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Ch 18 RAD 170
Grids
| Question | Answer |
|---|---|
| The purpose of a grid is to improve radiographic _____ in an image. | contrast (contrast will be increased) |
| The use of a grid will require an _______in exposure factors to maintain adequate density. | increase |
| Grids are contructed with ____ ____ placed vertically or slanted with radiolucent interspacing. | lead strips |
| ______ ____ have grid lines that are slanted so that they lie almost parallel with the diverging remnent radiation. | Focused grids |
| _____ of the grid during the exposure eliminates the grid lines on the image. | Movement |
| _____ _____, _______, and ____ ____ are intrinsic structural factors for grids. | grid ratio, frequency, focal range |
| As a general rule, a grid is empoyed when: | body part thickness exceeds 10 cm or kVp is above 60 |
| The first gird was made in 1913 by American radiologist ____ _____. | Gustav Bucky |
| ____ ____ is the ratio of the height of the lead strip to the width of the interspacing. | Grid ratio |
| The ____ the grid ratio, the more exposure required. | higher |
| A ____ is a series of radiopaque strips which alternate with radiolucent interspace strips. | grid |
| ____ _____ describes how well the grid will differentiate primary from secondary radiation. | Grid selectivity |
| What is the grid radio when the lead strips are 3.2 mm high and seperated by 0.2 mm? | grid ratio=h/d gr=16 |
| List the grid ratios and GCF: | 5:1 - 2 6:1 - 3 8:1 - 4 12:1 - 5 16:1 - 6 |
| When changing from one grid ratio to another, the following formula should be used: | mAs1/mAs2=GCF1/GCF2 |
| An increase in technique will ___ pt dose. | increase |
| A decrease in thickness will _____ scatter. | decrease |
| An increase in collimation will ____ scatter. | decrease |
| A lower Z# will have ____ scatter. | increased |
| How is the focused grid designed? | The lines are vertically slanted |
| How does the focused grid work? | The convergence line should be lined up so the divergence of the beam matches the lead strips. |
| ____ _____ is the number of lead strips per inch or cm. | Grid frequency |
| ___ ____ is the optimum range of distance from the tube to the grid | Focal range(SID) |
| As lead content _____, removal of scatter increases and therefore, contrast increases. | increases |
| Lead content is measured in _____. | grams/cm cubed |
| _____ grids should be angled along the long axis of the grid. | Linear |
| If the primary beam is angled into the lead, this will result in ___ ____. | grid cutoff |
| _____ ____ ____, ____ and ___ ____ are characteristics related to the use of grids. | contrast improvement factor, selectivity, bucky factor |
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