Which modality is designed to deliver a maximum dose to the tumor while minimizing dose to surrounding normal tissue?

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

Answer: (C)

The idea here is conformal dose delivery: shaping the high-dose region to fit the tumor so that most of the energy goes to the target while nearby normal tissues receive as little as possible. A linear accelerator delivers external beam radiotherapy with photons (or electrons) from outside the body. By using multi-leaf collimators to sculpt the beam and sophisticated planning (IMRT, VMAT, 3D-CRT) combined with image guidance, the treatment can be delivered from many angles and modulated in intensity. This allows a higher dose to the tumor prescription while actively reducing the dose to surrounding structures, achieving a favorable therapeutic ratio. Other modalities also aim for tight dose fall-off, but the LINAC-based approach is specifically designed around creating highly conformal, tumor-focused dose distributions.