“…In medical imaging, there are numerous examples of applications where data consistency conditions (also known as range conditions) play a central role in the image reconstruction step. The idea is that certain mathematical redundancies in the projection measurements can be exploited to identify the parameters of some systematic effect, such as abrupt patient movement (Welch et al 1998, Yu and Wang 2007, Leng et al 2007, beam-hardening scaling factors (Tang et al 2011), attenuation factors in emission tomography (Natterer 1983, Hertle 1988, Welch et al 2003, Defrise et al 2012, unknown patient outline (Natterer 1993, Laurette et al 1999, Mennessier et al 1999, or to synthesize missing projections (Defrise 1995, Patch 2002b or missing rays of truncated projections (Erlandsson et al 2000).…”