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; identifying a target portion of the cargo container in response to the information obtained; transmitting a target radiation beam along the target portion of the cargo container; 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.