[en] The significance and limitations of gamma-ray flow imaging are discussed, with the conclusion that there is a need for compact detectors with fast response. Scintillation crystals are the only practical gamma-absorbers which provide sufficient stopping efficiency over the whole energy range of interest (60 keV to 1.2 MeV). Experimental data on two scintillation light read-out devices are presented. One is the new EDPMT (electron-bombarded silicon diode photomultiplier tube) which is capable of count rates close to 10⁷ c.p.s. over a broad energy range when used with a GSO crystal. A proximity-focused EDPMT version can be made compact and allows tight stacking. The second device is a very compact and robust photodiode. This is a good alternative for low count-rate applications (<10⁵ c.p.s.) with gamma energies above approximately 600 keV. Both detectors are suitable for process tomography in general, not only flow imaging. (Author)