MD RADIOLOGY Flashcards
steps of how an x-ray is made
electricity -> Heat -> electrons -> xrays
xrays produced when high speed electrons hit metal targets
strongest to weakest light
gamma > xray > UV > visible light > infrared (UV) > microwave > radio
visible light is carried by what?
photons
XRAY emits a beam to the receptor. person standing in the middle between receptor and PID ( position indicating device) is called
attenuation
give a summary of how xray works
1) electricity generates heat
2) creates electrons
3) shoot out of PID ( tube head) to the receptor
4) attenuation ( object standing between) gets hit with radiation and projects it to receptor
what has higher energy, shorter or longer wavelength?
SHORTER (gamma)
2 types of ionization radiation?
ELECTROMAGNETIC
: electric and magnetic field ( radio waves, gamma, xray,micro, etc: )
PARTICULATE:
atomic nuclei or subatomic particles moving HIGH VELOCITY ( alpha and beta particles)
2 types of XRAY production ?
Bremsstrahlung ( brem: to break / rahlung: radiation)
Characteristic
what is brehmsstrahlung ?
PRIMARY source of x ray photons
electrons strikes target and brakes giving off energy
generates CONTINUOUS spectrum of energy
what is CHARACTERISTIC xray production
SECONDARY source xray photons
e knocks into another e and drop into lower energy orbital
emits photon of SPECIFIC energy
what is the primary and secondary source of xray photons?
Primary: bremsstrahlung
secondary: characteristic
what does cathode do?
tungsten filament produces electrons
what does anode do?
tungsten target converts electrons to xray photons
MATCH MATERIAL WITH FUNCTION:
copper / molybdenum / lead / glass / aluminum
focuses beam onto small focal spot dissipitates heat insulation filtration collimation
MOLYBDENUM: focusing cup focuses beam onto small focal spot
copper: dissipitates heat
glass: insulation
aluminum: filtration
lead: collumiation
intensity VS Energy
- electrons and photons ?
- how images look ?
INTENSITY
: QUANTITY of e/ #NUMBER of photons
: DENSITY: darkness of image
ENERGY:
QUALITY of e / ENERGY of photons
CONTRAST: difference in gray value
2 images are shown side by side. the R one is darker than the L one. describe their contrast and density
Darker One: higher intensity = higher density
lower energy = lower contrast
exposure time (s) affects what?
INTENSITY = density = darkness of image
lighter image has less exposure time which = less density
how does exposure time correlate to photons?
more time = more photons
tube current ( mA) effects what?
affects INTENSITY :
too much = too dark (too much photons reach sensor)
^ mA = ^ photons= ^ intensity = darker
tube potential (kVP) affects what?
affects INTENSITY and ENERGY !!!!! bOTH
too high = too gray
too low= too light
think about it… decreasing kVP increases contrast ( LIGHTER) and increases INTENSITY ( density)
what does filtration do to photons and involves what element ?
removes lower energy photons from beam to reduce exposure
aluminum
which is similair to beam hardening ?
filtration
tube potential
tube current
exposure time
filtration
collimation involved what element? how does it affect patient exposure ?
LEAD
reduces beam size to reduce exposure
what is the best shape collimation?
rectangular
how does distance correlate to photon emission and quality of the image?
^ distance: less photons = darker image
what is source to object distance? (SOD)
how far object is from xray source
what is object to image distance?
distance betweem object and sensor behind it
what happens to intensity when Source to object distance increases?
intensity decreases ( inverse square log)
quality of image when object to image distance gets smaller?
gets sharper
what is source to image distance ?
from xray source to sensor/film
OID + SOD
what source to object distance and object to image distance do we want?
max SOD
minimum OID
what is umbra?
shadow behind an image ( no light gets to)
what is penumbra?
side shadow
how does focal spote size and penembra correlate ?
smaller FSS = lower penebra + sharper the image
why does image have poor contrast?
high kvp / low filtration
what is coherant scattering?
how does it affect contrast?
photon contact OUTER e
decreases contrast !
what is photoelectric absorption?
what does it do to contrast?
incident photon contacts INNER e and forms ion pair
increase contrast
what is compton scattering?
whats it do to contrast?
photon contact OUTER e and forms ion pair
dec contrast
what is deterministic effect?
responses which increases in severity with increased dose . have threshold dose that needs to be met before something bad happens
what is stochastic effect?
effects that happen by chance do not have threshhold dose ( linear no-threshold model)
Direct vs inderest radiation chemistry
Direct:
- DIRECTLY affecting biologic molecules ( protein,dna)
- 1/3 biologic effect
Indirect:
- ionizing radiation converts water to FREE RADICALS alter biologic molecules (AFFECTS ENVIRONMENT SURROUNDING DNA such as salts, water, protein, O2) WHICH EFFECTS DNA
2/3 of biologic effects
which cells are more radiosensative ?
mitotically active ( sperm cells)
how many mSv is background radiation and mostly from what source?
3.1
RADON
manmade radiation how many mSv and from what source?
3.1
MEDICAL IMAGING
what is the average exposure to individuals living in US?
6.2 mSv ( 3.1 background + 3.1 manmade)
occupational exposure limits how many mSv per year?
50
when looking at radiograph and the image has radiolucent properties this means what?
R/L = dark
photons pass through tissue to reach film
when looking at radiograph and the image has radio opaque properties this means what?
r/o = light
photons are attenuated (blocked) do not reach film
what color would film be if took an image of nothing?
BLACK
photons pass right through
what is film emulsion made of?
silver halide crystals
what happens during DEVOLPMENT stage of film?
silver atoms turn black
what are the 4 steps of chemical film processing?
developing
fixing
washing
drying
during developer solution what is the first electron donor that reduces silver ions to metalic silver at latent image site ?
PHENIDONE
during developer solution, what provides an electron to reduce oxidized phenidone to origingal active state>
hydroquinone
what happens during FIXING STAGE of chemical processing >
remove undeveloped silver halide crystals from emulsion
what is the chemical in fixer solution that remove silver halide crystals ?
ammonium thiosulfate
what is PSP plates made of ?
Barium fluroihalide
what is CCD ( digital sensor dexis) made of ?
silicone
Film VS digital better contrast resolutin? spatial resolution? detector latitude ? detector sensitivty ( dose required to achieve standard gray level?)
contrast: film
s[atial: film
Detector latitiude : PSP
Sensitivity: CCD half F speed film
fastest FIlm speed and slowest speed
fastest: F
Slowest: A
A B C D E F
most common radiographic error?
ELONGATION
which view to see condyles better?
waters view
townes view
submentovertex view
townes ( angled PA Ceph of skull)
angle straight down middle of forehead
which view to see paranasal sinus?
waters view
townes view
submentovertex view
waters ( angled PA ceph of skull)
angling x-ray diagnol to back of head
which view to see zygomatic fractures
waters view
townes view
submentovertex view
submentovortex view
taking an image from floor straight up ti skull
bisecting angle techniques is when x-ray beam ray is angled in what way?
perpendicular to imaginary bisector between long axis of tooth and long axis of receptor
pano appears patient is smiling which way is his chin?
chin DOWN
what does the filament do in xray?
made of tungsten
in the cathode PRODUCE E
what does the anode and cathode produce ? what are they made of?
Cath: Electrons ( tungsten filament produces e)
Anode: Photons ( tung. electrons -> photons)
what is the xray tubehead and Position indicating device?
tubehead is the bdy of the xray PID is the tube that comes off that body
