In vivo photoacoustic (PA) mapping of sentinel lymph nodes (SLNs) using carbon nanotubes (CNTs) as a contrast agent
Sentinel lymph node biopsy (SLNB), a less invasive alternative to axillary lymph node dissection (ALND), is routinely used in clinic for staging breast cancer. In SLNB, lymphatic mapping with radio-labeled sulfur colloid and/or blue dye helps identify the sentinel lymph node (SLN), which is most likely to contain metastatic breast cancer. 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. In this study, we have demonstrated a non-invasive single-walled carbon nanotube (SWNT)-enhanced photoacoustic (PA) identification of SLN in a rat model. We have used single-walled carbon nanotubes (SWNTs) as a photoacoustic contrast agent to map non-invasively the sentinel lymph nodes (SLNs) in a rat model in vivo. We were able to identify the SLN non-invasively with high contrast to noise ratio (~90) and high resolution (~500 μm). Due to the broad photoacoustic spectrum of these nanotubes in the near infrared wavelength window we could easily choose a suitable light wavelength to maximize the imaging depth. Our results suggest that this technology could be a useful clinical tool, allowing clinicians to identify SLNs non-invasively in vivo. In the future, these contrast agents could be functionalized to do molecular photoacoustic imaging.
Additional Information© 2009 Society of Photo-Optical Instrumentation Engineers (SPIE). This work was supported by National Institutes of Health grants (R01 EB000712, R01 NS46214 (Bioengineering Research Partnerships), R01 EB008085, and U54 CA136398 (Network for Translational Research) - LVW) and the Office of the Vice President of Research at Stony Brook University, Carol M. Baldwin fund (SB). L.W. has a financial interest in Endra, Inc., which, however, did not support this work. The authors would like to thank Dr. Oleg Gang and Dr. Huming Xiong at the Center for Functional Nanomaterials, Brookhaven National Laboratory for access to the AFM, Mr. Tom Salagaj and Mr. Christopher Jensen at FirstNano/CVD Equipment Corporation for access to their CVD facilities and Dr. Eunah Lee at Horiba JvonYvon, Edison, NJ for the Raman Spectroscopy measurements.
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