An efficient framework for photon Monte Carlo treatment planning

Abstract

Currently photon Monte Carlo treatment planning (MCTP) for a patient stored in the patient database of a treatment planning system (TPS) can usually only be performed using a cumbersome multi-step procedure where many user interactions are needed. This means automation is needed for usage in clinical routine. In addition, because of the long computing time in MCTP, optimization of the MC calculations is essential. For these purposes a new graphical user interface (GUI)-based photon MC environment has been developed resulting in a very flexible framework. By this means appropriate MC transport methods are assigned to different geometric regions by still benefiting from the features included in the TPS. In order to provide a flexible MC environment, the MC particle transport has been divided into different parts: the source, beam modifiers and the patient. The source part includes the phase-space source, source models and full MC transport through the treatment head. The beam modifier part consists of one module for each beam modifier. To simulate the radiation transport through each individual beam modifier, one out of three full MC transport codes can be selected independently. Additionally, for each beam modifier a simple or an exact geometry can be chosen. Thereby, different complexity levels of radiation transport are applied during the simulation. For the patient dose calculation, two different MC codes are available. A special plug-in in Eclipse providing all necessary information by means of Dicom streams was used to start the developed MC GUI. The implementation of this framework separates the MC transport from the geometry and the modules pass the particles in memory; hence, no files are used as the interface. The implementation is realized for 6 and 15 MV beams of a Varian Clinac 2300 C/D. Several applications demonstrate the usefulness of the framework. Apart from applications dealing with the beam modifiers, two patient cases are shown. Thereby, comparisons are performed between MC calculated dose distributions and those calculated by a pencil beam or the AAA algorithm. Interfacing this flexible and efficient MC environment with Eclipse allows a widespread use for all kinds of investigations from timing and benchmarking studies to clinical patient studies. Additionally, it is possible to add modules keeping the system highly flexible and efficient.

Validation of the Swiss Monte Carlo Plan for a static and dynamic 6 MV photon beam

“…Note that in a previous work jaw and MLC transmission measurements have been performed for static situations in order to configure the properties of the jaw and the MLC beam modifier [6]. Thus, all the measurements used in this work for the static MLC, for the EDW as well as for the dynamic-IMRT have been validating these properties with respect to the implementation for the dynamic application.…”

“…The pre-clinical MC systems are described in the literature [6,7,8,9,10] and are used for research studies and to investigate certain clinical objectives.…”

“…In this work we focus on the Swiss Monte Carlo Plan (SMCP) [6], a GUI-based framework for photon MC treatment planning developed at the Division of Medical Radiation Physics at the Inselspital -University Berne. The SMCP allows investigations with respect to calculation times using different transport algorithms [14], but also to investigate clinical patient studies.…”

“…For such studies it is necessary to have a well commissioned and validated system available. Although some preliminary studies have been already performed to test the SMCP environment as discussed in [6], more extensive investigations are needed for its full commissioning and validation. We aim to validate the SMCP with respect to measured data for static and dynamic 6 MV photon beams for research and clinical purposes.…”

Assessing dose rate distributions in VMAT plans

“…This 12 mode provides fast analysis of the dose rates expected in a treatment or may be applied to a 13 subvolume defined in the treatment structure set. 14 On the other hand, in 2D plus time mode, the "color wash" dose display mode is mimicked, 15 enhanced by a scrollable time dimension. Instead of dose, dose rates are shown to provide all 16 information about the spatiotemporal variations during the fraction delivery.…”