Various design of 2-D time-encoded aperture system was investigated for both gamma and neutron imaging. The advantage of time-encoded imaging system for localization of radiological sources relies on its 360-degree horizontal field of view (FOV). Based on the previous report on the two-dimensional time-encoded imager (2D-TEI) for fast neutron, we have developed more attracting TEI systems also effectual for gammaray imaging. In this paper, three TEI systems with different encoding methods and configurations of detector and rotating mask will be demonstrated via Monte Carlo simulation. Lots of radiation scenes support that all these systems have an imaging capacity of multipoint and extended gamma/neutron sources. It is recommended that these designs will provide an alternative panoramic imaging way of search and localization of radioactive hot spots. © 2019 IEEE.