Ultrasound for the visualization and quantification of tumor microcirculation

Advances in ultrasound based methods for the non-invasive assessment of the tumor microcirculation are described. Two new ultrasound approaches are hi ghlighted. The first method relies on commercially available ultrasound con trast agents in combination with specialized nonlinear imaging sequences. N onlinear scattering by microbubble contrast agents provides a unique intrav ascular signature that can be distinguished from the echoes caused by surro unding tissues. Through destruction-reperfusion experiments it is possible to use microbubble contrast agents as a tracer revealing the kinetics of tu mor blood flow. The second ultrasound method for examining the microcircula tion involves the use of much higher frequencies. At frequencies on the ord er of 50 MHz, Doppler processing allows the direct assessment of flow dynam ics in realtime in arterioles as small as 15 mum. Three dimensional Doppler maps of flow patterning are presented. The strengths and weaknesses of the se new methods are discussed and the potential for their use in preclinical animal drug studies, clinical drug trials, and prognostic studies is descr ibed.