Final answer:
The exposure factors of 400 mA, 70 ms, and 78 kV were used to produce a radiographic density and contrast. A similar radiograph can be produced using higher mA and kV values and a lower exposure time.
Step-by-step explanation:
The exposure factors of 400 mA, 70 ms, and 78 kV were used to produce a particular radiographic density and contrast. A similar radiograph can be produced using 500 mA, 90 kV, and 28 ms.
The radiographic density and contrast depend on the combination of exposure factors. In this case, the increase in mA and kV and the decrease in exposure time (ms) help produce a similar radiographic image. The increase in mA increases the number of x-rays produced, resulting in higher density. The increase in kV increases the energy of the x-rays, leading to better penetration and contrast. The decrease in exposure time helps reduce the overall exposure but still maintains the desired image quality.