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Lymphoscintigraphy

Lymphoscintigraphy is a nuclear medicine technique to visualize regional lymphatic drainage, especially for mapping sentinel lymph nodes, from a site of radiopharmaceutical injection.

Radiopharmaceutical

Colloidal agents are used as these particles enter lymphatic channels and migrate to lymph nodes, where they are retained by macrophages. Commonly used agents vary worldwide due to regulatory approval status 1,2:

Technique

To map drainage from cutaneous lesions such as melanoma, radiotracer is injected intradermally around the lesion. Fine (25- or 27-gauge) needles are inserted nearly tangential to the skin, 5 to 10 mm from the lesion margin 1. Typically, two to four sites are injected. About 0.1-0.2 mL of tracer is deposited at each injection site, with a total activity of 7.4-37 MBq (200-1000 μCi1.

To map drainage from the breast, multiple techniques are available, listed here in order of decreasing popularity 2:

  • perilesional (intraparenchymal, peritumoral) injection: on the side of the lesion and generally around the lesion, whether superficial or deep; involving 3-4 mL containing 7.4-111 MBq (200-3000 μCi)
  • cutaneous injection: intradermal or subcutaneous at the skin superficial to the lesion; involving 0.2-1 mL containing 5.55-74 MBq (150-2000 μCi)
  • areolar region injection: injection at the areola rather than at or superficial to the lesion; involving similar volume and activity as the cutaneous injection method
  • intralesional injection: palpation- or image-guided injection into the tumor

Images are usually acquired with a planar gamma camera consisting of a large field-of-view detector, parallel-hole collimator, and energy setting appropriate for Tc-99m (140 keV). Dynamic and/or static acquisitions are performed until 45 minutes to an hour after injection, with the use of a cobalt-57 flood source as needed to outline the body 1. Alternatively, in regions of more complex anatomy such as the head and neck, SPECT-CT can be used for cross-sectional delineation.

The patient is taken to surgery, during which the surgeon can use a handheld gamma probe to localize the nodes containing the highest activity.

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Article information

rID: 73762
Synonyms or Alternate Spellings:
  • Lymphoscintigraphies

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Cases and figures

  • Case 1: breast lymphoscintigraphy
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