A New Approach in Radiation Therapy: Proton Grid Therapy
G Fois1, Y Prezado2*, (1) University of Cagliari, Monserrato, Cagliari, (2) IMNC-CNRS, Orsay, Ile de FranceSU-E-T-333 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To evaluate the interest of the development of grid therapy with protons. The main aim of this proof of concept was twofold: first, the evaluation of a possible gain in tissue sparing thanks to the spatial fractionation of the dose provided by the grid and second, to show that the more precise ballistics of protons offer a further gain with respect to MV GRID therapy.
Methods: Monte Carlo simulations (GATE v.6) have been used as a method to calculate the ratio of the peak-to-valley doses (PVDR) at different depths in a water phantom for several grid configurations (0.7 mm of beam width and 1.4, 2.1, 2.8 and 3.5 mm center-to-center distances). The beam energy considered was 105 MeV. The beam penumbras were also assessed as an important parameter for tissue sparing.
Results: Very high values of PVDR, significantly superior than the ones achieved in MV Grid therapy, were obtained. In addition, the penumbras are much more smaller than in the case of MV Grid therapy and of Gamma Knife radiosurgery.
Conclusion: The high PVDR obtained, the small penumbras and the absence of deposited dose after the Bragg Peak suggest a potential gain in tissue sparing in this new radiotherapy approach. This could be used to deposit higher and potentially curative doses in clinical cases where tissue tolerances are a limit for conventional methods. Biological experiments are warranted to assess the effects of proton grid therapy.