Ultrasound-induced orientation of discoid platelets and simultaneous changes in light transmission: preliminary characterisation of the phenomenon.

Discoid platelet suspensions were subjected to ultrasonic fields, in the 1-10 MHz frequency range and at estimated acoustic pressures in the range of 0.05-7.6 X 10(4) Pa. Absolute definition of the acoustic field/pressures was precluded by the small dimensions, and internal reflective surfaces, of the experimental configurations employed. Direct microscopy revealed platelet flow, in patterns consistent with theory for ultrasonically induced streaming. This ultrasonic effect was presumed to be accompanied by platelet orientation since it could be quantitated by simultaneous light transmission measurements. The preliminary characterisation of this phenomenon, defined as ultrasound induced light transmission change (USILTC) is reported, and indicates that it may be readily quantitated in a reproducible manner, but which shows a complex relationship both to pressure and frequency. In addition, qualitative characteristics of the response traces are apparent under certain conditions, particularly 5 MHz above 1 X 10(4) Pa, and may relate to platelet viability. Preliminary evidence is provided and discussed, which suggests that USILTC may be a useful model for studying certain ultrasound bioeffects, and may be a useful tool for indirectly assessing platelet morphology and viability for quality assurance purposes.