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# Ch 4

### Photographic Properties

Question | Answer |
---|---|

Photographic properties effect | Visbility, Density, Contrast |

Geometric Properties Effect | Sharpness, Recorded Detail, Distortion |

Radiographic Density | The overall blackness produced on the image after processing |

Controlling factor of Density | mAs |

Influencing factors of Density | kVp, Distance, Grids, Film-screen speed, collimation, anatomic part, anode heel effect, filtration, processing |

mAs= | Quantity |

kVp= | Quality |

The Law of Reciprocity | mA x s = mAs (200mA @ .10s = 20 mAs) |

The minimal change needed to correct density errors is determined by | multiplying or dividing mAs by 2. |

When greater change in mAs is needed.. | multiply or divide by 4, 8, etc |

___ kVp ___ Quantity of radiation striking the IR and ___ density. | Increases, increases, increases |

Increasing kVp by 15% will ___ density (math) | Double; __kVp x 1.15 = end kVp |

Decreasing kVp by 15% will ___ density (math) | Cut in half; ___kVp x .85 = end kVp |

To MAINTAIN density when kVp increases by 15% | Divide mAs by 2 kVp x 1.15 |

To MAINTAIN density when kVp decreases by 15% | Multiply mAs by 2 kVp x .85 |

To reduce patient dose ___ kVp ___ mAs | Increase; decrease |

As SID increase, | the xray bream intensity is spread over a larger area, this decreases the overall intensity of the xray beam raching the IR |

Inverse Square Law | I1/I2=SID2(squared)/SID1(squared) |

Density Maintenance Formula | mAs1/mAs2=SID1(squared)/SID2(squared) |

Increasing SID needs ___ mAs | More |

Grids | Grids absorb the scatter radiation exiting the patient; Limiting the amount striking the IR and improves image quality; they also absorb some of the transmitted radiaion exiting the pt and reduce the amount of density produced on the radiograph |

Grids are ___ for pt ___ for film | Bad; good The more efficient a grid absorbs scatter, the greater the increase in mAs is required |

Grid Conversion Factor | mAs1/mAs2=GCF1/GCF2 |

Grid Conversion FactorS | No grid 1 5:1 2 6:1 3 8:1 4 12:1 5 16:1 6 |

Film Screen Speed | The greater the speed the greater the density; When the speed of the system changes; mAs should be changed |

Film Screen Speed Formula | mAs1/mAs2=RS2/RS1 |

Anatomic Part | Thickness of the anatomic part affects the amount of xray beam attenuation that occurs; thick-absorbs more (decreasing density) thin-absorbs less (increasing density) |

Anatomic Part Conversion | For each 4-5cms of thickness, increase mAs x2 |

The best for an anode heel effect is ____ SID and a ___ field size | Short, Large |

Anode Heel Effect | The intensity along the longitudial axis of the primpart xray beam varies; this variance is called AHE AHE is a decrease in the primary beam intensity on the anode side of the tube |

Tube Filtration Contributors | These variations are so slight that they would have very little effect on density |

Compensating Filters Contributors | Produce uniform densities; mAs must be increased to maintain overall density |

Film Processing Contributors | Variability in temp, chemisty and transporting can adversely affect density |

Digital Imaging | Changes in mAs kVp SID will alter the I of radiation reaching the IR; The relationship b/t mAs and density is not the same for DR; Quality of image is adversly affected; Techs use more exposure then needed; The data can be altered to correct error in |

Relationship to Density: mAs | Direct |

Relationship to Density: kVp | Direct |

Relationship to Density: SID | Inverse to the square of the SID |

Relationship to Density: Grids | Inverse |

Relationship to Density: Relative Speed | Direct |

Relationship to Density: Collimation | Indirect |

Relationship to Density: Bigger pt | Inverse |

Relationship to Density: Generator output | Direct |

Created by:
rachelbeatty4