The Off Axis Ratio is defined as the dose at any point in a plane perpendicular to which axis?

The Off Axis Ratio (OAR) is defined in relation to the Central Axis (CAX) of the radiation beam. The OAR represents the ratio of the dose delivered at a point off of this central axis to the dose delivered at the central axis itself, at the same depth in tissue. It is crucial for understanding how dose distribution changes as you move away from the central beam's axis, which is typically where the maximum dose is delivered.

This definition is particularly important in the fields of radiation therapy and medical dosimetry because it helps ensure that radiation is administered safely and effectively to target tumors while minimizing exposure to surrounding healthy tissues. The concept of measuring the dose off the central axis is essential for treatment planning, as it allows medical professionals to account for variations in dose due to factors such as beam geometry and patient positioning.

The other options do not accurately capture this relationship. The Off Axis refers to areas away from the CAX but is not a specific axis itself. The Depth Axis pertains to measurements regarding the penetration of radiation but does not define where the off-axis measurement occurs. The External Axis is not a term commonly used in this context and thus would not relate to the determination of the Off Axis Ratio. Hence, the Central Axis is the