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Radiographic Grids
Control of Scatter Radiation... Radiographic Grids
| Question | Answer |
|---|---|
| What is the main reason for using a grid? | Improve Contrast, Reduce Scatter |
| What is the most important grid characteristic? | Grid ratio |
| Interspace material is... | radiolucent |
| _____ require sensors in the bucky drawer to measure the size of the cassette. | Automatic shuttering |
| What photon interaction do we get scatter from? | Compton |
| When the bucky drawer locks are adjusted, sensors automatically measure ____ and restrict ______. | cassette size, primary beam |
| Sensors are located on the tube stand to monitor _____. | SID |
| Where do we place the grid? | between the patient & IR |
| Undesirable absorption is______. | grid cut off |
| Guarantee of patient protection, clearer images, more reliable, eliminate error, save set up time are all_______. | advantages of automatic collimation |
| Increasing the OID which allows more scatter to miss the film and scatter emitted in all directions is... | Air gap technique |
| Mostly used inn cervical/chest area and SID must increase to compensate for increase in OID is ________. | Air gap technique |
| The most commonly used grid is .... | focused moving grid |
| _____ can be used to restrict the primary radiation for conventional radiography. | lead rubber masking |
| For the most patient protection use... | high kV |
| Placing sheets of lead rubber dividers on table into position so they absorb unnecessary radiation will ____ of radiograph. | increase contrast |
| Better and least patient exposure use _____ | no grid |
| ____ reduce tissue volume and are helpful in controlling scatter. | compression device |
| What is the downside of using air gap? | increase magnification |
| With compression device by lowering the body part, there is corresponding ____ in scatter. | reduction |
| Grid ratio produce most density with a ____. | 5:1 grid |
| The most effective device for reducing scatter is a _____. | grid |
| Grid ratio produces the least density with _____. | 16:1 grid |
| The most important way to reduce scatter production is ____. | collimation |
| Who built the first stationary grid? | Gustave Bucky |
| Grid composed of parrallel strips of lead/plastic | stationary |
| The grid absorbs ____ of secondary/scattered radiation. | 90% |
| Disadvantage of stationary grids are the lead strips cast a thin white line on radiograph, exposure must be ____ bc of this. | increased |
| The most popular stationary grids vary from ___ to ___ lines per inch. | 60 to 80 |
| Which grid produces the longest scale of contrast? | 5:1 |
| What grid has lead strips parrallel to each other and thickness decreases as they move to the edge? | parrallel |
| The thickness of lead strips decreasing at the edge is to try and overcome primary _____. | grid cut off |
| When the primary beam is absorbed by the lead strips this is called ____. | cut off |
| Which grid produces the highest contrast? | 16:1 |
| Parrallel grids are used with techniques under ____ and with portable units. | 100 kVp |
| When using a grid with a 1 way angle you ____. | angle longitudinally |
| All sides of strips are centered toward a single centered point at predetermined distance (grid of 40" SID) | focused grid |
| When 2 linear grids are accidentally placed on top of each other | Moire Effect |
| Higher grid frequency = | maximum line invisibility |
| less than ___ should be scatter radiation | 25% |
| Stationary to moving will increase patient dose ___. | 15% |
| 2 stationary grids used on top of each other, each at right angles, can be parrallel or focused. | cross hatch grid |
| With a cross hatch grid the least amount of positioning lattitude the ___ grid ratio | higher |
| CR must be centered to both grids and perpendicular to film and cannot have any angle with ___. | cross hatch grids |
| Angiography, trans table lateral fro mylegraphy, and shoot thru lateral hips use | cross hatch grids |
| Who invented the moving grid? | Dr. Hollis Potter |
| Moving the grid perpendicular to the direction of lead strips made them ____ | invisible |
| Exposure starting before grid reaches full speed, exposure continuing afer grid travel slowed/stopped, uneven movements, tube focus not centered, and synchronism off is all... | common causes of grid lines |
| What are the 3 types of moving grids? | Single stroke, reciprocating, oscillating |
| What is the most commonly used moving grid? | reciprocating |
| The process of manufacturing a grid and inclining its lead lines to a fixed focusing distance | canting |
| Because of grid impurities, never accept a grid unless you inspect it with an ____ | industrial radiograph |
| 2 physical properties responsible for efficiency of a grid inn removing scatter | grid ratio/grid frequency |
| The number of lines per inch is ______ | grid frequency |
| Ratio of the height to the distace is | r = h/d |
| As you increase grid ratio you ___ contrast and ____ density | increase, decrease |
| The higher grid ratio the better will be ____ of scatter and ___ radiographic contrast. | clean up, higher |
| The angle of transmission in low ratio grid is ____ than in high ratio(meaning more scatter & primary can pass through a lower ratio grid) | greater |
| Most portable are | 8:1 |
| Most stationary are | 12:1 |
| When converting from non grid to grid, change is best made by adjusting _____ | kVp |
| In grid frequency, the thinner the strips and greater the chance of scatter rays passing through the more _____ | number of lead strips per inch |
| Higher grid frequency the more _____ in the grid | grid material |
| As grid frequency increases grid ratio must also _____ to maintain frequency and also ___ patient dose. | increase, increase |
| Less than _____ of density should be scatter | 25% |
| Contrast improvement factor is ____ for radiographs taken with the grid removed | 1 |
| Use of a moving grid instead of stationary will require ___ more radiation exposure | 15% |
| Most common grid frequency used in rad dept. is ___ per inch | 100 lines |
| Purpose of interspace material is to maintain ___ between strips of lead | precise seperation |
| What are the 2 most used interspace materials | aluminum , plastic fiber |
| May provide soem filtration of scattered x-rays, produces less visible grid lines, absorbs more primary beam requiring higher techniques | aluminum interspace material |
| Usually preferred over aluminum b/c reduces patient exposure | plastic fiber interspace material |
| Does not absorb moisture | nonhygroscopic |
| ____ is easier to form and roll into sheets of precise thickness than ____ | aluminum, fiber |
| Amount of secondary radiation (thickness, density) kilovoltage used, capacity of x-ray generator are all factor in _____ | grid selection |
| The ____ grid ratio the more position lattitude we have | lower |
| _____ is based on positioning lattitude along with other factors | grid selection |
| The ___ the grid ratio the less positioning lattitude | higher |
| Parrallel grids have more ___ than focused and cross hatch have no_____ | lattitude , lattitude |
| Grids should be used when the body part is atleast___ thick (some say ___) | 12cm (16cm) |
| If grid is not used properly, film will exhibit | grid cut off |
| ___ occurs b/c primary beam gets absorbed closer to outside edges. | primary cut off in a parrallel grid |
| To try and overcome ____ in a parrallel grid we make lead strips thinner as they move away from center | primary cut off |
| When the SID is greater or lesser than the focusing distance and shows proper density in the center of radiograph and cut off on lateral edges | off distance cut off in a focused grid |
| In a focused grid when CR is not centered (area below CR will have density & rest white) and the grid is not parrallel with plane of the tube you will have ____ | off center, off level cut off |
| Occurs from stupidity and grid upside down | tube side vs film side |
Created by:
bmiller1226
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