A Simple Approach for Experimental Characterization and Validation of Proton Pencil Beam Profiles

Paulina Stasica,Jakub Baran,Jan Gajewski,Grzegorz Korcyl,Cristina Oancea,Marzena Rydygier,Carlos Granja,Monika Pawlik-Niedźwiecka,Nils Krah,Antoni Rucinski,Angelo Schiavi,Szymon Niedźwiecki

doi:10.3389/fphy.2020.00346

Abstract

A precise characterization of therapeutic proton pencil beams is essential for commissioning of any treatment planning system (TPS). The dose profile characterization includes measurement of the beam lateral dose profile in the beam core and far from the beam core, in the so called low-dose envelope, and requires a sophisticated detection system with a few orders of magnitude dynamic range. We propose to use a single-quantum sensitive Minipix Timepix detector, along with an in-house designed holder to perform measurements of the pencil beam dose profile in air and in water. We validated the manufacturer calibration of the Minipix Timepix detector in proton beams of various energies and compared the deposited energy spectra to Monte Carlo (MC) simulations. The precision of the lateral dose profile measurements has been systematically validated against Krakow proton facility commissioning data and dose profile simulations performed with MC codes Gate/Geant4 and Fred. We obtained an excellent agreement between Minipix Timepix measurements and simulations demonstrating the feasibility of the system for a simple characterization and validation of proton pencil beams. The proposed approach can be implemented at any proton therapy facility to acquire experimental data needed to commission and validate analytical and MC based TPS.

Highlights

The dosimetric advantage of proton beams in radiotherapy is due to their depth-dose distribution (Bragg curve), which allows us to minimize the dose deposited in healthy tissues and to maximize it in the tumor region [1, 2]
The microstructure of the proton beam produced by C-235 IBA cyclotron in Krakow consists of 0.79 ns micropulses generated with the frequency 106 MHz, which is common to all beam intensity settings
We propose using the technology of pixel semiconductor detectors, TIMEPIX from ADVACAM, for characterization of therapeutic proton pencil beams and validation of treatment planning system (TPS) and Monte Carlo (MC) simulations

Summary

Introduction

The dosimetric advantage of proton beams in radiotherapy is due to their depth-dose distribution (Bragg curve), which allows us to minimize the dose deposited in healthy tissues and to maximize it in the tumor region [1, 2]. According to data provided by the Particle Therapy Co-Operative Group (https://www.ptcog.ch/, 2020), there are 91 proton (or proton and carbon ion) radiotherapy facilities in operation, 33 under construction, and 27 in the planning stage all around the world. Upon startup of each new proton facility, for the purpose of launching a treatment planning system (TPS), a commissioning of the proton pencil beam is required. The beam commissioning, which includes, e.g., an experimental characterization of lateral and longitudinal beam profiles, is a demanding and time-consuming experimental procedure. We propose a new Experimental Characterization of Proton Beams approach for characterization of lateral beam profiles in air and in water to simplify the procedure of beam data library acquisition and TPS commissioning

Methods

Results

Conclusion