In this paper, we propose a Compact Asymmetrically Slotted Antipodal Vivaldi Antenna (CAS-AVA) design for MIMO imaging systems. The structure has the ability to extend the antenna bandwidth in low-end frequencies achieving a fractional bandwidth of 123,32 % (4.743-20 GHz). Good results are obtained in term of return loss, radiation pattern and gain. A time-domain study has been also performed to characterize the antenna behavior in case of an UWB pulse is used. To further validate our design, an application for MIMO imaging system is also proposed and evaluated. The antenna performances demonstrate that it is a good candidate for microwave imaging applications.