Receptor Exposure (Density) Flashcards
Radiographic Properties
All radiographic properties must be in balance in order to create what?
Radiographic Properties
a “good” quality image.
Two Categories of Radiographic Quality:
- What are the 2 categories of radiographic quality and what do they consist of?
Two Categories of Radiographic Quality:
Categories = photographic properties and geometric properties
- Photographic properties consist of: receptor exposure (brightness or radiographic density) and gray scale (contrast)
- Geometric properties consist of: spatial resolution (detail or sharpness of lines) and distortion
Quality Image must have:
What 4 things should a quality image have?
Quality Image must have:
- Minimum distortion
- Maximum sharpness of structural lines
- Proper gray scale or correct gray tones on image
- Sufficient radiation exposure to visualize body part (receptor exposure or brightness level - not too light or too dark)
Receptor Exposure / Density
Receptor exposure is what type of base system? Describe.
Density is what type of base system? Describe.
“Overall ___ of a radiographic image”
Receptor Exposure / Density
Receptor exposure = Digital base system = brightness of the image as viewed on the monitor
Density = Film base system = degree of blackening of radiograph due to accumulation of black metallic silver on the radiographic film
“Overall darkening of a radiographic image”
What’s wrong with the image? How would you change it to make it better?
What’s wrong with the image? How would you change it to make it better?
A little too light. Change mAs by 30%
What’s wrong with the image? How would you change it to make it better?
What’s wrong with the image? How would you change it to make it better?
Too dark. Make it lighter. 1/2 mAs.
What would determine how you would change this image?
What would determine how you would change this image?
What part you’re looking at –
If looking at chest - too dark
If looking at abdomen - too light
What’s wrong with the image? How would you change it to make it better?
What’s wrong with the image? How would you change it to make it better?
Too light. Go up 30% minimum.
What’s wrong with this image?
What’s wrong with this image?
Too dark and too black-white
- Oversaturation
Contrast or Gray Scale
What is contrast or gray scale?
Contrast or Gray Scale
- Visible differences between any two selected areas of density within the radiographic image.
- “Differences in shades of density”
Contrast
What kind of scale is this?
Contrast
Short scale - abrupt changes
What kind of contrast level is demonstrated in the image?
What kind of contrast level is demonstrated in the image?
Low scale contrast - don’t see a lot of differences
What kind of contrast level is demonstrated in the image?
What kind of contrast level is demonstrated in the image?
Low contrast scale - no proper gray scale
What kind of contrast level is demonstrated in the image?
What kind of contrast level is demonstrated in the image?
Low contrast scale - too black and white - not enough gray scale
What kind of contrast level is demonstrated in the image?
Why?
What kind of contrast level is demonstrated in the image?
High contrast scale - because has barium - much more white
Contrast
Anytime you have ___, it’s a higher contrast scale because of ___ on image.
Contrast
Anytime you have contrast, it’s a higher contrast scale because of white on image.
What’s wrong with this image? How could it be fixed?
What’s wrong with this image? How could it be fixed?
Too gray
Can change kVp, or use a grid
Recorded Detail
What is recorded detail?
What are other names used for recorded detail?
Recorded Detail
Recorded detail = sharpness of structural lines on radiographic image
Other names used = detail, sharpness of detail, definition, spatial resolution
Recorded Detail
What’s wrong with this image?
Recorded Detail
Recorded detail lost
Which image has better detail?
Which image has better detail?
Left
Right has lost detail
Distortion
What is distortion? What are some examples of distortion?
Anything we ___ or ___ is distortion.
Distortion
Distortion = misrepresentation of shape or size of a structure recorded on image
Example = foreshortening, elongation, magnification
Anything we rotate or oblique is distortion.
Receptor Exposure / Density
What is receptor exposure/density dependent on?
What measures the radiographic density on a film? How?
Using digital imaging, receptor exposure can be indicated by what?
Receptor Exposure / Density
Receptor exposure/density dependent on amount of radiation received by IR/film
Densitometer measures radiographic density on a film - by comparing incident light to transmitted light
Using digital imaging, receptor exposure can be indicated by dose index numbers
Human Visibility
What is the optical density range for humans?
Human Visibility
0.25 - 2.50
Digital Radiography Terms for Density
What is brightness?
What does window level describe?
Digital Radiography Terms for Density
Brightness = the same concept of density but it is displayed on a soft-copy monitor.
Window Level = describes the digital processing that produces changes in density/brightness.
Effects on Image Appearance
What makes radiography an art, not an exact science?
“____” for changes in technical factors are guidelines. Sometimes they only apply to a range of ___.
Effects on Image Appearance
Variables make radiography an art, not an exact science
“Rules” for changes in technical factors are guidelines. Sometimes they only apply to a range of circumstances.
Factors Affecting Density
Controlling or Influencing
___ controlling factor
- Multitude of ___ factors
- mAs reciprocity*
- Failure
- Short exposure times of < than ___ seconds
- Long exposures times of > than a ___ seconds
Factors Affecting Density
Controlling or Influencing
mAs controlling factor
- Multitude of influencing factors
- mAs reciprocity*
- Failure
- Short exposure times of < than 0.01 seconds
- Long exposures times of > than a few seconds
MAJOR CONTROLLING FACTOR OF DENSITY
What is the major controlling factor of density? What does it control?
MAJOR CONTROLLING FACTOR OF DENSITY
Major controlling factor of density = mAs
Controls = amount of radiation produced by controlling amount of electrons flowing across X-ray tube
Digital Radiography
What does the window level control?
What is critical in determining proper digital image receptor exposure?
Digital Radiography
Window Level will control the density level
Setting the correct mAs is still critical in determining proper digital image receptor exposure.
mAs
mAs and what are directly proportional?
What does that mean?
Ex) The radiologist wants you to repeat a knee film that is double the darkness it should have been. You used 60 kVp at 6 mAs.
What do you do? Film was too dark - how much?
mAs
- mAs and density are directly proportional
- Meaning in order to double the density on the radiographic image, you will double the mAs value
- In order to half the density on the radiographic image, you will half the mAs value.
Ex) The radiologist wants you to repeat a knee film that is double the darkness it should have been. You used 60 kVp at 6 mAs.
What do you do? Film was too dark - how much?
Double dark so cut the mAs in half.
6 mAs divide by 2 = 3 mAs
Minimum change for mAs in order to see a change:
What rule is used/what do you change your mAs value by to see a change in density?
Minimum change for mAs in order to see a change:
30% rule for mAs value to see change in density
50 mAs x .30 = 15 mAs
You must add 15 mAs to your mAs value in order to see your film become darker.
You must subtract 15 mAs from you mAs value in order to see your film become lighter.
Influencing Factors:
What do influencing factors influence? What will change if influencing factors change?
Influencing Factors:
Influencing factors influence density.
If influencing factors change, density changes
Kilovoltage
What does kVp control?
- ___ ___ of the beam
- Changes in kVp alter ___ of the beam
- Production of ___ ___ is affected by the kVp
- Patient’s ___ ___
Kilovoltage
kVp controls energy (strength and wavelength) of the electrons
- Penetration power of the beam
- Changes in kVp alter intensity of the beam
- Production of scatter radiation is affected by the kVp
- Patient’s radiation dose
Minimum Change in Density using kVp
What rule is used/what do you do to your kVp in order to see a minimum change in density?
Minimum Change in Density using kVp
In order to see a minimum changes in density you must change your kVp by 10%.
50 kVp at 5 mAs and the film was a little light.
50 x .10 = 5
You must use 55 kVp in order to make the film a little darker.
Double or Half the Density using kVp
What rule is used/what do you do to your kVp in order to double or half the density?
Double or Half the Density using kVp
In order to double or half the density, you must change kVp by 15%
60 kVp at 12 mAs film was double dark.
60 x .15 = 9 kVp
60 -9 —New kVp=51 kVp
Why not use kVp to change density?
Why not use kVp to change density?
Because it also changes
- Wavelength
- Penetration power of the beam
- Patient radiation dosage
- Scale of contrast
Anode Heel Effect
___ varies along the ___ ___ of the ___
What does the anode heel effect do?
Density up to ___% greater at the ___ side of the beam
Anode side = ___ intense
Cathode side = ___ intense
Where do we want thicker body parts?
Anode Heel Effect
Intensity varies along the long axis of the beam
The anode heel effect alters the intensity of the beam across the cathode/anode axis
Density up to 45% greater at the cathode side of the beam
Anode side = less intense
Cathode side = more intense
Where do we want thicker body parts? Cathode end
Source-Image-Distance (SID)
What does the inverse square law state?
What is inversely proportion to the square of the distance?
Shorter SID = ___ film AND Longer SID = ___ film (if same technique is used)
Source-Image-Distance (SID)
Inverse square law states that the intensity of the beam varies with the distance from the source of radiation.
Exposure is inversely proportion to the square of the distance
Shorter SID = darker film AND Longer SID = lighter film (if same technique is used)
Inverse Square Law vs New Mas Formula
What is inverse square formula?
What is the new mAs formula to maintain density?
Inverse Square Law vs New Mas Formula
Inverse Square Formula:
- Old Intensity = New Distance²
- New Intensity = Old Distance²
To Maintain Density: New mAs Formula
- Old mAs x New Distance²
- Old Distance²
Rules for SID Changes:
- Look for ___
- If SID doubles = ___ x mAs
- If SID is cut in half = ÷ mAs by ___
- Rule of Thumb:
- 40” to 72” = ___ x mAs
- 72” to 40” = ÷ mAs by ___
Rules for SID Changes:
- Look for doubles
- If SID doubles = 4 x mAs
- If SID is cut in half = ÷ mAs by 4
- Rule of Thumb:
- 40” to 72” = 4 x mAs
- 72” to 40” = ÷ mAs by 4
Object to Image Receptor Distance OID
What is an air gap grid?
Shorter OID = ___ film AND Longer OID = ___ film (if same technical factors are used)
Object to Image Receptor Distance OID
Air gap grid = the air space between the part and IR acts as a grid
so:
Shorter OID = darker film AND Longer OID = lighter film (if same technical factors are used)
Filtration
What does filtration do and why?
Increase filtration = ___ film AND Decrease filtration = ___ film (if same technical factors are used)
Filtration
Filtration removes longer wavelengths so that less radiation leaves the tube
Increase filtration = lighter film AND Decrease filtration = darker film (if same technical factors are used)
Beam Restriction “Collimation”
What do you cut off when you cone down?
smaller field side = ___ film VS larger field size = ___ film (if same technical factors are used)
Beam Restriction “Collimation”
What do you cut off when you cone down? Primary radiation field
smaller field side = lighter film VS larger field size = darker film (if same technical factors are used)
Anatomical Parts
Attenuation is the ___ in the number of ___ as they travel through the body ___.
smaller body parts = ___ film VS larger body parts = ___ film (if same technical factors are used)
Anatomical Parts
Attenuation is the decrease in the number of photons as they travel through the body thickness.
smaller body parts = darker film VS larger body parts = lighter film (if same technical factors are used)
Grids
What do grids do?
Grid = ___ film VS Nongrid = ___ film (if same technical factors are used)
Rule of Thumb:
- Non-Grid to Grid = ___ x mAs
- Grid to Non-Grid = ÷ mAs by ___
Grids
Grids remove scatter radiation from striking film (less radiation reaching film)
Grid = lighter film VS Nongrid = darker film (if same technical factors are used)
Rule of Thumb:
- Non-Grid to Grid = 4 x mAs (too light)
- Grid to Non-Grid = ÷ mAs by 4 (too dark)
Film/Screen Combinations
You will need to remember the ___, ___, and ___ of thefilm/screen.
faster the system = ___ film VS slower the system = ___ film (if same technical factors are used)
Film/Screen Combinations
You will need to remember the size, thickness, and speed of thefilm/screen.
faster the system = darker film VS slower the system = lighter film (if same technical factors are used)
Film Processing
You must process the film using the requirement of the ___. If you change the ___ of the developer or length of the ___ you will notice a change in the ___.
- Hotter Temp= ___ Film VS Cooler Temp = ___ film
- Longer Time= ___ Film VS Shorter Time = ___ film
Film Processing
You must process the film using the requirement of the manufacturer. If you change the temperature of the developer or length of the time you will notice a change in the density.
- Hotter Temp= Darker Film VS Cooler Temp = lighter film
- Longer Time=Darker Film VS Shorter Time = lighter film
Quick Tip:
If less radiation is produced or less radiation is reaching the IR, the overall brightness/density will ___.
If more radiation is produced or more radiation is reaching the IR, the overall brightness/density will ___.
Quick Tip:
If less radiation is produced or less radiation is reaching the IR, the overall brightness/density will decrease.
If more radiation is produced or more radiation is reaching the IR, the overall brightness/density will increase.
