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PRI test 1

TermDefinition
___________ is controlled by quantity (amount of radiation) reaching the IR Density
Can you change brightness levels? NO. Can only be manipulated/windowed, the monitor will make it look good. EI numbers show if correct.
________ has a direct proportional relationship with the quantity of xrays produced mA
Double the mA= _______ quantity of xrays doubles
mA controls filament heat while time tells how long
Increase mA increase heat, # of electrons produced, quantity of xrays produced and DENSITY (film)
What is optical density? The amount of blackness on an image. What you see.
Contrast a difference in density/ brightness levels
kV affects/influences the # of xray photons and controls the efficiency of xray production. And CONTRAST!! also effects density!
insufficient kV what is demonstrated quantum noise. lack of photons.
Subject contrast refers to absorption characteristics of anatomic tissue (tissue thickness, tissue mass/density, atomic #) radiographed + quality of xray beam
Image contrast refers to what you see on the image
Contrast resolution ability of IR to distinguish between objects having similar in subject contrast
gray scale # of different shades of gray that can be stored and displatyed in the DIGITAL image
scale of contrast range of densities visible on FILM
low subject contrast long scale
high subject contrast short scale
spatial resolution ability to image small objects that have high subject contrast. Anatomic details must be accurately recorded with greatest sharpness
distortion misrepresentaion of size or shape of the anatomic part.
size distortion Magnification! affectected by SID and OID.
shape distortion misrepresentation of objects image shape. elongation or foreshortening caused by angling of IR or part.
scatter unwanted exposure to IR resulting in fog (decreases image contrast), due to compton interactions. Resolution is the same just can't see it because of the fog. Digital needs collimation to reduce scatter, hypersensitivity.
Film= quantum ________ mottle
digital = quantum _________ noise
film screen imaging limited dynamic range, no post processsing can be done, cost of film,
chemical film processing order and time fixer, developer, water, dryer. time = 90 seconds
film density seen 0.25-2.5. anything below too light, anything above too dark
digital systems wide dynamic range (wide latitude), high EI # range
Who discovered xrays, what tube and when? Wilhelm Conrad Roentgen. Crookes tube (cold cathode gassy) November 8, 1895
Fluorescence instantaneous production of light as a result from interaction of some type of energy and some element or compound.
Who developed first hand-held fluoroscope Thomas Edison
What is xray? electromagnetic energy with dual nature capable of ionizing tissue. has short wavelengths.
long wave length=______ frequency Low. less powerful
short wave length= ______ frequency High. more powerful. allow xrays to easily penetrate
12 properties of xrays invisable, electrically neutral/no mass, travel speed of light, cannot be focused, polyenergetic, ionizing, can be absorbed or scattered, produces secondary radiation, causes bio/chemical changes, travels straight lines, causes fluorescense, & chem chang
3 cardinal principles time, sheilding & distance (most important)
3 requirements for xray production source/supply of electrons, method of accelerating electrons, target to slow/stop the electrons
2 target interactions in the tube brems & characteristic. heat is by product.
Bremsstrahlung interactions breaking/ slowing electron, majority of the interactions produced in radiology, below 70 kVp= 100% Brems, above 70 kVp= 85% Brems, avoids all orbital shells to get close to nucleus, energy lowers when changes direction.
Characteristic Interactions Requires at least 69.5 kVp to eject k-shell electron, below 70 kVp= 0% characteristic, above 70 kVp=15% characteristic, knocks out inner/ k shell electron, ionizes atom,
What happens when rotor (prep button) is activated? Cathode side. filament current (mA) heats up filament, electrons boiled off filament (thermionic emission) focusing cup keeps electron cloud together
What happens when rotor (prep button) is activated?Anode side. target begins to turn rapidly, quickly reaching top speed
What happens after activation of the rotor and exposure is initiated? Cathode side. negative charge repels electrons, the electrons then stream away cathode to anode (tube current)
What happens after activation of the rotor and exposure is initiated? Anode side. high positive charge attracts electrons in tube current, electrons strike anode, xrays & heat are produced
flow of electrons= ??? tube current, measured in mA
quality of xray beam = ? penetrating power
emission spectrum the range and intensity of xrays emitted changes with different exposure technique settings on the control panel
kV determines speed of electrons. Higher speed= higher _______ and __________ of primary beam. quality & energy. increased xray beam penetrability.
What happens when kVp is increased? how does curve move on the emission spectrum? increased photon energies of the beam. shifts up and to the right.
What happens when mAs is increased? how does curve move on the emission spectrum? quantity of xrays increases. curve goes straight up.
what does beam filtration do? absorbs low energy photons, reduces patient exposure
total protective filtration to patient =? glass window 0.5mm+ collimator mirror 1mm+ added filters/absorbers 1mm= 2.5 mm Al Eq
increasing filtration "hardens" beam, decreases quantity (low energy removed), higher quality, increases avg photon energy, DECREASES beam intensity
If filtration is added, how does the curve move on the emission spectrum? down and to the right
compensating filters produces more uniform exposure to IR on non-uniform anatomic areas
What is wedge filter used for? foot, femur
what is trough filter/ double (bilatera)l wedge used for? thorax
Anode heel effect xrays more intense on cathode side of xray tube. intensity of xrays decrease toward anode side. think FAT CAT!
Line focus principal relationship between actual and effective focal spot
actual focal spot area on anode target exposed to tube current electrons
effective focal spot focal spot size as measured directly under anode target
smaller anode angle= ? smaller effective focal spot size
Heat units (HU) HU=mA x time x kVp x generator factor
How to extend xray tube life warm up tube, avoid excessive heat generation, don't hold rotor button if not exposing, use lower mA and longer exposure time, don't move tube while energized, recognize unusual noises and report
process of image formation is due to __________ __________ of the xray beam as it interacts with anatomic tissue differential absorption
xray absorption of anatomic tissue is based on what? composition (atomic number and tissue density). eg. bone absorbs more xrays than muscle
As the primary beam interacts with anatomic part, photons are? (3) 1. abosrbed (photoelectric effect=white) 2. scattered (compton interaction=fog) 3. transmitted (w/o interaction=dark/gray)
attenuation definition the total reduction of # of srays remaining in xray beam after penetration through a given thickness
attenuation = _________ and ___________ absorption and scattering
Photoelectric interactions= _________ of xrays. And they appear ________ on an image. and interacts with what shells? absorption, bright/white, Kor L-shell (ionization occurs)
compton effect/scattering interacts with what shell? outer shell electron.
4 factors affecting beam attenuation tissue thickness, type of tissue, mass-tissue density, xray beam quality
tissue thickness: xrays are attenuated exponentially and reduced by _____% for each _________ cm of tissue thickness 50% and 4-5cm
type of tissue tissue composed of higher atomic number will increase beam attenuation. eg bone absorbs more than soft tissue
mass- tissue density increased compactness of anatomic particles will increase beam attenuation
xray beam quality higher kVp increases xray energy and will decrease beam attenuation.(shoots through tissue rather than getting absorbed)
exit = image-formation= remnant radiation is? composed of transmitted and scattered radiation
Visibility factors brightness and contrast
sharpness factors spatial resolution and distortion
factors affecting radiographic image quality visibility and sharpness factors
Created by: jveliz91