Final answer:
Brachytherapy is an internal radiation therapy that involves implanting radioactive seeds, ribbons, or capsules directly into or near a tumor to deliver localized radiation.
Step-by-step explanation:
The type of internal radiation therapy where seeds, ribbons, or capsules containing a radiation source are placed inside the body, in or near the tumor, is known as brachytherapy. This procedure involves the use of ionizing pellets or rods that produce photons in the form of x-ray or gamma ray directly at the tumor site, causing localized radiation. These pellets are surgically implanted and may contain radioisotopes like iodine-125, palladium-103, or cesium-131, which have short half-lives and thus become significantly less radioactive after treatment. In the case of rods, they are temporarily inserted and connected to a gamma source, delivering immediate radiation without leaving the patient radioactive post-treatment.