Measurements of in-air spot size of pencil proton beam for various air gaps in conjunction with a range shifter on a ProteusPLUS PBS dedicated machine and comparison to the proton dose calculation algorithms

In conclusion, spot size increment is dependent on the energy and air gap. The increase in spot size was more pronounced at lower energies ( <  150 MeV) for all air gaps. The comparison between the TPS calculated and measured spot sizes showed that the RS-MC is more accurate (within ± 0.3 mm), whereas the RS-PB overpredicted (up to 0.8 mm) the spot sizes when a range shifter (7.5 cm WET) and large air gaps are encountered in the proton beam path.
Source: Australasian Physical and Engineering Sciences in Medicine - Category: Biomedical Engineering Source Type: research