Conventional frequency evaluation of tumor cell death in response to treatment in vivo

In this study, we investigate for the first time the potential to quantify tumor responses to therapy in vivo, using spectral and signal envelope statistics analysis of conventional frequency ultrasound data. Tumors were grown in SCID mice using a human prostate cell line (PC-3) and treated in three groups consisting of combinations of ultrasonically stimulated micro-bubble anti-angiogenic treatment and 8 Gy doses of single fraction 100 kVp X-ray radiation. Data collection consisted of tumor images in addition to radiofrequency data prior to treatment administration and at 24 h following. Analysis of the normalized power spectra of 10-MHz data yielded an increase in mid-band fit of approximately 3.8±0.7, 4.6±0.8, and 5.8±0.7 dBr compared to data acquired before treatment. Spectral slopes were relatively invariant. However, the 0-MHz intercept followed the trend of the mid-band fit. Signal envelope changes were compatible with observations made from spectral data and linked to correlative increases in cell death. The aim of this research is to investigate the potential of conventional frequency ultrasound to noninvasively quantify response to cancer treatments, laying the groundwork for future investigation into the viability of 10-MHz ultrasound to be employed in a clinical setting.