Combined ultrasonic and photoacoustic system for deep tissue imaging
A combined ultrasonic and photoacoustic imaging system is presented that is capable of deep tissue imaging. The system consists of a modified clinical ultrasound array system and tunable dye laser pumped by a Nd:YAG laser. The system is designed for noninvasive detection of sentinel lymph nodes and guidance of needle biopsies for axillary lymph node staging in breast cancer patients. Using a fraction of the American National Standards Institute (ANSI) safety limit, photoacoustic imaging of methylene blue achieved penetration depths of greater than 5 cm in chicken breast tissue. Photoacoustic imaging sensitivity was measured by varying the concentration of methylene blue dye placed at a depth of 3 cm within surrounding chicken breast tissue. Signal-to-noise ratio, noise equivalent sensitivity, and axial spatial resolution were quantified versus depth based on in vivo and chicken breast tissue experiments. The system has been demonstrated in vivo for detecting sentinel lymph nodes in rats following intradermal injection of methylene blue. These results highlight the clinical potential of photoacoustic image-guided identification and needle biopsy of sentinel lymph nodes for axillary staging in breast cancer patients.
Additional Information© 2011 Society of Photo-Optical Instrumentation Engineers. This work was supported in part by grants from National Institutes of Health (R01 EB000712, R01 EB008085, R01 NS46214, and U54 CA136398 – the Network for Translation Research – to L.V.W.). L.V.W. has a financial interest in Endra, Inc., which, however, did not support this work.
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