A system and method for monitoring the inventory of a medical storage container such as a tray that has a required inventory of medical articles. An enclosure is used to isolate, scan, and take an inventory of the tray or other container of medical articles. The tray and each of the medical articles in the tray have RFID tags. The enclosure having a size differing from the size needed for a resonant frequency at the RFID frequency of operation of the tags. A probe is used to create a robust electromagnetic field standing wave of constructive interference in the enclosure and a program compares the scanned present inventory of the tray to the required inventory database and indicates any differences. Expired and recalled articles and substitutes for recalled articles are identified.