Lasers in Medicine
Year:2013 | Volume:10 | Issue:1|Papers Count:5

Background and Aim: This study evaluated the influence of storage time on micro- tensile bond strength of “two step etch and rinse adhesives” to treated enamel with Er; YAG laser.Materials and Methods: Human incisor teeth were sectioned to 8×8×2 Dimensions beams and randomly divided into 6 groups. Enamel surface of samples from three groups (III, IV, V) were prepared with Er; YAG laser. Single Bond 2 was used to bond a composite rod (Z250) to enamel surfaces. Each group was further divided into three subgroups according to water storage time; 24 hours (only for polymerization completion), 6 and 12 months. Micro-tensile bond strengths were determined under a crosshead speed of 0, 5mm/min using a universal testing machine and expressed in MPa. Data was statistically analyzed by ANOVA and Tukay post hoc test.Results: Two way ANOVA results showed significant effect of storage time on bond strength (p<0.001) but laser application was not significantly effective. Laser and storage time interaction effects were significantly different (p=0.001). Tukey HSD results demonstrated significant differences between stored groups. The micro-tensile bond strength of adhesives to lased and non lased enamel surfaces does not provide significant differences. However, bond strength was influenced by the storage time, being stronger with decrease of water storage duration.

Background and Aim: Hirsutism is one of disturbing symptoms of Polycystic Ovary Syndrome (PCO). One of the applications of lasers in dermatology is hair removal. The Comparison of Alexandritis laser application on PCO positive and negative women helps us to attain the number of necessary sessions for effective hair removal, and also necessary medicine for hirsutism treatment simultaneously with laser treatment in PCO positive women.Material and Methods: Forty five women with PCO symptoms went under treatment with Alexandritis Laser Team Italy upon an established protocol. Photographs were taken exactly before starting treatment and after each session. Hair numbers were counted randomly in 1×1 cm2 at the most hairy place. The total mean of hair reduction was calculated each session. The hair reduction rate at the PCO positive group was compared with the hair negative group. The assessment was performed in the PCO positive group after 3 treatment sessions and finally 6 months after last treatment session.Results: The mean hair reduction in the PCO positive group was 13.13%±11.52, 21.69%±16.35 and 32.54%±19.79 after first, second and third treatment sessions, respectively. The mean hair reduction rate in this group was 30.95%±17.77 (p<0.05) six months after last treatment session. Meanwhile, in the PCO negative group, the hair reduction rates were 25.61%±13.50, 47.35%±16.41, 57.78%±16.85 after first, second and third treatment sessions, respectively. This rate was 57.87±20.75 (p<0.05) six months after last treatment session in the PCO negative women. The hair reduction rate was lower at the PCO positive group compare than the PCO negative group (p<0.05). The PCO positive patients need concomitant medical therapy along with hair removal lasers. They may need more laser treatment sessions compare to the PCO negative patients.

Background and Aim: Fluorscence Tomography is Emerging as an important alternative to molecular imaging. Simultaneous detection of several biological processes in vivo is a common requirement in molecular imaging. Application of multiple fluorophores and multispectral approaches have been widely used for distinguishing fluorescence signals. But, in case of spectral overlapping isolation of signals requires using unmixing algorithms. In this study, the researchers used blind source unmixing method, Non-Negative Matrix Factorization (NMF), to decompose contributions of different fluorescent probes in Fluorescence Molecular Tomography (FMT) images.Methods: A cylinder tissue-like phantom containing 2 transparent tube with 0.5 millimeter inner diameter filled with different fluorophores (fluorescine and rhodamine). It was imaged by using experimental FMT setup at three different wavelengths. We performed NMF algorithm on multispectral measurement to resolve the relative contributions of fluorescent dyes. Multispectral projection was simulated and used as input of unmixing algorithms in simulation part of study. The projection images of each probes was simulated and used as reference data to evaluate performance of unmixing algorithm for simulated images.Results: Two set of data, each of them corresponded to isolated contribution of each fluorophore, were obtained as the result of performing the algorithm on multispectral measurements. The "root mean square error" (RMSE) was calculated between original reference and related unmixed images. The difference between "Peak signal to noise ratio" (PSNR) values was statistically significant for each reference image (p<0.01). It shows that the proposed algorithm works in an accurate manner. The correlation coefficient between unmixed images and related reference image was more than 97% in simulation study. Unmixing method based on NMF can be used as an efficient technique to unmix contribution of different florophores. The 3-D location of each florophore can be obtained separately by reconstructing of these unmixed image.

Background and Aim: Two main coronary arteries, left and right, have duty of blood pumping to the heart muscles. Coronary arteries disturbances (CAD) cause to provide different diseases. The most common diseases following the CAD are myocardial instability and/or infarction. Coronary thrombosis is most common reason for myocardial instability and/or infraction. The thrombosis is formed by atherosclerosis in more than 90% of the cases. The atherosclerotic plaques consist of cholesterol and calcium components. Ischemia is happened when the interior cross section of the artery decrease by 75% or more. The rate of death by acute myocardial infarction is one of third or fourth in the industrial or developing countries, respectfully. Laser angioplasty is a method that may beneficial to remove the atherosclerotic plaques, similar to balloon angioplasty. In this method, bunch of flexible optical fiber substitute balloon catheter and deliver ultra violet pulses to the tissue lead to vaporize the residual plaques and open the pathway. Many researchers pointed out that restenosis might be increased after laser angioplasty by ultraviolet pulses. The aim of this study is estimation of probability of longer wavelength especially with ultrashort pulses for low fluence ablation. This research evaluates range of laser parameters before any practical experiment in long wavelength angioplasty.Material and Methods: In this paper, laser pulse matter interaction equation has been solved and fluence threshold extracted in different conditions for Atherosclerotic plaque.If the fluence threshold of long wavelength laser ablation is lower than used fluence in short wavelength (Excimer laser), the utilization of long wavelength is reasonable. Furthermore, absorption coefficient calculated for different wavelength and time durations.Results: It is suggested to use laser with 800-1064 nm and duration shorter than 30 picoseconds.The nonlinear absorption coefficient of tissue has been considered and the results showed that usage of the mentioned wavelengths lead to reduce threshold fluence and increase nonlinear absorption coefficient. Other considerations relate to laser angioplasty in visible and long wavelength are discussed by the authors.

Background and Aim: Sentinel lymph node mapping is effective for breast cancer diagnosis and efficient treatment. Sentinel lymph node mapping is performed by using optical imaging. Recent studies indicate that excitation light leakage stranding is the most important factor in images acquired signal to noise ratio, and sensitivity can be affected and does not provide accurate diagnosis for lymph node sentinel. The aim of this project is to assess the impact of light leakage and sensitivity over the surgery fluorescence imaging system point spread function in tissue-like phantom.Material and Methods: Six different optical were designed and implemented with different combinations of lenses and filters include the laser, achromatic lenses and filters by using Zemax software.Appropriate position source-detector simulated with finite element method by NIRFAST software (Algorithm for numerical model and image reconstruction). Tissue-like phantom were made for imaging. The excitation light leakage was calculated by transmission ratio equation and point-spread function was determined by using "Full width at half maximum" (FWHM).Results: The best design consisted of two lenses and two filters (a filter between two lenses and other filters between phantom and objective lens) with a value of 0.192±0.002 light leakage (p<0.0006) and 22% improvement in the point spread function than the current designs, consisting of a lens and the filter, in a similar system. The method for reducing excitation light leakage is presented for validating collected signals for fluorescence imaging. The researchers can use correction coefficient to obtain accuracy intensity of fluorescence concentration.