Some Effects of Time Post-Mortem on Ultrasonic Transmission through Tissue Under Different Modes of Handling

Changes in the transmission of 4 MHz acoustic energy through beef spleen were measured as a function of time post-mortem for various handling methods. Samples were observed after either being kept cool and moist, dried at room temperature, or frozen then thawed and dried at room temperature. Transmitted energy through cool moist tissue was nearly constant for the first fifty hours but then decreased at a rate of 0.267 dB/h whereas dried tissue exhibited a steady decline of 0.067 dB/h. Frozen tissue was essentially opaque to ultrasound but after thawing and drying, it behaved like non-frozen dried tissue. A sample of human uterine tissue showed no changes in the first 1.5 h after removal.