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Published September 2008 | Published
Journal Article Open

Noninvasive photoacoustic identification of sentinel lymph nodes containing methylene blue in vivo in a rat model


Sentinel lymph node biopsy (SLNB) has become the standard method of axillary staging for patients with breast cancer and clinically negative axillae. Even though SLNB using both methylene blue and radioactive tracers has a high identification rate, it still relies on an invasive surgical procedure with associated morbidity. Axillary ultrasound has emerged as a diagnostic tool to evaluate the axilla, but it can only assess morphology and cannot specifically identify sentinel lymph nodes (SLNs). In this pilot study, we propose a noninvasive photoacoustic SLN identification system using methylene blue injection in a rat model. We successfully image a SLN with high optical contrast (146±41, standard deviation) and good ultrasonic resolution (∼500μm) in vivo. We also show potential feasibility for clinical applications by imaging 20- and 31-mm-deep SLNs in 3-D and 2-D, respectively. Our results suggest that this technology would be a useful clinical tool, allowing clinicians to identify SLNs noninvasively in vivo.

Additional Information

© 2008 SPIE. Paper 08070R received Feb. 28, 2008; revised manuscript received May 28, 2008; accepted for publication May 29, 2008; published online Sep. 15, 2008. We are grateful to Konstantin Maslov for experimental assistance. This research is sponsored in part by National Institutes of Health grants R01 EB000712 and R01 NS46214 (BRP).

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