E. James Jebaseelan Samuel

Molecular structure, vibrational spectra, NMR and UV spectral analysis of sulfamethoxazole

Fourier transform infrared (FTIR) and FT-Raman spectra have been recorded and extensive spectroscopic investigations have been carried out on Sulfamethoxazole (SMX). The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (DFT) using 6-31G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. (13)C and (1)H NMR chemical shifts results were given and are in agreement with the corresponding experimental values. The theoretically constructed FT-IR and FT-Raman spectra exactly coincide with experimental one. Besides, NBO, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

FTIR and FT Raman spectra and analysis of poly(4-methyl-1-pentene).

Poly(4-methyl-1-pentene) is the most widely used polymer in industry and medical products. Fourier transform infrared and Raman Spectra of poly(4-methyl-1-pentene) have been recorded in the range of 4000-400 and 4000-100 cm(-1), respectively. In the present investigation a detailed assignments of the observed fundamental bands of poly(4-methyl-1-pentene) has been analyzed in terms of peak positions and relative intensities. With the hope of providing more and effective information on the fundamental vibrations, a normal coordinate analysis has also been performed on poly(4-methyl-1-pentene) by assuming Cs symmetry. The simple general valence force field (SGVFF) method has been employed in normal coordinate analysis and the potential energy distribution (PED) has been calculated for each fundamental vibration. The PED contribution corresponding to each of the observed frequencies shows the reliability and accuracy of spectral analysis. The validity of the SGVFF method as a practical tool for complete analysis of vibrational spectra, for poly(4-methyl-1-pentene) is confirmed in the present work.

Current scenario of biomedical aspect of metal-based nanoparticles on gel dosimetry.

In past decades, the possibility of using high atomic number nanoparticle has gained interest in gel dosimetry to enhance the dose deposited in the tumor while using low radiation as well as for better imaging purposes. Sparing of healthy tissues and targeting the tumor part have become much more captivating with the help of these systems. The gel dosimetry is a the three-dimensional dosimeter for extracting the dose, which can be used along with the nanoparticles like gold, platinum, and silver, for better therapeutic efficiency for modern radiotherapy techniques. These nanoparticles of different size prepared either by chemical route or green synthesis and incorporated into the gel system respond in a different manner. Having wide applications in therapeutic field, this study reviews the use of gel dosimeters in the therapeutic procedures and also with the aid of nanoparticles so as to achieve dose enhancement. The biological activity of the various nanoparticles has been discussed.

Quantum mechanical and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV) investigations of antiepileptic drug Ethosuximide.

The Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of antiepileptic drug Ethosuximide (ETX) have been recorded and analyzed. In addition, the IR spectra in CCl(4) at various concentrations of ETX are also recorded. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of Density Functional Theory (DFT) method. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge Including Atomic Orbital (GIAO) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by Time-Dependent Density Functional Theory (TD-DFT) approach. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with observed spectra.

Structural, vibrational, electronic and NMR spectral analysis of 3-chloro-6-methoxypyridazine by DFT calculations

In this work, the FT-Raman and FT-Infrared spectra of 3-chloro-6-methoxypyridazine sample were measured to elucidate the spectroscopic properties of title molecule in the spectral range of 3500-50 cm(-1) and 4000-400 cm(-1), respectively. The molecular geometry and vibrational frequencies of 3-chloro-6-methoxypyridazine in the ground state were calculated using the DFT/B3LYP/6-31G(d),6-311G(d,p) level. The recorded FT-IR and FT-Raman spectral measurements favor the calculated structural parameters which are further supported by spectral simulation. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The UV-Visible absorption spectrum of the compound that dissolved in methanol was recorded in the range of 800-200 nm. The formation of hydrogen bond and the most possible interaction are explained using natural bond orbital (NBO) analysis. The isotropic chemical shift computed by (13)C and (1)H NMR analysis also shows good agreement with experimental observations. In addition, the molecular electrostatic potential (MEP) and frontier molecular orbitals (FMOs) analysis of the title compound were investigated using theoretical calculations.

Adaptive threshold segmentation of pituitary adenomas from FDG PET images for radiosurgery

In this study we have attempted to optimize a PET based adaptive threshold segmentation method for delineating small tumors, particularly in a background of high tracer activity. The metabolic nature of pituitary adenomas and the constraints of MRI imaging in the postoperative setting to delineate these tumors during radiosurgical procedures motivated us to develop this method. Phantom experiments were done to establish a relationship between the threshold required for segmenting the PET images and the target size and the activity concentration within the target in relation to its background. The threshold was developed from multiple linear regression of the experimental data optimized for tumor sizes less than 4 cm3. We validated our method against the phantom target volumes with measured target to background ratios ranging from 1.6 to 14.58. The method was tested on ten retrospective patients with residual growth hormone‐secreting pituitary adenomas that underwent radiosurgery and compared against the volumes delineated by manual method. The predicted volumes against the true volume of the phantom inserts gave a correlation coefficient of 99% (p<0.01). In the ten retrospective patients, the automatically segmented tumor volumes against volumes manually delineated by the clinicians had a correlation of 94% (p<0.01). This adaptive threshold segmentation showed promising results in delineating tumor volumes in pituitary adenomas planned for stereotactic radiosurgery, particularly in the postoperative setting where MR and CT images may be associated with artifacts, provided optimization experiment is carried out. PACS number: 87.57.nm, 87.57.uk

Hybrid positron emission tomography segmentation of heterogeneous lung tumors using 3D Slicer: improved GrowCut algorithm with threshold initialization

Abstract. This paper presents an improved GrowCut (IGC), a positron emission tomography-based segmentation algorithm, and tests its clinical applicability. Contrary to the traditional method that requires the user to provide the initial seeds, the IGC algorithm starts with a threshold-based estimate of the tumor and a three-dimensional morphologically grown shell around the tumor as the foreground and background seeds, respectively. The repeatability of IGC from the same observer at multiple time points was compared with the traditional GrowCut algorithm. The algorithm was tested in 11 nonsmall cell lung cancer lesions and validated against the clinician-defined manual contour and compared against the clinically used 25% of the maximum standardized uptake value [SUV-(max)], 40% SUVmax, and adaptive threshold methods. The time to edit IGC-defined functional volume to arrive at the gross tumor volume (GTV) was compared with that of manual contouring. The repeatability of the IGC algorithm was very high compared with the traditional GrowCut (p=0.003) and demonstrated higher agreement with the manual contour with respect to threshold-based methods. Compared with manual contouring, editing the IGC achieved the GTV in significantly less time (p=0.11). The IGC algorithm offers a highly repeatable functional volume and serves as an effective initial guess that can well minimize the time spent on labor-intensive manual contouring.

Dose-rate dependence of PAGAT polymer gel dosimeter evaluated using X-ray CT scanner

In recent years, X-ray CT imaging of polymer gel dosimeter has been applied to direct measurement of 3D dose distributions. This work presents the dependence of PAGAT polymer gel dosimeter response to different beam dose rate using X-ray CT scanner as an evaluation tool. The normoxic PAGAT polymer gel was prepared on bench top and irradiated to different doses at different dose-rate ranging from 0.5 to 5 Gy/min. After irradiation the dosimeter samples were imaged with X-ray CT scanner using appropriate scanning protocol. The results showed that PAGAT gel dosimeter formulations investigated in this study has the smallest dose rate dependence and the change in dose sensitivity amounts to 2 % over the dose rate interval studied.

Preliminary study on CT imaging of polymer gel radiation dosimetry

Summary Background New radiotherapy techniques such as stereotactic radiotherapy (SRT) stereotactic radiosurgery (SRS), three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiation therapy (IMRT) aim to deliver a high dose to the tumour while sparing the surrounding normal healthy tissues. As a result of these complicated treatment techniques there is a need for a 3-dimensional (3D) dose verification system. However, currently available dosimeters such as ion chambers, diodes, thermoluminescent dosimeters and films are limited to point (or) planar measurement. Multiple measurements are required to obtain the 3-dimensional dose distribution using the above dosimeters. Hence volumetric measurements are not feasible without multiple detectors (or) multiple measurements. Gel dosimetry attempts to meet the requirements of 3D radiation dose distribution. Gel dosimetry is tissue equivalent [1] and it acts as a phantom as well as dosimeter so there is no need for dose perturbation correction. Aim Radiation-induced polymerization in polymer gel dosimeters gives rise to a change in CT number which can be measured with X-ray computed tomography (CT). The aim of this study is to assess the feasibility of using the X-ray CT scanner for the evaluation of dose distribution in polymer gel dosimetry. Materials/Methods Polymer gel called PAGAT ( P oly a crylamide G elatin a nd T etrakis hydroxymethyl phosphonium) consisting of 3.5% (w/w) BIS, 3.5% (w/w) acrylamide, 5% (w/w) gelatin, 10 mM Tetrakis hydroxymethyl phosphonium (THP) and 88% (w/w) water was manufactured in normal atmospheric conditions. The gel was irradiated using a Siemens Primus linear accelerator. The radiation-induced change in CT number was evaluated using a Siemens Somatom Emotion CT scanner. The percentage depth doses and profiles were deduced. The same study was carried out using radiation field analyzer RFA-200 with RK-ion chamber and film and compared with polymer gel measurements. Results Polymer gel dosimetry measurement was in agreement with ion chamber and film measurements except for a slight deviation in the build-up region. Discrepancies found were due to analysis of image without image averaging and background subtraction. Conclusions This preliminary study was conducted to evaluate the feasibility of using X-ray CT-based polymer gel dosimetry for clinical use. The results of this study encourage further use of X-ray CT in conjunction with polymer gel for 3D radiation dose measurements.

Molecular structure and spectroscopic (FT-IR, FT-Raman, 13C, 1H NMR and UV) studies of 3,4-dihydroxy-l-phenylalanine using density functional theory

Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 3,4-dihydroxy-l-phenylalanine (3,4-DPA) in solid phase were recorded and analysed in this research. Along with this, the IR spectra in CHCl3 and the use of acetone as solvents of 3,4-DPA were also recorded. The equilibrium geometry, bonding features and harmonic vibrational frequencies were investigated with the help of density functional theory (DFT) method. The 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge including atomic orbital method and compared with experimental results. Stability of the molecule arising from hyperconjugative interactions and charge delocalisation was analysed using natural bond orbital analysis. The results show that charge in electron density (E D) in the σ* and π* antibonding orbitals and second-order delocalisation energies E(2) confirms the occurrence of intramolecular charge transfer within the molecule. UV–vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were analysed using the time-dependent (TD)-DFT approach. Finally, the calculation results were applied to simulate infrared and Raman spectra of the title compound, which showed good agreement with the observed spectra.