Moderator of 1 Session
Presenter of 1 Presentation
DEVELOMENT OF A MINI-BEAM COLLIMATOR WITH ADAPTABLE PEAK AND VALLEY WIDTHS AND SOURCE TO COLLIMATOR DISTANCES
Abstract
Background and Aims
Mini-beam irradiation is an innovative radiotherapy method utilizing spatial fractionation in order to reduce healthy tissue toxicity while controlling the tumor. To investigate this until yet not fully understood mechanism further, an adjustable collimator with variable peak-widths (PW) and valley-widths (VW) as well as customizable source to collimator distance (SCD) is needed. Generally, mini-beam collimators are expensive, require demanding production and cannot be easily adapted. Therefore, this study aims to design a customizable and adjustable low-cost mini-beam collimator which dosimetric parameters were evaluated.
Methods
A mini-beam holder skeleton was designed and 3D printed (80mmx80mm) to arrange successive tungsten plates (40mmx10mmx1mm) and 3D printed plastic plates (40mmx10mmx0.25mm-2mm) creating valley and peak regions, respectively. These plates can easily be exchanged and reproducibly stacked with three screws. Additionally, it is possible to vary the SCD by 3D printed angled plastic plates that perfectly fit the convergence at a certain distance. Thereby dose rates were varied from 4Gy/min to 216Gy/min. For the dosimetric characterization of the different configurations, EBT-XD films were irradiated with a Faxitron MultiRad 225.
Results
We created a collimator with exchangeable leaves to generate dose profiles with PW between 0.25mm and 2mm. For all setups, FWHM remains constant over the irradiated area and deviates by at most 10% relative to the collimator size. Peak and valley doses behave linearly to the applied doses and the peak to valley dose ratio (PVDR) for each of the different collimator setups remains constant up to 9.1 for the different setups.
Conclusions
To summarize, our novel adjustable collimator achieved dose profiles that are in accordance with the geometry, as well as homogeneity in peak and valley doses over the irradiated area. The next step will be to perform in vitro experiments for the different collimator parameters to investigate cell response for different peak widths, PVDR and dose rates.