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1.
J Nanosci Nanotechnol ; 20(2): 819-827, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31383077

RESUMO

Synthesis of pure Hafnium Oxide (HfO2), and HfO2 doped with Gadolinium (1, 3, 5 and 7 mol%) nanoparticles (NPs) had been carried out by Precipitation and co-precipitation method using the precursor solution of Hafnium (IV) chloride (HfCl4) and Gadolinium(III) chloride hexahydrate (GdCl3·6H2O) with Sodium hydroxide (NaOH) which was dissolved in deionized water. The synthesized compound was characterized and analyzed by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDX), UV-visible spectrophotometer, Photoluminescence (PL), Fourier Transform infrared spectroscopy (FTIR) and Raman spectroscopy. The result from X-ray diffraction showed that the Gd3+ concentration for 7 mol% had attended directly crystalline phase of Cubic HfO2 structure. Morphology and element analysis of the samples were analyzed using FESEM and EDX, which indicated cluster formation, fluffy and voids with highly agglomerated particles and EDX exhibited no extra peaks with other than constituent elements present in extrinsic HfO2. From UV Spectra it was observed that the optical band gap of both Intrinsic and extrinsic of HfO2 NPs were found to be 5.74 eV, 3.62 eV, 3.69 eV, 3.78 eV and 4.19 eV. The Photoluminescence Spectra showed the 313 nm emission line which might be due to 6P7/2→8S7/2 transition and the Raman Spectra clearly represented the monoclinic structure by showing the presence of Ag and Bg Modes and cubic structure because of the presence of F2g mode.

2.
J Fluoresc ; 29(3): 803-812, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31187405

RESUMO

With the emerging trend of personalized cancer treatment, there is a need to develop noninvasive/minimally invasive techniques for treatment monitoring. In this regard, in this work fluorescence analysis of blood plasma of breast cancer patients has been used for the evaluation of response to treatment. This approach delivers information not only about the change in biochemical constituents but also about the altered metabolic pathway. Spectral deconvolution method is employed to compute the fluorescence intensity, peak wavelength, and full-width half maxima for different endogenous fluorophores. The fluorescence measurements were made on blood plasma collected from 10 normal subjects, 10 pre-treated cancer patients, and 10 post-treated patients. Besides, variations in relative concentration of tryptophan, collagen, NADH, and FAD, peak shifts and broadening of peaks are observed for tryptophan, NADH, and FAD, in blood plasma of pre-treated cancer patients indicating both biochemical and microenvironmental changes at cellular level. Further, the spectral profile of blood plasma of post-treated patients found to be similar to blood plasma of normal subjects. Linear discriminant analysis showed that pre-treated and post-treated breast cancer is discriminated with a sensitivity and specificity of 100% and 100% respectively.

3.
Mol Pharm ; 16(2): 669-681, 2019 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-30601011

RESUMO

In this present study on understanding the taxol (PTX) binding interaction mechanism in both the ß-tubulin and bovine serum albumin (BSA) molecule, various optical spectroscopy and computational techniques were used. The fluorescence steady-state emission spectroscopy result suggests that there is a static quenching mechanism of the PTX drug in both ß-tubulin and BSA, and further time-resolved emission spectroscopy studies confirm that the quenching mechanism exists. The excitation-emission matrix (EEM), Fourier transform infrared, and resonance light scattering spectra (FT-IR) confirm that there are structural changes in both the BSA and ß-tubulin molecule during the binding process of PTX. The molecular docking studies revealed the PTX binding information in BSA, ß-tubulin, and modeled ß-tubulin and the best binding pose to further subject the molecular dynamics simulation, and this study confirms the stability of PTX in the protein complex during the simulation. Density functional theory (DFT) calculations were performed between the free PTX drug and PTX drug (single point) in the protein molecule active site region to understand the internal stability.

4.
J Chem Inf Model ; 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30481010

RESUMO

In this present study focus that determination of biologically significant N-Acetylneuraminic acid (NANA) drug binding interaction mechanism between bovine serum albumin (BSA) and human α-1 acid glycoprotein (HAG) using various optical spectroscopy and computational methods. The steady state fluorescence spectroscopy result suggests that the fluorescence intensity of BSA, HAG was quenched by NANA drug in a static mode of quenching. Further time- resolved emission spectroscopy measurements confirm that mode of quenching mechanism of NANA drug in BSA and HAG system. The FT-IR, excitation -emission matrix analysis confirms the presence of NANA drug in HAG, BSA system and fluorescence resonance energy transfer analysis calculation shows that the NANA drug energy transfer between HAG, BSA system. The molecular docking result shows good binding affinity in both protein complex and further molecular dynamics simulations and charge distribution analysis were performed to understand more insight binding interaction mechanism of NANA drug in HAG, BSA complex.

5.
Luminescence ; 33(4): 731-741, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29578306

RESUMO

In this study the interaction mechanism between newly synthesized 4-(3-acetyl-5-(acetylamino)-2-methyl-2, 3-dihydro-1,3,4-thiadiazole-2-yl) phenyl benzoate (thiadiazole derivative) anticancer active drug with calf thymus DNA was investigated by using various optical spectroscopy techniques along with computational technique. The absorption spectrum shows a clear shift in the lower wavelength region, which may be due to strong hypochromic effect in the ctDNA and the drug. The results of steady state fluorescence spectroscopy show that there is static quenching occurring while increasing the thiadiazole drug concentration in the ethidium bromide-ctDNA system. Also the binding constant (K), thermo dynamical parameters of enthalpy change (ΔH°), entropy change (ΔS°) Gibbs free energy change (ΔG°) were calculated at different temperature (293 K, 298 K) and the results are in good agreement with theoretically calculated MMGBSA binding analysis. Time resolved emission spectroscopy analysis clearly explains the thiadiazole derivative competitive intercalation in the ethidium bromide-ctDNA system. Further, molecular docking studies was carried out to understand the hydrogen bonding and hydrophobic interaction between ctDNA and thiadiazole derivative molecule. In addition the docking and molecular dynamics charge distribution analysis was done to understand the internal stability of thiadiazole derivative drug binding sites of ctDNA. The global reactivity of thiadiazole derivative such as electronegativity, electrophilicity and chemical hardness has been calculated.


Assuntos
Antineoplásicos/farmacologia , Benzoatos/farmacologia , DNA/química , Tiadiazóis/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/química , Benzoatos/química , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Cristalografia por Raios X , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Modelos Moleculares , Teoria Quântica , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Tiadiazóis/química , Células Tumorais Cultivadas
6.
J Biomol Struct Dyn ; 35(4): 817-828, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26999261

RESUMO

4-[3-acetyl-5-(acetylamino)-2,3-dihydro-1,3,4-thiadiazole-2-yl]phenyl benzoate from the family of thiadiazole derivative has been newly synthesized. It has good anticancer activity as well as antibacterial and less toxic in nature, its binding characteristics are therefore of huge interest for understanding pharmacokinetic mechanism of the drug. The binding of thiadiazole derivative to human serum albumin (HSA) has been investigated by studying its quenching mechanism, binding kinetics and the molecular distance, r between the donor (HSA) and acceptor (thiadiazole derivative) was estimated according to Forster's theory of non-radiative energy transfer. The Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) changes of temperature-dependent Kb was calculated, which explains that the reaction is spontaneous and exothermic. The microenvironment of HSA have also been studied using synchronous fluorescence spectroscopy, and the feature of thiadiazole derivative-induced structural changes of HSA have been carried using Fourier transform infrared spectroscopy and the Molecular modelling simulations explore the hydrophobic and hydrogen bonding interactions.


Assuntos
Biologia Computacional , Albumina Sérica/química , Albumina Sérica/metabolismo , Espectrometria de Fluorescência , Tiadiazóis/química , Tiadiazóis/metabolismo , Sítios de Ligação , Humanos , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Ligação Proteica , Conformação Proteica , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
7.
Artigo em Inglês | MEDLINE | ID: mdl-27475997

RESUMO

Urine has emerged as one of the diagnostically potential bio fluids, as it has many metabolites. As the concentration and the physiochemical properties of the urinary metabolites may vary under pathological transformation, Raman spectroscopic characterization of urine has been exploited as a significant tool in identifying several diseased conditions, including cancers. In the present study, an attempt was made to study the high wavenumber (HWVN) Raman spectroscopic characterization of urine samples of normal subjects, oral premalignant and malignant patients. It is concluded that the urinary metabolites flavoproteins, tryptophan and phenylalanine are responsible for the observed spectral variations between the normal and abnormal groups. Principal component analysis-based linear discriminant analysis was carried out to verify the diagnostic potentiality of the present technique. The discriminant analysis performed across normal and oral premalignant subjects classifies 95.6% of the original and 94.9% of the cross-validated grouped cases correctly. In the second analysis performed across normal and oral malignant groups, the accuracy of the original and cross-validated grouped cases was 96.4% and 92.1% respectively. Similarly, the third analysis performed across three groups, normal, oral premalignant and malignant groups, classifies 93.3% and 91.2% of the original and cross-validated grouped cases correctly.


Assuntos
Metaboloma , Neoplasias Bucais/metabolismo , Neoplasias Bucais/urina , Lesões Pré-Cancerosas/metabolismo , Lesões Pré-Cancerosas/urina , Análise Espectral Raman , Adulto , Idoso , Análise Discriminante , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Padrões de Referência , Adulto Jovem
8.
J Biomol Struct Dyn ; 34(6): 1264-81, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26368536

RESUMO

4-[(1Z)-1-(2-carbamothioylhydrazinylidene)ethyl]phenyl acetate [Ace semi],4-[(1Z)-1-(2-carbamothioylhydrazinylidene)ethyl]phenyl propanoate [Pro semi] from the family of thiosemicarbazones derivative has been newly synthesized. It has good anticancer activity as well as antibacterial and it is also less toxic in nature, its binding characteristics are therefore of huge interest for understanding pharmacokinetic mechanism of the drug. The binding of thiosemicarbazone derivative to human serum albumin (HSA) has been investigated by studying its quenching mechanism, binding kinetics and the molecular distance (r) between donor (HSA) and acceptor (thiosemicarbazone derivative) was estimated according to Forster's theory of non-radiative energy transfer using fluorescence spectroscopy. The binding dynamics has been elaborated using synchronous fluorescence spectroscopy, and the feature of thiosemicarbazone derivative induced structural changes of HSA has been studied by circular dichorism, Fourier transform infrared spectroscopy. Molecular modelling simulations explore the hydrophobic interaction and hydrogen bonding which stabilizes the interaction.


Assuntos
Modelos Moleculares , Conformação Molecular , Albumina Sérica/química , Tiossemicarbazonas/química , Sítios de Ligação , Dicroísmo Circular , Transferência Ressonante de Energia de Fluorescência , Humanos , Ligações de Hidrogênio , Ligação Proteica , Albumina Sérica/metabolismo , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Relação Estrutura-Atividade , Termodinâmica , Tiossemicarbazonas/metabolismo
9.
J Biochem Mol Toxicol ; 29(8): 373-81, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25906763

RESUMO

A newly synthesized 1, 4-bis ((4-((4-heptylpiperazin-1-yl) methyl)-1H-1, 2, 3-triazol-1-yl) methyl) benzene from the family of piperazine derivative has good anticancer activity, antibacterial and low toxic nature; its binding characteristics are therefore of huge interest for understanding pharmacokinetic mechanism of the drug. The binding of piperazine derivative to bovine serum albumin (BSA) was investigated using fluorescence spectroscopy. The molecular distance r between the donor (BSA) and acceptor (piperazine derivative) was estimated according to Forster's theory of nonradiative energy transfer. The physicochemical properties of piperazine derivative, which induced structural changes in BSA, have been studied by circular dichroism and those chemical environmental changes were probed using Raman spectroscopic analysis. Further, the binding dynamics was expounded by synchronous fluorescence spectroscopy and molecular modeling studies explored the hydrophobic interaction and hydrogen bonding results, which stabilize the interaction.


Assuntos
Piperazinas/química , Soroalbumina Bovina/química , Triazóis/química , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Simulação de Acoplamento Molecular , Ligação Proteica , Análise Espectral
10.
Biomed Pharmacother ; 69: 170-8, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25661354

RESUMO

Chitosan functionalized luminescent rare earth doped terbium nanoparticles (LaF3:Tb(3+)/chi NPs) as a drug carrier for methotrexate (MTX) was designed using a simple chemical precipitation method. The synthesized chitosan functionalized nanoparticles were found to be spherical in shape with an average diameter of 10-12nm. They are water soluble and biocompatible, in which the hydroxyl and amino functional groups on its surface are utilized for the bioconjugation of the anticancer drug, the methotrexate. The nature of MTX binding with LaF3:Tb(3+)/chi nanoparticles were examined using X-ray diffraction, zeta potential analyzer and transmission electron microscopy. The other interactions due to complex formation between MTX and LaF3:Tb(3+)/chi NPs were carried out by UV-Visible, steady and excited state fluorescence spectroscopy. The photo-physical characterization revealed that the adsorption and release of MTX from LaF3:Tb(3+)/chi NPs is faster than gold nanoparticles and also confirms that this may be due to weak interaction i.e. the Vander Waals force of attraction between the carboxyl and amino group of drug and nanoparticles. The maximum percentage yield and entrapment efficiency of 85.91±0.71 and 83.82± 0.14 were achieved at a stochiometric ratio of 4:5 of MTX and LaF3:Tb(3+)/chi nanoparticles respectively. In addition, antitumoral activity study reveals that MTX conjugated LaF3:Tb(3+)/chi nanoparticles show higher cytotoxic effect on MCF-7 breast cancer cell lines than that of free MTX.


Assuntos
Quitosana/química , Sistemas de Liberação de Medicamentos , Lantânio/química , Metotrexato/farmacologia , Nanopartículas/química , Térbio/química , Apoptose/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Humanos , Concentração Inibidora 50 , Células MCF-7 , Metotrexato/química , Nanopartículas/ultraestrutura , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Eletricidade Estática , Fatores de Tempo , Difração de Raios X
11.
J Fluoresc ; 25(1): 79-85, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25618462

RESUMO

Recently, deoxyribonucleic acid (DNA) based biomarker(s) detection has been employed for cancer diagnosis. Earlier reports have suggested the presence of more DNA in the saliva of oral squamous cell carcinoma (OSCC) than normal by electrophoresis technique. Based on these, steady state and excited state kinetics of salivary DNA has been performed with 27 normal subjects and 67 OSCC patients saliva using ethidium bromide as a probe to look for the possibility in discrimination between them. On statistical analysis the sensitivity and specificity of 88.9 and 94.0 % has been achieved from the fluorescence emission spectra and 88.9 and 92.5 % with that of fluorescence excitation.


Assuntos
Carcinoma de Células Escamosas , DNA/química , Etídio/química , Neoplasias Bucais , Saliva/química , Espectrometria de Fluorescência/métodos , Adulto , DNA/análise , Feminino , Humanos , Cinética , Masculino , Pessoa de Meia-Idade
12.
J Fluoresc ; 24(4): 1199-205, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24832355

RESUMO

Urine is one of the diagnostically potential bio fluids, as it contains many metabolites and some of them are native fluorophores. These fluorophores distribution and the physiochemical properties may vary during any metabolic change or at different pathologic conditions. Since urine is a multicomponent fluid, synchronous luminescence technique, a powerful tool has been adopted to analyse multicomponents in single spectrum and to resolve emission spectrum without much of photobleaching of fluorophores. In this study, urine samples of both normal subjects and cancer patients were characterised using synchronous luminescence spectroscopy with a Stokes shift of 20 nm. Different ratio parameters were calculated from the intensity values of the synchronous luminescence spectra and they were used as input variables for a multiple linear discriminant analysis across normal and cancer groups. The stepwise linear discriminant analysis classifies 90.3% of the original grouped cases and 88.6% of the cross-validated grouped cases correctly.


Assuntos
Neoplasias/urina , Pteridinas/urina , Riboflavina/urina , Adulto , Idoso , Feminino , Voluntários Saudáveis , Humanos , Medições Luminescentes , Masculino , Pessoa de Meia-Idade , Neoplasias/metabolismo , Neoplasias/patologia , Sensibilidade e Especificidade , Adulto Jovem
13.
J Biomed Opt ; 17(9): 97007-1, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23085924

RESUMO

Fluorescence excitation spectroscopy (FES) is an emerging approach to cancer detection. The goal of this pilot study is to evaluate the diagnostic potential of FES technique for the detection and characterization of normal and cancerous oral lesions in vivo. Fluorescence excitation (FE) spectra from oral mucosa were recorded in the spectral range of 340 to 600 nm at 635 nm emission using a fiberoptic probe spectrofluorometer to obtain spectra from the buccal mucosa of 30 sites of 15 healthy volunteers and 15 sites of 10 cancerous patients. Significant FE spectral differences were observed between normal and well differentiated squamous cell carcinoma (WDSCC) oral lesions. The FE spectra of healthy volunteers consists of a broad emission band around 440 to 470 nm, whereas in WDSCC lesions, a new primary peak was seen at 410 nm with secondary peaks observed at 505, 540, and 580 nm due to the accumulation of porphyrins in oral lesions. The FE spectral bands of the WDSCC lesions resemble the typical absorption spectra of a porphyrin. Three potential ratios (I410/I505, I410/I540, and I410/I580) were calculated from the FE spectra and used as input variables for a stepwise linear discriminant analysis (SLDA) for normal and WDSCC groups. Leave-one-out (LOO) method of cross-validation was performed to check the reliability on spectral data for tissue characterization. The diagnostic sensitivity and specificity were determined for normal and WDSCC lesions from the scatter plot of the discriminant function scores. It was observed that diagnostic algorithm based on discriminant function scores obtained by SLDA-LOO method was able to distinguish WDSCC from normal lesions with a sensitivity of 100% and specificity of 100%. Results of the pilot study demonstrate that the FE spectral changes due to porphyrin have a good diagnostic potential; therefore, porphyrin can be used as a native tumor marker.


Assuntos
Biomarcadores Tumorais/análise , Neoplasias Bucais/diagnóstico , Neoplasias Bucais/metabolismo , Porfirinas/análise , Espectrometria de Fluorescência/métodos , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
Photochem Photobiol ; 86(1): 77-86, 2010 Jan-Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19845540

RESUMO

The objective of this study was to assess the diagnostic potential of synchronous fluorescence (SF) spectroscopy (SFS) technique for the detection and characterization of normal and different malignancy stages of moderately differentiated squamous cell carcinoma (MDSCC), poorly differentiated squamous cell carcinoma (PDSCC) cervical tissues. SF spectra were measured from 45 biopsies from 30 patients in vitro. Characteristic, highly resolved peaks and significant spectral differences between normal and MDSCC, PDSCC cervical tissues were obtained. Nine potential ratios were calculated and used as input variables for a discriminant analysis across different groups. The potentiality of the SFS technique was estimated by two discriminant analyses. Discriminant analysis I performed across normal and abnormal (including MDSCC and PDSCC) cervical tissues classified as 100% both original and the cross-validated grouped cases. In discriminant analysis II performed across the three groups, normal, MDSCC and PDSCC, 100% of both original and the cross-validated grouped cases were correctly classified. Using the SFS technique, one can obtain all the key biochemical markers such as tryptophan, collagen, hemoglobin, reduced form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide in a single scan and hence they can be targeted as tumor markers in the detection of normal from abnormal cervical tissues.


Assuntos
Espectrometria de Fluorescência/métodos , Neoplasias do Colo do Útero/diagnóstico , Biomarcadores Tumorais/análise , Carcinoma de Células Escamosas/diagnóstico , Análise Discriminante , Feminino , Humanos
15.
Med Dosim ; 32(4): 305-15, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17980833

RESUMO

As per TG-43 dose calculation formalism, it is essential to obtain various dosimetric parameters such as the air-kerma strength, dose rate constant, radial dose function, and anisotropy function, as they account for accurate determination of dose rate distribution around brachytherapy sources. Most of the available reported Monte Carlo simulations were performed in liquid water phantoms with a bounded region of 30-cm diameter. In this context, an attempt was made to report the dosimetric parameters for various commercially available pulsed-dose rate (PDR) and high-dose rate (HDR) sources under unbounded phantom conditions, as the data may be used as input to treatment planning systems (TPSs) for quality control assistance. The air-kerma strength per unit activity, S(k)/A, was computed for various Iridium-192 ((192)Ir) sources in dry air medium. The air-kerma strength and dose rate constant for old PDR is (9.77 +/- 0.03) 10(-8) U/Bq and 1.124 +/- 0.001 cGyh(-1)U(-1); for new PDR, the values are (9.96 +/- 0.03) 10(-8) U/Bq and 1.124 +/- 0.001 cGyh(-1)U(-1); for old MHDR, the values are (9.80 +/- 0.01) 10(-8) U/Bq and 1.115 +/- 0.001 cGyh(-1)U(-1); for new MHDR, (9.80 +/- 0.01) 10(-8) U/Bq and 1.112 +/- 0.001cGyh(-1)U(-1); for old VHDR, the values are (10.32 +/- 0.01) 10(-8) U/Bq and 1.035 +/- 0.002 cGyh(-1)U(-1); for new VHDR, the values are (10.34 +/- 0.02) 10(-8) U/Bq and 1.096 +/- 0.001 cGyh(-1)U(-1). The computed radial dose function values and anisotropy function values are also in good agreement with available data.


Assuntos
Braquiterapia/métodos , Radioisótopos de Irídio/uso terapêutico , Método de Monte Carlo , Imagens de Fantasmas , Dosagem Radioterapêutica , Anisotropia , Humanos
16.
Med Phys ; 33(6): 1552-61, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16872062

RESUMO

The present work is primarily focused on the estimation of relative dose distribution and effective transmission around a shielded vaginal cylinder with an 192Ir source using the Monte Carlo technique. The MCNP4B code was used to evaluate the dose distribution around a tungsten shielded vaginal cylinder as a function of thickness and angular shielding. The dose distribution and effective transmission of 192Ir by 0.8 cm thickness tungsten were also compared with that for gold and lead. Dose distributions were evaluated for different distances starting from 1.35 cm to 10.15 cm from the center of the cylinder. Dose distributions were also evaluated sequentially from 0 degrees to 180 degrees for every 5 degrees interval. Studies show that all the shielding material at 0.8 cm thickness contribute tolerable doses to normal tissues and also protect the critical organs such as the rectum and bladder. However, the computed dose values are in good agreement with the reported experimental values. It was also inferred that the higher the shielding angles, the more the protection of the surrounding tissues. Among the three shielding materials, gold has been observed to have the highest attenuation and hence contribute lowest transmission in the shielded region. Depending upon the shielding angle and thickness, it is possible to predict the dose distribution using the MCNP4B code. In order to deliver the higher dose to the unshielded region, lead may be considered as the shielding material and further it is highly economic over other materials.


Assuntos
Método de Monte Carlo , Proteção Radiológica/métodos , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Neoplasias Vaginais/radioterapia , Feminino , Humanos , Proteção Radiológica/economia , Proteção Radiológica/instrumentação , Reto/lesões , Reto/efeitos da radiação , Valores de Referência , Eficiência Biológica Relativa , Medição de Risco , Fatores de Risco , Bexiga Urinária/lesões , Bexiga Urinária/efeitos da radiação , Vagina/lesões , Vagina/efeitos da radiação
17.
Med Dosim ; 30(4): 213-8, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16275563

RESUMO

A commercial metal oxide silicon field effect transistor (MOSFET) dosimeter of model TN502-RD has been characterized for its linearity, reproducibility, field size dependency, dose rate dependency, and angular dependency for Cobalt-60 (60Co), 6-MV, and 15-MV beam energies. The performance of the MOSFET clearly shows that it is highly reproducible, independent of field size and dose rate. Furthermore, MOSFET has a very high degree of linearity, with r-value>0.9 for all 3 energies. The calibration factor for 2 similar MOSFET detectors of model TN502-RD were also estimated and compared for all 3 energies. The calibration factor between the 2 similar MOSFET detectors shows a variation of about 1.8% for 60Co and 15 MV, and for 6 MV it shows variation of about 2.5%, indicating that calibration should be done whenever a new MOSFET is used. However, the detector shows considerable angular dependency of about 8.8% variation. This may be due to the variation in radiation sensitivity between flat and bubble sides of the MOSFET, and indicates that positional care must be taken while using MOSFET for stereotactic radiosurgery and stereotactic radiotherapy dosimetric applications.


Assuntos
Calibragem , Teleterapia por Radioisótopo , Radiometria/instrumentação , Radiocirurgia , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica , Reprodutibilidade dos Testes
18.
Photochem Photobiol ; 76(1): 81-90, 2002 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12126311

RESUMO

Delta-aminolevulinic acid-photodynamic therapy (ALA-PDT) has emerged as a useful technique in the treatment of superficial basal cell carcinoma, actinic keratosis, squamous cell carcinoma and tumors of other organs. Earlier reports mention that there is reappearance of protoporphyrin IX (PpIX) after photoirradiation of tumors. This property of reappearance of PpIX is being utilized to treat nodular tumors by fractionated light dose delivery. However, there is still no unanimously accepted reason for this reappearance phenomenon and the rate of resynthesis after PDT. On account of this, studies are carried out on the estimation of the pharmacokinetics of the ALA-induced PpIX in mice tumor models and the surrounding normal tissues before and after PDT. Further, a mathematical model based on a multiple compartment system is proposed to estimate the rate parameter for the diffusion of PpIX from the surrounding normal tissues into the tumor tissue (km) caused by photobleaching during PDT with irradiating fluences of 36.0 and 57.6 J/cm2. The km value at two different fluences, 36.0 and 57.6 J/cm2, are estimated as 3.0636+/-0.7083 h(-1) and 6.9231+/-2.17651 h(-1), respectively. Further, the rate parameter for the cleavage and efflux of ALA (k1) and the rate parameter for the evasion of PpIX from the tumor tissues after PDT (kt) were also estimated by fitting the experimental data to the developed mathematical model. The statistical significance of the estimated parameters was determined using Student's t-test. The experimental results and the rate parameters obtained using the proposed compartment model suggest that in addition to the earlier reported reasons, the invasion or diffusion of PpIX from the surrounding tissues to the tumor tissues after photoirradiation might also contribute to the reappearance of PpIX after PDT.


Assuntos
Protoporfirinas/farmacocinética , Neoplasias Cutâneas/tratamento farmacológico , 9,10-Dimetil-1,2-benzantraceno/toxicidade , Ácido Aminolevulínico/uso terapêutico , Animais , Carcinógenos/toxicidade , Feminino , Camundongos , Modelos Biológicos , Fotoquimioterapia , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/metabolismo
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