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Math 147
| Question | Answer |
|---|---|
| To maintain receptor exposure while increasing penetration, what technique should be used? | Increase kVp by 15% AND decrease mAs by a factor of 2 |
| You wish to halve receptor exposure while maintaining about the same number of photons. What would be the correct technique? | Decrease kVp by 15% (multiply by 0.85) |
| You want to double receptor exposure without increasing penetration. What technique should be used? | Multiply the mAs by 2 |
| How to decrease magnification? | Increase SID or Decrease OID |
| The technologist notices that the exposure is correct, but the image is grainy (quantum mottle). What new technique should be used? | decrease kVp by 15% AND increase mAs by a factor of 2 |
| To halve the exposure | Divide the mAs by 2 |
| Quantum Mottle (too few photons) | Increase mAs |
| Over-penetration (too high kVp) | Decrease kVp |
| SID= | SOD + OID |
| SOD = | SID - OID |
| OID = | SID - SOD |
| What if you don’t know the actual object size? | Use the distances instead |
| To maintain exposure when using a grid, we _____ the mAs! | Increase |
| Most Transmitted Photons & Fewer Small Angle Scattered Photons = | Less IR exposure |
| The remnant beam/exit radiation is made of | Most Transmitted Photons & Fewer Small Angle Scattered Photons |
| SID is | Image Size |
| SOD is | Actual Object Size |
| Grid Ratio Formula | Height of lead strip Divided by Width of interspace |
| A Higher Grid Ratio Means that | More Scatter was Absorbed |
| Grid Conversion Factor (GCF) Formula | mAs with grid Divided by mAs without grid |
| The GCF is used to _________ needed when using a specific grid ratio | Determine the new mAs |
| GCF of 1 = | None |
| GCF of 2 = | 5 : 1 |
| GCF of 3 = | 6 :1 |
| GCF of 4 = | 8 : 1 |
| GCF of 5 = | 10:1 & 12:1 |
| GCF of 6 = | 16 : 1 |
| X-rays are attenuated exponentially and generally reduced by approximately 50% for ___________ | Each 4 to 5 cm of tissue thickness |
| For every change of 4 to 5 cm | Adjust the mAs by a factor of 2 |
| kVp rule = | +2 kVp for each cm |
| 15% kVp is used to double receptor exposure ________ | When part thickness remains the same |
| Small changes (in beam quality) = | Appropriate compensation for thickness |
| Large changes (in beam quality) | Scatter Production, Subject Contrast, and potentially the need for a Grid |
| If you dont have a grid, your GCF is | 1 |
Created by:
user-2016295