Medical Physics B1 Flashcards
What is an x-ray?
High energy, electromagnetic radiation produced by accelerating electrons or high energy atomic transitions.
What are soft x- rays?
Have photon energies from 100eV to 10KeV
What are hard x- rays?
Have photon energies between 10KeV to a few hundred KeV
What happens to an object when its temperature is raised to 6000K?
The proportion of its IR decreases and there is now more visible and significant quantities of UV rays
Is there any way to distinguish between x-rays and gamma rays?
No
How are x-rays made in hospitals?
By firing high energy electron beams (up to 100KeV) at heavy metal targets, usually tungsten or a tungsten molybdenum alloy.
Why does only a small fraction of the energy beam gets converted into x-ray energy?
Because most of the electrons lose their energy gradually.
How can you increase the efficiency of the conversion of energy beams into x rays?
With accelerating voltage.
The probability of a photon being observed will stay constant if…
A mono-energetic beam passes through a mineral
Why do bones absorb more x-rays than soft tissue?
Bones have a higher density than the soft tissue. Their concentration in the minerals in particular.
What is a mammography used for and how does it work?
It’s used to find abnormal densities in the body and to find potential cancer.
How does a CT scan work?
The patient has many x-ray images taken from many different angles with a rotating camera.
Why can ionising radiation be used to kill cancer cells?
Dividing cells are more sensitive than that of quiescent cells.
