Lecture 16 Flashcards
What does tomography mean?
Technique to display cross section of body using x rays or ultrasound
What is a positron?
Electron but with positive charge
What does attenuation mean?
Different tissues absorb radiation to varying degrees. Units of attenuation called Hounsfield units
How to interpret an x ray
First consider what type of film it is- chest etc
Which way around is it- ap pa etc
Whether it is adequate
Is AP or PA better for chest x ray
PA as can see lungs better
What are x rays good and bad for?
Good for bones bad for soft tissues
What are CT’s good and bad for?
Good for bones and tumours bad for soft tissues
What is fluoroscopy?
Serial x rays taken in sequence normally after contrast- can see flow through the system
Good for looking at vasculature
What is PET positron emission tomography used for
Nuclear medicine so not used by radiologist. Uses radioactively labelled substance usually glucose. Use to see metabolic tumours and often combined with ct
How does MRI work?
Magnetic field causes hydrogen ions in tissues to line up north or south.
Some of these however are unmatched.
Radio frequency causes them to flip around and when frequency stops they return and emit energy which is detected and used to form an image.
T1- water black
T2- water white
Good for looking at soft tissue bad for bones
What is ultrasound used for?
Doppler effect can be taken advantage of to see movement in vessels
High frequency= poor penetration but good detail
Low frequency= poor detail but good penetration
Bad for bones and cant view air, quick and safe, good for looking at foetus
