Which feature is vital for the couch in a treatment planning CT scanner?

The feature that is vital for the couch in a treatment planning CT scanner is that it must be flat. A flat couch surface is essential to ensure accurate positioning and alignment of the patient during imaging. This helps in the reproducibility of positioning for subsequent treatment sessions and ensures that the anatomical structures are correctly aligned with the radiation beams. The flat surface minimizes the distortions or changes in anatomy that can occur if the patient is not lying flat, which is crucial for effective treatment planning and dosimetry. Accurate imaging leads to better treatment outcomes and is foundational in creating precise radiation treatment plans tailored to the patient's specific needs.