Quantitative ultrasound analyses of cell starvation in HT-29 pellets

Spectral analysis of ultrasound backscatter data has been shown to be sensitive to cellular changes, particularly due to apoptosis. Different therapies that seek to destroy cells work activate different cell death mechanisms, most commonly apoptosis, but also oncosis or ischemic death. Pellets of HT-29 colon adenocarcinoma cells were placed in PBS at room temperature over the course of 56 hours and were imaged with high-frequency (55 MHz) ultrasound and the raw RF data processed. Due to the lack of nutrients available to the cells, they underwent oncosis. Attenuation slope, speed of sound (SOS), spectral slope and midband fit (MBF) were estimated every 8 hours over the course of 56 hours to determine changes due to starvation. The spectral slope decreased through time, with an increase at 40 hours. Midband fit and attenuation both showed a trend through time with three phases with the first significant increase at 16 hours and a second significant increase at 40 hours. Speed of sound increased from 1513 m/s to 1534 m/s with time. A decrease in cellular number density and increase in inter-cellular debris is evident on histological slides. Results show different trends than observed for cells undergoing apoptosis, suggesting there are specific signatures that can be exploited to determine changes in cell morphology associated with different mechanisms of cell death.