Cyclic variation in reflectivity of isolated cardiomyocytes: a scanning acoustic microscopy study

Cyclic variation of myocardial integrated backscatter (IB) has been studied extensively. In normal myocardium, IB is low during contraction and high on relaxation. To gain more insight in this phenomenon, the influence of contraction on reflectivity was measured at a cellular level in this study. Reflectivity has been assessed using acoustic microscopy at 1.0 GHz under relaxation and contraction in 4 isolated rat myocytes. In the images it can be seen that myofibrils are probably the responsible scatterers. On contraction the cells, and the myofibrils and increase their diameter. Since these myofibrils are smaller than the wavelength of the applied ultrasound, one would expect an increase in reflectivity. This is in agreement with the authors' experiments, however still in contradiction with the observations in vivo at lower frequencies.