What effect does increasing the beam hardening have on image quality?

Increasing beam hardening affects image quality primarily by inducing partial volume artifacts. Beam hardening occurs when lower-energy X-ray photons are absorbed more than higher-energy photons as they pass through matter, such as body tissues. As a result, the average energy of the photons that reach the detector increases, leading to higher attenuation in denser tissues.

This phenomenon can cause artifacts that manifest as streaks or bands on the reconstructed images, particularly around areas with high-density differences, such as metal implants or contrast-enhanced structures. These partial volume artifacts arise because the CT images represent an average value of the attenuation coefficient over a volume of tissue, and when beam hardening occurs, it may not accurately reflect the true composition of that volume, especially in heterogeneous tissues.

In contrast, an increase in beam hardening does not typically improve contrast or resolution; rather, it can lead to a degradation in image quality. Blurring is also not a direct outcome of increased beam hardening; it is more related to factors such as motion artifacts or insufficient spatial resolution. Therefore, the correct understanding of the effects of beam hardening on image quality directly correlates with the induction of partial volume artifacts, making that the most accurate choice.