Introduction.- Terahertz Imaging Modality: State-of-the Art and Open challenges.- Terahertz Antenna Technology for Imaging and Sensing Application Devices.- Small-Gap Photoconductive Dipole Antenna for Imaging.- Analytical Framework of Small-Gap Photoconductive Dipole Antenna: Equivalent Circuit Model.- Directivity Enhancement of Terahertz photoconductive Antenna: Approach of frequency Selective Surface.- Highly-Directive Lens-Less Photoconductive Dipole Antenna Array for Imaging Applications.- Beam-Steering Characteristics of Highly-Directive Photoconductive Dipole Phase Array Antenna.- Terahertz Near-field Imaging and Sensing.- Aspects of Surface Plasmon Polaritons at Terahertz Frequencies.- Terahertz Integrated Devices and Systems for Imaging and Sensing.