Multileaf collimators (MLCs) are becoming increasingly important for beam shaping and intensity modulated radiation therapy (IMRT). Their unique design can introduce subtle effects in the patient/phantom dose distribution. The PEREGRINE 3D Monte Carlo dose calculation system predicts dose by implementing a full Monte Carlo simulation of the beam delivery and patient/phantom system. As such, it provides a powerful tool to explore dosimetric effects of MLC designs. We have installed a new MLC modeling package into PEREGRINE. This package simulates full photon and electron transport in the MLC and includes tongue-and-groove construction and curved or straight leaf ends in the leaf shape geometry. We tested the accuracy of the PEREGRINE MLC package by comparing PEREGRINE predictions with ion chamber, diode, and photographic film measurements taken with a Varian 2 1 OOC using 6 and 18 MV photon beams. Profile and depth dose measurements were made for the MLC configured into annulus and comb patterns. In all cases, PEREGRINE modeled these measurements to within experimental uncertainties. Our results demonstrate PEREGRINE's accuracy for modeling MLC characteristics, and suggest that PEREGRINE would be an ideal tool to explore issues such as (1) underdosing between leaves due to the ''tongue-and-groove'' effect when dose from multiple MLC patterns are added together, (2) radiation leakage in the bullnose region, and (3) dose under a single leaf due to scatter in the patient.

This report describes the first year of a project to design and construct multileaf collimators (MLC) to be used in proton radiotherapy. This research project is a joint collaborative effort between the University of Pennsylvania (HUP) and the Walter Reed Army Medical Center (WRAMC) and is part of a larger project to build a state-of-the-art proton radiotherapy facility in Philadelphia in collaboration with the Children's Hospital of Philadelphia (CHOP). The accomplishments during the start-up phase in the first year of the project are described in this report. (1) Assemble personnel required to perform the tasks listed in the Statement of Work, (2) Establish an efficient working relationship with the Radiation Therapy group at WRAMC, (3) Install the Monte Carlo simulation code GEANT4 and validate our use of it using published data, (4) Study, using GEANT4 and published data, the neutron production from and activation of MLCs made of different materials (e.g. tungsten, iron, and brass) to determine the optimal choice of material for patient and personnel safety, (5) Commence requirements definition process for remote telemedicine, and (6) Initial work on setting up a Web-based system to enroll patients into proton therapy clinical trials.

Clinical conformal radiotherapy is the holy grail of radiation treatment and is now becoming a reality through the combined efforts of physical scientists and engineers, who have improved the physical basis of radiotherapy, and the interest and concern of imaginative radiotherapists and radiographers. Intensity-Modulated Radiation Therapy de

The Physics of Conformal Radiotherapy: Advances in Technology provides a thorough overview of conformal radiotherapy and biological modeling, focusing on the underlying physics and methodology of three-dimensional techniques in radiation therapy. This carefully written, authoritative account evaluates three-dimensional treatment planning, optimization, photon multileaf collimation, proton therapy, transit dosimetry, intensity-modulation techniques, and biological modeling. It is an invaluable teaching guide and reference for all medical physicists and radiation oncologists/therapists that use conformal radiotherapy.

In this thesis, a tracking system was developed by modifying an add-on collimator, the Siemens Moduleaf, for realtime applications in radiotherapy. As the add-on collimator works almost completely autonomously of the linear accelerator (LinAc), no modifications to the latter were necessary. The adaptations to the Moduleaf were mainly software-based. In order to reduce the complexity of the system, outdated electronic parts were replaced with newer components where practical. Verification was performed by measuring the latency of the system as well as the impact on applied dose to a predefined target volume, moving in the leaf's travel direction. Latency measurements in software were accomplished by comparing the target and current positions of the leaves. For dose measurements, a Gafchromic EBT2 film was placed beneath the target 4D phantom, in between solid water plates, and moved alongside with it. Based on the results, a tracking-capable add-on collimator seems to be a useful tool for reducing the margins for the treatment of small, slow-moving targets. Radiotherapy is one of the most important methods used for the treatment of cancer. Irradiating a moving target is also one of the most challenging tasks to accomplish in modern radiotherapy.

Provides an account of the perspective, methodology, and experience in the physical and medical aspects of IMRT at Memorial Sloan-Kettering Cancer Center (MSKCC).