Michaelle Cadet, Utah Valley University
Breast cancer is the most common cancer among women in the United States. Tumor angiogenesis and its inhibition is an important aspect of oncology and the treatment of cancer. High-frequency ultrasound (10-100 MHz) is particularly sensitive to small vascular structures that are close in size to the ultrasound wavelength (15-150 _m). The ability to rapidly determine the degree of vascularization in small animals in vivo would provide a useful characterization tool for breast cancer studies. The objective of this study was to determine if direct ultrasonic measurements in the 10-100 MHz range could be used as a vascularization assay for breast tumors and other tissues. To accomplish this, six mice from the Huntsman Cancer Institute (Salt Lake City, Utah) with grafted breast cancer tumors (three control and three treated with an angiogenesis inhibitor called Avastin) were tested in vivo using through-transmission ultrasonic measurements. A second study was also performed at the Ludwig Boltzmann Institute for Experimental and Clinical Traumatology (Vienna, Austria), where the femoral artery in one hind leg of each of sixteen mice was ligated and tested over the time period of eight days. Eight of the ligated limbs were treated with vascular endothelial growth factor (VEGF) while the remaining eight ligated limbs were allowed to grow ischemic. The unligated limbs were controls. Results from the Huntsman Cancer Institute study indicated that breast tumors in Avastin-treated mice showed higher ultrasound velocities than control tumors. This can be ascribed to the vasculature in the nontreated tumors creating greater wave scattering in the tissue, thus decreasing the velocity. Results from the Boltzmann Institute study indicated that in mice with ligated femoral arteries, ultrasonic signals from ischemic limbs displayed a decrease in wave velocity over the test period as compared to the VEGF-treated limbs. However, both the ischemic and VEGF-treated limbs showed decreases in ultrasonic attenuation during the entire test period. Results from Avastin-treated mouse tumors and mouse limbs with ligated femoral arteries revealed that high-frequency ultrasound holds potential for measuring angiogenesis in vivo.