Test 2 - quizlet intro Flashcards
energy does not vanish it simply changes or ____ from one state to another
transits
energy in transit
radiation
__________: refers to radiation when an electron is removed from its orbital
ionization
What are 3 forms of Electromagnetic energy capable of ionizing matter?
x ray
gamma rays
UV light
Short frequency wavelengths exhibit (more or less) energy
Long frequency wavelengths exhibit (more or less) energy
Short frequency wavelengths exhibit more energy
Long frequency wavelengths exhibit less energy
What are some examples of Natural Ionizing Radiation and which source is the most common?
cosmic rays, terrestrial radiation and internally
deposited radionuclides. Radon Gas is the largest source of naturally ionizing radiation
Medical imaging is the largest source of man-made radiation that humans and domestic animals will receive but Radon Gas is the largest source of overall radiation
TRUE
Who discovered the x ray and when
wilhelm roentgen
Nov 8 1895
6 x ray properties
No charge
Invisibility
Penetrability of most matters dependent on Z(atomic #)
Ionization and biologic effect
Making compounds fluoresce and emit light
Travel at speed of light
3 components of the imaging system
xray tube
operating console
high voltage generator
cathode is what charge
negative
Initially low electrical current “heats” the filament slowly
analogous to a house-hold toaster or an incandescent light bulb. When the filament temp. is sufficiently high the outer shell electrons become unstable and after a jolt and a small rise in the filament current the electrons will “boil of” and to be ejected from the filament.
thermionic emission
When emitted from the filament the electrons are still in close proximity to the filament before being accelerated towards the anode. At that point the electron cloud maintains a very strong negative charge and repel any additional electrons to be emitted from the filament This process is known as _________-_________ effect
space-charge effect
purpose of having a duel focus on an anode?
When large body part is being imaged a current of 400mA or more is required, thus large filament and large focal spot will be used. A 300 mA or less is used while imaging the smaller parts. It is important to remember that if the small focal spot is used for larger anatomic imaging, this may significantly damage the x-ray tube.
anode is what charged
positive
2 sources of ionizing radiation
natural
man made
x rays are emitted ___ or in all directions
isotropically
The Cathode of an X-ray tube is composed of heat resistant filament made of __________ _________, wich has a high melting point of 3410 C
thoriated tungsten
what is the focusing cup and what does it do in the x ray tube?
The Cathode’s filaments are embedded in a metal focusing cup. The Focusing cup is (-) charged and electrostatically confines accelerated electrons beam towards their anode’s target or a small area of the anode known as focal spot
why is it important that the anode in an x ray tube rotates
Rotating anodes have significantly reduced potential heat damage to the tube
In order to maintain uniform tissue exposure the anode side must always face the (Thinner or Thicker) body part.
thinner
True/False: The grid will not reduce extrafocal radiation because it is not considered scatter radiation
TRUE
What is the purpose of the control panel
Permits selection of technical factors and initiation of radiographic exposures: mA, kV, Time
_______ modifies the voltage of incoming alternating-current (AC) electrical signals to increase or decrease the voltage in a circuit
transformer
True/False: Step-up transformer: Supplies the high voltage to the x-ray tube (voltage increases and current decreases)
TRUE
The Step-________ transformer: Supplies power to heat the filament of the x-ray tube (voltage decreases and current increases that heats the cathode’s filament needed for thermionic emission).
down
What does a Rectifier do? and what wave type do we normally use in diagnostic imaging?
Convert alternating current (AC) into direct current (DC)
required by the x-ray tube. A rectifier restricts current flow in an x-ray tube to one direction from cathode to anode only, thereby preventing damage to the x-ray tube filament. We use Full Waves.
why do we need a voltage rectifier
Rectification converts Alternating Current (AC) to Direct Current (DC) to ensure sustained flow of electrons to minimize any “ripple” effect and any “fluctuation” in the electrons’ current
True or False: High-frequency power Generator provides nearly constant potential voltage waveform, which virtually doubles the radiation improving the image quality and
minimizing the dose
TRUE
A __________ is a beam restrictive lead-lined device. Primarily used is to reduce the patient’s dose by restricting the x-ray beams to the desired anatomy
collimator
Added filtration uses ______________ “filters” inserted at the exit port of the tube’s window. Prime role is to “harden” the beam or to remove/absorb the x-rays of lower energy
aluminum
what does added filtration do for diagnostic imaging?
Improves the x-beam penetrability and lessens scatter radiation and dose. Half Value Layer (HVL) of some materials to attenuate 50% of primary x-ray beam
Contains the grid which serves to “remove” scatter radiation and improve the image quality. Cassette holder that houses radiographic cassette with the film or cassette for computed radiography
what is the bucky system
_______ Come in different sizes. 8X10”, 10X12’ and 14x17”. They are composed of plastic exterior with inserted double sided intensifying screens. The Screens will emit light photons when interacting with x-rays in order to reduce the patient’s dose by minimizing the number of x-ray photons (thus reduction in mAs) during film exposure
cassettes
True/False: Films, when exposed by light or x-rays the crystals turn into metallic Ag, “blackening” the film in contrast to “White” or unexposed areas corresponding the body parts that have completely absorbed the x-rays.
TRUE
what kind of radiography does NUHS use
computed radiography
how does radiography work
CR uses very similar equipment to conventional radiography except that in place of a film to create the image, an imaging plate (IP) made of photostimulable phosphor is inserted inside the cassette. The imaging plate housed in a cassette then placed under the body part to be examined and the x-ray exposure is made. Hence, instead of taking an exposed film into a darkroom and putting it through a sequence of chemical steps the CR imaging plate is being run through a special laser scanner, or CR reader, that reads and digitizes the image by generating the flow of electrons “analysed” and by computer as electronic data. The digitized image can then be viewed and enhanced using software that has functions very similar to other conventional digital image-processing software, such as contrast, brightness, filtration and zoom
True or False: Digital radiography is a form of diagnostic radiography where digital X-ray sensors are used instead of traditional photographic films or photostimulable phosphor plate
TRUE
Instead of X-ray film, _____ radiography uses a digital image capture device. This gives advantages of immediate image preview and availability by direct viewing on the computer screen.
digital
For Radiographic processing, how much time do each of these take:
1) Manual Processing
2) Automatic processing
3) Computed Radiography
4) Digital Radiography
1) Manual processing involved approximately 1- hour to process the film
2) Automatic processing is still being used and it takes about 3-minutes
3) Computed Radiography will develop manifest image in less than a minute
4) Digital Radiography is instantaneous
True or False: mAs is known as milliamperage per second and is usually responsible for the x-ray quantity or the Total number of electrons “flying” across the tube from cathode (-) to (+) anode
TRUE
If mAs is too high the film will be ______________
overexposed
What do you do the mAs if the film is too black?
cut (lower) mAs by 50%
What does kVp stand for? and what does it refer to?
kilovoltage peak. This refers to the amount of energy that an x-ray beam possesses.
True/False: Kvp is directly related to the degree of x-ray “penetrability” or quality i.e. an ability to pass through or being absorbed/attenuated by certain matter. X-ray quality is controlled by kVp
TRUE
A change of ___% in kVp is needed to notice visible film changes
4%
A change of 10-15 kVp is equivalent to ___% change in mAs
50% Which one of these equals 50 mAs 1) 500mA x 0.50 sec 2) 200mA x 0.25 sec 3) 350mA x 0.10 sec
2) 200mA x 0.25 sec = 50 mAs
True or False: Reducing time of exposure will result in greater radiation dose reduction to the patient
TRUE
A ___% change in mAs is required to observe any change in eye perceivable optical density
30%
Most diagnostic radiography ranges roughly between ___-____kVp
30-150 kVp
What is the average kVp used for each of these x-ray techniques
1) Cervical
2) Hand
3) Lateral Lumbar
1) 70 kVp for a cercial x-ray
2) 55 kVp for a hand x-ray
3) 90 kVp for a lateral lumbar x-ray
what is the 10 kVp rule and what are its parameters?
The 10 kVp rule states that by manipulating the tube voltage by 10-kVp will result in the same image density change as by either increasing or reducing the mAs by 50%.
We should remember, however that the 10 kVp rule does not apply to the radiographic images acquired at less than 60-kVp or greater than 100-kVp
True or False: Increase in focal spot will also cause an increase in Penumbra
TRUE
what is Penumbra and where is it seen?
Penumbra- (paene)- Latin for “ almost, nearly”. Penumbra seen as “blurring” of the shadows of an image with lowering of “sharp edges” corresponding to the object’s shape
True/False: Change in penumbra is directly proportionate to changes in the object film distance (OFD). Increasing OFD will result with increase of Penumbra
TRUE
Radiation intensity is inversely related to the square of the distance from the source (x-ray tube). Therefore when the distance from the source is doubled, the radiation
intensity is reduced by a factor of fourth (1/4) and When the distance is halved, the intensity is increased by a factor of four
inverse square law
