Which property of the target is significant for the output of a kilovoltage therapy unit?

The atomic number (Z) of the target material is significant for the output of a kilovoltage therapy unit because it directly influences the efficiency of x-ray production. In kilovoltage therapy, high-energy photons are generated when high-speed electrons collide with the target material, typically made of tungsten or another heavy metal.

Higher atomic number materials are more effective at producing x-rays due to their increased number of protons and electrons, which enhances the likelihood of interactions that lead to x-ray emission. Specifically, a higher atomic number increases the likelihood of characteristic x-ray production and a greater quantity of Bremsstrahlung radiation. This results in a higher intensity of the x-ray beam, which is crucial for effective radiation therapy.

While density and atomic mass could have some effects on the properties of a target material, they do not have the same direct relationship with x-ray output as atomic number does. Weight is not a relevant factor in this context, as it does not influence the efficiency of x-ray generation in kilovoltage therapy. Therefore, understanding how atomic number affects x-ray production in therapy units is essential for optimizing treatment plans and ensuring effective dosimetry.