Which factor controls the penetrating power of an X-ray beam?

The penetrating power of an X-ray beam is primarily controlled by the kilovolt peak (kVp) setting. kVp determines the energy level of the X-ray photons generated during the exposure process. Higher kVp values result in X-rays with greater energy, which enables them to penetrate denser materials and tissues more effectively. This is particularly important in diagnostic imaging, where varying thicknesses and densities of body parts need to be imaged adequately.

In contrast, mAs (which refers to the product of current and time) affects the quantity or number of X-ray photons produced but does not influence their energy and penetrating ability. Exposure time, while also relevant for determining the total amount of radiation the detector receives, does not impact the energy of the X-ray photons themselves. Film type relates more to the sensitivity and contrast of the resultant image rather than the inherent properties of the X-ray beam. Thus, kVp is the key factor in controlling the penetrating power of an X-ray beam.