High-frequency ultrasound: Determination of the lowest frequency required for cellular imaging and detection of myocardial disease

We have previously demonstrated that a 600 MHz transducer enables the visualization of cellular detail in specimens of myocardium. However, lower-frequency transducers are more practical and provide better tissue penetration for possible in vivo application of this technique. This study was designed to ascertain the lowest frequency at which cellular detail can be imaged. We performed ultrasound imaging of 5 μm sections of 14 samples of myocardium. Each specimen was examined serially with 600 MHz, 400 MHz, 200 MHz, and 100 MHz transducers. Normal cardiac myocytes and pathologic phenomena such as fibrosis, cell fallout, and round cell infiltration were clearly identified with a 600 MHz transducer. Although there was a slight decrease in resolution, normal and pathologic phenomena were also identified with 400 and 200 MHz transducers. However, cellular detail could not be adequately identified with a 100 MHz transducer. In conclusion, transducer frequencies of 600 to 200 MHz enable visualization of cell detail and detection of pathologic changes in the myocardium. A transducer frequency of at least 200 MHz is probably required for possible in vivo application of this technique.