Where is the accelerator photon beam calibration carried out for clinical dosimetry?

The calibration of the accelerator photon beam for clinical dosimetry is predominantly carried out in a water phantom because water closely mimics human tissue in terms of density and energy absorption characteristics. This makes it an ideal medium for accurate measurement of dose distribution delivered by the photon beam.

Water phantoms provide a uniform environment for the beam, allowing for precise readings and ensuring consistency across different measurement conditions. They also facilitate the measurement of various dosimetric parameters, such as depth dose, beam profile, and output factors, which are critical for effective treatment planning and ensuring patient safety.

Additionally, using a water phantom allows for the assessment of the beam’s performance in a way that can be translated to clinical conditions, where biological tissues are predominantly water. As a result, measurements taken in a water phantom can be reliably used to calibrate and set up treatment beams for patient use.