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Grids
H C Grids
| Question | Answer |
|---|---|
| are used to control scatter radiation | Grids |
| tools to decrease scatter | The grid, lower kVp ,Decreasing the field size, Decreasing the body part thickness |
| Grid was developed by | Gustav Bucky in 1913 |
| When you use a grid you ______ the dose to the patient which will _______the mAs | increase increase |
| The grid only allows x-rays through that are traveling in | straight lines |
| Grids clean up | scatter radiation |
| Grids consist of carefully fabricated sections of | radiopaque material (grid lines) alternating with sections of radiolucent material (interspace material) |
| Grid ratio | height of the grid/width of the interspace material |
| Moving grids aka | reciprocating aka oscillating grids |
| clean up scatter radiation better | High ratio grids |
| GRID FREQUENCY | Usually 60-110 lines per inch |
| Grids with high frequency show | less distinct grid lines |
| High frequency grids usually will also have | a higher grid ratio |
| The grid lines are made of | lead |
| The interspace material is made of | aluminum or plastic |
| Both the front and back covers of the grid are usually made of | aluminum |
| 60-80 grid lines per inch will have to be | shaken |
| Most grids have an improvement factor of between | 1.5 and 2.5 |
| many shades of gray | low contrast |
| black and white | high contrast |
| CONTRAST IMPROVEMENT FACTOR | K = Radiographic contrast with a grid/ Radiographic contrast without a grid |
| the amount of increase in radiographic technique needed because a Bucky is being used | BUCKY FACTOR |
| As the Bucky factor increases | the radiographic technique and patient dose increases |
| BUCKY FACTOR | = Patient dose with a grid/ Patient dose without a grid |
| Parallel grid | all the lead strips are parallel to each other |
| developed by Hollis Potter | Moving grid |
| more difficult to manufacture than parallel grids but there is no grid cutoff | Focused grid |
| this is the type used most | focused grid |
| Grid Cut Off | the grid line absorb to much photons because of the distance of the tube it to far or to close and causes cut off on the film |
| problems that cause grid cut off | Off level grid, Off center grid, Off focus grid ,Upside down grid |
| is due to the grid being backwards and the film is very dark center and light sides | upside down grid |
| AIR GAP TECHNIQUE | does not use a grid |
| A gap between the body part and the film | AIR GAP TECHNIQUE |
| Improves image contrast | Air Gap Technique |
| Put grid lines crosswise and lengthwise | Crossed grid |