Upgrade to remove ads
Terms in this set (30)
Who developed radiographic grids?
Primary goals of radio graphic grids
- Reduce scatter
- scatter does not contribute to image quality + reduces image contrast
- improve image contrast
T/F: The thicker the body is, the more Compton scattering occurs... Grids clean this up & maintain contrast in the image
- lead strips
- thin W/ high absorption
- high atomic number
+ absorb all other photons entering at arbitrary angles
-maintains precise separation of grid strips
• aluminum- has a higher atomic #; high absorption, more sturdy; but does absorb some of the primary beam.
• plastic- has lower atomic #; less absorption of primary beam but absorbs moisture when wet + can be warped
* transmits only photons that are directed in a straight line from the X-ray tube to the IR.
- thickness of the grid strips (T)
- width of interspace material (D)
- height of grid (h)
Thickness of the grid strip
Width of interspace material
Height of the grid
- Defines effectiveness in reducing scatter through absorption
R = h/D
- then whatever number you get you change into a ratio- (x:1)
When height of grid decreases and width of interspace material stays the same, what happens to the grid ratio?
Grid ratio decreases
T/F: The higher the grid ratio; the more grid strip material it has.
When width of interspace material goes down, what happens to the grid ratio?
Grid ratio increases
Higher grid ratio =
- more scatter reduction (more scatter absorption)
Lower grid ratio=
-less scatter reduction
More grid strips
- More chance for absorption and less toleration for slightly angled scatter.
- The number of lead strips per cm.
- ranges from 25-45 lines per cm
- higher grid frequency = more Ana strips per cm to absorb scatter photons
- higher grid ratio- more grid material versus interspace material to absorb scattered photons.
-higher absorption= higher technique requirement to maintain IR exposure.
Calculating great frequency
- Great frequency is the number of great strips per centimeter
10,000 um= 1cm
higher frequency grid =
Less distinct grid lines (you can see lines less on images)
Lower frequency grid =
More distinct grid lines
Contrast improvement factors
- Ability of the grade to improve contrast
- A contrast improvement factor of one = no improvement
- 1.5 to 2.5 is typical
-Higher the contrast improvement factor, the better the contrast improvement
- Affected by patient thickness and body composition - We can't control this! ( ex: If using the same grade on one person to the next, the CIF will be different between the two exams)
- Grids require a patient does increase by changing mAs Because inner space material does absorb some of the primary beem
- In order to keep exposure and IRthe same, technique must be increased with grids.
- The amount of necessary increase for specific grade ratio = Bucky factor
As kVp increases, scatter _______
As scatter increases, absorption in the grid strips ________ Instead of passing through the inter space material to the IR.
As absorption increases, technique factor must be ________ In order to maintain proper IR exposure.
What is the minimum kVp for using a grid?
What is the body thickness needed to use a grid?
No grid 1
5:1 2x original mAs
6:1 3x original mAs
8:1 4x original mAs
10:1. 4.5x original mAs
12:1. 5x original mAs
16:1 6x original mAs
Bucky factor formula
Mas1/mas2 = Bucky factor1/Bucky factor 2
T/F: When going from no grid to any other factor just multiply the mAs times that Bucky factor.
Ex: using no grid at 5 mAs; to a 8:1 grid
- 5 * 4 = 20 mAs <—- new mAs
THIS SET IS OFTEN IN FOLDERS WITH...
Intro to digital errors & post processing manipula…
Grid type errors
YOU MIGHT ALSO LIKE...
RAD 115 - CH 20 HW
OTHER SETS BY THIS CREATOR
Digital artifact/processing errors
Viewing digital images post processing
Digital radiographic technique
OTHER QUIZLET SETS
Klinisk biokjemi og fysiologi
IAH 2 Review