Sentinel Node Study

A sentinel node scan is a nuclear medicine procedure in which a small amount of radioactive tracer (radiopharmaceutical) is injected under the skin and imaged using a gamma camera, mapping the lymphatic system around an area requiring surgery.

The lymph node (known as the Sentinel node) closest to the abnormality is identified, allowing the surgeon to later remove this lymph node during surgery.

This procedure is normally done before surgery to remove a breast lesion or a melanoma, and surrounding lymph nodes.

  • Before your procedure

    What to bring

    • Your referral form
    • Any relevant previous imaging
    • Your Medicare card and any concession cards


    • A referral from your doctor or medical specialist, and an appointment is required for this procedure.
    • You will normally be admitted to the hospital on the morning of your surgery before being taken to Apex Radiology for the sentinel node study prior to your scheduled surgery time. Occasionally the sentinel node scan is performed on the day before surgery.
  • During your procedure

    When you attend your appointment at Apex Radiology you will be asked to answer a few safety questions, remove any jewellery, watches etc, then change into an examination gown.

    A technologist will explain the procedure to you and position you for the scan. The technologist will then inject the tracer beneath the skin. The tracer is administered after some local anaesthetic is administered, it is done as a single injection technique. This does mean that pain is kept to a minimum, there maybe be some discomfort associated with the injection.

    The scanning process starts after a short delay, during the scan you may breathe normally but must try not move. The initial imaging takes from 10 to 30 minutes, after which a break maybe required with delayed imaging (allowing more time for the tracer to migrate through the lymphatic vessels).

    The gamma camera is a large square radiation detector which sits close to the area being examined. In this procedure, it also rotates around the body while acquiring images (SPECT) for 15 minutes. You will experience no unusual sensations or discomfort during the scan. The images may be combined with a low dose CT (Computed Tomograph) scan done at the same time on the same scanner. This combined SPECT/CT improves the accuracy of the information obtained, and adds just a few minutes to the procedure time.

    Once the sentinel lymph node imaging is complete, it’s the location of the Sentinel node will be marked on your skin.

    Please allow up to four hours for the entire scanning procedure.

  • Risks and side effects

    Nuclear medicine examinations are considered very safe with almost no reported adverse reactions attributable to the radiopharmaceuticals used in these examinations. Nuclear Medicine studies require very small doses of gamma radiation and are only performed where the benefits of the examination are deemed to outweigh any potential risks. At Apex Radiology you can be assured that using the latest technology and with staff trained in radiation reduction techniques, radiation doses are kept as low as reasonably possible.

    If you are worried or concerned about having a Nuclear Medicine study you should discuss this with your referring doctor or medical specialist before coming for your examination. If you think you may be pregnant, please inform our Nuclear Medicine team before your examination.

    For further information regarding radiation safety please visit:

  • Who will perform and report my examination?

    At Apex Radiology your stress test procedure will be carried out by a Nuclear Medicine Technologist who has a degree in Medical Radiation Science and is accredited by the Australian Health Practitioner Registration Agency (AHPRA). Your images will be reviewed along with your relevant medical history, and any other imaging, and be reported by our Nuclear Medicine credentialed radiologist or Nuclear Medicine physician (a medical doctor specialising in the interpretation of Nuclear Medicine studies).

  • After your procedure

    The radioactive tracer will decay over time and the body will eliminate any residue through the kidneys and bowel and you are free to resume normal activities. If you are caring for a small child, or breastfeeding, we may ask you to take some minor precautions.

  • How do I receive my results?

    Your images will be sent with you to theatre for the surgeon to refer to during your surgery. A report of your procedure will also be sent to your referring doctor.

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