What happens to signal intensity when part thickness increases without a corresponding increase in radiographic technique?

When part thickness increases without a corresponding increase in radiographic technique, the result is a decreased signal intensity and increased Compton interactions. This occurs because a thicker part tends to absorb more of the x-ray photons passing through it.

As the thickness of the material increases, there are more potential interactions for the photons, as they have a greater distance to travel through the tissue. This results in a higher likelihood of interactions occurring, particularly Compton scattering, where x-ray photons collide with electrons in the matter, losing energy and scattering in different directions.

As more x-ray photons undergo these interactions, fewer photons reach the image receptor. This leads to decreased signal intensity, resulting in a less clear image, often with increased noise. In clinical practice, if the technique is not adjusted to compensate for the increased thickness — such as by increasing the kilovoltage (kV) or milliampere-seconds (mAs) — the resulting image will not accurately represent the anatomy of interest. Thus, the correct understanding highlights the relationship between part thickness, signal intensity, and Compton interactions.