GATE Monte Carlo approach to heterogeneity dose distribution in small fields used in radiation therapy.

The Accurate dosage prediction in Radiation Therapy is challenging, prompting a need for precision beyond conventional clinical Treatment Planning Systems (TPS). Monte Carlo-based methods are sought for their superior accuracy. The aim of this study is to compare dose distributions between the ACUROS algorithm and the GATE platform in various tissue densities and field sizes, focusing on smaller fields. This study was initiated with a homogeneous validation of the TrueBeam STX system, using measurements obtained from the Centre Hospitalier Interregional Edith Cavell (CHIREC) in Brussels. The validation compared dosimetric functions (Percentage Depth Dose (PDD), Dose profile (DP) and Collimator scatter fraction (CSF)) employing the GAMMA index with a 2% / 2 mm criterion tolerance. Following this, heterogeneous studies examined dose distributions between the ACUROS algorithm and the GATE platform in various tissue densities and field sizes, with a specific focus on smaller fields. Simulations were conducted using both platforms on chest phantoms with heterogeneous slabs representing bone, lung, and heart, each housing a central tumor. The impact of electronic equilibrium on tumors for different small field sizes was evaluated. Results showed a remarkable 99% agreement between measurements and GATE calculations in the homogeneous validation of the TrueBeam STX system. However, in heterogeneous studies, ACUROS consistently overestimated lung doses by up to 8% compared to GATE simulation, especially evident with a flattening filter and smaller beam sizes at density interfaces. This highlights significant dose estimation discrepancies between ACUROS and GATE, emphasizing the need for precise calculations. The findings support exploring Monte Carlo-based methods for enhanced accuracy in Radiation Therapy treatment planning.

Preparations based on minerals extracts of Calicotome villosa roots and bovine butyrate matter: Evaluation in vitro of their antibacterial and antifungal activities.

OBJECTIVE: The use of preparations based on minerals extracts of Calicotome villosa and butter is born from the misuse of drugs without specific microbiological analyzes. Seventeen different preparations were performed. The antibacterial and antifungal activities were determined on five bacteria and two fungi strains respectively. MATERIAL AND METHODS: C.villosa ashes are obtained by incineration of roots plant at 498°C for 4hours. They are analyzed to determine the shape of the particles and the mineral constituents by scanning electronic microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) techniques respectively. The effectiveness of preparations or tablets is measured in solid medium. It allows to calculating the diameter of the inhibition zone for the antibacterial activity as well as the diameter of mycelia growth and the critical values (MIC, MFC, IC50 and IC90) for the antifungal activity. Finally, the results are compared to the activity of a commercial positive control aiming to give value of the observed activity. RESULTS: SEM observations reveal the presence of nanoparticles agglomerated with size of about 50nm. The EDX analyzes indicate the presence of Fe, Na, Al, Mg, Si, K, Ca, O2 and C. Among all the results, the preparation (Bs+A) or (Bsd+A) can completely inhibit the growth of two fungal pathogens. The activity of the preparation is faced with the activity of the synthetic fungicide nystatin. CONCLUSION: The efficacy of the preparation (Bs+A) or (Bsd+A) is larger than that of nystatin against Aspergillus sp. and Fusarium sp. The preparation could serve as natural antifungal for the pharmaceutical industry.

Preparations based on minerals extracts of Calicotome villosa roots and bovine butyrate matter: Evaluation in vitro of their antifungal activity.

OBJECTIVE: The use of preparations based on minerals extracts of Calicotome villosa and butter is born from the misuse of drugs without specific microbiological analyzes. Seventeen different preparations were performed. The antibacterial and antifungal activities were determined on five bacteria and two fungi strains respectively. MATERIAL AND METHODS: C. villosa ashes are obtained by incineration of roots plant at 498°C for 4hours. They are analyzed to determine the shape of the particles and the mineral constituents by scanning electronic microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques respectively. The effectiveness of preparations or tablets is measured in solid medium. It allows to measure the diameter of the inhibition zone for the antibacterial activity as well as the diameter of mycelia growth and the critical values (MIC, MFC, IC50 and IC90) for the antifungal activity. Finally, the results are compared to the activity of a commercial positive control aiming to give value of the observed activity. RESULTS: SEM observations reveal the presence of nanoparticles agglomerated with size of about 50nm. The EDX analyzes indicate the presence of Fe, Na, Al, Mg, Si, K, Ca, O2 and C. Among all the results, the preparation (Bs+A) or (Bsd+A) can completely inhibit the growth of two fungal pathogens. The activity of the preparation is faced with the activity of the synthetic fungicide nystatin. CONCLUSION: The efficacy of the preparation (Bs+A) or (Bsd+A) is higher than that of nystatin against Aspergillus sp. and Fusarium sp. The preparation could serve as natural antifungal for the pharmaceutical industry.

Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications.

Silver tantalate (AgTaO3) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application.

Evaluation of the Block Matching deformable registration algorithm in the field of head-and-neck adaptive radiotherapy.

BACKGROUND AND PURPOSE: To compare the accuracy of the Block Matching deformable registration (DIR) against rigid image registration (RIR) for head-and-neck multi-modal images CT to cone-beam CT (CBCT) registration. MATERIAL AND METHODS: Planning-CT and weekly CBCT of 10 patients were used for this study. Several volumes, including medullary canal (MC), thyroid cartilage (TC), hyoid bone (HB) and submandibular gland (SMG) were transposed from CT to CBCT images using either DIR or RIR. Transposed volumes were compared with the manual delineation of these volumes on every CBCT. The parameters of similarity used for analysis were: Dice Similarity Index (DSI), 95%-Hausdorff Distance (95%-HD) and difference of volumes (cc). RESULTS: With DIR, the major mean difference of volumes was -1.4 cc for MC, revealing limited under-segmentation. DIR limited variability of DSI and 95%-HD. It significantly improved DSI for TC and HB and 95%-HD for all structures but SMG. With DIR, mean 95%-HD (mm) was 3.01 ± 0.80, 5.33 ± 2.51, 4.99 ± 1.69, 3.07 ± 1.31 for MC, TC, HB and SMG, respectively. With RIR, it was 3.92 ± 1.86, 6.94 ± 3.98, 6.44 ± 3.37 and 3.41 ± 2.25, respectively. CONCLUSION: Block Matching is a valid algorithm for deformable multi-modal CT to CBCT registration. Values of 95%-HD are useful for ongoing development of its application to the cumulative dose calculation.

Room temperature synthesis and high temperature frictional study of silver vanadate nanorods.

We report the room temperature (RT) synthesis of silver vanadate nanorods (consisting of mainly beta-AgV O(3)) by a simple wet chemical route and their frictional study at high temperatures (HT). The sudden mixing of ammonium vanadate with silver nitrate solution under constant magnetic stirring resulted in a pale yellow coloured precipitate. Structural/microstructural characterization of the precipitate through x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the high yield and homogeneous formation of silver vanadate nanorods. The length of the nanorods was 20-40 microm and the thickness 100-600 nm. The pH variation with respect to time was thoroughly studied to understand the formation mechanism of the silver vanadate nanorods. This synthesis process neither demands HT, surfactants nor long reaction time. The silver vanadate nanomaterial showed good lubrication behaviour at HT (700 degrees C) and the friction coefficient was between 0.2 and 0.3. HT-XRD revealed that AgV O(3) completely transformed into silver vanadium oxide (Ag(2)V(4)O(11)) and silver with an increase in temperature from RT to 700 degrees C.

Mechanical, tribological, and biocompatibility properties of ZrN-Ag nanocomposite films.

Nanocomposite films of ZrN-Ag were produced by reactive unbalanced magnetron sputtering, and their structural, chemical, mechanical, tribological, haemocompatibility, and antibacterial properties were studied as a function of film composition. The films formed a dense and homogeneous microstructure whereby nanocrystals of Ag are distributed evenly throughout the ZrN matrix. For small additions of silver, the hardness was found to increase, whereas the elastic modulus was found to decrease drastically. In the process of optimizing the deposition conditions, three kinds of coatings were prepared on 316 L surgical steel and tested by accelerated electrochemical polarization tests in order to detect the influence of Ag and the value of the bias potential on the corrosion performance of the system. Films produced under the optimum deposition conditions were, subsequently, deposited on medical grade Ti-Al-V and worn against ball-bearing steel using a ball-on-disk tribotester in bovine serum and were found to have superior tribological properties compared with single-phase ZrN coatings. The haemocompatibility of the films was assessed by investigating the adsorption of human serum albumin and fibrinogen on samples with different phase compositions. Quantification of the protein adsorption was carried out using spectroscopic ellipsometry, which confirmed the haemocompatibility of the films. Antibiotic activity of the films was quantified by incubating the films in bacterial cultures, namely, Staphylococcus epidermis, Staphylococcus aureus, and Escherichia coli. Films with a silver content > 10% exhibited superior antibacterial activity compared with the uncoated samples.

Evaluation of a stochastic approach to 2D-3D intensity-based registration.

this paper assesses a new 2D-3D rigid registration method based on stochastic clustering and an enhanced estimator for mutual information. It combines precision, accuracy and acceptable computation time. Spine datasets (fluoroscopy and computed tomography) with their gold standard transformations are used. Both optimization method and similarity measure are assessed separately using standardized evaluation methodologies. Sub-millimeter accuracy and the high convergence rate obtained within one minute are compared to other quasi-global optimization processes such as particle filtering.

Vacuum ultra-violet spectroscopic ellipsometry study of single- and multi-phase nitride protective films.

This paper reports on a systematic investigation of the optical properties of Ta(1-x)Zr(x)N single-phase and ZrN-Ag multi-phase films fabricated by unbalanced magnetron sputtering using vacuum ultraviolet spectroscopic ellipsometry (VUV-SE). VUV-SE is a newly developed technique that was used to evaluate the strength and energy of the interband electronic excitations/transitions in these films. The energy of the interband transition was found to be altered by any changes in the elemental composition for single-phase materials. For example, it was found to increase with the increase in the covalent character of the bond as more Zr atoms are substituted for by Ta atoms in the ZrN rock-salt structure. In contrast, the peak positions did not vary in the multi-phase structures because the constituent phases were immiscible and retained their electronic structure. However, the strength and width of the interband transition were found to change to reflect changes in phase composition and microstructure. The optical and electronic properties of these materials were simulated using density functional theory (DFT) within the generalized gradient approximation. The calculated refractive indices and density of states were in good agreement with the VUV-SE data.

Physical and chemical properties of sputter-deposited TaC(x)N(y) films.

The structural, electronic, optical, and mechanical properties of stoichiometric TaC(x)N(y = 1-x) were simulated using an ab initio calculation based on density functional theory (DFT) within the generalized gradient approximation. The calculations revealed the theoretical lattice parameter, density of states, refractive index, and elastic constants as a function of carbon and nitrogen content. TaC(x)N(y) films were subsequently produced on Si wafers using unbalanced magnetron sputtering. The structural, optical, and mechanical properties were measured using x-ray diffraction/transmission electron microscopy, vacuum ultraviolet spectroscopic ellipsometry, and nanoindentation, respectively. The computational and experimental properties were compared. The lattice parameter, the energy of the 2p bands in the density of states, and the energy of the interband transitions were found to decrease with increasing C content. No significant changes in the elastic constants were observed as a result of substituting N atoms with C atoms. The hardness and the elastic modulus were in the 40 and 380 GPa range, respectively. The experimental Young's modulus was much smaller than the computational one and this discrepancy was attributed to the nanocrystalline nature of the films. Also, the elastic constants were found to decrease dramatically for over-stoichiometric films.