Tumor Vascular Assessment using Contrast and Photoacoustics

This recent study by Bar-Zion et al. in the prominent journal, Cancer Research, highlights the significance and validity of contrast-enhanced ultrasound and photoacoustics (PA) to assess vascularity in tumors and to monitor efficacy of treatment dynamically over time. Both vascular morphology and functional perfusion and oxygenation were assessed and validated with histology.

Article Summary:
Tumor vascularity, perfusion and the tumor microenvironment are associated to tumor aggressiveness and response to treatment
Blood lakes are static pools of blood in tumors, indicative of leaky vessels
Neither blood lakes or necrotic regions have functional vasculature
Study used 3 tumor models (2 hind-limb models, 1 orthotopic breast model)
Differences between tumor models were seen in the size and presence of functional vessels and the presence of hypoxia; differences were confirmed with histology
PA + contrast allowed differentiation of blood lakes and necrotic regions
Both were non-perfused (detected with contrast)
Blood lakes have high hemoglobin; necrotic regions have low hemoglobin (detected with photoacoustics)
PA + contrast detected decreased blood flow rate and perfusion after treatment
Decreased vascularity confirmed with histology
Detected a 40% decrease in tumor oxygenation in treated vs. control mice
Histology confirmed a 45% increase in hypoxia in treated vs control mice
This study concludes that combined contrast-enhanced ultrasound and photoacoustics can accurately:
Assess morphology and function in tumor vasculature
Differentiate between viable tissue, necrotic regions and blood lakes within tumors
Monitor treatment efficacy with high correlations with histological assessments
1. Bar-Zion A, Yin M, Adam D, Foster FS. Functional Flow Patterns and Static Blood Pooling in Tumors Revealed by Combined Contrast-Enhanced Ultrasound and Photoacoustic Imaging. Cancer Res. June 2016. doi:10.1158/0008-5472.CAN-16-0376.