Table 2.

Features and capabilities of the non-adaptive (na-) and the adaptive (a-) pMMC

	na-pMMC	a-pMMC
Step size	Restricted by varying HU values	Adaptive choice of macro step
Energy deposition	Linear rescaling of deposited energy depending on covered fraction of macro step	Stopping power approximation over multiple voxels of varying HU value
Trajectory approximation	Hinge step, but macro step is interrupted at voxel boundary of varying HU value	Hinge step at 30% of macro step size, passes multiple voxels of varying HU value
Dose calculation accuracy	within 1% or 1 mm compared to full MC
Efficiency: homogeneous geometries	very good
Efficiency: inhomogeneous geometries	limited	very good