نتایج جستجو برای: dosimetry linear accelerator add on mlc recommissioning
تعداد نتایج: 8622156 فیلتر نتایج به سال:
background: attenuation coefficient (μ) plays an important role in calculations of treatment planning systems, as well as determination of dose distributions in external beam therapy, dosimetry, protection, phantom materials and industry. so, its exact measurement or calculation is very important. the aim of this study was to evaluate the μ in different points in the water phantom analytically ...
Background: High-energy linear accelerator (linac) is a valuable tool and the most commonly device for external beam radiation treatments in cancer patients. In the linac head, high-energy photons with energies above the threshold of interaction produce photoneutrons. These photoneutrons deliver the extra dose to the patients in the planning treatment and increase the risk of secondary cancer.O...
Background: Accurate small radiation field dosimetry is essential in modern radiotherapy techniques such as stereotactic radiosurgery (SRS) and intensity modulated radiotherapy (IMRT). Precise measurement of dosimetric parameters such as beam profile, percentage depth doses and output factor of these beams are complicated due to the electron disequilibrium and the steep dose gradients. In the p...
This study evaluates changes in the dosimetric characteristics of a Varian Millennium 80-leaf multileaf collimator (MLC) in a radiation field. In this study, dose rate, scatter factor, percentage depth dose, surface dose and dose in the buildup region, beam profile, flatness and symmetry, and penumbra width measurements were made for 6-MV and 15-MV photon beams. Analysis of widths between 50% d...
MC treatment planning techniques provide a very accurate dose calculation compared to ‘conventional’ deterministic treatment planning systems. In the present work, PLanUNC (PLUNC), a set of software tools for radiotherapy treatment planning (RTP), is compared with MCNP5 (Monte Carlo N-Particle transport code) by calculating dose maps inside the RANDO phantom, utilized as the patient model, irra...
Very high energy electrons (VHEE) in the range from 100-250 MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetry properties compared with MV photons from contemporary medical linear accelerators. Due to the need for accurate dosimetry of small field size VHEE beams we have performed dose measurements using EBT2 Gafchromic® film. Calibrat...
Individual QA for IMRT/VMAT plans is required by protocols. Sometimes plans cannot pass the institute's QA criteria. For the Eclipse treatment planning system (TPS) with rounded leaf-end multileaf collimator (MLC), one practical way to improve the agreement of planned and delivered doses is to tune the value of dosimetric leaf gap (DLG) in the TPS from the measured DLG. We propose that this ste...
Linear accelerators used in radiation therapy treatments usually provide the capability of irradiating with different dose rates. The medical physicist may choose arbitrary the dose rate to use, although the relative biological effectiveness (RBE) varies with this physical parameter. In this work the measurements of absorbed dose of the x-ray beams from a Varian 6 MV linear accelerator CLINAC 6...
Background: Radiotherapy with large mantle field is an effective technique in increasing the risk of secondary cancers among HL (Hodgkin Lymphoma) patients; therefore, it is essential to choose an effective treatment field including the least medical conditions in radiotherapy.Objective: The present study aimed to plan separate fields for neck and mediastinum using various energies, to compare ...
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