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What is the accrediting body in radiography that accredits schools?
Joint Review Committee on Education in Radiologic Technology (JECERT)
What are the two professional societies and what do they do?
- American Society of radiologic Technologists (ASRT) - Education and representation
- Massachusetts Society of Radiologic Technology (MSRT) - Holds conferences
What are the two societies that give individual certification?
- American Registry of Radiologic Technologists (ARRT)
- Massachusetts Dept of Public Health, Radiation Control Program
What are the two radiologist organizations?
- American College of Radiology - sets standards of radiology
- American Medical Association (AMA) - sets standards in medical field
What are basic protective equipment for tech?
- Full apron
- Thyroid shield
- Leaded glasses
- Leaded walls
What are basic protective equipment for patients?
- Half apron
- Rolling shields
- Gonad shields
- Shadow shields
positively charged subatomic particle of an atom
subatomic particle of an atom pocessing no charge
subatomic particle of an atom possessing a negative charge
What is the atomic mass number?
Number of protons plus the number of neutrons in an atom
What is an atomic mass unit?
Equal to the mass of all the particles of the atom (it is the most precise way of measuring)
What is electron binding energy?
The amount of energy required to remove an electron from its orbital shell
What is the electromagnetic spectrum?
Different forms of electric and magnetic disturbances in space
What is wave length?
The distance between two corresponding point on a wave
What is amplitude?
Intensity of a waves maximum height
What is frequency?
The number of waves that pass a given point over a given period of time
What is an ion?
An atom that has gained or lost an electron
What is the valance?
The number of electrons in the outermost shell of an atom. It determines chemical combining characteristics
What is matter?
any substance that has form and occupies space
What is energy?
The ability to do work
what is the Octet Rule?
No more than 8 electrons can be in the outer shell
Frequency and wave length are ______ related
Frequency and energy are ________ related
Which side of the x-ray tube is negative and which side is positive?
The cathode side is negative and the anode side is positive.
What is the filament made of and what are its dimensions?
- Coiled tungston wire .1-.2 mm thick
- 1-2 mm thickness of coil
- 7-15 mm long
Describe what happens in the focusing cup
- Possesses a slight negative charge
- Keeps electron cloud in check
- Tube heats up and electron cloud forms
- When there is no more room for the electrons this is called the Space Charge Effect
What is the anode target made of?
Mellidinum with a graphite backing
What are the two causes of tube failure?
- 1. Filament breakage
- 2. Ball bearing failure
what is the stator?
Magnetic induction motor with feramagnetic plates
Describe Bremmstralung interactions
- Electron enters field, losses energy, and is released as a Bremmstralung photon.
- At or above 69.5 kVp 80-90% of photons are Bremms
- Below 69.5 kVp 100% are Bremms
Describe a K Shell or Characteristic reaction
Electron comes in and knocks out a a k shell electron. Electrons from other shells move in to fill the hole. A cascade effect happens. As electrons move they release energy in the form of x-ray photons
What is the percent above 69.5 kEv that a characteristic reaction will occur?
What does isotropic mean?
They go in all different directions
What are the types of filtration?
- Inherent-Anything that is built into the tube (oil, envelope, glass, collimator and mirrors)
- Added-Aluminum that is added outside the tube
What are the measurements of tube filtration and how do we measure it?
- Inherent=1.5mm of aluminum equivalent
- Added=1mm of equivalent
- Measured in half value layer: the amount of aluminum equivalent to reduce the beam by half
- It gets rid of low energy x-rays that contribute to dose but not to image
What are the prime factors?
- mAs-Tube current, milliamperage x exposure time. Determines amount of electrons in electron cloud
- kVp-Measure of the penetrability of the x-ray beam
- Distance-(inches) Has a very strong effect on the intensity of the beam. Inversely proportional to beam strength
What is the reciprocity law?
The same radiographic film density will result from different mA and time selections, provided that the mAs totals are equal
What is the relationship that kVp has on contrast
They are inversely related-Increased kVp decreases contrast
What is the 15% rule?
A 15% change in kVp doubles density
what is the exposure maintenance formula (a.k.a. mass maintenance formula)
Provides technique correction for change in SID. Maintains the same film density.
What is density?
The overall blackening of the film
What is the minimum percentage to visualize change in density in a radiogram?
If you're S# is too low then you are...
What does the window width control?
It controls contrast.
What does the anode heal effect do?
Alters the intensity of the beam across the cathode/anode axis
What is the percent difference between the cathode and anode sides of the tube?
Density up to 45% greater on cathode side
What is the relationship of SID to density?
- They are inverse
- As SID increases, density decreases
What is the relationship of density to filtration?
- They are inversely related
- Increased filtration will decrease density
What is the relationship of beam restriction (collimators) to density?
- Inversely related
- Increased collimation decreases production of scatter and therefore unwanted density
What is the relationship to between mAs and Density?
- There is a direct relationship
- An increase in mAs will increase density
What is the relationship between kVp and density?
They are direct
What is the relationship between part thickness and density?
- It is indirect
- The thicker the part the less dense the radiograph
what is the relationship between grids and density?
- They are inverse
- Higher grid ratio means less scatter which means less unwanted density
What is the relationship between screen speed and density?
- They have a direct relationship
- The faster the screen the more density
What is the relationship between processing and density?
They have a direct relationship
What is the relationship between kVp and contrast?
- They are inversely related
- An increase in kVp decreases contrast
What is the percentage to see a visible difference in contrast?
What is the percentage that is significant enough to do a repeat?
What are three ways to increase contrast on a lumbar spine?
- Use appropriate kVp
- Use a grid
What is the relationship between filtration and contrast?
- Increased detail decreases contrast
What is the relationship between OID and contrast?
Does a change in SID make a change in contrast?
What is the relationship between use of a grid and contrast?
- Using a grid increases contrast by getting rid of scatter
What is the relationship between part thickness and contrast?
- The thicker the part the less contrast
What is the relationship between tissue opacity and contrast?
What is the relationship between collimation and contrast?
- Increased collimation means less scatter and more contrast
What is the relationship between processing and contrast?
What is the relationship between screen vs. non screen and contrast?
- Using a faster screen will increase contrast
How do we measure recorded detail?
line pairs per mm with a line pair test tool
What is the modulation transfer function?
a measurement of detail. How well you represent the actual object. Measured by 0-1
What are the factors that effect detail?
- Focal spot size
- film/screen combinations
What is the relationship between OID and detail?
- They are inverse
- As OID decreases, detail increases
What is the relationship between SID and detail?
- They have a direct relationship
- If SID decreases, detail increases
What is the relationship between focal spot size and detail?
- they are indirect
- Decreased focal spot size increases detail
What is the relationship between film/screen combinations and detail?
- The faster the screen speed the less detail
- Non screen gives best detail
What is the relationship between motion and detail?
- They are inverse
- More motion means less detail
What are the types of motion and how can they be reduced?
- Voluntary-talking or moving
- Involuntary-heartbeat, paristalsis, seizures, tremors, unconscious breathing
- Communication, positioning, immobilization techniques
You get ______ penumbra with more OID
and _______ penumbra with less OID
What is the formula to determine magnification factor?
How do you determine SOD?
Subtract the OID from the SID
What is the formula to find out an object size?
Image size/MF=Actual size
what are the two types of distortion?
- Size distortion (magnification)
- Shape distortion
Shape distortion is based on ______ and __________
- CR angulation
- Part angulation
What is differential absorption?
varying degrees of absorption of the x-ray beam as it passes through materials of different densities contained within the subject
What is attenuation?
Reduction of the intensity of the x-ray beam as it passes through anatomic tissue
What are the three different ways the x-ray beam can be attenuated?
What happens in the photoelectric effect?
Incident photon enters subject atom and ejects an inner shell electron. Cascade effect occurs. Very low energy characteristic photons are released. They do not have enough energy to effect the image. Are completely absorbed by the patient
What does an increase in kVp do when it comes to the photoelectric effect?
Increased kVp decreases the amount of photoelectric and increases the amount of transmission
What are the two types of scattering?
Describe coherent scattering and occurence
- X-rays interact with subject atom. Atom becomes excited and releases energy in a different direction.
- Contributes to dose but very unlikely to hit IR
- Occurs below 10 kEv
Describe Compton's scattering and its occurrence
- Incident photon ejects outer shell electron. Ejected electron may go on to have other interactions. Remaining energy is released in the form of a scattered photon. Contributes to dose and to film fog.
- Can occur at any energy level
- % of interactions that are Compton's increase with an increased kVp
Describe transmission and its occurrence
- x-ray photon passes through without any interaction
- Occurrence increases with increased kVp
What are the different layers of the film?
- Adhesive layer
What are the characteristics of the film base?
- Gives the film form
- Chemically neutral
What are the characteristics of films adhesive layer?
- chemically and electrically neutral
- sticks the emulsion to the base
What are the characteristics of the films emulsion layer?
Active layer-has silver halide crystals, has the gelatin that the crystals are in
What does film's supercoat do?
What kind of charge does the sensitivity speck possess?
A positive charge
Describe Gurney Mott theory
All the electrons that are created when bombarded with photons from x-rays are attracted to the sensitivity specks. The sensitivity specks become negative and attract a collection of atomic silver. The latent image forms when the crystals turn black
What are the layers of the screen?
- Base layer
- Reflecting layer
- Phosphor layer
What are the characteristics of a screens base layer?
- Chemically inert
What are the characteristics of a screens reflecting layer?
- Light is produced isotropically
- some screens reflect the light, some screens absorb it
- Absorbing screens get higher detail
What are the characteristics of a screens phosphor layer?
Converts x-rays to light
What is the difference between phosphorescence and florescence?
- Phosphorescence absorbs light and releases it slowly
- Florescence-ligt stops when energy stops. Like turning off a light. Has a lot of lag
What is the formula to determine the new mAs when using a different screen speed?
Describe what happens in a cassette
X-rays interact with phosphor layer, photons come into phosphor layer, excites material and releases electrons, electrons move into conductive layer leaving holes in phosphor layer. The holes left are the latent image.
If an image has an EI# of 1800 is it over exposed or under exposed?
What is pixel pitch?
The space between the DEL's on in the DR detector
What is the order from least to most dense of anatomic and added tissues?
air, fat, muscle, bone, metal
An asthenic person is
A hyposthenic person is
A sthenic person is
- Near Average
What is a negative contrast material?
What is a positive contrast material?
What are the mAs increase percentages for casts?
- 25-30% for fiberglass
- 100% for large or wet casts
- 50-60% for small to medium plaster
Additive pathology has a _________ atomic #
What are the two kinds of Coherent scattering?
- Thompson-photon acts with single electron then released
- Rey-photon interacting with all electrons then released (does not impact image)
What is the primary purpose of the grid?
To improve contrast by decreasing scatter
What is the scatter that contributes to film fogging?
When do we need to use a grid?
- When part thickness measures more than 10cm
- When we are using a kVp above 60
What are the primary disadvantages to grid use?
- Grid lines on film
- Requires increase in technique/increased dose
What are grids constructed of and how?
- Lead strips going in one direction
- Separated by radioluscent interspace material (typically aluminum)
What is the grid frequency?
The number of lead strips per inch of cm
What is a grid frequency range?
- 60-200 lines/inch
- 25-80 lines/cm
What are the two types of grid patterns?
Lead content is greater in a grid with
a high ratio and low frequency
What are the two types of grids?
- Parallel-lines straight up and down
- Focused-lines are angled to match the divergence of the x-ray beam
What is the formula to find the grid ratio?
- Grid Ratio=h/D
- h=height of the lead strips
- D=the distance between them
What are the two types of moving grips?
- Reciprocating-motor drives grid back and forth during exposure
- Oscillating-Electromagnet pulls grid to one side then releases it during the exposure
What is the formula to find the grid conversation factor?
- GF=mAs with grid/mAs without grid
What are the GCF for common grid ratios?
No grid=1, 5:1=2, 6:1=3, 8:1=4, 12:15, 16:1=6
List grid errors that result in grid cutoff
- Off level grid
- Off center
- Off focus
- Upside-down grid
- Moire effect-when grid lines are parallel to scan lines
How many inches of OID do you need to reduce scatter?