background: because of the adverse effects of ionizing radiation on fetuses, prior to radiotherapy of pregnant patients, fetal dose should be estimated. fetal dose has been studied by several authors in different depths in phantoms with various abdomen thicknesses (at). in this study, the effect of maternal at and depth in fetal dosimetry was investigated, using peripheral dose (pd) distributio...

background and objective: hypothyroidism is a known consequence of the external beam radiotherapy to the neck encompassing the thyroid gland for over 40 years. the aim of this study was to find out the incidence of hypothyroidism in patients with head and neck cancer treated with radiotherapy, when radiation portals included whole of the thyroid gland. materials and methods: this prospective no...

background and aims. at present, cone beam computed tomography (cbct) has become a substitute for computed tomography (ct) in dental procedures. the metallic materials used in dentistry can produce artifacts due to the beam hardening phenomenon. these artifacts decrease the quality of images. in the present study, the number of artifacts as a result of beam hardening in the images of dental imp...

We present an empirical analytic approximation for the luminosity \de-enhancement" factor HD in e e collisions, as a function of the disruption parameters Dx, Dy, the hour-glass parameters Ax, Ay, and the beam aspect ratio R x= y. We treat Gaussian beams with essentially arbitrary aspect ratio, assuming only that the vertical beam size is less than or equal to the horizontal beam size and that ...

Beam orientation optimization (BOO) is a key component in the process of intensity modulated radiation therapy treatment planning. It determines to what degree one can achieve a good treatment plan in the subsequent plan optimization process. In this paper, we have developed a BOO algorithm via adaptive l(2, 1)-minimization. Specifically, we introduce a sparsity objective function term into our...

BACKGROUND AND PURPOSE The optimal intensity fluence profile of a beam depends on the profiles of other beams but most optimizations assume fixed beam orientations, a priori. Breast cancer radiotherapy attempts to cover the target and to spare critical structures such as the heart and lungs. The study aims are (1) to determine and document the optimal two-beam orientation that best spares the h...

Objective: The aim of the present study is to simulate 6 MV and 18 MV photon beam energies of a Siemens Primus Plus medical linear accelerator (Linac) and to verify the simulation by comparing the results with the measured data.Methods: The main components of the head of Siemens Primus Plus linac were simulated using MCNPX Monte Carlo (MC) code. To verify the results, experimental data of perce...

The Fermilab photoinjector produces electron bunches of 1–12 nC charge with an energy of 16–18 MeV. Detailed measurements and optimization of the transverse emittance have been carried out for a number of beam line optics conditions, and at a number of beam line locations. The length of the bunches has also been measured, first for an uncompressed beam (as a function of the charge) and then for...

Nondiffracting beams are of interest for optical metrology applications because the size of the beam does not change as the beam propagates. However, accuracy can be increased if the diameter of the beam is smaller. One technique for accomplishing this is to use the dark axial intensity profile associated with a higher-order nondiffracting Bessel function beam. We generate these higher-order Be...