Grids Flashcards
no grid
1
5:1
2
6:1
3
8:1
4
8:1
4
grades are primarily used to improve image contrast, especially one radio graphing any part that measures…….
10 cm or greater
what is the grid composed of
lead strips that absorbs secondary radiation that would otherwise fog the image
grid ratio
grid ratio = height of lead strips/ distance between strips
* the higher the grid ratio= cleans up more scatter
10:1
5
12:1
5
16:1
6
if the height of the led strips is 1.6 mm in the distance between the led strips is 0.1 mm the ratio of the grid is?
1.6/0.1 = 16
grid ratio 16:1
* DONT FORGET :1
A grid has led strips of 5 mm high, 0.5 mm apart and 1.6 mm wide. What is the current ratio?
5/0.5 = 5
5:1 grid
* distract is the 1.6 mm wide!!!
if your answer doesn’t come out to a normal grid ratio, you used the wrong factor!!!
what is the grid conversion formula
mAs1/ mAs2= GCF1/GCF2
Off level grid errors
occurs when the tube is angled across the long axis of the grid strips.
-can be a result of improper tube or grid positioning
Off center grid error
central ray of the beam is off center from the center of a focused grid
- overall loss of RE across the entire image
Off focus grid error
happens when a grid is used at a distance other than that specified focal range
Upside down grid error
if the grid is used upside down it will result in serve grid cut off
The morie effect
happens more in mobile x ray or cross table hips
- happens to CR cassettes
- a wavy artifact caused by grid lines running parallel to the laser scanning motion
a grid should be employed when
- a body part is over 10 cm
- Kvp is above 60
Grids improve
contrast
Higher grid ratio allows ______ scatter radiation to pass through
less
interspace material options for grids
- carbon fiber
- aluminum
- plastic
NEVER LEAD
what is a stationary grid
used for table top x rays or mobile radiography
- doesn’t move during exposure
moving grid
table or wall bucky
the grid moves during exposure
focused grid
the SID has to be correct
only used at a certain SID
grid cut off
an unwanted absorption of primary x-rays we want the primary beam to pass through the grid to the IR. Ideally, only the scatter radiation is absorbed
- most often seen the parallel grids
air gap technique is an alternative method to using _____
grids
image receptor is placed 10-15 cm from the patient.
a large portion of scattered x rays will not interact with the IR
fluoro uses
lower grids
