Measurement techniques, modeling strategies and pitfalls to avoid when implementing a mini MLC in a non dedicated planning system.

Background And Purpose: Ghent University Hospital investigated the feasibility of the Pinnacle system for planning intracranial stereotactic treatments. The aim was to perform precise dose computation using the collapsed cone engine for treatment delivery with the Moduleaf mini-MLC mounted on an Elekta accelerator.

Material And Methods: The Moduleaf was commissioned using dose rate corrected data recorded by a diamond detector and using data measured by cylindrical chambers each limited to restricted field sizes.

The importance of accurate linear accelerator head modelling for IMRT Monte Carlo calculations.

Two Monte Carlo dose engines for radiotherapy treatment planning, namely a beta release of Peregrine and MCDE (Monte Carlo dose engine), were compared with Helax-TMS (collapsed cone superposition convolution) for a head and neck patient for the Elekta SLi plus linear accelerator. Deviations between the beta release of Peregrine and MCDE up to 10% were obtained in the dose volume histogram of the optical chiasm. It was illustrated that the differences are not caused by the particle transport in the patient, but by the modelling of the Elekta SLi plus accelerator head and more specifically the multileaf collimator (MLC).

MCDE: a new Monte Carlo dose engine for IMRT.

A new accurate Monte Carlo code for IMRT dose computations, MCDE (Monte Carlo dose engine), is introduced. MCDE is based on BEAMnrc/DOSXYZnrc and consequently the accurate EGSnrc electron transport. DOSXYZnrc is reprogrammed as a component module for BEAMnrc.

Application of monomer/polymer gel dosimetry to study the effects of tissue inhomogeneities on intensity-modulated radiation therapy (IMRT) dose distributions.

Background And Purpose: When planning an intensity-modulated radiation therapy (IMRT) treatment in a heterogeneous region (e.g. the thorax), the dose computation algorithm of a treatment planning system may need to account for these inhomogeneities in order to obtain a reliable prediction of the dose distribution.

An isocenter position verification device for electronic portal imaging: physical and dosimetrical characteristics.

The physical and dosimetrical characteristics of a device, designed to visualize the isocenter position on electronic portal images, were examined. The device, to be mounted on the gantry head of the accelerator, containing five spheric lead markers, was designed in order to visualize the isocenter position on portal images. A quality control device was designed to check the reliability of this technique.