Chan Kyo Kim MD, PhD, Presenter: Nothing to Disclose

Boem Ha Yi MD, PhD, Abstract Co-Author: Nothing to Disclose

Omid Yeganeh MD, Abstract Co-Author: Nothing to Disclose

Wenjin Cui, Abstract Co-Author: Nothing to Disclose

Christopher Barback, Abstract Co-Author: Nothing to Disclose

Robert Frederick Mattrey MD, Abstract Co-Author: Investigator, Bracco Group

Indirect lymphosonography where microbubbles (MB) are injected subcutaneously within the sentinel lymph nodes (SLN) drainage field was developed to non-invasively detect, mark and possibly stage the SLN pre-operatively. Early clinical data suggest accurate localization but limited characterization. Since entry into the lymph duct (LD) is limited to particles <200nm, entry of a few micron-sized MBs aided by massage maybe sufficient for detection but insufficient for characterization. While nanobubbles (NB) would have an advantage, they are more fragile and less effective as ultrasound (US) contrast agents. In this study we hypothesized that the greater entry of NBs could overcome the limited US performance to improve SLN filling.

10^8 MBs of Definity (1-3µm) (Lantheus Medical Imaging) or a new formulation of DSPC/DSPE-PEG and perfluorohexane (0.2-1µm) in 0.2ml were injected in either footpad of 6 normal rabbits. The Siemens Sequoia 15L8 probe was fixed over the popliteal node that was imaged with CPS. Immediately after injection, a few MBs entered the LD to place an ROI over the SLN and its afferent LD. The US field was cleared and the footpad massaged for 20 sec. A time-intensity curve (TIC) was constructed in real-time using a prototype Siemens software that analyzes the linearized CPS data but also uses the B-mode data to correct for motion while scanning at low MI and 15 frames/sec. At 20 minutes or when the TIC returned to baseline, the US field was cleared and the 20-sec massage repeated until peak enhancement and the process repeated until no enhancement occurred. The TIC following the 1st massage and the number of massages that refilled the SLN following each injection were recorded.

Both agents enhanced the SLN and LD after massage. NBs caused greater SLN (p=0.003) and LD (p=0.001) enhancement that lasted for 20min vs. 8 min. The SLN refilled >20 times following a NB dose but only 8 times following a MB dose (p= 0.001).

NBs not only improve the filling of the duct and SLN, but also provided more functional bubbles at the injection site. We will next compare their ability to characterize nodes.

Nanoscale bubbles increase duct filling and node enhancement and provide more functional bubbles at the injection site to refill the duct and node to improve detection and possibly characterization.

Kim, C, Yi, B, Yeganeh, O, Cui, W, Barback, C, Mattrey, R, Optimizing Microbubble Formulation for Indirect Lymphosonography: Quantitative Comparison of Nanobubbles vs. Standard Microbubbles.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13020896.html