Intro Flashcards
Radiographs are _____ (good/bad) at contrast resolution.
bad
Why do we choose radiology as a modality?
idk we shouldn’t it sucks :(
jk jk
accurate representation of orientation and relationship b/t anatomic structures
correct reproduction of anatomy ± pathology
cheap, fast, ubiquitous, good at spatial resolution if adjacent
List the Roentgen signs and tell me why they’re important.
they are important bc they help you figure out if something is abnormal or not, and why it is abnormal
size, shape, number, position/location, density/opacity, structure, function
Suzy Says “No, Please Don’t Slap Freddy”
Why do we dislike radiographs?
poor detail due to limited contrast
radiation risk
bad at special resolution if overlapping
need >1 view! (2 views min., but depends on what you’re looking at)
error rates high, interpretation result of complex perceptual mechanisms, previous experience plays a large role, attitude impacts interpretation
tell me about the basic physics (yuck) of a radiograph/radiation
x-rays generated in X-ray tube, cloud of electrons formed at the cathode in the tube. electrons travel across tube until they get to anode at the focal spot. electrons lose their energy when they hit anode, and photons (x-rays) are produced, radiating in a cone shape from focal spot.
what is the focal spot?
area of the anode which receives the beam of electrons from cathode. - apparent source of x-rays
what is the byproduct of x-ray production and how to mitigate this?
heat!!
mitigated by rotating anode or focal spot
x-rays radiate out in a cone shape from the focal spot and are directed towards the patient. how do we make sure the cone isn’t huge or going away from the patient?
collimation and shielding
the quality and quantity of x-rays detected are controlled by multiple factors. tell me about them.
generation - mA/mAs, kVp, distance, grids
absorption/subject factors - density, thickness
detector - DR vs CR vs plain film
what is kVp? what happens when you increase kVp?
kilovoltage peak. the speed of electron flow across the tube
increase kVp = increase speed when electrons hit target = greater penetration of x-rays = high PRESSURE hose –> able to penetrate thicker/denser material
What is mA/mAs? What happens when you increase mA or mAs?
Milliamperage or milliamere second. the amount of current flowing through the tube
increase mA = increase amount/volume of X-rays produced = high VOLUME hose –> increase amount of black on image (increase density)
2x mAs = _____x density/blackness of image
2x
increase kVp = ______ scatter = _____ contrast
increase scatter
decrease contrast
what does the “grid” do?
reduce scatter to increase contrast
only lets xrays through that are in line with focal spot (like a sieve)
what is contrast?
the number of shades of grey between black and white
high contrast = whites and blacks on image, less shades of grey, more difference between shades
low contrast = more shades of grey, less blacks and whites, less difference between shades - picture looks sort of hazy