The combination of imaging and therapy has opened the very promising Theranostics domain with magnetic hyperthermia being a very promising domain. However, imaging systems should not interact with the magnetic field. In this work we have tested the recent C-series of SensL SiPM with 3mm pixel size, 4×4 arrays, coupled to different scintillators and irradiated with various gamma energies. The evaluation of the SiPM arrays shows that 1x1mm pixel size can be clearly resolved at PET energies for GAGG:Ce and CsI:Na and 1.5×1.5mm in SPECT imaging for CsI:Na. The best energy resolution was measured equal to 10.5% under 511keV irradiation for the 2×2mm GAGG:Ce; 16% under 511keV irradiation for the 1×1mm GAGG:Ce and 22% under 120keV irradiation for the 1×1mm CsI:Na. In addition, measurements with position sensitive photomultipliers have been carried out, to evaluate the effect of the magnetic field on the imaging performance of the system. While the effect of the magnetic field outside the coil is small, optimal images will be obtained if the imaging system is placed inside the coil, something that can be achieved only by using SiPMs.