What happens to the dose at central axis with different depths in relation to beam flatness?

In radiation therapy, the concept of beam flatness is crucial when considering the dose distribution along the central axis at varying depths. Beam flatness refers to the uniformity of the dose delivered across the radiation field. As the depth of tissue increases, the dose typically does not increase uniformly due to several factors, including the attenuation of the beam energy and the effects of scatter within the tissue.

At shallow depths, the dose may be relatively high, but as one moves deeper into the tissue, the dose commonly decreases. This reduction occurs because the X-rays or electrons lose energy as they penetrate through the tissues, and the tissue density can also affect how much dose reaches deeper structures.

Additionally, the presence of the buildup region near the surface and the gradual onset of dose fall-off deeper in the tissue can contribute to an overall decrease in dose at central axis with increasing depth. Therefore, it is accurate to state that the dose generally decreases with depth due to these cumulative effects in the context of beam flatness. This understanding is essential for medical dosimetrists to ensure accurate treatment planning and delivery.