Intraoperative Identification and Guidance of Breast Cancer Microfoci Using Ultrasound and Near-Infrared Fluorescence Dual-Modality Imaging.

The traditional method of labeling the nonpalpable breast cancer is placing a guidewire or metal marker guided by ultrasound or stereographic mammogram prior to surgery. However, the wire localization has a risk of displacement and could be an obstacle in the surgical course. To avoid these issues, we tried to combine the near-infrared (NIR) fluorescence dye dioctadecyltetramethyl indotricarbocyanine iodide (DiR) and microbubbles (MBs) to realize the dual-modality imaging for breast cancer microfoci intraoperative identification and guidance as a more efficient workflow. First, 24 mice were divided into three groups, injected with DiR nanoparticles (NPs), DiR MBs, and DiR MBs + ultrasound (US), and then, in vivo and ex vivo NIR fluorescence imaging was conducted. The distinction of fluorescence imaging intensity at the tumor site among the three groups was statistically significant (P < 0.001). Group 3 (DiR MBs + US) exhibited the highest fluorescence imaging intensity; the distinctions between group 3 and group 1 (DiR NPs) and group 3 and group 2 (DiR MBs) were both statistically significant (P = 0.001, P = 0.003), while the distinction between group 1 and group 2 was not statistically significant (P = 1.0). The results above validated the advantage of fluorescence imaging by using ultrasound-targeted MB destruction. Second, two kinds of subcutaneous breast cancer mice models [4T1-luc(n = 5)/MCF-7(n = 3)] received tumor resection, and NIR fluorescence and bioluminescence images were obtained to detect tumor residuals. We found that the small residual tumor tissues, metastatic lymph nodes, and even the surrounding infiltrated tissue all can be indicated by the fluorescence imaging and verified with bioluminescence and histological examination. In addition, the residual tumor cells appeared as tumor recurrence 22 days post operation and was confirmed with contrast-enhanced ultrasound (CEUS) in vivo. Thereby, ultrasound-targeted DiR MB destruction and then conversion into DiR NPs was feasible for intraoperative identification and guidance of nonpalpable breast cancer foci.