What is the likelihood of coherent scatter occurring?

Coherent scatter, also known as classical or unmodified scatter, occurs when low-energy photons interact with matter. This interaction results in the scattering of the photon without a loss of energy, as it simply changes direction. In the context of diagnostic imaging and fluoroscopy, coherent scatter primarily takes place when X-rays interact with atoms in the tissues being examined.

The likelihood of coherent scatter occurring is relatively low compared to other types of interactions, such as photoelectric absorption and Compton scatter, which are more common in medical imaging. The percentage option chosen reflects a typical value supported by various studies: around 5% of the interactions can be attributed to coherent scatter in diagnostic X-ray procedures.

This proportion is significant enough to consider during imaging, as coherent scatter can contribute to image noise and reduce overall image quality. However, it is not predominant in terms of the total photon interactions within diagnostic imaging contexts, which is why the selected likelihood percentage is more realistic than higher percentages listed in the other choices.