Medical procedure related objects (e.g., instruments, supplies) tagged with transponders (e.g., RFID transponders, dumb transponders) are accounted for in a medical or clinical environment via an accounting system using a number of antennas and interrogators/readers. A first set of antennas and RFID interrogator(s) interrogate portions of the environment for RFID tagged objects, for example proximate a start and an end of a procedure. Shielded packaging and/or shielded receptacles shield tagged objects, preventing interrogation except for those objects in unshielded portions of the environment. A shielded receptacle may include an antenna to interrogate the contents thereof in a relatively noise-free environment. A data store may maintain information including a current status or count of each instrument or supply, for instance as checked in or checked out. A handheld antenna and/or second set of antennas interrogates a body of a patient for retained instruments or supplies tagged with dumb transponders.