Goal: Abnormalities of microvascular morphology have been associated with tumor angiogenesis for more than a decade, and are believed to be intimately related to both tumor malignancy and response to treatment. However, the study of these vascular changes in-vivo has been challenged due to the lack of imaging approaches which can assess the microvasculature in 3-D volumes noninvasively. Here, we use contrast-enhanced "acoustic angiography" ultrasound imaging to observe and quantify heterogeneity in vascular morphology around solid tumors.
Methods: Acoustic angiography, a recent advance in contrast-enhanced ultrasound imaging, generates high-resolution microvascular images unlike anything possible with standard ultrasound imaging techniques. Acoustic angiography images of a genetically engineered mouse breast cancer model were acquired to develop an image acquisition and processing routine that isolated radially expanding regions of a 3-D image from the tumor boundary to the edge of the imaging field for assessment of vascular morphology of tumor and surrounding vessels.
Results: Quantitative analysis of vessel tortuosity for the tissue surrounding tumors 3 to 7 mm in diameter revealed that tortuosity decreased in a region 6 to 10 mm from the tumor boundary, but was still significantly elevated when compared to control vasculature.
Conclusion: Our analysis of angiogenesis-induced changes in the vasculature outside the tumor margin reveals that the extent of abnormal tortuosity extends significantly beyond the primary tumor mass.
Significance: Visualization of abnormal vascular tortuosity may make acoustic angiography an invaluable tool for early tumor detection based on quantifying the vascular footprint of small tumors and a sensitive method for understanding changes in the vascular microenvironment during tumor progression.