radiology Flashcards
name the order of the rays
radio, micro, infrared, vl, UV, xrays, gamma (most dangerous)
focal spot
- located on the anode
- area on target where focusing cup directs electrons from filament. Sharpness of radiograph increases as size of this spot decreases (can be done by dec angulation)
why is tungsten the best
- high atomicc number, high melting point, thermal conductivity, low vapor pressure
bensons line focus principle
- smaller the anode tilt, the smaller the effective focal spot
cathode
- in mA, contains the filament
anode
- positive
- kV, contains focal spot and tungsten target
mA determines
number of e made, increasing this will increase quantity of xray beams
kVp
(kVp is for AC, KvC is for DC which is better)
determines energy of the xrays produced
- increases the quality of the xray
filtration
reduces intensity, increases the mean energy so less rad to patient
target object distance
- increase it means increased image sharpness!!
photoelectric absorption
- the scatter ray that interacts with matter to form the image
particulate radiation
alpha, beta, cathode
compton scatter
- most interaction, cause of scatter
coherent scatter
least common scatter
attenuation
absorption of individual photons in the beam by atoms in tissues or photons being scattered
beam hardening
- increase mean energy and decrease intensity
cell cycle and radiosensitivity
- less radiosensitive in g1, least in s phase, most in g2 and m phase
chromosome aberration
occurs when rad before DNA synth
chromatid abberation
after dna synth rad
what cells are rad resistant and which are most
- fully differentiated cells
- lymph ccells are MOST
where does most radiation come from
radon and ct scan
best radiographic practice
- usse E/F speed film
- rare earth screen for films
- use CBCT for region of interest
personal protection
stand more than 6 ft away, use backscatter shield
- use long cone head
- stand at 90 to 135 degrees from central beam
collimators
rectangular is 66% less area than round!