Small animal models have been widely used in cardiovascular research when studying the development and treatment of different diseases. This kind of research has promoted the development of noninvasive techniques to assess cardiac tissue and blood vessels of small animals. Recently, we have developed a high-frequency ultrasound imaging system for small animals, in particular, mouse and rat models. In this work, we aim to elucidate the usefulness of using spectral analysis of the received radiofrequency (RF) ultrasound signals to extract quantitative parameters to assess mechanical properties of cardiac and vascular tissues. A custom system that employs high-frequency single-element ultrasound transducers (30–120 MHz) is used for scanning. Various signal and image processing techniques are applied on the received ultrasound signals to reconstruct high resolution B-mode and spectral images. In vitro imaging of isolated heart and vessels of APOE-KO “knock-out” mouse model with atherosclerosis was performed. Power spectral densities (PSD) of RF signals were evaluated within various regions of interests (ROI) including degassed water, normal cardiac tissue, and cardiac tissue with atheroma. Various parameters were extracted from the power spectrum such as the maximum power (Pmax), the frequency at maximum power (Fpeak), and the variance of power spectrum (Pvar). Results of the preliminary spectral analysis indicated larger values for the Pmax, Fpeak, and Pvar parameters for ROI contains atheroma than other regions. For example using the envelop data, the normalized maximum power (Pmax) value for cardiac tissue with atheroma was 0.0 ± 0.789 (dB), whereas for normal tissues it was about −13.71± 0.267 (dB). These results suggest the use spectral images as a quantitative method when assessing mouse hearts and blood vessels noninvasively.
Characterization of skin aging through high‐frequency ultrasound imaging as a technique for evaluating the effectiveness of anti‐aging products and procedures: A review