Which parameter is directly proportional to the exposure delivered to the patient?

The parameter that is directly proportional to the exposure delivered to the patient is the milliampere (mA). When mA is increased, it results in a higher quantity of x-ray photons being produced during a fluoroscopy or radiographic exposure. This increase in photon production leads to a larger dose being delivered to the patient.

Moreover, mA directly influences the intensity of the x-ray beam. Therefore, by manipulating this setting, radiologic technologists and operators can effectively control the amount of radiation the patient receives during the procedure.

Other parameters, while important in radiologic procedures, do not have the same direct relationship to patient exposure. For instance, kilovoltage peak (kVp) affects the energy and penetrating power of the x-rays rather than the quantity directly. The thickness of the filter influences the quality of the beam by removing low-energy photons, thus impacting patient exposure less directly. Lastly, the target to panel distance will affect the exposure in terms of beam dispersion and intensity loss due to the inverse square law, but again, it is not as directly linked to exposure as mA is.