Overview
Radiation therapy (RT) treatment planning systems (TPS) are commercially available for routine treatment planning for hospitals. However, cutting edge techniques constantly arise that are not immediately available or reflected in these TPSs. To this end, a TPS is required for experimental purposes that ideally can work in unison with the commercial TPSs. Also, low-cost treatment techniques exist - such as Co60 - that hospitals in developing countries can afford, but not necessarily the accompanying expensive TPS software. To encourage community involvement and ensure transparency, an open-source system is preferred, for which the SlicerRT toolkit is a natural host platform.
The External Beam Planning (EBP) SlicerRT module has been developed to become this open-source treatment planning system.
Representation of external beam treatment geometry
The linear accelerator treatment planning machines are extremely complex pieces of machinery with many geometric parameters to set during a treatment planning process. Manual adjustment of these parameters (such as gantry angle) is already possible in the EBP module. However, it is extremely hard to
1. Understand the actual physical consequences of such a parameter change
2. Keep the internal geometry consistent with the standard IEC coordinate system structure
So a transformation logic is needed to correctly simulate the IEC standard, as well as a user interface that represents the parameters and their effects on the different components of a linac. This representation can be a 3D model of a stylistic linear accelator device that helps the user clearly understand geometric state of the linac.
Orthovoltage radiation therapy
Non-melanoma skin cancer (NMSC) is the most common cancer diagnosed. Among Canadians, the lifetime risk of being diagnosed with NMSC has increased by two to three times from 1960s to 1990s. Three main modalities of RT of NMSC currently used are orthovoltage x-rays range (50 to 180 kV), megavoltage electron beams (6 to 20 MeV) and surface mould brachytherapy using radioactive sources. Orthovoltage x-ray therapy is an effective radiation treatment for superficial lesions of the 5 mm depth in the skin (Kauvar et al. 2015). Considering the simplicity of
technique and sharp beam penumbra Orthovoltage RT is often preferred over surface mould brachytherapy or electron therapy.
Commercial treatment planning systems for Orthovoltage x-ray based dose planning are not available. Currently, all cases in our clinic (like other clinics worldwide) are planned using clinical mark ups, visualizing paper based isodose charts for standard beam and phantom
geometries. The EGSnrc/BEAMnrc and EGSnrc /DOSXYZnrc Monte Carlo codes (National Research Council, Canada (NRCC), Ottawa) have been used by other researchers to calculate Orthovoltage x-ray dose distributions in select clinical cases. The goal is to facilitate clinical treatment planning using these freely available tools through interfacing them with 3D Slicer.
