Dose 2016

When can a plastic phantom be considered water-equivalent?

In kV photon beams

8cm diameter

•Energy deposition is mainly due to photo-electric effect and although one would expect that solid plastics with Z eff close to that of water would be water equivalent, recent research has shown otherwise.

•Departure from water equivalence worsens at low kV beams.

•It is thus important to check equivalence with water also in kV beams (comparison of relative dose data, and back scatter factors )

Hill et al, Med Phys, 37 (8), 2010 p4355-