In-vivo quantitative analysis of the angiogenic microvasculature in tumor-bearing rats using multiple scattering: A preliminary study

Abstract

We propose a method to quantify the vascular density in vascular networks using contrast-enhanced multiple scattering. We measured the diffusion constant D and transport mean free path L* from the time evolution of the incoherent intensity in a rat model of cancer. An 8 MHz linear transducer array was used to record the backscattered signals from subcutaneous fibrosarcoma tumors and control tissue. The coherent and incoherent contributions to the backscattered intensity were separated, and the growth rate of the incoherent contribution was measured, giving the D and L*, knowing the effective speed of sound. By translating the linear array along the tumor, mapping of L* was achieved. Tumors were implanted in the right flank of four rats, and the contralateral side served as control. Acoustic angiography and measurements of the incoherent intensity were performed. The mean L* values in control and tumor tissue were significantly different (105.27 + /- 30.96 micron and 41.28+ /- 14.23 micron, respectively, p = 8.4033 × 10-49). The mean distance between vessels was estimated from acoustic angiography images using Monte-Carlo simulations, and was in agreement with the experimentally calculated values of L* (r = 0.9507, p = 1.4957 × 10-9).

Study of Poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM) Microgel Particle Induced Deformations of Tissue-Mimicking Phantom by Ultrasound Stimulation

“…8,9 While the effect of ultrasound on microgel deformability has not been studied previously, interactions between ultrasound and highly deformable droplets and microbubbles have been studied in the past few decades for diagnostic and therapeutic applications. 10 Ultrasound contrast agent (UCA) microbubbles are used in combination with ultrasound insonification for numerous applications, including contrast-enhanced ultrasound imaging, 11,12 enhancing effectiveness of high intensity focused ultrasound (HIFU) treatments, 13 multiple scattering based quantitative ultrasound tissue characterization, 14 targeted drug delivery, 15 enhancing drug uptake by tumors, 16 and noninvasive molecular imaging. 17 Advanced technologies such as advanced droplet vaporization (ADV) allow for the use of liquid-based agents, rather than gas bubbles, that phase transition into gas bubbles upon insonification with ultrasound.…”