Grids
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
|
|
||||
|---|---|---|---|---|---|
| What is the purpose of the Grid? | To improve radiographic contrast, To absorb scattered radiation before it reaches
the IR
🗑
|
||||
| What is Transmission responsable for? | the dark areas of a radiograph
🗑
|
||||
| What is Absorption responsable for? | the light areas of a radiograph
🗑
|
||||
| What does scatter do to an X-ray? | creates fog and lowers contrast
🗑
|
||||
| What increases scatter? | kV increases, Field size increases, thickness of part increases, atomic number decreases
🗑
|
||||
| What are the indications for Grid use? | when the part thickness is more than 10 cm, and when the kV is higher than 60
🗑
|
||||
| Who created Grids, and when? | Dr. Gustav Bucky in 1913
🗑
|
||||
| What are Grids constructed of? | Radiopaque lead strips that are separated by radiolucent interspace material, usually Aluminum
🗑
|
||||
| Who improved the design of Grids, and how? | Dr. Hollis Potter. He made the grid lines run in the same direction and made them move during exposure.
🗑
|
||||
| How do you find the Grid Ratio? | Grid Ratio = H/D
🗑
|
||||
| With a high grid ratio, what scale of contrast is there? | short scale of contrast
🗑
|
||||
| T\F: A higher grid ratio is better at removing scatter radiation. | True
🗑
|
||||
| What is the typical grid ratio? | 5:1 to 6:1
🗑
|
||||
| What is Grid Frequency? | the number of lead strips in the grid per inch or cm
🗑
|
||||
| T\F: Lower frequency grids have thinner lead strips. | False : Higher frequency grids have thinner leas strips.
🗑
|
||||
| What type of grid contains the greatest amount of lead and is most effeciant in absorbing radiation? | High ratio, low frequency grids
🗑
|
||||
| T\F: As the lead content increases, the removal of scatter decreases, and the contrast decreases | False: As the lead increases, removal of scatter increases, and contrast increases.
🗑
|
||||
| What are some types of grid patterns? | Crosshatched, linear, Rombic, and consentric.
🗑
|
||||
| What does a crosshatched pattern look like? | It has both horizontal and vertical lead strips
🗑
|
||||
| What does a linear pattern look like? | lead strips run the length of the grid in one direction
🗑
|
||||
| What does a Rombic pattern look like and where is it used? | Looks like a wavy pattern and is used mostly in Europe
🗑
|
||||
| What does a Consentric pattern look like? | A circular pattern that is evergrowing and is used mostly in Japan
🗑
|
||||
| What type of grid has a higher margin of error? | the linear pattern
🗑
|
||||
| What are the types of linear grids? | focused and parallel
🗑
|
||||
| What do focused linear grids look like? | the lead strips are angled which matches the beam divergence
🗑
|
||||
| What is Canting? | When the lead strips are angled to match the beam divergence
🗑
|
||||
| What does improper centering on a linear grid result in? | Peripheral cut off
🗑
|
||||
| What does a parallel linear grid look like? | the lead strips are all parallel to one another
🗑
|
||||
| What is a downfall of using a parallel linear grid? | absorbs a large amount of the primary beam.
🗑
|
||||
| What is reciprocating grid movement? | the grid is moved back and fourth by a motor during exposure.
🗑
|
||||
| What is oscillating grid movement? | a electromagnet that pulls the grid to the side and releases it during exposure.
🗑
|
||||
| What is the grid conversion factor? | GCF = mAs with grid \ mAs without grid
🗑
|
||||
| What happens to the density of a radiograph when a grid is used? | decreases
🗑
|
||||
| What is the Potter-Bucky diaphragm, and what does it do? | it is the Bucky we use today, it moves the grid during exposure.
🗑
|
||||
| What formula is used when converting from one grid ratio ot another? | mAs of 1 over mAs of 2 = GCF of 1 over GCF of 2
🗑
|
||||
| What does the ICRU do? | the International Commission of Radiologic Units and Measurements evaluate grid performance by two criteria; selectivity and contrast imporvement ability.
🗑
|
||||
| What does selectivity describe? | the ability of the grid to allow the primary radiation to reach the IR and prevent scatter
🗑
|
||||
| T\F: high lead content grids are more selective. | True
🗑
|
||||
| What is the "K" factor? | the contrast improvement ability which is a comparison of contrast of an image with a grid to that of an image without a grid
🗑
|
||||
| What are the typical ranges of the contrast improvement factor? | 1.5 an 3.5
🗑
|
||||
| When the "K" factor is increased, what is incrased as well? | Contrast
🗑
|
||||
| What can you do to avoid grid errors? | proper aligmnent between tube and grid
🗑
|
||||
| What does improper alignment of the tube and the grid cause? | cut off
🗑
|
||||
| What are some types of grid errors? | off level, off center, off focus, upside down, morie effect
🗑
|
||||
| What is Moire effect? | the grid lines must be running in the same direction as the movement of the laser beam that is scanning the imaging plate.
🗑
|
||||
| What is the Air-Gap technique? | places a space between the part and the grid. a 10" gap has the same effect as a 15:1 grid
🗑
|
||||
| What happens when the grid is upside down? | severe peripheral grid cut off will occur
🗑
|
||||
| What does it mean when the grid is off focused? | the gird has a specified distance as the focal range. if a distance of 44 SID is required and a 72" SID is used, the result will be grid cut off on the peripheral edges of the image
🗑
|
||||
| What does it mean when the grid is off center? | the CR is off center and the result is a decrease in exposure across the entire image.
🗑
|
||||
| What does it mean when the grid is off level? | when the tube is angled, an off level grid error occurs with a focused grid and it is the only positioning error possible with a parallel grid.
🗑
|
Review the information in the table. When you are ready to quiz yourself you can hide individual columns or the entire table. Then you can click on the empty cells to reveal the answer. Try to recall what will be displayed before clicking the empty cell.
To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Created by:
aimee291020
Popular Radiology sets