Which treatment involves insertion of low-intensity radioactive nuclides inside the body close to the tumor?

• A. External Beam
• B. Brachytherapy
• C. Linear Accelerators
• D. Cobalt-60 Unit (Gamma Knife)

Answer: (B)

Placing radioactive sources directly inside or very close to the tumor is brachytherapy. This approach delivers the radiation dose right at the target, with a rapid fall-off that helps spare surrounding healthy tissue. The sources can be low-dose-rate seeds that stay in place for weeks or permanently, or high-dose-rate sources that are inserted temporarily through catheters and removed after a short treatment, giving a localized high dose to the tumor. In contrast, external beam approaches deliver radiation from outside the body using machines like linear accelerators, and the Gamma Knife uses multiple external cobalt-60 sources rather than implanted material. So the description of low-intensity radioactive nuclides inserted inside the body near the tumor points to brachytherapy.