0000000000481637
AUTHOR
Marcin Bieniasiewicz
Determination of boundaries between ranges of high and low gradient of beam profile
Abstract Aim This work addresses the problem of treatment planning system commissioning by introducing a new method of determination of boundaries between high and low gradient in beam profile. Background The commissioning of a treatment planning system is a very important task in the radiation therapy. One of the main goals of this task is to compare two field profiles: measured and calculated. Applying points of 80% and 120% of nominal field size can lead to the incorrect determination of boundaries, especially for small field sizes. Materials and methods The method that is based on the beam profile gradient allows for proper assignment of boundaries between high and low gradient regions …
Competing species system as a qualitative model of radiation therapy
To examine complex features of tumor dynamics we analyze a competing-species lattice model that takes into account the competition for nutrients or space as well as interaction with therapeutic factors such as drugs or radiation. Our model might be interpreted as a certain prey–predator system having three trophic layers: (i) the basal species that might be interpreted as nutrients; (ii) normal and tumor cells that consume nutrients, and (iii) therapeutic factors that might kill either nutrient, normal or tumor cells. Using a wide spectrum of parameters we examined survival of our species and tried to identify the corresponding dynamical regimes. It was found that the radiotherapy influence…
[P149] Beam profile characteristic points designation for off-axis, wedged and FFF beams
Purpose The main aim of this work is the search of characteristic points of a beam profile and application of these points for the TPS commissioning purposes. The comparison between profiles during the commissioning of the treatment planning system is a very important procedure. It is impossible to designate a field size for the off-axis, wedged and FFF beams directly using the definition of the on-axis symmetric field size. This work demonstrates how to compute good indicators of the field size that can be used for commissioning and QA purposes. Methods The proposal is to use profile inflection points as the beam profile characteristic points. The comparison of distances between inflection…
Measurements of neutron radiation and induced radioactivity for the new medical linear accelerator, the Varian TrueBeam
Abstract Contemporary linear accelerators applied in radiotherapy generate X-ray and electron beams with energies up to 20 MeV. Such high-energy therapeutic beams induce undesirable photonuclear (γ,n) and electronuclear (e,e'n) reactions in which neutrons and radioisotopes are produced. The originated neutron can also induce reactions such as simple capture, (n,γ), reactions that produce radioisotopes. In this work measurements of the non-therapeutic neutrons and the induced gamma radiation were carried out in the vicinity of a new medical accelerator, namely the Varian TrueBeam. The TrueBeam is a new generation Varian medical linac making it possible to generate the X-ray beams with a dose…