For a 15cm x 15cm field at SSD=80 cm, what is the PSF for a 6 MV beam?

To determine the Picket Fence Calibration Factor (PSF) for a specific field size and source-to-surface distance (SSD) using a 6 MV beam, it is essential to understand the relationships between field size, SSD, and PSF.

PSF accounts for changes in the dose distribution that occur due to the geometry of the beam and the characteristics of the radiation itself. For a 6 MV beam, the PSF is influenced by factors such as tissue density, beam energy, and the depth of dose maximum.

In this case, a 15 cm x 15 cm field at an SSD of 80 cm typically generates a PSF value that has been previously established through experimental data or reference protocols. The PSF value you provided, which is 1.015, reflects the calibration needed to accurately calculate the dose delivered to the patient based on the setup described.

This specific PSF indicates that the dose measured at the depth of interest should be multiplied by this factor to obtain the correct value. The value of 1.015 suggests a slight increase in dose due to the field size and the specifics of the beam characteristics at that SSD.

In summary, the rationale for selecting the PSF of 1.015 for a