Complex sentence: The Protection Quantities are a calculated effect of radiation on organs of the body using a "phantom" which is a acomputational model which attempts to take into account a number of complex effects such as shielding and scattering of radiation.
Split into simpler sentences: The Protection Quantities are a calculated effect of radiation on organs of the body using a phantom. This is a computational model which attempts to take into account a number of complex effects such as shielding and scattering of radiation.