Which action demonstrates understanding of the planning phase for radiation therapy?

• A. Imaging such as CT or MRI is used to plan radiation therapy
• B. Imaging is not required for planning
• C. No planning is needed before radiation therapy
• D. Imaging is used only after radiation therapy

Answer: (A)

The planning phase relies on imaging to map the patient’s anatomy and precisely define the target and nearby organs. A CT scan provides the 3D geometry and density information needed to calculate how the radiation will deposit dose in tissue, while outlining the tumor and organs at risk to create accurate target volumes. MRI adds superior soft-tissue detail when needed to refine those contours. This imaging guides how beams are arranged, what energies and doses are used, and how the patient is positioned and immobilized to ensure the plan translates accurately to the treatment days. Without imaging to tailor the plan to the actual anatomy, the dose could miss the tumor or spare too little of the surrounding healthy tissue.

Imaging after therapy serves for response assessment, not for planning future treatments, and stating that imaging isn’t required for planning contradicts how dose delivery is safely and effectively mapped.