Biochemical state in tissue can be detected through ultrasound signal

Three-dimensional (3D) cell cultures, such as spheroids, are indispensable models for investigating cellular behaviors and responses under conditions that closely resemble in vivo environments. Conventional imaging techniques, including optical microscopy, are often limited by penetration depth and phototoxicity, complicating the analysis of structural and biochemical changes within dense 3D systems. This study demonstrates the application of ultrasound imaging for the non-invasive evaluation of internal dynamics in cancer spheroids over a 15-day period. Scattering-based acoustic parameters revealed spatial variations in brightness and density, correlating with cellular proliferation, apoptosis, and necrosis. Brightness values in central regions progressively decreased after Day 3, approaching near-zero by Day 15, reflecting necrotic core formation. Artificial inhibition of myosin contractility significantly influenced these patterns, providing insights into biomechanical contributions to spheroid organization. The findings establish ultrasound imaging as a label-free, high-penetration technique capable of addressing critical challenges in 3D culture analysis, offering new opportunities for studying cellular dynamics and therapeutic responses in spheroids and organoid models.