Over 50% of cancer patients will receive radiotherapy treatment at least once. Most patients are receiving photon radiotherapy. In this work very high energy electron (VHEE) radiotherapy is being studied as a potential replacement for photon radiotherapy. VHEE beams have a favorable depth dependence and the penumbra of VHEE pencil beams stays small deep inside the patient. Therefore, using VHEE radiotherapy can potentially result in a lower dose being delivered to the organs at risk (OAR) in comparison with clinically used volumetric modulated arc therapy (VMAT). New accelerator techniques allow VHEE beam generators to fit in standard radiotherapy treatment bunkers. Therefore, VHEE therapy can reduce the equipment costs in comparison with proton therapy and it can increase the treatment quality in comparison with photon therapy. In this work the VHEE treatment plans are compared with clinically used VMAT treatment plans for prostate and lung cancer.

VHEE treatment plans were generated for 6 patients with prostate cancer and 3 patients with lung cancer. First, the pencil beam dose distributions were calculated for each patients using a Monte Carlo particle simulation tool called TOPAS MC. Thereafter, the optimal intensities of the pencil beams were calculated using iCycle, an automated optimization tool, which calculates the optimal treatment plan. The VHEE treatment plans are generated with 9, 18 and 36 beams and the energies that are used are: 100, 200, 300 and 400 MeV. The treatment plans were normalized to a 99% PTV coverage of 95% of the prescribed dose.

For the prostate case, the 100 MeV VHEE treatment plans deliver more dose to the organs at risk (OARs) than the VMAT plan. The 18 beam 300 and 400 MeV VHEE treatment plans showed a dose reduction in the mean dose of the patient, the rectum, the anus and the bladder, but a dose increase to the left and right femoral heads. The 18 beam 400 MeV treatment plan reduced the dose to all OARs in comparison with the VMAT plan, for the lung cases. Increasing the number of beams of the VHEE treatment plan reduces the dose to the OARs, for both the prostate and the lung cases. Increasing the energy of the electron beams also reduces the OAR dose for both cases.

VHEE plans reduce the dose to the healthy tissue, while keeping the PTV dose constant and can therefore be considered as a possible replacement for photon radiotherapy.

Cancer is a disease that causes almost 10 million deaths each year. Currently, there is no perfect treatment for it. However, there is a promising treatment called proton radiotherapy. This works almost the same as one of the older cancer treatments called photon radiotherapy. However, radiotherapy with protons has an advantage in comparison with radiotherapy with photons. This advantage lies in the way the protons lose their energy when going through tissue. The protons deliver most of their dose in a very small region. Cause of this advantage, proton radiotherapy can deliver a lot of dose into the tumour while minimizing the dose delivered into healthy tissue. But this advantage can change into a disadvantage when the location of the tumour moves a few millimeters.
Therefore ideally a scan is taken each time the patient comes in, so the location of the tumour is known very accurately. After the scan it is best to immediately create a treatment plan and do the treatment session. But creating a treatment plan takes to much time to be able to do that. Mainly, this is because the calculation of the dose distribution is not fast enough. This report studies a faster method for the calculation of the dose distribution. The method is derived by the Medical Physics \& Technology group from TU Delft. This method is currently not accurate enough to use for treatment planning. The problem of the method is that the dose due to nuclear interactions is not included correctly. The goal of this report is to make the method more accurate by adding the nuclear dose caused by secondary particles formed due to inelastic nuclear interactions to the dose calculated by the existing method.
The nuclear dose is calculated using a convolution of a kernel with the proton flux. The nuclear dose of the following secondary particles is calculated: alpha particles, deuteron particles and secondary protons. Adding the nuclear dose caused by these three secondary particles increased the accuracy of the model by 0.36 percent. However adding the nuclear dose calculation increased the time needed to calculate the dose distribution with 18625 percent. By calculating the convolution using the fast Fourier transform this could be decreased by a factor of 11. However adding the nuclear dose calculation to the fast method increases the time needed to calculate the dose distribution too much. Therefore the calculation of the dose distribution is not fast enough to scan a patient and immediately start with the best possible treatment plan using the fast method with the nuclear dose calculation added.