Cameran Mecham, Utah Valley University
Tissue vascularization, or angiogenesis, is the principal means of promoting and sustaining life as well as allowing for cell differentiation. Angiogenesis allows for the proliferation of tissue and is also a significant precursor to benign and malignant tumor growth. As tumors grow, their cells send chemical signals, known as growth factors, to outlying blood vessels that promote the growth of new vasculature. Previous studies with breast tumors and ligated femoral arteries in mice have indicated that high-frequency ultrasound (10-100 MHz) may be sensitive to angiogenesis. The ultrasonic parameters found to be most sensitive are wave velocity and attenuation.
The goal of this project is to further explore the connection between high-frequency ultrasound and vascularization. This project used early stage chick embryos as a model organism due to the lack of cartilaginous structure that could impede wave propagation through the tissue, thus interfering with the ultrasonic signal associated with angiogenesis. The rapid progression of angiogenesis additionally makes early stage chick embryos a suitable model organism for this project. Chick embryos begin to differentiate the hemangioblasts after roughly 24 hours, and have fully functional blood islands and blood vessels after 72 hours. The objective of this study was to develop and test the ultrasonic measurement methods with unfertilized eggs.
The methods for this project were as follows. Yolk and albumin from a fertilized chicken egg were removed from the shell and placed in a petri dish. The petri dish was placed in an incubator for 72 hours at 16 ˚F to facilitate embryogenesis. A 50-MHz immersion transducer was placed in contact with the yolk to transmit ultrasonic pulses through the developing embryo to an identical transducer coupled to the bottom of the petri dish. The transducers were connected to a high-frequency pulser-receiver and oscilloscope outside the incubator via cables, and ultrasonic measurements were collected in pitch-catch mode every 15 minutes during the incubation period. Data was analyzed by measuring the timeof- flight and amplitude of the ultrasonic pulses to determine the ultrasonic wave velocity and attenuation as a function of embryo growth time. For this study, unfertilized eggs were used to develop and test the above methods.
Testing has shown that the transducer-embryo measurement setup provides strong ultrasonic signals from unfertilized yolks in petri dishes. The signal characteristics are well suited for velocity and attenuation measurements. Additionally, testing has shown that ultrasonic waveforms can be collected automatically for periods of several hours from ultrasonic transducers positioned on samples in an operating incubator. The next stage of this project will comprise actual testing of chick embryos in the incubator.