Introduction: Wedge filters are commonly used in radiation oncology for eliminating hot spots and creating a uniform dose distribution in optimizing isodose curves in the target volume for clinical aspects. These are some limited standard physical wedges (15°, 30°, 45°, 60°), or creating an arbitrary wedge angle, like motorized wedge or dynamic wedge, ... The new formulation is...

In compliance with the RDR [2], the baseline configuration for the positron source is based on a helical undulator passed by an electron beam of 150GeV. About 500m downstream the resulting photon beam hits a thin target, creates electron-positron pairs; the emerging positrons are collected and accelerated. The photon beam is circularly polarized, the spectrum is shown in Fig. 1 (left plot). The...

Deterministic photon-photon interactions are a long-standing goal in optical science. Using an atomic ensemble inside a cavity, we demonstrate the mutual cross modulation of two continuous light beams at the level of individual photons. The originally uncorrelated beams derived from independent lasers become anticorrelated, as evidenced by an equal-time cross-correlation function g^{(2)}=0.89(1...

This paper reports on the investigation of the double K-shell ionization of metallic aluminum induced by photon and electron impact. The experimental method consisted to measure the K hypersatellite spectra resulting from the radiative decay of double 1s vacancy states by means of high-resolution x-ray spectroscopy using a Bragg-type von Hamos crystal spectrometer. Measurements of the photon-in...

Background: Skyshine describes the radiation scattered by the atmosphere above a LINAC facility to a point on the ground. The aim of this study was to measure the skyshine photon dose rates from two different (9 MV and 18 MV) medical linear accelerators. Materials and Methods: The photon beam was directed upward (180° gantry position), with a maximum photon field size (40 × 40 cm2) at the isoce...

External photon beam radiotherapy is usually carried out with more than one radiation beam in order to achieve a uniform dose distribution inside the target volume and an as low as possible a dose in healthy tissues surrounding the target. ICRU Report No. 50 recommends a target dose uniformity within +7% and –5% of the dose delivered to a well defined prescription point within the target. Moder...

This study is to investigate three common potential setup uncertainties during Linac commissioning and annual QA and to evaluate how these uncertainties propagate into the quality of beam profiles and patient dosimetry using gamma analysis. Three uncertainty scenarios were purposely introduced for gantry position tilted from 0 ̊ 3 ̊ (scenario 1), isocenter position misaligned from 0 6 mm (scenari...

A Monte Carlo model of an Elekta Precise linear accelerator has been built and verified by measured data for a 6 and 10 MV photon beam running with and without a flattening filter in the beam line. In this study the flattening filter was replaced with a 6 mm thick copper plate, provided by the linac vendor, in order to stabilize the beam. Several studies have shown that removal of the filter im...

PURPOSE By default, the 4-mm wide leaf-pairs of the Elekta Beam Modulator MLC not used for field shaping are moved to under the primary collimator to minimize the leakage dose. The trade-off is the increased beam delivery time in the case of IMRT. This study examines the dosimetric impact and improved delivery efficiency by allowing the unused leaf-pair as 2mm gap to stay within the PTV apertur...