What does IMRT stand for and what is its main aim?

• A. Conventional 3D conformal radiotherapy; uses fixed beams without modulation.
• B. Intensity-modulated radiotherapy; it modulates beam intensity across angles to conform dose and spare normal tissue.
• C. Brachytherapy; internal radiation source.
• D. Proton therapy; uses protons to spare normal tissue.

Answer: (B)

The main idea here is how IMRT shapes the dose delivery. IMRT stands for Intensity-Modulated Radiotherapy, and its goal is to modulate the intensity of the radiation beams as they come from different angles so the high-dose region hugs the tumor while keeping the dose to nearby normal tissues as low as possible. This is achieved with devices like multileaf collimators and optimization algorithms that plan how each beam’s intensity should vary across its cross-section and across angles. In contrast, conventional 3D conformal radiotherapy uses fixed beam shapes without within-beam modulation, brachytherapy delivers radiation from inside the body, and proton therapy uses protons with their distinct depth dose to spare tissue. So IMRT’s main aim is to achieve precise dose conformality and organ-at-risk sparing by modulating beam intensity.