The Off Axis Ratio can be used to determine the dose at which points?

The Off Axis Ratio (OAR) is a critical concept in radiation therapy used to assess the dose distribution around the central axis of a radiation beam. Specifically, it is defined as the ratio of the dose at a given point off the central axis to the dose at a reference point, usually along the central axis of the beam.

When evaluating the dose at off-axis points, the OAR helps dosimetrists understand how the radiation dose diminishes or varies as one moves away from the central axis. This is essential for planning treatment because it ensures that the prescribed dose is delivered to the target volume while minimizing exposure to surrounding healthy tissues.

OAR is particularly valuable when dealing with non-uniform fields or when utilizing beams that may have varying characteristics off-axis, such as in the case of intensity-modulated radiation therapy (IMRT) and other advanced techniques. By using OAR, dosimetrists can make precise dose calculations at locations where the dose distribution is not uniform, ensuring effective and safe radiation delivery.