Which properties of the vascular architecture are reflected by dynamic contrast-enhanced ultrasound imaging of dispersion and wash-in rate? A comparison with acoustic angiography

Tumor growth requires angiogenesis and neovascularization, resulting in the formation of microvessels which differ in their morphology from those of healthy tissue. These vascular abnormalities result in altered blood flow dynamics, which can be assessed by dynamic contrast-enhanced ultrasound (DCE-US). Two distinct approaches are typically employed in DCE-US: the assessment of either perfusion or dispersion parameters from the measured time intensity curves. In this paper, we look at longitudinal trends of wash-in-rate (WIR), a perfusion parameter, and correlation coefficient, a dispersion parameter, in 3 fibrosarcoma xenograft models. We compare them to the microvascular density (MVD) extracted from acoustic angiography (AA), a high resolution technique enabling the delineation of microvessels. We also compare spatial parameter distributions acquired with both imaging modalities. The performed analysis indicates that WIR reflects MVD, while no microvascular parameter that reflects the correlation coefficient has been identified. We hypothesize that the correlation coefficient reflects properties of smaller vessels than those visible with AA.