please ask some questions Aims To investigate the synergistic anti-tumor efficacy and mechanism of perfusion enhancement effect by ultrasound stimulated microbubbles cavitation USMC combined with PD-L

What is the focus of this study?
How were the tumor-bearing mice divided into groups for the study?
What system was used for USMC treatment and what were the treatment parameters?
What were the methods used to assess the anti-tumor efficacy of the treatment?
What were the four aspects explored to determine the synergistic mechanisms of USMC combined with anti-PD-L1?
What was the concentration of anti-PD-L1 in tumors in the combined group compared to the monotherapy group?
How did CEUS prove tumor perfusion enhancement in the combined group and what did IF show regarding vessel density?
How did the combination therapy improve the tumor immune microenvironment?
What was the result of ELISA analysis regarding tumor hypoxia in the combined group?
What conclusion was drawn from the study regarding the effectiveness of USMC combined with anti-PD-L1 therapy