity with subsequent peak stimulation and greater stimuli (beyond a threshold value) may not have any influence or inhibit the vital activity. The implications of LLLI on human osteoblasts and influencing tooth movement in orthodontics were discussed. Human osteoblasts were cultured in minimum essential medium (MEM) complete medium consisting 10% fetal bovine serum and 1% antibiotics. Cells grown in complete medium were plated onto 96 well plate, allowed to adhere for 4-5 hours and were exposed to GaAlAs lasers at 6 , 12, 18, 24, 30, 36, 45, 60, 75, and 90 seconds. The cells treated with xiii LLLI were assessed for cell proliferation at 24, 48 and 72 hour intervals. A calorimetric cell proliferation assay (WST-1) assay was performed according to manufacture's instructions. The results indicated that at 24 hours the 6 and 12 seconds doses significantly inhibited proliferation compared to the control. At 48 hours the 30 seconds exposure significantly increased proliferation. At 72 hours time interval, cell proliferation was observed in a dose dependent pattern with a minimum at 6 seconds with peak proliferation at 18 seconds. A gradual decrease in cell viability was observed in the cells treated beyond this dose with a maximum inhibition seen at 60 seconds. At 75 and 90 seconds no difference was observed between the control and experimental group. To establish efficient acquisition of adequate quantities of alkaline phosphatase, cells were grown in 12 well plates in complete medium or osteogenic medium. These cells were exposed to LLLI for 18, 48, and 60 seconds. The activity of early osteogenic differentiation marker alkaline phosphatase (ALP) was investigated 10 days post exposure. Our results demonstrated that alkaline phosphatase activity at 2.4 - 7.3 J/cm2 with 48 - 60 seconds of exposure, and an incident power ranging from 85-269mw significantly increased. The findings suggest that these irradiated cells obeyed the Arndt Shulz Law governing cellular response to applied energy. Further this research indicates the possible role of LLLT to accelerate tooth movement in orthodontics. Complete disclosure of low level laser parameters is essential in order to accurately compare findings of researchers.

published_or_final_version / abstract / Physics / Master / Master of Philosophy

Os retalhos cutâneos são amplamente utilizados na cirurgia plástica, principalmente na reparadora. Após o procedimento operatório, uma das principais complicações é a isquemia, podendo ocasionar a necrose do retalho. Vários recursos têm sido estudados com o intuito de aumentar a viabilidade desses retalhos. Dentre esses recursos, o laser de baixa intensidade é uma alternativa de tratamento, uma vez que pode promover um aumento da microcirculação e da neoformação vascular. Entretanto, existem discrepâncias na literatura em relação aos parâmetros empregados no uso do laser de baixa intensidade, principalmente das fluências utilizadas nos tratamentos. Este estudo teve como objetivo verificar o efeito de diferentes fluências do laser de 670nm, na viabilidade do retalho cutâneo randômico em ratos. Foram utilizados 100 ratos, da linhagem Wistar, distribuídos em 5 grupos de 20 animais cada. O retalho cutâneo randômico de base cranial foi realizado com dimensões de 10 X 4 cm e uma barreira plástica foi interposta entre o mesmo e o leito doador. O grupo 1 (controle) foi submetido à simulação de tratamento com o aparelho desligado. O grupo 2 foi submetido à radiação laser com fluência de 3 J/\'CM POT.2\'. Os grupos 3, 4 e 5 foram irradiados com fluências de 6 J/\'CM POT.2\', 12 J/\'CM POT.2\' e 24 J/\'CM POT.2\', respectivamente. Todos os grupos experimentais receberam a radiação laser imediatamente após o procedimento operatório e nos 4 dias subseqüentes, utilizando-se a técnica pontual em contato em 24 pontos distribuídos sobre e ao redor do retalho. No sétimo dia pós-operatório, as porcentagens da área de necrose dos retalhos foram avaliadas pelo método do gabarito de papel e também foi coletada uma amostra do retalho de 10 animais de cada grupo, escolhidos aleatoriamente, para a realização da contagem dos vasos sangüíneos. O grupo 1 apresentou média de área de necrose de 49,92%; o grupo 2 - 41,84%; o grupo 3 - 36,51%; o grupo 4 - 29,45% e o grupo 5 - 20,37%. Na contagem dos vasos, o grupo 1 obteve média de 65,2; o grupo 2 - 92,6; o grupo 3 - 105,5; o grupo 4 - 128,7 e o grupo 5 - 171,0. Na análise estatística, realizou-se a ANOVA, seguida do teste de comparações múltiplas de Tukey. Os resultados mostraram que todos os grupos experimentais apresentaram valores estatisticamente significativos comparados ao grupo controle, sendo que o grupo 5 apresentou a menor área de necrose e o maior número de vasos quando comparado aos demais grupos deste estudo (p < 0,01). O teste de correlação linear de Pearson indicou alta correlação negativa entre a porcentagem de necrose e o número de vasos dos retalhos (-0,972 / p = 0,0001). O laser de baixa intensidade (670nm) aplicado com fluência de 24 J/\'CM POT.2\' foi mais eficaz no aumento da viabilidade do retalho cutâneo randômico em ratos, comparado às outras fluências utilizadas neste estudo. / Skin flaps are widely used in plastic surgery, mainly in repair surgeries. After this reconstructive procedure, one of the main consequences is the decrease of blood flow in the area, which can be responsible by tissue necrosis. In this context, a lot of studies have investigated treatments able to increase the viability of the flap and the low level laser therapy (LLLT) has been chosen as an efficient treatment to reduce post-injury inflammatory processes and to stimulate the formation of new blood vessels. However, the use of a wide range of fluences by different authors and the lack of standardized experimental conditions make it difficult to compare published results. The aim of this study was to investigate the dose-response effects of 670nm laser on the viability of random skin flap in rats. One hundred Wistar male rats were used in this study. The animals were divided into 5 groups: group 1 (control group); group 2 (treated with 3 J/\'CM POT.2\'); group 3 (treated with 6 J/\'CM POT.2\'); group 4 (treated with 12 J/\'CM POT.2\') and group 5 (treated with 24 J/\'CM POT.2\'). The skin flap was made on the back of all animals studied (dimensions: 10 x 4 cm) and before the sutures were done, a plastic sheet was interposed between the flap and the donor site. Laser irradiation was performed immediately after the surgery and on days 1, 2, 3 and 4 post-surgery. The irradiation was made punctually, on 24 points on the skin surface and around it. The percentage of the necrosis area of the flap was calculated by the paper template method at the day 7 postoperative. Moreover, a sample of the skin flaps was collected from 10 rats of each group, which were chosen aleatory, to performe the count of the blood vessels. The animals of all treated groups showed statistically significant differences when compared to the control group (necrosis area: 49, 92%). The necrosis area of the treated groups were 41,82% (group 2), 36,51% (group 3), 29,45% (group 4) and 20,37% (group 5). In the count of blood vessels, group 1 showed the mean of 65,2; group 2 - 92,6; group 3 - 105,5; group 4 - 128,7 and group 5 - 171,0. The ANOVA test, followed by the Tukey test, for multiple comparasions were used. The results showed that all experimental groups showed statistically lower values for the necrosis area compared to the control and a higher number of blood vessels in the skin flap. It can be observed that the best results were found in the animals of group 5 (p < 0,01). In addition, the Pearson coefficient showed a significant negative correlation between necrosis area and the number of vessels (-0,972 / p = 0,0001). This present study has demonstrated that the 670nm laser was efficient to increase the viability of the skin flap, at all fluences used, with a tendency of reaching better results at higher dosages (24 J/\'CM POT.2\').