Dose 2016

Finite sized pencil beams (FSPB or beamlets)

Pre-integrated over a finite beam area. Reduces time for super-position, but requires constant energy fluence over beamlet area.

1cm 2

1.25MeV SSD=80cm

U Jelen, et al (2005) Phys Med Biol 50 , 1747-66.

Ostapiak, et al (1997) Med Phys 24 , 743-50.

Mainly for fast calculations in IMRT optimization. However, the width of a beamlet can not be larger than the resolution of the grid used for fluence optimization.