What causes quantum noise in radiographic images?

Quantum noise in radiographic images is primarily caused by the insufficient number of photons reaching the image receptor. When the number of incoming photons is low, there can be fluctuations in the amount of radiation detected in different areas of the image. This results in random variations in opacity, which manifests as noise on the radiograph—contributing to a grainy or mottled appearance. Since each image is formed by counting the individual photons, having too few photons can disproportionately affect the signal-to-noise ratio and lead to diminished image quality.

In contrast to this, aspects like excessive radiation exposure can enhance the overall brightness and reduce noise, while inadequate filtration and signal interference usually do not pertain directly to quantum noise but rather to image clarity or other types of artifacts. Therefore, the key factor behind quantum noise relates to the quantity of photons hitting the detector, making the accurate number crucial for high-quality radiographic imaging.