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Ultrasound localization microscopy (ULM) unveils the microvascular structures using microbubbles (MBs) flowing in the circulatory system. As ULM relies on the precise localization and tracking of individual MBs, using high MB concentrations yields to high localization errors and ULM failure. ULM is, therefore, constrained to low MBs concentrations, leading to long acquisition times. To tackle this limitation, in this study, we propose an approach based on the injection of distinct monodisperse MBs, each characterized by a specific resonance behavior. As a proof of concept, we acquired and analyzed ultrasound data from a vascular phantom, where we singularly injected two monodisperse MB populations. Data were collected using an ULA-OP equipped with an Esaote LA533 probe. Pulses with a center frequency of 3 MHz and a bandwidth of 1MHz were utilized for imaging. MBs with diameters equal to 2.5 and 4.1 μm were injected in the phantom. MBs uncoupling was then performed exploiting the differences in the second harmonic signal intensity generated by the two MB populations. Results demonstrate the feasibility of monodisperse MBs uncoupling, enabling the use of higher microbubble concentrations for ULM, and thus, reducing acquisition time.
Tuccio et al. (Fri,) studied this question.