Module Overview

Radiotherapy Physics and Radiobiology

The first part of this module deals with the basic elements of radiobiology, with particular attention paid to the mathematical modelling of cell-level radiobiological processes, and subsequently to the application of basic radiobiological modelling at the level of tumour control in oncological calculations. The students basic knowledge of cellular biology is applied to the understanding of the radiochemical processes which take place in the cell after exposure to ionising radiation and their effect on genomic integrity and intrinsic radiosensitivity. The student is exposed to current concepts relevant to DNA repair and molecular signalling cascades, with particular regard to their use in the explanation of different modes of radiatively induced cell death. In this context various mathematical models of the reaction of cells to radiatively induced cell injury are explored extensively, and their use in the prediction of radiotherapeutic response in practical oncological situations is detailed. The biophysical aspects of tumour control and chemotherapy are also explored. The student therefore develops an understanding of the role of the application of biophysics and mathematical descriptions of biological processes in radiotherapy.


The second part of the module deals with radiotherapy physics and dosimetry of ionising radiations in photon and charged particle radiotherapy. The student’s knowledge of the interaction processes between photonic ionising radiations and charged particles in matter are applied to the explanation of radiation dose deposition in the human body.  Particular regard is given to methodologies for the calibration of the output of megavoltage radiotherapy systems, and the use of such calibration information in the calculation of the dose. Some attention is paid to the physics of dosimeters and the physical principles of dosimetry, and also to the physical and engineering aspects of radiotherapy systems. These concepts are then illustrated in the calculation of therapeutic organ doses in clinical situations.

Module Code

PHYS 4836

ECTS Credits


*Curricular information is subject to change


Cell and tissue biology in brief. The cell cycle. The physics and chemistry of radiation absorption. DNA repair processes. Chromosome aberrations. Cell death processes and radiation signalling. Reparable Damage. Intrinsic Radiosensitivity in Normal and Malignant cells; proliferation kinetics after irradiation. Non-targeted effects. Dose rate effects. The oxygen effect. Radiosensitization and Radioprotection. Cell survival curves. Acute effects and radiocarcinogenesis. Application to Radioepidemiology and Radiation Protection. Linear energy transfer and relative biological effectiveness.

Target theory, single target and multi-target inactivation. Linear-Quadratic and Incomplete Repair Models of radiation survival. Lethal-Potentially Lethal and Saturable Repair Models. Therapy fractionation. Early responding and late responding tissues, incomplete repair and continuous irradiation. Fractionated LQ model and Biologically Equivalent Dose. Repopulation and tumour control. Clinical therapy calculations.

Photon and Charged Particle Interactions with Matter.

Review of Photon interactions with matter (Rayleigh Scattering. Photoelectric Effect. Compton Scattering. Pair Production). Combination of effects; Energy Dependence. Linear attenuation coefficients, mass energy attenuation. Radiation deposition and stopping power. Particle energy deposition and stopping.



X-ray spectral fluence. Dose, Energy Imparted and Kerma; Radiation Equilibrium. Phantom Principles. Tissue-Air-Ratio’s; Peak-Air-Ratio’s. Back-Scatter Factor. Percentage Depth Dose; Bragg Peak. Phantom Bragg-Gray Cavity Theory. Assumptions. Ionisation Chambers. Film and Scintillation Detectors. Diode Dosimetry. Calorimeters. Code of Practice for Dosimetry.


Radiotherapy Equipment

MV X-ray Units. Specification of beam quality, Filtration. Radiation Distribution in Air and Phantoms. Central Axis Depth Dose and Isodose Curves. IMRT and Applications.

Co-60 Therapy Units. Specifications and beam quality. Co-60 Therapy Units. Applications in clinical scenarios.


Radionuclide Therapy and Brachytherapy

Nuclear Medicine Therapy overview. Physical and Radiobiological Protocols. MIRD dosimetry. General preparation and monitoring procedures. Specific Radiation Protection. Special therapy procedures.


Students will learn through lectures, use of computer based learning software (including online quizzes / problem solving), tutorials (in the form of problem solving workshops) and laboratory practicals. In addition use of a flipped-lecture approach will incoroprate interactive problem solving and peer-learning in-class.

Self directed learning is encouraged using tutorial questions, use of on-line resources and quizzes.


Module Content & Assessment
Assessment Breakdown %
Formal Examination48
Other Assessment(s)52