Application of the medical linear accelerator ELEKTA AXESSE in the study of sorption properties of impurities and absorption coefficients of medium and heavy chemical elements

In this article, the authors propose a new technique for measuring linear attenuation coefficients on the medical linear accelerator Elekta Axesse. Linear attenuation coefficients were obtained for four samples at different concentrations of substances at a gamma-ray energy of 6 MeV. A unified ionization chamber was used as a detector to register the transmitted gamma-ray beam through the samples under study. Linear absorption coefficients were obtained for elements B, C, O, S, Fe, Ba taking into account their concentration, as well as taking into account the different mass inclusion of paraffin in the samples under study, which is acyclic hydrocarbons CnH2n+2. The measurement results showed that taking into account certain components in impurities leads to relatively small, but quite noticeable differences in the determination of the total absorption coefficients. This is especially important to take into account for determining the concentration of light elements in samples. To determine the content of medium and heavy chemical elements, taking into account the content of light elements can be neglected. The use of a 6 MeV gamma-ray beam made it possible to reduce the errors in determining the absorption coefficients, since their dependence on energy in the region of applicable gamma-ray energies is not so great in comparison with the low-energy region, in which the shell effects for heavy elements will introduce significant contribution.

Relative output factors of different collimation systems in truebeam STx medical linear accelerator

The IAEA TRS483 and TRS398 Code of Practices (CoP) were used to calculate relative output factors for small photon beams of 6X, 6XFFF energies shaped by High Definition Multileaf Collimator (HDMLC), jaws and cones mounted on TrueBeam STx medical linear accelerator (Varian Medical Systems), respectively. A comparison between these results were made. The results show a large discrepancy in relative output factor curves found among different collimation systems of the same equivalent field sizes and between the CoPs. Therefore, the specific beam modelling in treatment planning system for each type of the collimation system to be used for small fields maybe required for better computational accuracy.

Dosimetric characterization of medical linear accelerator Photon and Electron beams for the treatment accuracy of cancer patients

In radiotherapy treatment planning process, quality assessment (QA) is indispensable for achieving accuracy and avoidance of treatment errors. In this perspective, present study focused on the Photon and Electron beams characterization of a medical linear accelerator (LINAC) to ascertain dosimetric QA in Absolute and Reference dosimetry. In this connection, the beam outputs were investigated in terms of Dmax and Dw,max (dose at depth dmax) in absolute dosimetry for Photon and Electron beams, respectively. In accordance with the measured Dmax and Dw,max parameters, Photon and Electron beam outputs were standardized to ensure standard output of 1 cGy/MU. In reference dosimetry, the parametric evaluation was performed for dosimetric QA in terms of percent depth dose (PDD), beam profile flatness and symmetry, output factors: Scp, Sc, Sp with varying field size (FS) ranging from 4´4 cm2 to 40´40 cm2 normalized at FS 10´10 cm2 for the 6 MV and 10 MV Photon beams. The measured PDDs at 10 cm depth (D10) were found to be 66.8% and 73.6% for 6 MV and 10 MV Photon beams, respectively, with significantly small deviation of 1% and 0.8% in comparison with an international PDD protocol of British Journal of Radiology-25 (BJR -25). In the case of Electron beams characterization, PDD was verified with 10´10 cm2 cone/applicator, beam profile flatness and symmetry were analyzed at the field sizes ranging from 6´6 cm2 to 25´25 cm2 normalized at 10´10 cm2 cone/applicator, and Electron cone ratios were investigated for a given cone/applicator relative to the 15´15 cm2 one for the 6, 9, 12, 15 MeV Electron energies. The PDDs of all the Electron beams revealed reasonable consistency with manufacturer’s estimations of 90%, 80%, and 50% PDDs at various depths of ionization.

Green dielectric solids using PLA and luffa fiber modified by the medical linear accelerator

Biodegradable electronic devices are presently in command in various sectors mainly in the health care system. The present work comprehends the dielectric properties of biodegradable composites made from biodegradable polymer poly (lactic) acid (PLA) and natural fiber of luffa cylindrical (LC) fabricated using micro compounding and injection molding. LC fibers are agricultural waste, rich in cellulose.LC fibers were exposed to a 6 MeV electron beam of doses 0.5Gy, 1.0Gy, 2.0Gy, 4.0Gy, and 10.0 Gy generated from a medical linear accelerator(LINAC) in presence of air. Such low doses are normally used for the treatment of cancer patients and not for modifying polymers where doses in the range of 20-200KGy are used. The effect of such low irradiation dose on fiber and study if any significant changes taking place is the innovative aspect of the present work. The effects of irradiation dose on dielectric constant and ac conductivity were investigated at different temperatures 260C, 40oC, 60oC, and 80oC while keeping the frequency constant. The increase in dielectric constant from 57 in virgin PLA at 260C,500Hz to a maximum of 84 in the composite sample due to reinforcement of low dose irradiated LC fibers recording a 49% increase is an important result of the investigation.

Biodegradable dielectricmaterial using PLA and luffa fiber modified by medical linear accelerator

Biodegradable electronic devices are presently in command in various sectors mainly in health care system.The present work comprehends the dielectric properties of biodegradable composites made from biodegradable polymer poly (lactic) acid (PLA) and natural fiber of luffa cylindrica (LC) fabricated using microcompounding and injection molding. LC fibers are an agricultural waste, rich in cellulose.LC fibers were exposed to 6 MeV electron beam of doses 0.5Gy, 1.0Gy, 2.0Gy, 4.0Gy and 10.0 Gy generated from medical linear accelerator(LINAC) in presence of air. Such low doses are normally used for treatment of cancer patients and not for modifying polymers where doses in the range of 20-200KGy are used. The effect of such low irradiation dose on fiber and study if any significant changes taking place is the innovative aspect of the present work. The effects of irradiation dose on dielectric behavior such as dielectric constant and ac conductivity were investigated at different temperatures 260C, 40oC, 60oC and 80oC while keeping frequency constant. The increase in dielectric constant from 57 in virgin PLA at 260C,500Hz to a maximum of 84 in composite sample due to reinforcement of low dose irradiated LC fibers recording 49% increase is an important result of the investigation.