What is beam flatness?

Flatness is usually defined at 10 cm depth, and in order to achieve this, the beam must exhibit horns near the surface. Horns are required due to differential hardening in the flattening filter. In the center, the beam is hardened and therefore penetrates more resulting in more fluence at 10 cm depth.

What is flatness and symmetry in radiotherapy?

Symmetry is the ratio of the dose rates at symmetrical points on either side of the beam axis and flatness is the ratio of maximum to minimum dose anywhere in the beam.

What is a flattening filter in radiotherapy?

Abstract. Purpose: The flattening filter (FF) has traditionally been used to flatten beams or create uniform fields in conformal and intensity-modulated radiation therapy (IMRT) but reduces the dose rate.

What is output of linac?

The linac output is calibrated to deliver 1.0 cGy per monitor unit (MU) at the depth of maximum output. Beams of photons or electrons pass through a monitor chamber located in the linac head which turns off the beam once the prescribed MU is delivered.

What is flattening filter in Linac?

It is well known that the flattening filter in a standard linac acts as an attenuator, the beam hardener and the scatterer. Obviously, the removal of the FF results in an increase in dose rate, softening of the x-ray spectra, reduction in head scattered radiation, and the nonuniform beam profile.

What is beam quality in radiotherapy?

The beam quality correction factor, , which corrects for the difference in the ionization chamber response between the reference and clinical beam quality, is an integral part of radiation therapy dosimetry. The uncertainty of is one of the most significant sources of uncertainty in the dose determination.

What is the use of proton?

Proton therapy, also called proton beam therapy, is a type of radiation therapy. It uses protons rather than x-rays to treat cancer. A proton is a positively charged particle. At high energy, protons can destroy cancer cells.