Sentinel node identification using microbubbles and contrast-enhanced ultrasonography

Sentinel lymph node (SLN) biopsy has become the recommended method for surgical staging of the axilla in patients with breast cancer. Grey-scale axillary ultrasonography (US) combined with US-guided biopsy is a widely used preoperative staging procedure but has limited sensitivity. US contrast agent "microbubbles", when injected intradermally, have been shown to have the potential to enter the breast lymphatics, travel rapidly to the axilla, and visualize the putative SLNs. This review illustrates the SLN identification technique using intradermal injection of microbubbles and contrast-enhanced US. The injection method, lymphatic visualization techniques, grey-scale and contrast-enhanced US images of the putative SLNs are reviewed and exemplified.