This thesis presents the development of low-noise CMOS image sensors for radio-molecular imaging. The development is described in two directions: firstly, from the technology point of view to reduce the pixel noise level, and secondly from the design point of view to reduce the pixel readout circuits noise level. With respect to the SNR and readout noise, the low-noise CMOS imager proposed in this thesis shows a promising performance for the new gamma-ray detector for radio-molecular imaging.