Acoustic enhancement with fundamental imaging and CPS imaging: comparison between nano-scale PFOB lipidic particles and C3F8 lipidic microbubbles,a vitro experimental study

Abstract

Objective To prepare two kinds of nano-scale ultrasound contrast agents, perfluorooctyl bromide(PFOB) lipidic particles and perfluoropropane(C3F8) lipidic microbubbles, and compare their characteristics of acoustic enhancement with fundamental imaging and contrast pulse sequence(CPS) imaging in vitro. Methods Physico-chemical properties of PFOB lipidic particles and C3F8 lipidic microbubbles were measured, including morphous, size distribution, Zeta potential, concentration and stability. PFOB lipidic particles with and without biotin, C3F8 lipidic microbubbles with and without biotin were prepared, respectively. Size distribution of four contrast agents were measured, before and after adding avidin. Then, four kinds of ultrasound contrast agents were imaged with both fundamental and CPS imaging before and after avidin was added. Signal intensities were compared using METLAB software. Results ①Addition of avidin had no effect on particle diameters of control lipidic particles/microbubbles. However, the particle diameters of biotinylated lipidic particles and microbubbles were both enlarged with the addition of avidin (P<0.05). ②With fundamental imaging, neither control nor biotinylated PFOB particles were visible before adding avidin. After avidin was added, significant signal enhancement from biotinylated PFOB particles was detected (P<0.05); while control PFOB particles were still unvisible.However, with fundamental imaging, both control and biotinylated C3F8 microbubbles manifested ultrasonic backscatter before and after adding avidin, without significant difference between their signal intensity. ③CPS imaging couldn′t detect nonlinear signal from biotinylated PFOB particles neither before nor after the addition of avidin. However, CPS imaging could detect nonlinear signal from biotinylated C3F8 microbubbles both before and after adding avidin, without significant difference in their signal intensity. Conclusions Compared to C3F8 microbubbles, PFOB particles have better particle size controllability, and higher signal-to-noise (target to nontarget signal) ratio, thus are more suitable for targeted contrast ultrasound imaging. Key words: Ultrasonography; Microbubbles; Liposomes; Perfluorooctyl bromide