The tracer decays to the theatre list, not to yours. Injection timing and the same-day against day-before choice, what the operating theatre needs, the handover that has to exist in writing, and the scheduling failures that waste a dose.
The tracer decays to the surgeon's timetable, not to the department's. Everything difficult about sentinel node work follows from that sentence, and almost none of it is technical. A department that can acquire an excellent lymphoscintigram will still waste doses and cancel patients if the booking arrangement between nuclear medicine and theatre is informal.
So the useful way to plan this service is backwards: fix how the two departments talk to each other first, and treat the imaging as the easy part.
Sentinel node localisation uses a technetium-labelled colloid injected at the site the surgical protocol specifies: peritumoural or subareolar and intradermal for breast, intradermal around the scar or lesion for melanoma, submucosal or peritumoural for head and neck. The injection technique is a shared decision between the surgeon and the nuclear medicine physician, and it should be written down as a departmental protocol rather than agreed case by case, because injection depth changes which nodes are seen.
Technetium's roughly six-hour half-life gives you two workable patterns:
Whichever pattern is used, the imaging is a mapping exercise rather than a diagnostic one: dynamic imaging to see the drainage channel where the protocol calls for it, delayed static views to establish the node position, and SPECT/CT where planar images are ambiguous. In practice that means head and neck cases, trunk melanoma, and any case where a node projects over or near the injection site. If the department has SPECT/CT, this is one of the studies where it genuinely changes the operation.
One more detail belongs to the imaging side: the skin mark. Mark the patient in the position they will be operated in, not in the position they were imaged in. A mark placed with the arm by the side and an operation performed with the arm abducted puts the mark somewhere the surgeon does not need it, and this is a repeated and avoidable error.
The intraoperative gamma probe is theatre equipment that lives on a nuclear medicine service contract, which is exactly the sort of item that falls between two departments.
The blue dye protocol, where used, is the surgical backup and has its own consent and skin-staining discussion. It does not remove the need for the probe check.
The theatre list start time drives the injection time. Nuclear medicine cannot set it and should stop trying. What nuclear medicine can do is impose structure on the interface.
Also decide in advance what happens when a patient is injected and the operation is then cancelled. It happens, it is nobody's fault, and it needs a recorded administered dose, an explanation to the patient, and a decision about whether the case can be rebooked within the useful life of the tracer or has to start again.
Before the patient goes to theatre there should be a written report and a map available to the surgical team, not a report dictated later that afternoon. It should state how many nodes were seen, in which basins, their relationship to the injection site, and anything unexpected such as drainage crossing the midline or to an unusual basin.
Two practical points. Do not assume the theatre has a PACS workstation, or that it is on the same network segment; if it does not, print the images and send them with the notes. And agree the counting convention with the surgeon in writing: what count rate constitutes a hot node, whether ex-vivo counting of the excised node is done and recorded, what background is measured against, and when the search stops. These are surgical protocol decisions, and the two teams need to be operating on the same rule rather than two similar ones.
Shine-through from the injection site is the standard difficulty in breast and head and neck cases. The report should say where the injection site activity is and how close it lies to the node, because that determines whether the surgeon can trust the probe near the primary.
Staff doses from this work are low, but low is not the same as unmanaged, and an inspector will ask for the written arrangement rather than a reassurance. The local rules should cover who handles the specimen, how a radioactive specimen is labelled and transported, what histopathology does with it and for how long it is held before processing, contamination monitoring, waste disposal, and the arrangement for pregnant staff in theatre and in the laboratory.
Agree the histopathology procedure with the laboratory before the first case, not when the first pot arrives with a radiation label on it. Their concern is legitimate and easily answered in advance; answered badly on the day, it can stop the service for a month.
Every one of those is an arrangement problem rather than an equipment problem, which is why the service is best set up by putting the surgeon, the theatre manager, the nuclear medicine physician and the technologist in one room for an hour before the first case, and writing down what they agree.