We present a large-format focal plane array sensor for THz imaging. Each pixel of the sensor array consists of an 85μm×92μm lithographically fabricated wideband dual-slot antenna, monolithically integrated with an ultra-fast diode tuned for the 0.6-1.2 THz band. The small antenna footprint enables a densely packed THz imaging array. Concurrently, optimum impedance matching was implemented for maximum pixel sensitivity, enabling real-time image acquisition. The video rate response time (25 Hz) achieved by the THz focal plane array sensor enables, for the first time, the practical realization of THz computed tomography. Cross-sectional images of representative objects were captured in less than 2 minutes for tomography reconstruction. We demonstrate sub-millimeter image resolution as well as unique quantitative and qualitative information about the test samples in the THz band.