Let and radiation biological effectiveness Flashcards
What is LET stand for
Linear energy transfer
What is LET
A measure of the rate at which energy is transferred from ionising radiation to soft tissue, per unit of distance travelled by the photon.
Unit Kiloelectron volt per micrometer
What varies LET
the speed, and charge of the particle involved
What are low LET particles
Photons and electrons
What are High LET particles
Protons, neutrons, and alpha particles
What are the highest LET
Heavy charged particles
Is high or low LET good for diagnostic imaging, what is the other used for.
Low LET, higher is used for therapeutic purposes
As let increases the severity of the radiation…
Increases
How do gamma and xrays work with LET
While gamma rays (and x-rays) have no mass or charge, they can still interact with matter, less frequently than charged particles. LET is primarily relevant to charged particles, which transfer energy directly to electrons in tissues. For gamma rays, their LET is low because they interact mainly through processes like the photoelectric effect, Compton scattering, or pair production, which involve indirect energy transfer. Thus, although they don’t have mass or charge, they still deposit energy in tissues over distance, just less efficiently.
How does particulate radiation (alpha particles) work with LET
Particulate radiation (e.g. alpha and beta particles) have mass and/or charge and have an increased probability of interactions with tissue
*They lose energy quickly with distance resulting in many ionisations in a short distance, therefore are more destructive to biologic matter
As LET increases the potential to produce biological damage..
Increases
What type of damage (indirect or direct) do high and low LET cause
High LET causes direct damage
Low LET causes indirect damage
Why does high LET cause more damage
because, as charged particles (like alpha particles) move through matter, they lose energy and slow down, causing them to transfer more energy to the surrounding atoms with each subsequent interaction. This means that as the particle travels further, its ability to ionize surrounding atoms increases, resulting in a higher LET. High LET radiation (like alpha particles) causes more significant biological damage in a shorter distance compared to low LET radiation (like gamma rays).
True or False, LET is another method of expressing radiation quality
True
What is RBE
Relative Biological Effectiveness
