Assessment of tumor vasculature for diagnostic and therapeutic applications in a mouse model in vivo using 25-MHz power Doppler imaging

Objective: The blood flow rate in the microcirculation associated with angiogenesis plays an important role in the progression and treatment of cancer. Since the microvascular status of tumor vessels can yield useful clinical information, assessing changes in the tumor microcirculation could be particularly helpful for tumor evaluation and treatment planning. Methods: In this study we used a self-developed 25-MHz ultrasound imaging system with a spatial resolution of 150 μm for assessing tumor-microcirculation development and the pattern of the vasculature in three tumor-bearing mice in vivo based on power Doppler images. The total Doppler power (DP) and color pixel density (CPD) revealed the presence of functional vessels distributed throughout a tumor volume. The vasculature distributions in the core and periphery were compared to the regulation of vasculature function, which facilitated determination of when the tumor grew rapidly. Results: The data obtained from a quantified analysis of power Doppler images indicated that the tumor vascularity initially increased throughout the tumor. Both DP and CPD increased rapidly in the tumor periphery when the tumor volume exceeded 10 mm³. Conclusion: Our preclinical findings suggest that power Doppler imaging could be useful for detecting the changes in tumor vascular perfusion and for determining the optimal treatment timing when a tumor begins its rapid volumetric growth.