Final Answer:
The exposure factors of 200 mA, 0.25 s, 70 kVp, and a 12:1 grid will produce the shortest scale of contrast.
Step-by-step explanation:
The scale of contrast in radiography refers to the range of densities or shades of gray in an image. Short-scale contrast, also known as high contrast, results in an image with predominantly black and white tones and fewer shades of gray.
The factors influencing contrast include milliampere-seconds (mAs), kilovoltage peak (kVp), and the use of a grid. In this scenario, a higher mA (200 mA) and lower exposure time (0.25 s) contribute to increased radiation intensity. The higher kVp (70 kVp) influences the penetration of the X-rays. Additionally, the use of a 12:1 grid helps control scatter radiation.
Mathematically, the product of mA and exposure time (mAs) represents the quantity of radiation exposure. In this case, 200 mA multiplied by 0.25 s equals 50 mAs. The combination of higher mA, lower exposure time, and increased kVp contributes to a shorter scale of contrast, emphasizing the extremes of black and white in the radiographic image.
In summary, the given exposure factors (200 mA, 0.25 s, 70 kVp, 12:1 grid) collectively produce a high-contrast image with a short scale of contrast, enhancing the visibility of structural details with distinct black-and-white differentiation.