1. A method of determining a presence of items of interest within a cargo container, the method comprising: obtaining information from an initial radiation scan of at least one of the cargo container and contents therein, the obtaining comprising: transmitting a screening radiation beam along a screening portion of the cargo container at a screening scan rate; detecting radiation received in response to the transmitting the screening radiation beam; and analyzing the detected radiation received in response to the transmitting the screening radiation beam to develop information regarding the initial radiation scan; identifying a target portion of the cargo container in response to the information obtained, wherein the screening portion is larger than the target portion; transmitting a target radiation beam along the target portion of the cargo container at a target scan rate, the target scan rate being different than the screening scan rate; detecting radiation received in response to the transmitting; analyzing the detected radiation for a presence of items of interest; and in response to the analyzing, generating a first signal indicative of the presence of the items of interest, or generating a second signal indicative of an absence of the items of interest.