Question

How can the SOBP be generated (either in passive scattering or scanning beam technique).

Answer 1

A  'spread-out Bragg peak' (SOBP) is created by somewhat varying the energy of the incident proton beam, using various energies with appropriate weighting to produce a flat, level SOBP. (Such a uniform dose covering the tumor is required.) There exists one analytic method of determining the weights appropriate to creating an SOBP, that of Bortfeld and Schlegel, but it gives a tilted SOBP. The present method, derived using MCNPX Monte Carlo calculations, provides a correction to the Bortfeld–Schlegel weights which gives a flat, level SOBP. The corrected weight calculation can be useful in theoretical work and as a starting point in determining the weights for a proton beam used in cancer treatment.