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RAD170 Chapter 38
Math Formulas
Question | Answer |
---|---|
How is the variable kVp theory used to maintain exposure with varying part thickness? | increase 2 kVp for each 1 cm increase in part size |
How is the fixed kVp theory used to maintain exposure with varying part thickness? | 2x or 1/2 mAs for each 4-5 cm change in part size |
What is the 15% rule? | To maintain exposure: Increase kVp 15% & 1/2 mAs Decrease kVp 15% & 2x mAs |
What formula is used to maintain exposure at varying distances? | Exposure Maintenance Formula: mAs1/mAs2=d1^2/d2^2 |
How do you calculate grid ratio? | height of lead strips/distance between them |
What are the grid conversion factors? | no grid=1 5:1=2 6:1=3 8:1=4 12:1=5 16:1=6 |
What is the formula for grid conversions? | mAs1/mAs2=GCF1/GCF2 |
What is the formula for relative speeed conversions? | mAs1/mAs2=RS2/RS1 |
What is the inverse square law formula? | I1d1^2=I2d2^2 |
What are the generator factors? | single phase=1 3 phase 6 pulse=1.35 3 phase 12 pulse=1.41 high frequency=1.45 |
What is the formula to calculate heat units? | HU=mAs x kVp x generator factor |
How do you calculate magnification factor? | SID/SOD |
How do you calculate object size? | image size/magnification factor |