Assessment of Very High Energy Electron therapy as a clinical modality for external beam therapy

Assessment of Very High Energy Electron therapy as a clinical modality for external beam therapy

Dijkstra, Jasper (TU Delft Mechanical, Maritime and Materials Engineering)

Lathouwers, D. (mentor)
Heijmen, Ben (graduation committee)

Delft University of Technology

2020-10-02

Very high energy electron (VHEE) radiotherapy is being investigated as a potential replacement of photon therapy. VHEE pencil beams have a small penumbra and strong depth dependence for radiotherapy when compared to photons. This allows a lower dose to healthy tissue. Generating these high electron energy beams could be achieved by using laser accelerators. These accelerators allow the equipment to be smaller than currently possible and make it possible to fit them in a standard radiotherapy treatment bunker. This makes VHEE a potential middle ground between photon and proton therapy in relation to equipment costs and treatment quality. The purpose of this project is to compare photon based Intensity Modulated Ra­diation Therapy (IMRT) and VHEE treatment plans for treatment of prostate cancer.  For 10 prostate cancer patients IMRT treatment plans were generated with 23 beams. These plans were optimized using Erasmus MC in-house developed Erasmus-iCycle automated treatment plan optimization tool. The dependence of VHEE plan quality on beam energy (200, 300 and 400 MeV) and number of equi-angular beams (9, 18 and 36) was investigated. The treatment plans were optimized using the multi-criterial optimizer Erasmus-iCycle. For each patient VHEE pencil beam dose distributions were pre-calculated using TOPAS MC, a Monte Carlo simulation program based on Geant4.  Results: VHEE treatment plans show either a reduced or similar mean OAR dose when compared to IMRT treatment plans except for the 9 beam 200 MeV plan which was worse compared to IMRT. All treatment plans were normalized to a PTV coverage of 99 % V57Gy.  It is found that the mean rectum dose reduces from 13.5 Gy for IMRT to between 9.2 and 11.9 (p=0.002-0.004) for the VHEE plans. For the anus dose a reduction in mean dose was found for all VHEE treatment plans except for the 9 beam 200 MeV and the 18 beam 200 MeV VHEE treatment plans. The mean anus dose reduced from 12.4 Gy for IMRT to 7.0 - 10.6 Gy (p=0.002-0.014) for the VHEE treatment plans. The bladder dose reduced from 20.1 Gy to between 15.2 and 18.2 Gy (p=0.002).  Increasing the number of VHEE beams in a treatment plan reduces the OAR dose. Comparing 9, 18 and 36 beam treatment plans with 300 MeV. The mean rectum dose reduces from 14.0 Gy for the 9 beam plan to 11.1 Gy (p=0.002) and 9.9 Gy (p=0.002) for the 18 and 36 beam plan, respectively. The same pattern is found for the anus and bladder.  Treatment plans with a higher beam energy reduces the dose to OAR. The mean rectum dose reduces from 13.4 Gy for the 200 MeV plan to 11.1 (p=0.002) and 10.0 (p=0.002) Gy for the 300 and 400 MeV plans. The same pattern is found in the mean bladder dose with 18.2 Gy, 16.8 Gy (p=0.002) and 15.9 Gy (p=0.002). The right femoral head maximum dose increases from 28.0 Gy for 200 MeV to 29.4 Gy(p=0.002) and 29.6 Gy (p=0.049) for the 300 and 400 MeV treatment plans.  VHEE is a potential replacement for IMRT due to the reduced dose to healthy tissue while maintaining similar target coverage compared to IMRT. By increasing the number of beams and/or the electron beam energy we can further reduce doses to the healthy tissue.  

Radiotherapy
Radiation therapy
VHEE

http://resolver.tudelft.nl/uuid:9967d889-a042-46dc-99b7-421385eea43a

Student theses

master thesis

© 2020 Jasper Dijkstra