Which of the following is directly proportional to the dose delivered to the patient?

The choice indicating that mAs is directly proportional to the dose delivered to the patient is correct. In radiography, mAs stands for milliampere-seconds, which is a measure of the quantity of radiation produced during an exposure. Increasing the mAs value results in a higher tube current and longer exposure time, thereby increasing the overall radiation dose that the patient receives. A higher mAs also enhances the image quality by improving the signal-to-noise ratio, making it essential to balance dose and image quality effectively.

In contrast, while SID (Source to Image Distance) and kVp (kilovolt peak) can influence the image quality and the overall radiation exposure, they do not have a direct linear relationship with the dose delivered to the patient in the same way that mAs does. Specifically, increasing SID typically decreases the dose due to the inverse square law, whereas increasing kVp enhances the penetration power of the x-rays but does not directly correlate with increased dose. The percentage of characteristic radiation is a more complex concept and doesn't directly relate to the amount of dose received by the patient like mAs does. Thus, mAs is the parameter that most directly correlates with radiation dose, making it the correct choice.