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Identifier

000373934

Title

Προσομοίωση ακτινοθεραπευτικών τεχνικών έκτοπης οστεοποίησης και καρκίνου του μαστού με μεθοδολογία Monte Carlo:υπολογισμοί δόσεων ακτινοευαίσθητων οργάνων

Alternative Title

Simulation of radiotherapeutic techniques for heterotric ossification and breast cancer using Monte Carlo methods:calculation of radiosensitive organ doses.

Author

Μπέρρης, Θεοχάρης Β

Thesis advisor

Μαζωνάκης, Μιχαήλ

Abstract

The treatment of cancer with radiotherapeutic techniques constitutes a widespread practice. Nevertheless, radiotherapeutic applications are not limited to the treatment of cancer. There are also benign diseases for which radiotherapy has comparable or even greater effectiveness than other potential treatments. An example of such a disease is heterotopic ossification. Many clinics worldwide utilize radiation therapy to treat heterotopic ossification. Due to the risk for second cancer induction following radiation exposure of the patient, the physician should be able to quantitatively weigh up the expected benefit against the detriment of the treatment in question. The need to perform such estimations becomes greater for young patients who are expected to live long after irradiation takes place. Except for radiation treatment of benign diseases, the risk for second cancer induction due to irradiation is important in the case of cancers with good prognosis, such as breast cancer. The first step towards the quantification of second cancer risk is the determination of radiation doses, absorbed by the various radiosensitive organs of the patient. However it is difficult to directly measure organ doses provided that it is not possible to insert dosimeters in the patient’s body. A way to get over this obstacle is to simulate radiotherapeutic techniques using human-like phantoms. Recently, advances in computer technology have made possible to simulate radiation therapy techniques using suitable computer codes. Today, computational methods are widespread in the field of Medical Physics because of their usefulness, low cost and precision of the calculations they can perform. In the current study, in order to exploit the power of computational techniques, therapies of heterotopic ossification and breast cancer were simulated using Monte Carlo methods. A large part of the total effort was dedicated to the construction of a simulated model of the photon beam produced by a Phillips SL 75/5 linear accelerator. The simulated beam model was verified by comparing calculated dosimetric quantities to measurements performed on the real linear accelerator. The way the model was constructed allowed the calculation of certain actinometrical characteristics of the photon beam, such as particle flow and spectral distribution, and their correlation to dosimetric quantities, such as percentage depth dose and dose profiles in a water phantom. An investigation of the effect of the electron beam parameters on the photon beam characteristics was also realized. The investigation confirmed the reliability of the simulation. Finally, the photon beam model was combined with a mathematical phantom in order to simulate radiation therapy of heterotopic ossification and breast cancer. Radiation doses to radiosensitive organs of the mathematical phantom were calculated for all treatments in question. The effect of radiation field size on organ doses was investigated. The effect of suitably placed lead blocks on organ doses was also studied for the fields where they are typically used.

Language

Greek

Subject

Breast cancer

Dose

Heterotopic ossification

Monte carlo

Radiation protection

Radiation therapy

Radiology

imulation

Έκτοπη οστεοποίηση