Marcos Tadeu Tavares Pacheco

DOSE AND WAVELENGTH OF LASER LIGHT HAVE INFLUENCE ON THE REPAIR OF CUTANEOUS WOUNDS

OBJECTIVE The objective of the present study was to compare histologically the effect of GaAlAs (lambda 830 nm, phi approximately 2 mm(2), 35 mW) and InGaAlP (lambda 685 nm, phi approximately 2 mm(2), 35 mW) lasers, alone or in association with doses of 20 or 50 J/cm(2) on cutaneous wounds in the dorsum of the Wistar rat. BACKGROUND DATA The healing time of surgical wounds is of extreme importance and it is usually associated with a post-operative period free of infection and with less pain and inflammation. MATERIALS AND METHODS Sixty Wistar rats were divided into seven groups: Group I - control (non-irradiated); Group II - lambda 685 nm, 20 J/cm(2); Group III - lambda 830 nm, 20 J/cm(2); Group IV - lambda 685 nm and lambda 830 nm, 20 J/cm(2); Group V - lambda 685 nm, 50 J/cm(2)); Group VI - lambda 830 nm, 50 J/cm(2); and Group VII - lambda 685 nm and 830 nm, 50 J/cm(2). The animals were sacrificed 3, 5, and 7 days after surgery. RESULTS Light microscopic analysis using H&E and Picrosírius stains showed that, at the end of the experimental period, irradiated subjects showed increased collagen production and organization when compared to non-irradiated controls. Inflammation was still present in all groups at this time. CONCLUSION Group IV (lambda 830 nm and lambda 685 nm, 20 J/cm(2)) presented better results at the end of the experimental period. It is concluded that low-level light therapy (LLLT) can have a positive biomodulatory effect on the repair of cutaneous wounds.

Raman spectroscopy study of atherosclerosis in human carotid artery.

Fourier-transform (FT)-Raman spectroscopy has been used for identification and evaluation of human artherosclerotic lesions, providing biochemical information on arteries. In this work, fragments of human carotid arteries postmortem were analyzed using a FT-Raman spectrometer operating at an excitation wavelength of 1064 nm, power of 200 mW, and spectral resolution of 4 cm(-1). A total of 75 carotid fragments were spectroscopically scanned and FT-Raman results were compared with histopathology. Discriminant analysis using Mahalanobis distance was applied over principal components scores for tissue classification into three categories: nonatherosclerotic, atherosclerotic plaque without calcification and with calcification. Nonatherosclerotic artery, atherosclerotic plaque, and calcified plaque exhibit spectral signatures related to biochemicals presented in each tissue type, such as bands of collagen and elastin (proteins), cholesterol and its esters, and calcium hydroxyapatite and carbonate apatite, respectively. Spectra of nonatherosclerotic artery were then classified into two groups: normal and discrete diffuse thickening of the intima layer (first group) and moderate and intense diffuse thickening of the intima layer (second group). FT-Raman could identify and classify the tissues found in the atherosclerotic process in human carotid in vitro and had the ability to identify alterations to the diffuse thickening of the intima layer and classify it depending on the intensity of the thickening.

Rapid Identification of Bacterial Species by Fluorescence Spectroscopy and Classification Through Principal Components Analysis

This work presents the development of a method for rapid bacterial identification based on the autofluorescence spectrum. It was demonstrated differences in the autofluorescence spectrum in three bacterial species and the subsequent separation, through the Principal Components Analysis (PCA) technique, in groups with high likeness, that could identify the bacteria in less than 10 min. Fluorescence spectra of 60 samples of 3 different bacterial species (Escherichia coli, EC, Enterococcus faecalis, EF and Staphylococcus aureus, SA), previously identified by automated equipment Mini API, were collected in 10 excitation wavelengths from 330 to 510 nm. The PCA technique applied to the fluorescence spectra showed that bacteria species could be identified with sensitivity and specificity higher than 90% according to differences that occur within the spectra with excitation of 410 nm and 430 nm. This work presented a method of bacterial identification of three more frequent and more clinically significant species based on the autofluorescence spectra in the excitation wavelengths of 410 and 430 nm and the classification of the spectra in three groups using PCA. The results demonstrated that the bacterial identification is very efficient with such methodology. The proposed method is rapid, ease to perform and low cost compared to standard methods.

Compound parabolic concentrator probe for efficient light collection in spectroscopy of biological tissue

We describe a compound parabolic concentrator (CPC)-based probe for enhanced signal collection in the spectroscopy of biological tissues. Theoretical considerations governing signal enhancement compared with conventional collection methods are given. A ray-tracing program was used to analyze the throughput of CPCs with shape deviations and surface imperfections. A modified CPC shape with 99% throughput was discovered. A 4.4-mm-long CPC was manufactured and incorporated into an optical fiber-based near-infrared Raman spectrometer system. For human tissue samples, light collection was enhanced by a factor of 7 compared with collection with 0.29-NA optical fibers.

Analysis of Near-infrared Raman Spectroscopy as a New Technique for a Transcutaneous Non-invasive Diagnosis of Blood Components

Abstract. Near-infrared Raman spectroscopy can be a new technique for physical evaluations, allowing the measurement of lactic acid concentrations, in blood or muscles, during the physical activity in a transcutaneous non-invasive way. Lactic acid accumulation in the human body is one of the factors that leads to fatigue and therefore it should be continually monitored during physical training. Our proposal is to use Raman spectroscopy to monitor the lactic acid present in an athlete without interrupting his exercise for sample collection. The experimental set-up for Raman spectroscopy comprised a near infrared laser at 830 nm, a Kaiser f/1.8 spectrometer and a liquid nitrogen cooled CCD detector. The radiation from the exciting laser is blocked in the collecting system by Kaiser holographic filters. A personal computer controls the entire system, saving and processing the Raman spectra. Experiments were undertaken to verify the presence of lactic acid in the Raman spectra of solutions of lactic acid in human serum and in blood from a Wistar rat. After these two experiments, another was developed in vivo in a Wistar rat, injecting intraperitoneally 1 ml of a 0.12 mol/l lactic acid aqueous solution. An optical fibre catheter touching the skin of the rat groin, over the ileac vein collected the Raman signal. The presence of lactic acid was detected inside a live organism, in a transcutaneous non-invasive way. The minimum lactic acid concentration that the equipment can detect was also studied. An experiment was undertaken for that purpose, in which the laser illuminated directly a quartz cuvette containing solutions with decreasing lactic acid concentrations up to values near to the physiological level in the human body. The results indicated that the technique can be suitable for the physical evaluation of athletes.

Discriminating model for diagnosis of basal cell carcinoma and melanoma in vitro based on the Raman spectra of selected biochemicals

Abstract. Raman spectroscopy has been employed to identify differences in the biochemical constitution of malignant [basal cell carcinoma (BCC) and melanoma (MEL)] cells compared to normal skin tissues, with the goal of skin cancer diagnosis. We collected Raman spectra from compounds such as proteins, lipids, and nucleic acids, which are expected to be represented in human skin spectra, and developed a linear least-squares fitting model to estimate the contributions of these compounds to the tissue spectra. We used a set of 145 spectra from biopsy fragments of normal (30 spectra), BCC (96 spectra), and MEL (19 spectra) skin tissues, collected using a near-infrared Raman spectrometer (830 nm, 50 to 200 mW, and 20 s exposure time) coupled to a Raman probe. We applied the best-fitting model to the spectra of biochemicals and tissues, hypothesizing that the relative spectral contribution of each compound to the tissue Raman spectrum changes according to the disease. We verified that actin, collagen, elastin, and triolein were the most important biochemicals representing the spectral features of skin tissues. A classification model applied to the relative contribution of collagen III, elastin, and melanin using Euclidean distance as a discriminator could differentiate normal from BCC and MEL.

Use of 660-nm Diode Laser in the Prevention and Treatment of Human Oral Mucositis Induced by Radiotherapy and Chemotherapy

OBJECTIVE The aim of this multidisciplinary study was to evaluate quantitatively and qualitatively the effect of a 660-nm diode laser in the prevention and treatment of human oral mucositis (OM) in patients suffering from head and neck cancer who had undergone radiotherapy and chemotherapy. BACKGROUND DATA OM is a severe oral lesion resulting from the toxic effects of treatment for cancer in the head and neck region. Low-level laser therapy is indicated to prevent and treat this oral complication and may be used alone or in association with conventional drug treatment, producing pain relief and wound repair. METHODS This study included 72 patients with head and neck cancer treated at the Cancer Hospital of Mato-Grosso, Brazil, and divided into a control group (C; n = 36) and a laser group (L; n = 36). Laser therapy was performed in combination with radiotherapy and chemotherapy twice a week using a diode laser (lambda = 660 nm, power = 30 mW, spot size = 2 mm, energy = 2 J per point). RESULTS Statistically significant differences were observed between the two groups. Patients in group L usually did not present with OM or pain, but all patients in group C presented with OM ranging from Level I to III associated with pain. This difference was significant from week 1 on, increased until week 4 and remained stable up to week 7. CONCLUSION Laser therapy was effective in preventing and treating oral effects induced by radiotherapy and chemotherapy, thus improving the patients quality of life.

Raman spectroscopy: A powerful technique for biochemical analysis and diagnosis

The present work focuses on the recent applications of Raman spectroscopy (RS) on biochemical analysis and diagnosis of several biological materials with or without pathological alterations. Important published works about Raman spectroscopy and its use for medical applications were critically reviewed, including articles form our group in order to evaluate the state of the art of the subject. The potential for sample characterization with RS associated to the possibility of analysisin situ makes this instrumental technique in a very auspicious tool of biochemical analysis. RS can promote a significant improvement in the chemical identification and characterization of biological systems, clinical diagnosis and prognosis regarding several diseases and quality of life of innumerous patients. The spectroscopic evaluation is based on the analysis of the Raman spectrum regarding the identification of fingerprint bands of main biological macromolecules, such as nucleic acids, proteins and fat, present in the tissue structure. This review evaluates the employment of RS in diagnosing such pathological manifestations as well as the efforts focused on the instrumental development to biomedical applications. Furthermore, advantages and limitations of this kind of approach are discussed in order to improve the biochemical analysis and diagnosis of several diseases.

Vicker's hardness and Raman spectroscopy evaluation of a dental composite cured by an argon laser and a halogen lamp

We present the results of the Vickers hardness test and the use of near-infrared Raman spectroscopy (RS) to measure in vitro the degree of conversion (DC) of a bis(phenol)-A-glycidyl-dimethacrylate-based composite resin, photoactivated by both a halogen lamp (power density=478 mW/cm(2); 8-mm diameter spot) and an argon laser (power density=625 mW/cm(2); 7-mm diameter spot). The degree of conversion was estimated by analyzing the relative intensities between the aromatic C=C stretching Raman mode at 1610 cm(-1) and the methacrylate C=C stretching Raman mode (1640 cm(-1)) on top and bottom surfaces. For the hardness evaluation, the samples were embedded in polyester resin and three indentations with a 50-g load for 10 s were made on the top surface. The higher relative DC values achieved by the photoactivation of a composite resin by the argon laser suggest a better biocompatibility in the bottom surface. The correlation test showed that the higher Vickers hardness number (VHN) values were associated with higher DC values. The derivative analysis showed a greater curing rate from 5 to 20 s of exposure. The comparison of VHN and DC values with both light sources at each curing time showed that a small change in conversion is related to a large change in hardness. Raman spectroscopy is more sensitive to changes in the first stages of curing reaction than later ones, and the Vickers hardness assay is more sensitive to changes in the last stages.

Discrimination of Basal Cell Carcinoma and Melanoma from Normal Skin Biopsies in Vitro Through Raman Spectroscopy and Principal Component Analysis

OBJECTIVE Raman spectroscopy has been employed to discriminate between malignant (basal cell carcinoma [BCC] and melanoma [MEL]) and normal (N) skin tissues in vitro, aimed at developing a method for cancer diagnosis. BACKGROUND DATA Raman spectroscopy is an analytical tool that could be used to diagnose skin cancer rapidly and noninvasively. METHODS Skin biopsy fragments of ≈ 2 mm(2) from excisional surgeries were scanned through a Raman spectrometer (830 nm excitation wavelength, 50 to 200 mW of power, and 20 sec exposure time) coupled to a fiber optic Raman probe. Principal component analysis (PCA) and Euclidean distance were employed to develop a discrimination model to classify samples according to histopathology. In this model, we used a set of 145 spectra from N (30 spectra), BCC (96 spectra), and MEL (19 spectra) skin tissues. RESULTS We demonstrated that principal components (PCs) 1 to 4 accounted for 95.4% of all spectral variation. These PCs have been spectrally correlated to the biochemicals present in tissues, such as proteins, lipids, and melanin. The scores of PC2 and PC3 revealed statistically significant differences among N, BCC, and MEL (ANOVA, p<0.05) and were used in the discrimination model. A total of 28 out of 30 spectra were correctly diagnosed as N, 93 out of 96 as BCC, and 13 out of 19 as MEL, with an overall accuracy of 92.4%. CONCLUSIONS This discrimination model based on PCA and Euclidean distance could differentiate N from malignant (BCC and MEL) with high sensitivity and specificity.