160 may be adapted to emit gamma rays x rays and or beta electrons i e radiation having an energy of at least 10 kev for some applications the radiation source 166 666 may comprise a radioisotope or a miniature radiation generator in some aspects of the disclosure radiation source 166 666 may comprise a miniature x ray generator such as those described in one or more of the following references u s pat nos 6 134 300 and 6 353 658 to trebes et al haga a et al u201c a miniature x ray tube u201d applied physics letters 84 12 2208 2210 2004 and gutman g et al u201c a novel needle based miniature x ray generating system u201d phys med biol 49 4677 4688 2004 such a miniature x ray generator or x ray tube may be used for radiation source 160 instead of a radioisotope to illuminate the colon contents with x ray photons turning such a generator on and off as needed typically reduces exposure of the subject to radiation in addition the energy range can be better controlled and the flux may be higher for the on periods without increasing subject total exposure it should be appreciated that the capsule 150 350 450 550 650 may include more than one radiation source 166 666 according to various aspects the capsule 150 350 450 550 650 may comprise one or more gamma and or x ray radiation sources and or sources.