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1. Diagnostic Imaging > 6. Grid Cutt-off > Flashcards

6. Grid Cutt-off Flashcards

1
Q

What type of grid is best in mobile/portable work?

A

Linear Parallel

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2
Q

What are the 4 grid rules regarding the grid errors (off center, off level, off focus, and upside down) for crossed grids?

A
  1. Can center anywhere on the grid
  2. You cannot tilt/angle the grid or tube
  3. The longer FGD the better, especially for larger field size
  4. Being upside down is not an issue
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3
Q

What are the 4 grid rules regarding the grid errors; (off center, off level, off focus, and upside down) for linear parallel grids?

A
  1. Center anywhere on grid with a small field size
  2. Must angle with the grid lines
  3. The longer FGD the better, especially for larger field size
  4. Being upside down is not an issue
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4
Q

What are the four grid errors?

A
  1. off-center
  2. off level
  3. off focus
  4. upside down
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5
Q

What are the 4 grid rules regarding the grid errors; (off center, off level, off focus, and upside down) for linear focused grids?

A
  1. Have to be centered anywhere on the line otherwise off-Axis/Lateral decentering will occur and the divergent beam will not line up with the angle of the lead strips
  2. Angle WITH the grid lines otherwise complete grid cutoff
  3. For the divergent beam to line up with the angled grid strips properly we need to be at the appropriate SID
  4. Severe grid cut-off wil occur if upside down
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6
Q

What is the difference between partial and complete cut-off?

A
  1. Complete cut-off: Effects the entire image
  2. Partial cut-off: Cut-off only occurred on one half/side/peripheries
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7
Q

With a higher grid ratio, will there be more or less negative effects with grid errors?

A

More negative effects

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8
Q

What does off center mean?

A

CR is not centered at the correct spot/line

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9
Q

What does off-level mean?

A

CR is angled against the grid lines

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10
Q

What does off focus mean?

A

Grid type and SID do not match

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11
Q

When do combination grid errors usually occur?

A

Mobile radiography

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12
Q

What does a combination error mean?

A

The CR is Off-Center & off-focused

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13
Q

With a linear focused grid, where do we see grid cut off when using too high of an SID and being off centered?

A

See the grid cut off on the side we centered on

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14
Q

With a linear focused grid, where do we see grid cut off when using too low of an SID and being off centered?

A

See the grid cut off on the side we did NOT center on

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15
Q

What technology now days is used to get rid of grid lines?

A

Grid suppression software

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16
Q

What are the two types of moving grids? Define them.

A
  1. Reciprocating: Moves side to side
  2. Oscillating: Moves in circular fashion
16
Q

What is the air gap technique?

A

-Alternative to using a grid
-Based on increasing the OID to decrease scatter

17
Q

What are the benefits of using the air gap technique?

A

Less patient exposure (we aren’t using grid, so we don’t need to increase dose)

18
Q

What are the cons of the air gap technique?

A

More magnification

19
Q

How do you fix magnification when using the air gap technique?

A

When you increase OID by 2.54 cm (1inch), increase SID by 30 cm (1ft)

20
Q

Should you use a higher or lower grid ration when using a higher kVp?

A

Higher

21
Q

What are crossed focused grids?

A

-Two linear focused grid and turning one 90 degrees and CR is centered on the middle dot
-SGD and x ray beam/CR (perpendicular) never changes

22
Q

Can you angle the grid or tube with a crossed focused grid?

A

No

23
Q

When are crossed focused grids used?

A

Used in angiography, cardiology (Biplane radiography)

24
Q

How do crossed focused grids clean up scatter?

A

Cleans up scatter in all directions by matching the angle of the photons

25
Q

What is a QA and QC Program?

A

Grids have to fall under this program; ensures that grids are in the proper position and the detent locks are where they should be

1. Diagnostic Imaging (17 decks)

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