Ultrasonic tissue characterization of infarcted myocardium by scanning acoustic microscopy.

The purpose of this study was to ultrasonically characterize infarcted human myocardial tissue at the microscopic level by scanning acoustic microscopy. Infarcted myocardial specimens from ten cases with acute myocardial infarction were studied. Specimens were formalin fixed, paraffin embedded and sectioned to 10-micron thickness. A specially developed scanning acoustic microscope system, operating in the 100- to 200-MHz ultrasound frequency range, was used for the measurements. The values of the attenuation constant were 0.94 +/- 0.04 dB/mm/MHz in normal myocardium, 0.71 +/- 0.12 dB/mm/MHz in degenerated myocardium, 0.88 +/- 0.47 dB/mm/MHz in granulation tissue and 1.75 +/- 0.11 dB/mm/MHz in fibrosis. The values of sound speed were 1620.2 +/- 8.2 m/s in normal myocardium, 1572.4 +/- 10.6 m/s in degenerated myocardium, 1590.2 +/- 32.5 m/s in granulation tissue and 1690.3 +/- 9.1 m/s in fibrosis. The ultrasonic properties of the diseased myocardium at the microscopic level will provide important information for ultrasonic tissue characterization at the macroscopic level.