Abstract
Intricate variations and poor visual access result in the difficulties in studying ultrasound targeted imaging using an animal model. Here, we propose a simple phantom model based on the maleimide-cysteine interaction between maleimide bubbles and natural gelatin, as depicted in Fig. 1(a). DSPE-PEG2000-maleimide (3 mol%) were used to fabricate maleimide bubbles. Porcine gelatin (4% w/v) was used to prepare flat phantoms and flow phantoms. The flat phantoms were used to quantify the relationship between the densities of adherent maleimide bubbles and their acoustic responses. The flow phantoms were used to study the adhesion behaviors of flowing maleimide bubbles with and without applying an acoustic radiation force. An optical microscope and a 40-MHz ultrasound imaging system were adopted in the experiments. The optical image and corresponding ultrasound image (C-scan mode) presented in Fig. 1(b) and (c), respectively, indicate that abundant maleimide bubbles anchored to the surface of a flat phantom without losing their acoustic activity. The intensity of ultrasound backscattered signal can achieve 40 dB at a density of 1.47×105 adherent-bubbles/mm2. The adherent bubbles exposed to 300-kPa ultrasound pulses can be disrupted rapidly. However, increasing the adhesion density to 3.62×105 adherent-bubbles/mm2 can prolong their lifetime by up to 40 minutes. The maleimide bubble in a 1-mm diameter chamber with a flow rate of 3 mL/h can adhere to the chamber wall, as shown in Fig. 1(d). Applying one acoustic radiation force substantially increases the bubble adhesion efficiency, as shown in Fig. 1(e). In this work we propose a simple phantom model providing the flowing bubbles, adherent bubbles, and tissue mimicking structure for studying ultrasound targeted imaging. Potential applications of this model include evaluating the performances of different ultrasound targeted imaging strategies, as well as the efficacies of various acoustic radiation forces applied for enhancing targeting efficiency