Doppler Ultrasound-Visible SignalMark Microspheres are Better Identified than HydroMARK® Clips in a Simulated Intraoperative Setting in Breast and Lung Tissue

Preoperative breast and lung markers have significant drawbacks, including migration, patient discomfort, and scheduling difficulties. SignalMark is a novel localizer device with a unique signal on Doppler ultrasound. We aimed to evaluate intraoperative identification of SignalMark microspheres compared with HydroMARK® clips. We also assessed the safety and efficacy of SignalMark in the lung. Twelve breasts of lactating pigs were injected with SignalMark or HydroMARK® by a breast radiologist, and subsequently identified using a standard ultrasound machine by three surgeons blinded to marker location. Time to identification of each marker was recorded, with a maximum allotted time of 300 s. To further demonstrate efficacy in lung parenchyma, a second cohort of pigs underwent lung injections. A total of eight SignalMark markers and four HydroMARK® clips were placed in pig breasts. Overall, the surgeons correctly identified SignalMark 95.8% of the time (n = 23/24) and HydroMARK® clips 41.7% of the time (n = 5/12) within 300 s (p < 0.001). The mean time to identification was significantly faster for SignalMark, at 80.8 ± 20.1 s, than for HydroMARK®, at 209.4 ± 35.2 s (p < 0.002). For the lung injections, all 10 SignalMark markers were visible on Doppler ultrasound at the time of placement, and at the 7- and 21-day time points. Surgeons identified SignalMark in significantly less time than HydroMARK® clips in a simulated intraoperative setting, and SignalMark was easily viewed in the lung. These results suggest that SignalMark is a feasible option for efficient intraoperative localization of non-palpable breast and lung tumors using ultrasound guidance.