Quantitative Ultrasound for the Monitoring of Novel Microbubble and Ultrasound Radiosensitization

There is a need for cancer imaging to provide “real-time” information about the metabolic and cellular responses of tumours. Quantitative ultrasound techniques have recently been demonstrated to be a potential method of assessing tumour response at the cellular level. Anti-cancer treatments administered to xenograft-bearing mice consisted of radiotherapy and a novel antivascular therapy utilizing encapsulated microbubble agents in the presence of ultrasound. Radiation dose and microbubble concentrations were varied and the treatment modalities were given in combination to assess the possible enhancement of tumour cell death. Quantitative methods were used to non-invasively assess responses. Results demonstrated statistically significant changes in backscatter parameters (midband fit, spectral intercept) in tumours treated with high doses of radiotherapy or a high concentration of microbubbles. Combined treatments demonstrated further increases in ultrasound parameters. Histopathologic assessment was used and tumour cell death was found to correlate with increases in ultrasound parameters.