Radiology 1 Flashcards
Properties of x-rays and how it can be used to create a radiograph
- high energy (to penetrate matter)
- can ionize atoms
- varies in wavelength and energy
- Creates a series of Silhouettes
How can x-rays cause biological damage?
- They can ionize atoms (mutation and death)
- cancer
- effect on growth and development
- reduced lifespan
- premature aging
- Cataract
Whole body limit of occupational radiation exposure? (mrem/yr)
5,000
3 main principles of radiation protection
distance, time, and shielding
What is the mA selector?
Controls current to the anode (x-ray quantity)
- more current= more x-rays produced
- toast analogy
What is the mAs selector?
mA x Time (msec) = mAs
- x-ray quantity
What is the kVp selector?
Energy of the beam and number of x-rays
(quantity AND quality)
- determines CONTRAST
energy of beam (quality) = penetrating power
What is the focal spot selector?
2 filaments in the cathode (small and large)
small image= high detail
large image = low detail
What is the timer?
number of x-rays in beam , (quantity) - (msec)
How to control scatter radiation?
Collimated beams and grids
What is scatter radiation?
Only a small % of radiation goes all the way through the object and onto the film
it decreases the contrast of image
What is a collimated beam?
- limits the beam to an area of interest
- collimator knobs on machine (=, ||)
- decreases scatter
- improve image quality
What is a grid?
Alternating strips of lead
- prevents scatter from reaching film
- improves contrast
2 steps to forming a radiograph (think cathode/anode?
- prep
- electrons are made by an electrical current through a filament (cathode)
- high voltage- so hot it glows
- expose
- x-rays are produced when the electrons interact with the metal in the anode, and shoots out an x-ray beam
What are the 5 basic radiographic opacities ? (from highest attenuation to lowest)
Metal Bone Soft tissue Fat Air
What is summation effect?
overlapping of 2 objects adds to the opacity
2 dimes or 2 kidneys overlapping
What is the silhouetting effect?
2 objects of the same density will blend together
-causes border effacement
(almonds/diamonds in water or fluid in abdomen)
What is magnification distortion?
image is larger when it is further away
right kidney looks bigger on film
What is image distortion?
When the image is not in the center, it will look distorted
paper clip looks smaller at an angle or bones looking different sizes
How does motion impact a radiograph?
it will blur the image
Proper orientation of radiographs
cranial to caudal (left to right, or top to bottom) dorsal to ventral (top to bottom) Right to left use markers mark film for each patient/hospital/date
