2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach.

Purpose: This work presents an original algorithm that converts the signal of an electronic portal imaging device (EPID) into absorbed dose in water at the depth of maximum.

Methods: The model includes a first image pre-processing step that accounts for the non-uniformity of the detector response but also for the perturbation of the signal due to backscatter radiation. Secondly, the image is converted into absorbed dose to water through a linear conversion function associated with a dose redistribution kernel.

Intensity modulated arc therapy in bilaterally irradiated head and neck cancer: a comparative and prospective multicenter planning study.

A dosimetric comparison was made of Helical Tomotherapy (HT) and Rapid'Arc(®) (RA) in 115 patients with head and neck carcinoma included in a prospective and multicentric study. HT and RA provided highly conformal plans that easily complied with dose volume constraints for organs at risk. HT reduced high doses to the planning target volumes (PTVs) compared to RA and provided a more homogeneous dose distribution but with an increased Non Tumoral Integral Dose (NTID) than RA.

Electron beam quality correction factors for plane-parallel ionization chambers: Monte Carlo calculations using the PENELOPE system.

Simulations of three plane-parallel ionization chambers have been used to determine directly the chamber- and quality-dependent factors fc,Q, instead of the product (Sw,air p)Q, and kQ,Q0 (or kQ,Q,int) for a broad range of electron beam qualities (4-20 MeV) using divergent monoenergetic beams and phase-space data from two accelerators. An original calculation method has been used which circumvents the weakness of the so far assumed independence between stopping-power ratios and perturbation factors. Very detailed descriptions of the geometry and materials of the chambers have been obtained from the manufacturers, and prepared as input to the PENELOPE 2003 Monte Carlo system using a computer code that includes correlated sampling and particle splitting.

Morphometric and histological changes in the vascular wall after external radiation for the prevention of intimal hyperplasia.

Background: Recent reports describe spontaneous dissections and aneurysms after coronary and peripheral artery irradiation for the prevention of intimal hyperplasia. We investigated histological changes and the vasomotor reaction in the vascular wall after external radiation for the prevention of intimal hyperplasia in rabbits.

Materials And Methods: The aorta was experimentally injured in 34 rabbits who were then assigned to one of three groups: irradiation with 20 Gy; with 25 Gy; and a control group with no irradiation.