Grid Flashcards

1
Q

Why are Grids needed?

  • As the ___ interacts with the patient’s ___, ___ radiation is created.
  • Remember ___ Interaction!
  • ___ radiation has ___ energy level than the primary beam so it will produce a “___” on the x-ray film.
  • Fog = unwanted ___ on the radiographic image. This will make the film look ___.
A

Why are Grids needed?

  • As the primary beam interacts with the patient’s tissue, scatter radiation is created.
  • Remember Compton Interaction!
  • Scatter radiation has lower energy level than the primary beam so it will produce a “fog” on the x-ray film.
  • Fog = unwanted density on the radiographic image. This will make the film look gray.
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2
Q

Gustav Bucky

  • Inventor of the ___– 1913
  • Function is to: “___” or “clean up” the ___ before reaching the ___.
A

Gustav Bucky

  • Inventor of the grid– 1913
  • Function is to: “stop” or “clean up” the scatter radiation before reaching the IR.
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3
Q

Purpose of the Grid

  • Improves radiographic ___ (or gray scale- eliminates ugly gray) in the image by:
  • ____ scattered radiation before it reaches the image receptor

NOTE: Does not save ___ to patient!

A

Purpose of the Grid

  • Improves radiographic contrast (or gray scale- eliminates ugly gray) in the image by:
  • Absorbs scattered radiation before it reaches the image receptor

NOTE: Does not save radiation dosage to patient!

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4
Q

Where are grids placed?

Grids are placed between the ___ and the ___

  • When to use a grid:
  • If the body part is over ___ and if ___ kVp or higher
A

Where are grids placed?

Grids are placed between the patient and the IR

  • When to use a grid:
  • If the body part is over 10 cm and if > 60 kVp or higher
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5
Q

Basic Grid Construction

  • ___ lead strips (can see on film) - lead strips will stop the ___
  • • Separated by ___ (can’t see on film)interspace material

– Typically ___ or ___
- ___ pass through the interspace

A

Basic Grid Construction

  • Radiopaque lead strips (can see on film) - lead strips will stop the scatter radiation
  • • Separated by radiolucent (can’t see on film) interspace material

– Typically aluminum or plastic
-Primary beam pass through the interspace

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6
Q

Grid Dimensions

• 1.) GRID RATIO

• h = the ___ of the ___ strips
• D = the ___ between the strips
- the ___ of the interspace material
• ___ or ___ material

A

Grid Dimensions

• 1.) GRID RATIO

• h = the height of the radiopaque strips
• D = the distance between the strips
- the thickness of the interspace material
Aluminum or plastic material

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7
Q

Grid Ratio

  • ___ of lead strips divided by ___ between the lead strips

– Grid ratio = __/__

A

Grid Ratio

  • Height of lead strips divided by distance between the lead strips

– Grid ratio = h/D

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8
Q

Grid Ratio Example

  • If a grid has an interspace of 0.5mm, the thickness of the lead strips is .025mm and lead strips that are 3mm high, what is it’s grid ratio?

● GR = __mm/__mm
● GR = __:__

A

Grid Ratio Example

  • If a grid has an interspace of 0.5mm, the thickness of the lead strips is .025mm and lead strips that are 3mm high, what is it’s grid ratio?

● GR = 3mm/0.5mm
● GR = 6:1

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9
Q

Why is Grid Ratio important?

  • Higher grid ratio = More ___ in ___
  • Typical grid ratio range is ___ to ___

higher ratios usually used with bariatric patients - lower ratios are usually used for extremities due to less body thickness

A

Why is Grid Ratio important?

  • Higher grid ratio = More efficient in removing scatter
  • Typical grid ratio range is 5:1 to 16:1

higher ratios usually used with bariatric patients - lower ratios are usually used for extremities due to less body thickness

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10
Q

2.) Grid Frequency

  • The number of lead strips per ___ or ___

● Frequency range
– ___-___ lines/in
– ___-___ lines/cm
Most Common: ___-___ lines/inch

● Typically higher frequency grids have ___ lead strips

Benefits: adding more lead removes more scatter

A

2.) Grid Frequency

  • The number of lead strips per inch or cm

● Frequency range
60-200 lines/in
25-80 lines/cm
Most Common: 85-103 lines/inch

● Typically higher frequency grids have thinner lead strips

Benefits: adding more lead removes more scatter

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11
Q

Digital Imaging Systems

● Very high-frequency grids
– ___ lines/in

  • ___ lines/cm

● Recommended for use with ___ systems
- Minimizes ___ appearance

A

Digital Imaging Systems

● Very high-frequency grids
103-200 lines/in

  • 41-80 lines/cm

● Recommended for use with digital systems
- Minimizes grid line appearance

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12
Q

In General…

● Lead content is greater in a grid with a ___ ratio and ___ frequency
● As ___ content increases, ___ increases and therefore ___ increases

A

In General…

● Lead content is greater in a grid with a high ratio and low frequency
● As lead content increases, removal of scatter increases and therefore contrast increases

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13
Q

Disadvantages of using a Grid

● ___ radiation dose to the patient when changing from screen cassette (___):

–Higher ratio = ___ (more lead)
higher ___ to the patient

A

Disadvantages of using a Grid

Higher radiation dose to the patient when changing from screen cassette (tabletop):

–Higher ratio = more radiation (more lead)
higher radiation dose to the patient

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14
Q

Rule of Thumb:

  • Non-Grid to Grid

–___ mAs by ___
3 mAs at 55 kVp for finger non-grid but changing to Grid
___ x/ ___ = ___ mAs

● Grid to Non-Grid
–___mAs by ___
160 mAs at 70 kVp for KUB using a Grid but change to non- grid
___ x/ ___ = ___ mAs for Non-Grid

A

Rule of Thumb:

  • Non-Grid to Grid

multiply mAs by 4
3 mAs at 55 kVp for finger non-grid but changing to Grid
3 x 4 = 12 mAs

● Grid to Non-Grid
Divide mAs by 4
160 mAs at 70 kVp for KUB using a Grid but change to non- grid
160/4 = 40 mAs for Non-Grid

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15
Q

Potter-Bucky Diaphragm

  • Dr. ____ made improvements to the use of grids
  • Realigned lead strips to ___
  • ___ grid during ___ to make lines ___ on image
A

Potter-Bucky Diaphragm

  • Dr. Hollis Potter made improvements to the use of grids
  • Realigned lead strips to run in one direction
  • Moved grid during exposure to make lines invisible on image
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16
Q

Stationary Grid Vs. Moving Grid

  • Examples of a moving grid:
    1. ___ Grid – a ___-driven grid which moves the grid “___ motion” during the exposure. (Advantage: didn’t allow human eye to see lead lines on image)
    2. ___ Grid – a ___-like device in the ___ of the bucky tray. A strong ___ pulls the grid in a ___ fashion around the grid frame.
A

Stationary Grid Vs. Moving Grid

  • Examples of a moving grid:
    1. Reciprocating Grid – a motor-driven grid which moves the grid “back and forth motion” during the exposure. (Advantage: didn’t allow human eye to see lead lines on image)
    2. Oscillating Grid – a spring-like device in the corners of the bucky tray. A strong electromagnet pulls the grid in a circular fashion around the grid frame.
17
Q

Grid Patterns

● ___ or ___ (Dr. ___)
● ___Grid

● ___(Parallel or Focused)

A

Grid Patterns

Criss-cross or cross-hatched (Dr. Bucky)
Rhombic Grid

Linear (Parallel or Focused)

18
Q

Criss-Cross or Cross-Hatched

● Two linear grids ___ at ___ to each other.

● Advantage: Best ___

● Disadvantage:

  • ___ must be centered ___ to ___ at all times (no ___)
  • Grid must remain ___
  • ___ to the patient

Linear grid and cross-hatch= best cleanup

A

Criss-Cross or Cross-Hatched

● Two linear grids superimposed at right angles to each other.

● Advantage: Best grid clean up

● Disadvantage:

  • CR must be centered perpendicular to grid at all times (no CR angulation)
  • Grid must remain flat
  • Higher radiation dose to the patient

Linear grid and cross-hatch= best cleanup

19
Q

Rhombic Grid:

● Lead strips are placed ___ degrees to each other. (___ shape)
● Allowed for ___ the ___ in ___
– But only ___ degree angles

A

Rhombic Grid:

● Lead strips are placed 45 degrees to each other. (diamond shape)
● Allowed for angling the tube in any direction
– But only 5 degree angles

20
Q

Linear Grid

● Lead strips run the ___ of ___

● ___ angle CR ___ the lead strips

● Allows ___ to be ___ along the ___ of grid without obtaining “___”

A

Linear Grid

● Lead strips run the length of cassette

Can not angle CR against the lead strips

● Allows primary beam to be angled along the long axis of grid without obtaining “cut-off”

21
Q

Two types of linear grids

  • ___ - Lead strips are ___ to each other (grids can be used at longer SID, 72” before grid cutoff)
  • ___ - Lead strips match the ___ ////||||\\ (everything points to the center of the grid, ex 40”)
A

Two types of linear grids

  • Parallel - Lead strips are || to each other (grids can be used at longer SID, 72” before grid cutoff)
  • Focused - Lead strips match the divergence of beam ////||||\\ (everything points to the center of the grid, ex 40” )
22
Q

Parallel Linear Grids

● All lead strips are ___

● Absorb ___ of primary beam
– Resulting in ___

● Best used at ___

A

Parallel Linear Grids

● All lead strips are parallel to one another

● Absorb a large amount of primary beam
– Resulting in some cut-off

● Best used at long SID

23
Q

Parallel Grid:

● Cons:
– Can not be used at ___

– WHY???

A

Parallel Grid:

● Cons:
– Can not be used at short SID

– WHY???

because parallel grid doesn’t match the divergent line in CR

24
Q

Focused Linear Grids

  • Lead strips are angled to ___
  • ___ lead strips ___ the center of the grid
  • Canting of the grid /////////||||||||\\\\\\
  • Convergence Line= ___ from the ___ of the grid to the ___ of the lead strips ___ the grid.
A

Focused Linear Grids

  • Lead strips are angled to match divergence of beam
  • Outside lead strips tilt toward the center of the grid
  • Canting of the grid /////////||||||||\\\\\\
  • Convergence Line= distance from the face of the grid to the point of convergence of the lead strips above the grid.
25
_Focused Linear Grids_ \_\_\_ or \_\_\_: distance that which to use the grid. * ___ positioning latitude - \_\_\_results in peripheral cut-off at the sides of the image - Only useful at \_\_\_ - Higher ratio grids require \_\_\_ ● Cons: – More ___ to purchase –Must be careful to use ___ at the correct \_\_\_
_Focused Linear Grids_ **Grid Radius** or **Focal Range**: distance that which to use the grid. * **Narrow** positioning latitude - **Improper centering** results in peripheral cut-off at the sides of the image - Only useful at **preset SID distance** - Higher ratio grids require **careful alignment with tube** ● Cons: – More **expensive** to purchase –Must be careful to use **grid** at the correct **SID**
26
_Grid Latitude:_ ● “room" or ___ of ___ when using a grid - Grid Radius was 45-72” SID ... You place the grid at 43” SID. Was you image good? Depends of the grid’s \_\_\_\_. With a ___ ratio, \_\_\_. With a ___ ratio, not as good.
_Grid Latitude:_ ● “room" or **margin** of **error** when using a grid - Grid Radius was 45-72” SID ... You place the grid at 43” SID. Was you image good? Depends of the grid’s **latitude**. With a **high** ratio, **good**. With a **low** ratio, not as good.
27
_Grid Cut Off_ * “Unwanted ___ of the primary beam.” * Occurs when the ___ of the grid are ___ the \_\_\_. * Will cause the image to be \_\_\_.
_Grid Cut Off_ * “Unwanted **attenuation** of the primary beam.” * Occurs when the **lead lines** of the grid are **absorbing** the **primary beam**. * Will cause the image to be **too light**.
28
_Common Causes of Grid Cut Off:_ ● Angle... (detent) ● Lateral... (lines of grid no longer matching primary beam) ● Angle... (lopsided IR) ● Wrong... ● Using... (focus grid) ● Moire... (digital systems)
_Common Causes of Grid Cut Off:_ ● Angle **CR against the grid lines** (detent) ● Lateral **decentering of the grid** (lines of grid no longer matching primary beam) ● Angle **grid against the CR** (lopsided IR) ● Wrong **distance with either parallel or focus grids** ● Using **the grid upside down** (focus grid) ● Moire **effect (digital systems)**
29
_Off Center Grid: Lateral decentering_ ● Common problem with \_\_\_ ● You must make sure the ___ matches the ___ of the grid \_\_\_. ● Density will appear ___ to ___ on the image. –“center to the \_\_\_”
_Off Center Grid: Lateral decentering_ ● Common problem with **focus grids.** ● You must make sure the **divergence beam** matches the **canting** of the grid **strips.** ● Density will appear **dark to light** on the image. –“center to the **bucky tray**”
30
_Off-level Grid_ ● Common on \_\_\_. ● Grid not the ___ (not level) or ___ to the CR. ● Density will appear ___ to ___ on the ___ of the image.
_Off-level Grid_ ● Common on **portables**. ● Grid not the **same plane** (not level) or **perpendicular** to the CR. ● Density will appear **dark to light** on the **edges (sides)** of the image.
31
_Off-focus grid:_ ● Grid used ___ of the ___ SID range. ● Density will appear ___ on ___ of the image but correct density ___ of the image. ● What about a parallel grid used at a short SID? ___ in middle, ___ light
_Off-focus grid:_ ● Grid used **outside** of the **intended** SID range. ● Density will appear **lighter** on **each side** of the image but correct density **in the center** of the image. ● What about a parallel grid used at a short SID? **Dark** in middle, **both sides** light
32
_Upside down Grid_- ● Focus grid – lead strips are now ___ the ___ of the primary beam. ● Density will be ___ in the middle of the image but ___ on the sides. ● ___ change when comparing to using a ___ outside of the \_\_\_.
_Upside down Grid_- ● Focus grid – lead strips are now **opposing** the **divergence** of the primary beam. ● Density will be **okay** in the middle of the image but **light** on the sides. ● **More abrupt** change when comparing to using a **focus grid** outside of the **focus range**.
33
_Moire Effect_ ● ___ systems –When grid lines are \_\_\_to \_\_\_lines ● ___ grids can prevent this phenomenon
_Moire Effect_ ● **Digita**l systems –When grid lines are **parallel** to **scan** lines ● **High frequency** grids can prevent this phenomenon
34
35
_Grid lines can appear if:_ ● Pressure... ● Improper... ● Using... ● Grid was...
_Grid lines can appear if:_ ● Pressure **on the grid** ● Improper **centering of x-ray tube to grid** ● Using **a grid outside of the focal range** ● Grid was **not moving during the exposure**
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37
_Air Gap Grid:_ ● An ___ to the use of a grid. ● Method reduces ___ reaching the \_\_\_. ● Place the patient (part) \_\_\_cm or ___ away from the film. (\_\_\_ OID = ___ grid ) ● Scatter radiation leaving the patient’s body as a ___ of energy will interact with ___ in the \_\_\_. ● This technique will improve \_\_\_….BUT – \_\_\_ of the patient is created! Decreases ___ of the image
_Air Gap Grid:_ ● An **alternative** to the use of a grid. ● Method reduces **scatter radiation** reaching the **IR**. ● Place the patient (part) **10-15 cm** or **4-6”** away from the film. (**10”** OID = **15:1** grid ) ● Scatter radiation leaving the patient’s body as a **low level** of energy will interact with **particles** in the **air**. ● This technique will improve **contrast**….BUT – **Magnification** of the patient is created! Decreases **recorded detail** of the image