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Open access

Toshizo Katsuda, Rumi Gotanda, Tatsuhiro Gotanda, Takuya Akagawa, Nobuyoshi Tanki, Tadao Kuwano, Atsushi Noguchi and Kouichi Yabunaka

Abstract

The strength and density change of the ultraviolet (UV) ray of Gafchromic EBT2 were investigated. Previous studies suggested that UV-A rays can be substituted for the x-ray double-exposure technique to correct Gafchromic EBT2’s non-uniformity error. In this study, we aimed to determine the appropriate strength of UV-A rays for irradiating an active layer that would correct the non-uniformity error of Gafchromic EBT2.

UV-A rays with a wavelength of 375 nm were used to irradiate Gafchromic EBT2 in various durations, and the resulting density change was investigated. To correct Gafchromic EBT2’s non-uniformity error, a pre-irradiation with a UV-A lamp was conducted at a distance of 72 cm for 30 min. To determine the most appropriate irradiation duration, a UV light-emitting diode generating UV-A of 375 nm was used to irradiate the Gafchromic EBT2 film with varying durations of 1, 2, 3, 4, 5, 10, 15, 20, 25, and 30 min at a distance of 5.3 cm. A 12.7 diameter region of interest was set by the irradiation area, and a histogram of pixel values was created. The condition options were decided based on two important requirements: 1) no zero values of the mode and seconds exist, and 2) the 1/10 value of the mode intersects both histogram sleeves.

In the case of Gafchromic EBT2, the irradiation strength was 85.43 mJ/cm2 for one minute in which the pixel value of mean ± SD was 255.34 ± 213.29. The irradiation duration of 4 min was the border duration of the above two conditions. When a UV ray of 375 nm wavelength is used to irradiate Gafchromic EBT2 as a substitute for x-ray exposure, the 4-min pre-irradiation duration (341.74 mJ/cm2) is demonstrably sufficient.

Open access

Sandhyarani Bandari, Anand Rao Jakkula and Malla Reddy Perati

Abstract

In this paper, radial vibrations of an infinitely long fluid-filled transversely isotropic thick-walled hollow composite poroelastic cylinder are investigated in the framework of poroelasticity. The cylinder consists of two concentric cylindrical layers namely, core (inner one) and coating (outer one), each of which retains its own distinctive properties. A comparative study has been made between the thick-walled hollow composite poroelastic cylinder and that of fluid-filled one. Frequency is computed against the ratio between the thickness to inner radius of the composite cylinder at various anisotropic ratios. Another comparative study is made between the results of current case and that of isotropic case by making Young’s modulus and Poisson ratio values of isotropic and that of transversely isotropic in the transverse direction equal. Numerical results are depicted graphically and then discussed.

Open access

Aysan Mohammad Namdar, Mohammad Mohammadzadeh, Murat Okutan and Asghar Mesbahi

Abstract

A review on the radiobiological modeling of radiation-induced hypothyroidism after radiation therapy of head-and-neck cancers, breast cancer, and Hodgkin’s lymphoma is presented. The current review is based on data relating to dose-volume constrains and normal tissue complication probability (NTCP) as a function of either radiobiological or (pre)treatment-clinical parameters. Also, these data were explored in order to provide more helpful criteria for radiobiological optimization of treatment plans involving thyroid gland as a critical normal organ.

Open access

Harsh Sardana and Mahavir Singh

Abstract

The aim of this research paper is to reduce the drag of SUV by using a vortex generator and to calculate the pressure and turbulence profile across the vehicle. The Ahmed Reference Model is taken as a benchmark test. Computational fluid dynamics (CFD) simulation with and without vortex generator is performed at different velocities across the SUV similar to TATA Sumo. The performance of Vortex generator is analyzed at different velocities to obtain the particular velocity at which it will have the minimum value of drag. The end results are henceforth analyzed and a comparative study has been performed with the experimental data given by Gopal and Senthikumar on SUV. And finally it is found that the 10 % of drag reduction is achieved using vortex generator.

Open access

Bilalodin, Kusminarto, Gede Bayu Suparta, Arief Hermanto, Dwi Satya Palupi and Yohannes Sardjono

Abstract

The genetic algorithm method is a new method used to obtain radiation beams that meet the IAEA requirements. This method is used in optimization of configurations and compositions of materials that compose double layered Beam Shaping Assembly (BSA). The double layered BSA is modeled as having two layers of material for each of the components, which are the moderator, reflector, collimator, and filter. Up to 21st generation, the optimization results in four (4) individuals having the capacity to generate the most optimum radiation beams. The best configuration, producing the most optimum radiation beams, is attained by using combinations of materials, that is by combining Al with either one of CaF2 and PbF2for moderator; combining Pb material with either Ni or Pb for reflector; combining Ni and either FeC or C for collimator, and FeC+LiF and Cd for fast and thermal neutron filter. The parameters of radiation resulted from the four configurations of double layer BSA adequately satisfy the standard of the IAEA.

Open access

Al. Cheremensky

Abstract

Mechanical systems of Cosserat–Zhilin are introduced as the main object of rational (non-relativistic) mechanics on the base of new notions of vector calculus—sliders and screw measures (bi-measures).

Open access

Samuel N. A. Tagoe, Samuel Y. Mensah and John J. Fletcher

Abstract

Objectives: The present study aimed to generate intensity-modulated beams with compensators for a conventional telecobalt machine, based on dose distributions generated with a treatment planning system (TPS) performing forward planning, and cannot directly simulate a compensator.

Materials and Methods: The following materials were selected for compensator construction: Brass, Copper and Perspex (PMMA). Boluses with varying thicknesses across the surface of a tissue-equivalent phantom were used to achieve beam intensity modulations during treatment planning with the TPS. Beam data measured for specific treatment parameters in a full scatter water phantom with a 0.125 cc cylindrical ionization chamber, with a particular compensator material in the path of beams from the telecobalt machine, and that without the compensator but the heights of water above the detector adjusted to get the same detector readings as before, were used to develop and propose a semi-empirical equation for converting a bolus thickness to compensator material thickness, such that any point within the phantom would receive the planned dose. Once the dimensions of a compensator had been determined, the compensator was constructed using the cubic pile method. The treatment plans generated with the TPS were replicated on the telecobalt machine with a bolus within each beam represented with its corresponding compensator mounted on the accessory holder of the telecobalt machine.

Results: Dose distributions measured in the tissue-equivalent phantom with calibrated Gafchromic EBT2 films for compensators constructed based on the proposed approach, were comparable to those of the TPS with deviation less than or equal to ± 3% (mean of 2.29 ± 0.61%) of the measured doses, with resultant confidence limit value of 3.21. Conclusion: The use of the proposed approach for clinical application is recommended, and could facilitate the generation of intensity-modulated beams with limited resources using the missing tissue approach rendering encouraging results.

Open access

Hideharu Miura, Shuichi Ozawa, Tsubasa Enosaki, Masahiro Hayata, Kiyoshi Yamada and Yasushi Nagata

Abstract

We investigated the gantry-angle classifier performance with a fluence map using three machine-learning algorithms, and compared it with human performance. Eighty prostate cases were investigated using a seven-field-intensity modulated radiotherapy treatment (IMRT) plan with beam angles of 0°, 50°, 100°, 155°, 205°, 260°, and 310°. The k-nearest neighbor (k-NN), logistic regression (LR), and support vector machine (SVM) algorithms were used. In the observer test, three radiotherapists assessed the gantry angle classification in a blind manner. The precision and recall rates were calculated for the machine learning and observer test. The average precision rate of the k-NN and LR algorithms were 94.8% and 97.9%, respectively. The average recall rate of the k-NN and LR algorithms were 94.3% and 97.9%, respectively. The SVM had 100% precision and recall rates. The gantry angles of 0°, 155°, and 205° had an accuracy of 100% in all algorithms. In the observer test, average precision and recall rates were 82.6% and 82.6%, respectively. All observers could easily classify the gantry angles of 0°, 155°, and 205° with a high degree of accuracy. Misclassifications occurred in gantry angles of 50°, 100°, 260°, and 310°. Machine learning could better classify gantry angles for prostate IMRT than human beings. In particular, the SVM algorithm had a perfect classification of 100%.

Open access

Naman Jain

Abstract

This paper presents the mathematical model to solve the topological optimization problem. Effect of higher order element on the optimum topology of the isotropic structure has been studied by using 8-node elements which help in decreasing the numerical instability due to checkerboarding problem in the final topologies obtained. The algorithms are investigated on a number of two-dimensional benchmark problems. MATLAB code has been developed for different numerical two dimensional linear isotropic structure and SIMP approach is applied. Models are discretized using linear quadratic 4-node and 8-node elements and optimal criteria method is used in the numerical scheme. Checkerboarding instability in the final topology is greatly reduces when incorporated 8-node element instead of 4-node element which can be confirmed through comparing the final topologies of the structure.

Open access

Maede Hasan Abdali, Karim Khoshgard and Abdolazim Sedighi Pashaki

Abstract

Purpose: To develop a multiple logistic regression model as normal tissue complication probability model by least absolute shrinkage and selection operator (LASSO) technique in breast cancer patients treated with three-dimensional conformal radiation therapy (3D-CRT), we focused on the changes of pulmonary function tests to achieve the optimal predictive parameters for the occurrence of symptomatic radiation pneumonitis (SRP).

Materials and methods: Dosimetric and spirometry data of 60 breast cancer patients were analyzed. Pulmonary function tests were done before RT, after completion of RT, 3, and 6 months after RT. Multiple logistic regression model was used to obtain the effective predictive parameters. Forward selection method was applied in NTCP model to determine the effective risk factors from obtained different parameters.

Results: Symptomatic radiation pneumonitis was observed in five patients. Significant changes in pulmonary parameters have been observed at six months after RT. The parameters of mean lung dose (MLD), bridge separation (BS), mean irradiated lung volume (ILVmean), and the percentage of the ipsilateral lung volume that received dose of 20 Gy (IV20) introduced as risk factors using the LASSO technique for SRP in a multiple normal tissue complication probability model in breast cancer patients treated with 3D-CRT. The BS, central lung distance (CLD) and ILV in tangential field have obtained as 23.5 (20.9-26.0) cm, 2.4 (1.5-3.3) cm, and 12.4 (10.6-14.3) % of lung volume in radiation field in patients without pulmonary complication, respectively.

Conclusion: The results showed that if BS, CLD, and ILV are more than 23 cm, 2 cm, and 12%, respectively, so incidence of SRP in the patients will be considerable. Our multiple NTCP LASSO model for breast cancer patients treated with 3D-CRT showed that in order to have minimum probability of SRP occurrence, parameters of BS, IV20, ILV and especially MLD would be kept in minimum levels. Considering dose-volume histogram, the mean lung dose factor is most important parameter which minimizing it in treatment planning, minimizes the probability of SRP and consequently improves the quality of life in breast cancer patients.