Retraction: Minimal skin dose increase in longitudinal rotating biplanar linac-MR systems: examination of radiation energy and flattening filter design (2016 Phys. Med. Biol.61 3527). (2nd April 2020) - Keyvanloo, A; Burke, B; St. Aubin, J; Baillie, D; Wachowicz, K; Warkentin, B; Steciw, S; Fallone, B G