A mobile radiography unit moves between an isolation room and a surgical suite where sterile trays are opened for a myelogram, and the technologist must decide how to process the cassette cover, the tabletop, and the spinal needles. Which infection-control assignment correctly separates disinfection of surfaces from sterilization of invasive items with proper technique?

The correct assignment follows noncritical versus critical classification: tabletops, mobile units and cassette covers touch intact skin or no patient tissue, so daily cleaning plus hospital-grade disinfection using medical aseptic technique controls environmental transmission between isolation and surgical areas without requiring sterility. Disinfecting spinal needles with hospital disinfectant using sterile handling fails on processing level because myelogram needles entering the subarachnoid space are critical invasive items that must be supplied sterile, and low- or intermediate-level disinfection cannot ensure spore elimination. Sterilizing the tabletop and mobile unit with steam pressure using surgical technique fails on application because large environmental surfaces are not amenable to autoclaving and do not require a sterile field, so surgical asepsis is misapplied where medical asepsis with disinfection is appropriate. Disinfecting myelogram tray instruments with hospital disinfectant using medical technique fails on field maintenance because once trays are opened for myelography the instruments join the sterile field and must remain sterile through surgical asepsis, not medical asepsis. An exam caveat is to pair each item with both correct level and correct technique, since stems often keep one element correct to distract. A practical check is to confirm disinfectant contact time and dilution, verify tray chemical indicators and intact wrap, and use single-use factory-sterilized needles without reprocessing.