Prime Factors Flashcards
The emission (production) of x-ray photons is controlled by…
- X-ray tube construction
- Filtration (get rid of long wavelengths)
- Tube housing
- Prime factors
Does the RT have control over prime factors?
Yes
What are the 4 prime factors that affect the emission of x-rays (in overhead tube)?
- Kilovoltage (kVp)
- Milliamperage (mA)
- Time or seconds (s) - note: mA x s = mAs
- Distance ([D] = SID)
Prime exposure factors are ____ the technologist ___.
The technologist’s job is to know how to ___ these ___ to produce _____.
Prime exposure factors are VARIABLES the technologist CONTROLS.
The technologist’s job is to know how to COMBINE these FACTORS to produce HIGH QUALITY RADIOGRAPHS.
What 2 factors affect x-ray emission? What do they measure?
- Quantitative factors - measurement of the number of x-ray protons in useful beam
- Qualitive factors - measurement of the penetrating ability of the useful beam
Name some quantity factors as well as quality factors
Quantity factors - mA, seconds, kVp, distance, filtration
Quality factors DEPEND ON kVp, filtration
Milliamperage
- ___ is the standard abbreviation
- measurement of the _____ or ____ of ___ flowing per ___
- ___ controls the ____ that is applied to the ___
- as ___ increases, so does the number of ___ flowing from the ___ to ___ in X-ray tube
Milliamperage
- mA is the standard abbreviation
- measurement of the TUBE CURRENT or NUMBER of ELECTRONS flowing per SECOND
- mA controls the HEAT that is applied to the FILAMENT WIRE
- as mA increases, so does the number of ELECTRONS flowing from the CATHODE to ANODE in X-ray tube
mA and quantity are…
which means…
mA and quantity are DIRECTLY PROPORTIONAL
which means IF THE mA IS DOUBLED, SO IS THE QUANTITY OF TUBE CURRENT OR ELECTRONS
What are the common diagnostic ranges of mA stations?
- 200 to 400 mA will…
- 800 to 400 will…
What are the common diagnostic ranges of mA stations? 20 mA - 1200 mA
- 200 to 400 mA will DOUBLE AMOUNT OF TUBE CURRENT OR NUMBER OF ELECTRONS “BOILED” OFF OF THE FILAMENT
- 800 to 400 will CUT THE NUMBER OF ELECTRONS IN HALF
Define time/seconds
as exposure time increases…
What will 0.05 to 0.10 do?
What will 0.8 to 0.4 do?
Define time/seconds - LENGTH OF TIME THE HEAT IS APPLIED TO THE FILAMENT WIRE
as exposure time increases, MORE ELECTRONS ARE BOILED OFF THE FILAMENT WIRE
What will 0.05 to 0.10 do? DOUBLES THE ELECTRONS
What will 0.8 to 0.4 do? HALVES THE ELECTRONS
Time or seconds of exposure and quantity are…
Time or seconds of exposure and quantity are DIRECTLY PROPORTIONAL TO THE NUMBER OF TUBE CURRENT OR ELECTRONS OR X-RAY PHOTONS
Time selections
- short exposure times are…
- older equiptment expresses time in…
- new equiptment expresses time in…
Time selections
- short exposure times are USEFUL IN REDUCING MOTION ARTIFACTS
- older equiptment expresses time in FRACTIONS
- new equiptment expresses time in SECONDS OR MILLISECONDS (ms)
mA and seconds are directly ____ to the ____
- if the mA or seconds doubles, so does the ____ or ___ of _____
- if the mA or seconds is cut in half, so does the _____ or ___ of _____
mA and seconds are directly PROPORTIONATE to the TUBE CURRENT
- if the mA or seconds doubles, so does the TUBE CURRENT or NUMBER of ELECTRONS
- if the mA or seconds is cut in half, so does the TUBE CURRENT or NUMBER of ELECTRONS
mA x s = mAs
- mAs is the…
- mAs control…
*
mA x s = mAs
- mAs is the QUANTITY OR NUMBER OF ELECTRONS PER SECOND
- mAs control DENSITY OF THE RADIOGRAPHIC FILM
What is density?
The overall blackening or darkening of the film
OR
overall brightness of the image on the monitor
What is the formula for mAs, s, and mA?
MUST KNOW FORMULAS!!
- mAs = mA x s (ex, 300 mA x .025 = 75mAs)
- s = mAs/mA (ex, 75 mAs / 300 mA = 0.25 s)
- mA = mAs/s (ex, 50 mAs / 0.10 = 500 mA)
30% rule for mAs
- a change of 30% is needed in the mAs value in order to…
50 mAs x .30 = 15 mAs
- If image needs to be ____ : 50 mAs + 15 mAs = 65 mAs
- If image needs to be ____: 50 mAs -15mAs = 35 mAs
30% rule for mAs
- a change of 30% is needed in the mAs value in order to MAKE A NOTICEABLE DIFFERENCE IN THE DARKENING/LIGHTENING OF THE FILM
50 mAs x .30 = 15 mAs
- If image needs to be DARKER : 50 mAs + 15 mAs = 65 mAs
- If image needs to be LIGHTER : 50 mAs -15mAs = 35 mAs
Double density
- mA is the majority controlling factor for…
- Doubling the mAs will…
- Halving the mAs will…
Double density
- mA is the majority controlling factor for RADIOGRAPHIC DENSITY
- Doubling the mAs will DOUBLE THE DARKENING OF THE FILM
- Halving the mAs will HALF THE DARKENING OF THE FILM
Reciprocity Law - 1875 Bunsen and Roscoe
- studied the relationship of the _______ to the ____
- as long as the mAs value is the same, what doesn’t matter?
Reciprocity Law - 1875 Bunsen and Roscoe
- studied the relationship of the EXPOSURE OF RADIATION to the FILM REACTIONS
- as long as the mAs value is the same, what doesn’t matter? WHAT mA OR TIME STATION IS SELECTED
ex) 25 mA x 2s = 50 mAs
100 mA x 5s = 50 mAs
200 mA x .25 = 50 mAs
kVP
- controls…
- higher kVp will…
- increases…
- Relationships:
- as kVp increases _____ increases (but not directly proportional)
- as kVp increases, _____ decreases
kVP
- controls BOTH THE QUANTITY AND QUALITY OF X-RAY BEAM
- higher kVp will INCREASE INTERACTIONS OCCURRING AT THE ANODE TARGET
- increases PENETRATING POWER OF THE BEAM
- Relationships:
- as kVp increases NUMBER OF PHOTONS increases (but not directly proportional)
- as kVp increases, WAVELENGTH decreases
- kVp is known as…
- volts in a unit of…
- kilo is…
so 50 kVp is ____ volts
70 kVP is ____ volts
- kVp is known as KILOVOLTAGE PEAK
- volts in a unit of FORCE OR POWER
- kilo is 1,000
so 50 kVp is 50,000 volts
- 70 kVP is 70,000 volts
- Increasing the kVP on the control panel will cause…
Remember: volts is the ____ or ___ that cause ____ to move. The higher the _____, the higher the _______ in the X-ray tube.
- Increasing the kVP on the control panel will cause AN INCREASE IN THE SPEED AND ENERGY OF THE ELECTRONS TRAVELING FROM THE CATHODE TO THE ANODE IN THE X-RAY TUBE
Remember: volts is the ELECTRICAL PRESSURE or FORCE that cause ELECTRONS to move. The higher the VOLTAGE, the higher the POTENTIAL DIFFERENCE in the X-ray tube.
What 7 things does kVp control?
- Potential difference of the x-ray tube
- Penetration of the x-ray beam
- Energy of the beam
- Wavelength of the beam
- Quality and quantity of the beam
- Radiation dosage to the patient
- Speed of electrons
kVp is the primary controlling factor of the radiographic ____ or ____
- radiographic ___ is the visible differences between ___________ on the radiographic film. The degree of ____ to ___ to ____ shades of the film
kVp is the primary controlling factor of the radiographic CONTRAST or GRAY SCALE
- radiographic CONTRAST is the visible differences between 2 ADJACENT DENSITIES on the radiographic film. The degree of WHITE to GRAY to BLACK shades of the film
kVp as a controlling factor
- kVp should be used to control…
- kVp will affect the density on the film but…
kVp as a controlling factor
- kVp should be used to control THE CONTRAST ON THE FILM
- kVp will affect the density on the film but SHOULD NOT BE USED TO CONTROL THE DARKENING
10% rule of kVp
- a change of 10% is needed to…
change kVp by 10% = 70 x .1 = 7
70 kVp + 7 kVp = 77 kVp (a little ____)
70 kVp - 7 kVp = 63 kVp (a little ___)
10% rule of kVp
- a change of 10% is needed to MAKE A NOTICEABLE DIFFERENCE IN THE DENSITY ON A RADIOGRAPHIC FILM
change kVp by 10% = 70 x .1 = 7
70 kVp + 7 kVp = 77 kVp (a little DARKER)
70 kVp - 7 kVp = 63 kVp (a little LIGHTER)
15% rule for kVp
- increasing kVp by 15% will…
- decreasing kVp by 15% will…
70 kVp x .15 (15%) = 10.5
70 + 10.5 = 80.5 kVp (____ density)
70 - 10.5 = 59.5 kVp (60) (___ density)
15% rule for kVp
- increasing kVp by 15% will DOUBLE THE DENSITY ON THE FILM
- decreasing kVp by 15% will HALF THE DENSITY ON THE FILM
70 kVp x .15 (15%) = 10.5
70 + 10.5 = 80.5 kVp (DOUBLES density)
70 - 10.5 = 59.5 kVp (60) (HALF the density)
Distance or SID
- SID is…
- the ____ of the x-ray beam will vary with the changes in the ____
- increase SID =
- decrease SID =
Distance or SID
- SID is SOURCE OF RADIATION TO THE IMAGE RECEPTOR DISTANCE
- the INTENSITY of the x-ray beam will vary with the changes in the DISTANCES
- increase SID = DECREASE INTENSITY
- decrease SID = INCREASE INTENSITY
Standard SIDs
tabletop or bucky radiography =
chest radiography and other selected exams =
Standard SIDs
tabletop or bucky radiography = 40” or 100cm
chest radiography and other selected exams = 72” or 180cm
As you increase the distance, the x-ray beam begins to…
As you increase the distance, the x-ray beam begins to DIVERGE THUS SPREADING OUT THE ENERGY OF RADIATION
What is inverse square law?
Intensity of radiation is inversely related to the square of the distance
As SID increases, what decreases? (and vise versa)
As SID increases, beam intensity decreases
as beam intensity increases, SID decreases
Doubling the distance of the X-ray tube will ______ of the beam by a factor of ___.
36” SID to 72” SID (radiation will ___ by __)
Doubling the distance of the X-ray tube will DECREASE THE INTENSITY of the beam by a factor of 4
36” SID to 72” SID (radiation will DECREASE by 4)
Cutting the distance in half will…
40” SID at 4 mR
20” SID at 16 mR
Cutting the distance in half will INCREASE THE INTENSITY BY A FACTOR OF 4
40” SID at 4 mR
20” SID at 16 mR
If you took a film at 40” SID and repeated the exam using 60” SID using the same technical factors, what would happen to the density of the radiographic image?
Image would be too light
What does the exposures (film density) maintenance formula do?
- Provides technique correction for change in SID
- Maintains the same film density
Rule of thumb
Insensity of the beam and new mAs to maintain density both can…
Rule of thumb
Insensity of the beam and new mAs to maintain density both can RELATE TO FACTORS OF 4
Digital Image Receptor Systems
- Density and contrast (controlled through…)
- Still, the IR must receive…
- What does not allow the production of acceptable image quality?
Digital Image Receptor Systems
- Density and contrast (controlled through POST-PROCESSING)
- Still, the IR must receive PROPER EXPOSURE
- What does not allow the production of acceptable image quality? EXTREMELY HIGH OR LOW EXPOSURES
Density =
mAs =
kVp =
Density = OVERALL DARKENING OF THE IMAGE
mAs = major controlling factor of density (because controls number of electrons)
kVp = controls contrast
