What primary factor is altered to control contrast in radiography?

In radiography, control of image contrast primarily involves adjusting the kilovoltage peak (kVp). The kVp setting determines the energy level of the X-ray beam and affects the penetrating power of the radiation. Higher kVp values increase the amount of scatter radiation and create a wider range of densities on the film or detector, leading to lower contrast. Conversely, lower kVp values produce less penetrating power, resulting in higher contrast due to a narrower range of densities.

By altering kVp, radiographers can manipulate the image to highlight specific anatomical details or pathologies as required. Therefore, kVp is the primary factor influencing image contrast during radiographic imaging. Adjusting this parameter allows for better visualization of structures based on the desired quality of the image.

While other factors, such as milliamperes-seconds (mAs), source-to-image distance (SID), and object-to-image distance (OID), can influence exposure and image quality, they do not have the same direct impact on contrast as kVp does.