6.3 Radiation oncology Flashcards
What is radiation oncology
Treatment of cancer with high energy x-ray beams
What is fractionation?
giving the radiation in smaller doses rather than one go
What are the mechanisms of radiation injury?
Ionizing radiation Single strand DNA breaks Double strand (lethal) Template distribution Cell death
What kind of strands do you need to break to be lethal?
Double stranded
What is the effect of oxygen in radiation?
Cells next to blood vessels will have higher oygen content and will die first. As this happens other cells will move closer to the vessel.
Fractionation allows for more tumour cells to become oxygenated and thus resistant cells will become sensitive to radiation
What are the benefits of fractionation?
Kills more cells - improves tumour response
Allows normal tissues to survive at that dose more effectively
Allows susceptible cancer cells to cycle into radiation sensitive phase
Allows re-oxygenation of tumours rendering cells more sensitive
Allows normal tissue to repair
What are the 4 R’s of radiation?
Repair of cellular injury
Repopulation of surviving viable cells
Re-distribution within the division cycle
Re-oxygenation of the tissue
Which phases of the cell cycle does radiation work on?
M and G2
What are the acute effects of radiation?
Mucosal, erythema, epilation and fatigue
What are the late effects of radiation?
Effects on bone growth, second malignancy, hormonal, neurological and skin necrosis
What determines the time of effects of radiation?
The turnover time of cells
What is the aim for radiotherapy in the future?
Deliver in a more effective and safe way in less time
What are the types of radiation?
External beam
Brachytherapy (cervical)
Integration
What is the equation to work out total body irradiation?
Energy absorbed = Mass x 4 Gy/4.18
Define ionizing radiation
Radiation with enough energy to remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized
