Manojit Pramanik et al 2009 Phys. Med. Biol. 54 3291 doi:10.1088/0031-9155/54/11/001
Manojit Pramanik1, Kwang Hyun Song1, Magdalena Swierczewska2, Danielle Green2, Balaji Sitharaman2 and Lihong V Wang1
Show affiliationsSentinel lymph node biopsy (SLNB), a less invasive alternative to axillary lymph node dissection (ALND), has become the standard of care for patients with clinically node-negative 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 successfully imaged the SLN in vivo by PA imaging (793 nm laser source, 5 MHz ultrasonic detector) with high contrast-to-noise ratio (=89) and good resolution (~500 µm). The SWNTs also show a wideband optical absorption, generating PA signals over an excitation wavelength range of 740–820 nm. Thus, by varying the incident light wavelength to the near infrared region, where biological tissues (hemoglobin, tissue pigments, lipids and water) show low light absorption, the imaging depth is maximized. In the future, functionalization of the SWNTs with targeting groups should allow the molecular imaging of breast cancer.
General scientific summary. Sentinel lymph node biopsy (SLNB) is an invasive tool used for clinical breast cancer staging. The alternative non-invasive photoacoustic imaging method presented here may eventually lead us to non-invasive axillary staging. Other non-invasive methods, such as axillary ultrasound, can show lymph nodes but cannot specifically identify the sentinel node. On the other hand, the photoacoustic technique can specifically identify the SLN. In this technique, a contrast agent (here we used single-walled carbon nanotubes) is injected into the tissue. After a few minutes these agents accumulate in the SLN and help identify the node in the photoacoustic images. Various optical absorbers can be used (such as methylene blue, gold nanocages, gold nanorods, etc) for this purpose, but we have chosen single-walled carbon nanotubes because of their broad optical absorption range and ability for targeted imaging.
For more information on this article see medicalphysicsweb.org
87.85.Qr Nanotechnologies-design
42.62.Be Biological and medical applications
43.80.Qf Medical diagnosis with acoustics (in PACS, see also 87.63.D−)
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
Issue 11 (7 June 2009)
Received 21 January 2009, in final form 2 March 2009
Published 8 May 2009
Manojit Pramanik et al 2009 Phys. Med. Biol. 54 3291
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