When measuring SSD, which of the following is true for a 100 cm SAD machine?

In the context of a 100 cm Source-to-Axis Distance (SAD) machine, the proper measurement of Source-to-Skin Distance (SSD) is crucial for delivering accurate radiation therapy doses. The statement that SSD should be within 100 cm accurately reflects clinical practice.

This distance means that the SSD can be less than, equal to, or occasionally adjusted to be slightly more than the 100 cm reference used in SAD measurements, but it must always remain within reasonable limits for safety and efficacy during treatment. The allowance for variance enables tailoring the treatment plan based on the specific anatomy and needs of individual patients while considering the machine’s design and capabilities.

In contrast, the other proposed statements focus on strict relationships between SSD and SAD that do not accommodate the flexibility necessary for different treatment setups and patient anatomies. By allowing SSD to be within 100 cm, the treatment setup can effectively consider various clinical scenarios without compromising therapeutic intent or safety.