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Evaluation of the Septal Penetration and Scattering Effect in the Parallel Slat Collimator Gamma Camera On the Range Quantification in Proton Therapy : A Geant4 Monte Carlo Simulation Study

E Malekzadeh1 , H Rajabi2 , F Kalantari3*, (1) ,Tarbiat Modares University, Tehran, Iran, (2) ,Tarbiat Modares University, Tehran, Iran, ,(3) University of Texas,Dallas, USA


(Monday, 7/15/2019) 3:45 PM - 4:15 PM

Room: Exhibit Hall | Forum 6

Purpose: The range uncertainty is one of the limiting factors in the use of protons in radiotherapy. One of the promising methods for range verification to overcome this limitation is the use of the parallel slat camera based on prompt gamma imaging. However, due to the high energy of prompt gammas, in these cameras, septal penetration and scattering could have an effect on quantification of the range. So, in this study, the effect of these parameters on the obtained range from the camera was evaluated.

Methods: The simulation was performed using the geant4 toolkit. The parallel slat camera characteristics extracted from the available references. The detection profiles were considered for point and linear photon sources with the energy of 4.4 MeV and for prompt gammas induced during the PMMA phantom irradiation with 230 MeV energy protons. Detection Profiles with and without considering the septal penetration and scattering obtained for 2, 5, 10, 15 mm displacement. The range calculated for different situations.

Results: It was observed that neglecting the penetration and scattering in the septal leads to an underestimating the absolute value of the range up to 5 mm in measurements with 1-2 mm standard deviation for 109 particle history in the simulation

Conclusion: This work indicates that the septal penetration and scattering have an effect on range quantification and it varies according to the type of source, detection energy window, and amount of source displacement in realistic parallel slat camera. It was also determined that, If the system considered to be ideal, the estimation of the range is independent of the mentioned parameters.


Gamma Cameras, In Vivo Dosimetry, Protons


TH- External Beam- Particle therapy: Proton therapy - motion management(intrafraction)

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