Custom blocking provides better conformity compared to treatment utilizing which of the following?

Custom blocking is designed to achieve optimal dose distribution by closely conforming to the shape of the treatment target, which results in better sparing of surrounding healthy tissues while delivering prescribed doses to the tumor. When comparing this approach to treatment utilizing multi-leaf collimators (MLC), it's essential to understand the functionality and limitations of MLCs.

While MLCs are versatile and can quickly shape the radiation beam for various tumor geometries, they might not always achieve the same level of physical conformity as custom blocks, particularly in complex or irregularly shaped targets. This is due to the finite width of the leaves that can lead to gaps or over-coverage at the edges of the treatment area, which may not effectively limit the radiation exposure to surrounding healthy tissue as finely as custom blocks can. Custom blocks can be precisely manufactured to match the contours of a tumor, ensuring that the radiation dose is delivered exactly where needed, without the compromise associated with leaf width or arrangement.

In comparison, standard blocks, beam modifiers, and 3D conformal radiation therapy (CRT) may not provide the same level of individualized anatomical adaptation as custom blocking does. Standard blocks typically have fixed sizes and shapes, beam modifiers include materials that adjust the intensity rather than the shape