Portable detection apparatus and method

A portable detection apparatus, comprising:

• a) a housing;
• b) a first detector within the housing configured to detect ionizing radiation comprising background radiation and secondary radiation from a subject;
• c) a second detector within the housing configured to detect the background radiation;
• d) a shield within the housing surrounding the first and second detectors and defining a shield aperture around the first and second detectors configured to facilitate radiation from the subject to enter the housing;
• e) a radiation blocking member configured to substantially block at least a portion of the ionizing radiation entering the housing through the shield aperture from reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation;
• and
• f) a processor module connected to the first and second detectors configured to determine the amount of ionizing radiation detected by the first detector attributable to the secondary radiation;
• wherein the detection apparatus has an operating sensitivity capable of detecting an activity of at least about 460 Bq within the subject using a 5 minute scan.