Magister en Física Médica

Facultad de Física

Computer simulation of the radiation response of hypoxic tumours

Dr. Ignacio Espinoza, Instituto de Física PUC



Fecha y hora: 16 de Octubre de 2013, 16:00 hrs


Abstract:In radiotherapy, it is important to predict the response of tumours to irradiation prior to the treatment. This is especially important for hypoxic tumours, which are known to be highly radio-resistant. Mathematical modelling based on the dose distribution and biological input parame­ters may help to improve this prediction and to optimize the treatment plan. In this presentation a radio­biological model is shown, which simulates the growth and the response to radiotherapy of tumours considering patient-specific information of the tumour. The model is based on voxels, containing tumour, capillary, normal and dead cells. Radiation-induced killing of tumour cells is calculated by the LinearQuadratic Model (extended for considering hypoxia). Proliferation and resorption of cells are modelled by exponential laws. Computed tomography, positron emission tomography and magnetic resonance imaging may be used for the initial characterisation of the tumour. To simulate the response of hypoxic tumours properly, special emphasis was put on the description of the intratumoural oxygenation. For this, a second complementary model was developed to simulate the microscopic oxygen distribution, considering as input the vascular fraction per voxel, which is in principle measurable non-invasively in patients, and assuming certain vascular architectures. The oxygen distribution is obtained by solving a reaction-diffusion equation using the Particle Strength Exchange method. Including the fractionation regime and the planned dose distribution of the radiation treatment, the spatial-temporal behaviour of the tumour is simulated. The model describes the appearance of hypoxia during tumour growth and the reoxygenation processes during radiotherapy. The tumour control probability can be calculated as well. The results are in accordance with published results. 


Lugar: Sala de seminario física experimental