Radiology Flashcards
How does an X-Ray form an image?
- current heats cathode
- electrode emitted and hit anode
- rays penetrate patient and scatter
- image formed
What lets X-rays through?
- air lets all rays through
- soft tissue lets some through
- cortical bone lets none through
What are X-rays good for?
- things surrounded by black air or white bone to to see something that is destroying bone
What are the negatives of X-ray?
- densities must be different to show pathology
- can cause DNA mutations
What are contrast studies?
use dense elements to block X-rays to help see tissue outlines eg enema or arthrogram
What is CT good for?
- can differentiate between tissue of similar density
- x-rays fired form all angles so gives a cross section
What is bad about CT?
- gives large doses of radiation
- very similar densities can’t be distinguished
How does ultrasound form an image?
uses crystals to convert electrical energy to acoustic with a transducer to give a cross sectional picture of soft tissue
Why is ultrasound good?
cheap easy safe good for tendons and muscles fluid is shown well
Why is ultrasound bad?
can’t be used on fat patients
bone blocks it so can’t be used on brain
gas blocks it
result is dependent on operator
Why is MRI dangerous?
can cause heat or cold burns
deafness
can’t be used on those with surgical implantables
What are strengths of MRI?
good for brain, muscle, tendons, spinal canal, interior of joints
What is bad about MRI?
expensive
takes ages
claustrophobic
contraindicated in some patients
