射線進入和出來的位置頭發都可能受到影響。問放療醫生吧

https://www.oncolink.org/support/side-effects/skin-hair-nail-side-effects/hair-loss-alopecia-from-radiation-treatment

Radiation therapy will generally cause hair loss to the body part that is being treated. For example, if your arm were treated with radiation, you may lose any hair on your arm, but the hair on your head would not be affected. The degree of hair loss will depend on several factors, including the size of the area being treated and the total dose of radiation being given. Hair loss is greatest within the treatment field, but may also occur in the area where the radiation beam exits the body.