Term
| What types of imaging does radiology include? |
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Definition
-CT
-diagnostic and interventional radiology
-nuclear medicine
-ultrasound
-MRI
-radiation therapy |
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Term
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Definition
| high energy electromagnetic radiation |
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Term
| Who discovered x-rays, and when? |
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Definition
| Wilhelm Conrad Rontgen in 1895 |
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Term
| What was Rontgen working on when he discovered x-rays? |
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Definition
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Term
| What was Rontgen's first image? |
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Definition
| his wife's hand where he could see her bones and rings |
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Term
| What award did Rontgen win? |
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Definition
| Nobel Prize for Physics in 1901 |
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Term
| Who did the first clinical radiograph, and of what? |
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Definition
-Dr Frost = fractured forearm
-Dr Cox = gunshot wound |
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Term
| What society was founded in 1900? |
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Definition
| American Roentgen Ray Society (ARRS) |
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Term
| Who produces the first animal radiographs? |
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Definition
| Josef Eder in 1896 (dead small animals) |
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Term
| What veterinary organization was founded in 1962? |
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Definition
| American College of Veterinary Radiology (ACVR) |
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Term
| What is ionizing radiation? |
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Definition
-has the ability to eject an electron from its orbit
-has high frequency and short wavelength |
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Term
| What is the relationship between wavelength, frequency, and energy? |
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Definition
| increased wavelength = decreased frequency = decreased energy |
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Term
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Definition
| electrons are accelerated from the negative cathode to the positive anode |
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Term
| How are electrons accelerated from cathode to anode? |
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Definition
| there's a high voltage differental between the two (kVp) |
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Term
| What are the adjustable components of the x-ray machine that determine radiograph quality? |
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Definition
|
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Term
|
Definition
-milliamperes
-the number of electrons liberated from the cathode |
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Term
| What is the souce of electrons? |
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Definition
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Term
| What does the size of the cathode determine? |
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Definition
-size of electron beam
-size of target on the anode (focal spot)
therefore, the size of the origin of the x-ray beam |
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Term
| What is the souce of x-ray product as the accelerated electrons from the cathode filament interact with the atoms of the metallic target? |
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Definition
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Term
| What is the anode composed of? |
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Definition
| tungsten (high atomic number and melting point) |
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Term
| What determines the speed/energy of the electrons? |
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Definition
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Term
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Definition
| -reduces temperature by spread x-rays out but keeps focal spot small |
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Term
| What are the advantages of a rotating anode? |
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Definition
-When a high tube current is used (more than 100 mA), it can spread the heat over a larger surface area
-anode angle can be decreased for the same number of electrons, therefore the image quality is better |
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Term
| What type of anode is seen in portable x-ray machines? |
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Definition
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Term
|
Definition
| non-uniform x-rays due to the anode angle because some of the x-rays were absorbed by the anode (target) |
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Term
| How does one compensate for the heel effect? |
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Definition
| placing thicken portion of the patient towards the cathode |
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Term
| What are the two types of x-rays produced in an x-ray tube? |
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Definition
-general (braking or bremsstrahlung) radiation
-characteristic (collisional) radiation |
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Term
| What is collisional radiation? |
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Definition
-an electron is ejected from its orbit
-an electron from a higher shell drops down into lower shell
-energy produced |
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Term
| What is bremsstrahlung radiation? |
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Definition
-predominant type of x-rays produced in a tube
-electron passes through an atom, slows down and curves due to positive nucleus
-slowing down gives off energy (x-ray and heat) |
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Term
| How much of the energy emitted from bremsstrahlung is heat vs x-rays? |
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Definition
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Term
| X-rays have a wide spectrum of energy. What happens to low energy x-rays? |
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Definition
-not useful for diagnostics
-aluminum filter in x-ray tube remove them |
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Term
| What is the mean energy of x-rays? |
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Definition
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Term
| What is the relationship between kVp and x-ray energy? |
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Definition
| the mean energy of the x-rays is 1/3 the max kVp (max electron energy) |
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Term
| What determines the quantity of electrons? |
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Definition
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Term
| What is the main reason for filtration of x-rays? |
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Definition
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Term
| What are the two main reasons for collimation in diagnostic radiology? |
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Definition
-radioprotection (restricts beam so the amt of primary and scatter radiation is reduced)
-image quality (reduced scatter = better contrast) |
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Term
|
Definition
| process by which x-ray beam energy is reduced as it passes through a tissue |
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Term
| Attenuation of the x-rays depends on four things. Name them. |
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Definition
-x-ray energy (kVp)
-tissue thickness
-density
-atomic number of object being radiographed |
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Term
| What is the photoelectric effect? |
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Definition
-responsible for contrast (good!)
-happens when an inner shell electron gets bumped out, resulting in a photoelectron, a positive ion, and a little x-ray energy that is absorbed quicky
-explains why better contrast is achieved with low kVp |
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Term
| What is the probability of the photoelectric effect? |
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Definition
k x Z^3 / E^3
Z = atomic number of object
E = power of x-ray energy |
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Term
| When does the photoelectric effect occur most often? |
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Definition
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Term
| What is the Compton effect? |
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Definition
-results in deviation of incoming x-rays from its initial path with a loss of energy (BAD!)
-x-ray encounters outer shell electron and bumps it out, scattering an emitted x-ray |
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Term
|
Definition
| more scatter radiation from the Compton effect and less contrast |
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Term
|
Definition
-the degree of film blackness
-directly related to how many x-ray have reached the film (gone through patient) |
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Term
| What determines film density? |
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Definition
| mAs, and to a lesser extent kVp |
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Term
|
Definition
-focal-film distance
-the distance of the x-ray tube to the film |
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Term
| What is the relationship of FFD to film density? |
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Definition
| decreased FFD = increase film density |
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Term
| What is the inverse square law? |
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Definition
-the x-ray beam intensity changes as a function of the square of the distance
-if FFD is doubled, the intensity decreases by 4 (1/4) |
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Term
| What is the relationship between mAs and kVp when making a diagnostic image? |
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Definition
| as one goes up, the other must go down, as to keep the film density at the correct level |
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Term
| How does mAs affect radiographic density? |
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Definition
| mAs and film density have a direct relationship (doubling mAs = double film density) |
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Term
| How does kVp affect radiographic density? |
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Definition
-in the 40-100 kVp range, you need to +/- 10% of kVp to make the radiograph twice/half the original film density
-in the 100 kVp range, make that 15% |
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Term
|
Definition
-the difference in opacity between two region on the radiograph
-we don't want TOO much contrast, we need shades of gray |
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Term
|
Definition
-the number of shades of gray in an image
-we want this! |
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Term
| What determines contrast? |
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Definition
-energy of x-rays (kVp)
-difference in density and Z between two regions |
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Term
| What happens to contrast as the kVp goes up? |
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Definition
-contrast decreases
-latitude (shade of gray) increases |
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Term
| What kVp setting is preferred for thoracic radiographs and why? |
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Definition
-high kVp
-increases latitude
-need extra energy to get through thickness |
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Term
| what kVp setting is preferred for bone radiography and why? |
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Definition
-low kVp
-maximizes contrast to get good bone detail |
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Term
| What affects film density? |
|
Definition
|
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Term
| What affects film contrast? |
|
Definition
|
|
Term
|
Definition
-determined by size of film crystals
-has inverse relationship to image quality |
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Term
| Describe the intensifying screens in the film cassette. |
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Definition
-improves efficiency of the x-ray system (amplifier)
-faster screens provide less detail
-emit a certain wavelength of light, so must match the film |
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Term
| Describe the emulsion, crystal size, exposure requirements, and film quality in fast screen/fast film. |
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Definition
-thick emulsion
-large crystal
-requires less exposure
-grainier image |
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Term
| What is the most common source of degraded image quality? |
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Definition
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Term
| What are some common technical errors affecting film quality? |
|
Definition
-increased or decreased film density
-loss of film contrast
-localized areas of increases/decreased film density
-blurred images
-grad artifacts |
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Term
| What would cause increased film density error? |
|
Definition
-too high kVp or mAs
-decreased FFD
-overestimating thickness
-use of grid technique without a grid |
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Term
| What would cause decreased film density error? |
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Definition
-too low kVp or mAs
-increased FFD
-underestimating thickness
-loading two films in a cassette
-use of slower film |
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Term
| What would cause loss of film contrast error? |
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Definition
-darkroom lead
-back scatter
-out of date film |
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Term
| What would cause localized areas of increased film density error? |
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Definition
|
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Term
| What would cause localized areas of decreased film density error? |
|
Definition
-foreign material on film
-bent film |
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Term
| What would cause a blurred image error? |
|
Definition
-patient motion
-cassette or table motion |
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Term
| What would cause grid artifacts? |
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Definition
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Term
| What is a technique chart? |
|
Definition
-based on the measured thickness, we can increase of decrease kVp (with relatively same mAs)
-used to standardize how to make radiographs and to ensure that the image quality is good |
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Term
| What are the pros and cons to computer radiography (CR)? |
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Definition
pros: no need to modify existing machinery, cassettes can be used for more than one machine
cons: needs a film reader (maintenance), 30-60 second read time |
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Term
| What is computer radiography (CR)? |
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Definition
-image plate contains image
-plate reader has laser that reads latent image
-analog signal converted to digital signal
-plate erased so it can be reused |
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Term
| What is direct digital radiography (DDR)? |
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Definition
captures x-rays as they exit patient without using plate reader
-two types: CCD, and flat panel (direct and indirect conversion) |
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Term
| What is the direct flat panel DDR? |
|
Definition
-directly attached to a computer
-thin film transistor array directly reads out image |
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Term
| What is the indirect flat panel DDR? |
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Definition
-scintillator converts x-rays to visible light
-diode turns light to electric signal to get image readout |
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Term
| What are the pros and cons to direct flat panel DDR? |
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Definition
pros: 4 second reading, better resolution
cons: expensive, directly attached to computer |
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Term
|
Definition
| -scintillator releases light, lens makes it smaller, goes through CCD detector, then get image readout |
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Term
| What are the pros and cons to CCD? |
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Definition
pros: less expensive than flat panel
cons: attached to table, some light photons lost during optical reduction therefore less resolution |
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Term
| How many megapixels are medical grade monitors? |
|
Definition
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Term
|
Definition
| Digital Imaging and Communication in Medicine |
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Term
| What type of imaging stands up to legal scrutiny and why? |
|
Definition
-DICOM
-images cannot be altered
-header contains patient info
-image file has a unique ID# |
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Term
| Where are digital images stored? |
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Definition
| PACS (picture archiving and communication system) |
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Term
|
Definition
-transmission of image from one doctor to another for interpretation
-use DICOM |
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