Why are bow-tie filters used in CT x-ray systems?

Bow-tie filters are specifically designed to shape the x-ray beam before it enters the patient during a CT scan. The primary function of these filters is to reduce the radiation dose received by the patient. By altering the beam profile, bow-tie filters provide more exposure to the central region of the image where the patient is the thickest and attenuate the x-rays at the edges where the patient is thinner.

This beam shaping helps to ensure that adequate image quality is maintained while minimizing unnecessary radiation exposure to areas of the body that do not require as much dose. Because patients can be at risk for radiation effects, especially during repeated imaging, the use of bow-tie filters is an important aspect of radiation safety in CT imaging protocols.

Enhancing image resolution, assisting with image reconstruction, or improving contrast resolution are not the primary functions of bow-tie filters; therefore, while those factors can be influenced by various other technical aspects of CT imaging, bow-tie filters are specifically implemented for dose reduction.