introduction the use of cut-outs in electron applicators make changes on output, isodose, and percentage depth dose (pdd) curves. these changes and electron beam dose distribution in the form of three-dimensional (3d) can be measured by gel dosimeters. materials and methods dosimetry was performed with and without a square shield (6×6 cm2 field). the energies were 4, 9, and 16 mev and phantom w...

introduction range and diffusion of positron-emitting radiopharmaceuticals are important parameters for image resolution in positron emission tomography (pet). in this study, geant4 toolkit was applied to study positron diffusion in soft tissues with and without a magnetic field for six commonly used isotopes in pet imaging including 11c, 13n, 15o, 18f, 68ga, and 82rb. materials and methods gea...

PURPOSE In recent times, longitudinal field MRI-linac systems have been proposed for 6 MV MRI-guided radiotherapy (MRIgRT). The magnetic field is parallel with the beam axis and so will alter the transport properties of any electron contamination particles. The purpose of this work is to provide a first investigation into the potential effects of the MR and fringe magnetic fields on the electro...

In principle, the concept of flat initial radiation-dose distribution across the beam is unnecessary for intensity modulated radiation therapy. Dynamic leaf positioning during irradiation could appropriately adjust the fluence distribution of an unflattened beam that is peaked in the center and deliver the desired uniform or nonuniform dose distribution. Removing the flattening filter could lea...

This work introduces a new technology for electron intensity modulation, which uses small area island blocks within the collimating aperture and small area island apertures in the collimating insert. Due to multiple Coulomb scattering, electrons contribute dose under island blocks and lateral to island apertures. By selecting appropriate lateral positions and diameters of a set of island blocks...

A novel geometry has been proposed for a hybrid magnetic resonance imaging (MRI)-linac system in which a 6 MV linac is mounted on the open end of a biplanar, low field (0.2 T) MRI magnet on a single gantry that is free to rotate around the patient. This geometry creates a scenario in which the magnetic field vector remains fixed with respect to the incident photon beam, but moves with respect t...

Previously published FFT dose calculations and their verifications have been performed for field sizes greater than 10 cm x 10 cm with photon energies up to 18 MV [Zhu and Boyer, Phys. Med. Biol. 35, 351-368 (1990)]. With a smaller field size at megavoltage energies, lateral electronic disequilibrium exists in low density inhomogeneities which is not handled properly by the FFT calculations. In...

Introduction: Total skin electron irradiation technique is used in treatment of the mycosis fungoid. The implementation of this technique requires non-standard measurements and complex dosimetry methods. Operating procedures for total skin electron irradiation and its dosimetry vary in different radiation therapy centers in the world. In this article, validation of TSET techniq...

We analyze the energy band structure of a two-dimensional electron gas in a periodic magnetic field of a longitudinal antiferromagnet by considering a simple exactly solvable model. Two types of states appear: with a finite and infinitesimal longitudinal mobility. Both types of states are present at a generic Fermi surface. The system exhibits a transition to an insulating regime with respect t...