| A | B |
|---|
| Ratio | A comparison of two numbers (e.g., 1:2). |
| Proportion | Two ratios that are equal (used in exposure adjustments). |
| Direct Proportion | When one value increases, the other increases (e.g., mAs and exposure). |
| Inverse Proportion | When one value increases, the other decreases (e.g., SID and intensity, via inverse square law). |
| Exponent | A number that shows repeated multiplication (important for square/square root in formulas). |
| Square Root (√) | Used in formulas for geometric calculations (e.g., magnification factor). |
| mA (Milliamperes) | Tube current; number of electrons flowing per second. |
| Time (Seconds) | Length of exposure. |
| mAs (Milliampere-seconds) | Product of mA × time; controls total radiation quantity. |
| kVp (Kilovolt Peak) | Tube potential; controls beam penetration (quality). |
| SID (Source-to-Image Distance) | Distance between tube and receptor. |
| OID (Object-to-Image Distance) | Distance between patient and receptor. |
| Inverse Square Law | Intensity of radiation is inversely proportional to the square of the distance. Formula: 𝐼 1 / 𝐼 2 = ( 𝐷 2 2 / 𝐷 1 2 ) I 1 /I 2 =(D 2 2 /D 1 2 ) |
| Density Maintenance Formula (mAs formula) | Used when changing SID but wanting to maintain image density. Formula: 𝑚 𝐴 𝑠 1 / 𝑚 𝐴 𝑠 2 = ( 𝑆 𝐼 𝐷 1 2 / 𝑆 𝐼 𝐷 2 2 ) mAs 1 /mAs 2 =(SID 1 2 /SID 2 2 ) |
| 15% Rule | Increasing kVp by 15% ≈ doubling density (mAs), and vice versa. |
| Exposure Indicator (EI/ S-number) | Numeric value showing whether the image was underexposed, correctly exposed, or overexposed. |
| Gray (Gy) | Unit of absorbed dose. |
| Sievert (Sv) | Unit of dose equivalent (biological effect). |
| Air Kerma | Measure of radiation in air (exposure). |
| Half-Value Layer (HVL) | Thickness of a material that reduces beam intensity by half. |
