External beam radiation therapy is delivered from which location?

External beam radiation therapy is delivered from which location?

• A. From outside the body
• B. From inside the body (brachytherapy)
• C. Through intravenous infusion
• D. Orally

Answer: (A)

External beam radiation therapy delivers radiation from outside the body, using a machine such as a linear accelerator to aim the beam at the tumor through the skin. The treatment plans shape and direct the dose with angles and shielding to concentrate energy in the tumor while minimizing exposure to surrounding healthy tissue. This external delivery is what distinguishes it from other methods. Brachytherapy places the radiation source inside the body near or within the tumor, so it’s not external. Intravenous infusion or oral administration would treat the cancer systemically, not by directing a beam from outside the body, so they are not external beam approaches.

External beam radiation therapy delivers radiation from outside the body, using a machine such as a linear accelerator to aim the beam at the tumor through the skin. The treatment plans shape and direct the dose with angles and shielding to concentrate energy in the tumor while minimizing exposure to surrounding healthy tissue. This external delivery is what distinguishes it from other methods. Brachytherapy places the radiation source inside the body near or within the tumor, so it’s not external. Intravenous infusion or oral administration would treat the cancer systemically, not by directing a beam from outside the body, so they are not external beam approaches.