CONTRAST ASSISTED ULTRASOUND IMAGING OF TUMORS

University Of California Davis, Davis CA

Investigators

Linked publications & trials

Abstract

[unreadable] DESCRIPTION (provided by applicant): With the advent of anti-angiogenic cancer therapies, effective treatment will require imaging techniques and other surrogates that can establish the optimal dose, provide an early assessment of efficacy, and reduce toxicity associated with systemic delivery of hydrophobic drugs. Ultrasound can play a major role in both the assessment of therapeutic efficacy and the improvement of therapeutic delivery. While molecular imaging will be important for understanding angiogenesis and anti-angiogenic therapies, ultrasound can continually evaluate the cumulative effects of biochemical pathway changes on the resulting vascular structure and function. Over the past four years of this project, a new contrast-assisted ultrasound imaging technique has been developed that can assess angiogenesis through an estimate of microvascular flow rate and density in tumors. The ultrasound technique is unique in that phase inversion and subharmonic acquisition are combined to achieve a clear image of an ultrasound contrast agent, and its motion over time. As a result, a contrast agent to tissue ratio exceeding 27 dB is achieved. Preliminary studies in a rat tumor model have shown that microvascular density and flow rate can be estimated over time, and the resulting map of viable tumor volume correlates with histology. Tumors that reach 1-3 centimeters in diameter demonstrate heterogeneous perfusion and include regions with a blood velocity less than 1 mm/s. Human studies of the performance of this new technique during established chemotherapy will be conducted in this renewal. Pre-clinical studies with new anti-angiogenic drugs will also be conducted in a cross-modality study to create spatial maps of flow rate, vascular density, vascular permeability, and glucose metabolism, using ultrasound, PET, and CT. In implanted rat and spontaneous dog tumor models, a small molecule inhibitor of VEGF,bFGF, and PDGF receptor tyrosine kinase activity is the anti-angiogenic drug that will be applied. As correlates, P53, bFGF, and VEGF expression and apoptosis and cell proliferation will be evaluated. The resulting flow, permeability, and metabolic data will be used to create measures that predict the success or failure of a therapy. Since these hydrophobic drugs are now suspended in Cremophor for human use, a final aim is to develop acoustically-activated drug delivery vehicles that provide an alternative to the toxicity of Cremophor.