ESTRO 2023 - Abstract Book

S1747

Digital Posters

ESTRO 2023

Conclusion SPLASHLET offers the first LET painting with voxel-wised ultra-dose-rate and high-dose conformity treatment using proton beam therapy which is feasible to be implemented in the clinical setting without introducing any additional hardware. Such a technique takes full advantage of degree of freedom enabling high quality treatment with potential biological optimization with LET painting.

PO-1979 Poly-ether-ether-ketone: An improved bone replacement material compliant with proton radiotherapy

G. Katsifis 1 , M. Jennings 2 , D. McKenzie 1 , M. Jackson 3 , N. Suchowerska 1

1 The University of Sydney, VectorLAB, School of Physics, Sydney, Australia; 2 Townsville Hospital and Health Service, Department of Medical Physics, Townsville, Australia; 3 Prince of Wales Hospital, Department of Radiation Oncology, Sydney, Australia Purpose or Objective Patients presenting for radiation therapy with metallic implants require specific attention in treatment planning. Although implant avoidance and correction algorithms have offered workable, but not always accurate solutions for photon beams [1, 2], in proton beams, the higher density and atomic number implant materials can cause a significant shift in the Bragg Peak and consequently the dose distribution [3]. This perturbation results in overdosing healthy tissue and underdosing the target (~ +/- 25%) [3]. An innovative alternate approach is to change the implant material to Poly-ether-ether-ketone (PEEK): a thermoplastic polymer with a density and stopping power close to water, which we have shown to have material properties viable for use as bone replacement [4]. In this work we demonstrate the effect of a PEEK implant on the dose distribution from multiple proton beams using both Monte Carlo methods and radiation treatment planning systems. Materials and Methods Monte Carlo simulations using GATE/Geant4 [5] were used to determine the effect of an implant, designated to water, PEEK or titanium, on the dose distribution when exposed to a proton beam of energies (E_0=80,130,200), incident on a 30 cm water phantom with a 5 mm PEEK/titanium implant placed at a depth of 50 mm (Figure 1). A parallel study performed using the beam data of a proton treatment system calculates the dose distribution on a patient with an implant, which is designated to be either bone, titanium or PEEK. In each case the implant is either in the beam, partially in the beam or next to the beam, and repeated with positional displacements. Results Figure 1 shows the depth dose curves for a proton beam incident on the 30 cm cube phantom. When the implant is titanium, the Bragg Peak shifts towards the entrance surface but is influenced by the location of the implant relative to the position of its Bragg Peak. The peak dose for titanium shifted slightly for proton energies of 130 and 200 MeV with a more significant shift at 80 MeV, where the Bragg Peak occurred within the titanium implant. Figure 2 depicts the 2D dose profile for a 130 MeV proton beam for PEEK/titanium implants, indicating a reduction in range from the titanium implant.