Both beam shaping using custom blocks and multi-leaf collimators (MLCs) aim to minimize what?

The primary goal of both beam shaping with custom blocks and the use of multi-leaf collimators (MLCs) is to minimize the radiation dose delivered to normal tissues surrounding the tumor. This is vital in radiation therapy, where protecting healthy tissues is crucial to mitigating side effects and preserving quality of life for patients undergoing treatment.

Custom blocks are designed to conform to the shape of the tumor while blocking radiation to the surrounding healthy tissue. Similarly, MLCs consist of individual leaves that can be adjusted in real-time to shape the radiation beam to match the tumor's contours, allowing for precise targeting of the treatment area. By optimizing the beam shape, both methods effectively reduce the volume of normal tissue exposed to unnecessary radiation, thus enhancing the therapeutic ratio—maximizing tumor control while minimizing toxicity to normal cells.

Other choices do not accurately reflect the primary objective of these techniques. Treatment duration may vary with different methods, but it is not the central goal of beam shaping. Likewise, while proper beam shaping can assist in stabilizing patients, minimizing the need for immobilization is not its primary focus. The amount of shielding required is generally more related to the overall treatment plan and less about the function of custom blocks and MLCs specifically.