The paper demonstrates a complete acquisition chain of a 300GHz to 1THz image sensor with on-chip multiplexing in a 0.13μm bulk silicon CMOS technology. The pixel consumes less than 100μW and has a responsivity of 90kV/W at 300GHz and of 1.8kV/W at 1.05THz respectively. High resolution and contrast THz images revealing the inner structure of tree leaves are presented. These results show that multi-frequency and room temperature imaging systems are possible in cost-effective CMOS technologies.