1. A method of radioactive-emission-measurement, comprising: providing a SPECT camera for the detection of single emissions, which camera having a region of interest having a volume of at least 5×5×5 cm and a side closer to said region of interest; arranging said camera so that said region of interest coincides with a human body; imaging the region of interest from different orientations, using at least three detecting blocks each arranged to view said region of interest at a different orientation from others of said blocks, wherein said imaging comprises detecting at least 1 of every 5000 photons emitted from at least one radioactive-emission source located within said region-of-interest volume, through a collimator positioned in front of at least one pixel of each of the detecting blocks thereby blocking gamma and beta radiation and defining a viewing angle of at least 0.005 steradians; and reconstructing a SPECT volumetric radioactive-emission image from said detected photons at a resolution of 7 mm Full Width Half Maximum (FWHM) or better, said resolution defined under conditions of irradiation by a substantially line source of radioactive emission, with an activity of 5 mCi, within said region-of-interest volume, at a distance of at least 100 mm from said side.