Differentiation between acutely ischemic myocardium and zones of completed infarction in dogs on the basis of frequency-dependent backscatter

Abstract

The goal of this work was to determine whether the frequency dependence of apparent backscatter coefficient (not corrected for attenuation within the myocardium) could differentiate completed, remote infarction from acute myocardial injury in vivo. Myocardial infarcts were produced in six dogs by coronary artery occlusion. One to 12 months later, acute ischemic injury was induced in each dog by ligation of a coronary artery that supplied a region of myocardium adjacent to the established infarct. Infarct, ischemic, and normal regions were interrogated with a 5-MHz, circular, 0.5-in. diam, broadband, focused, piezoelectric transducer mounted in a water-filled stand-off device placed against the exposed, beating heart. Apparent backscatter coefficients were measured over the range of frequencies from 3-7 MHz. The frequency dependence was obtained from the slope of log apparent backscatter coefficient versus log frequency. No significant difference in frequency dependence was found between normal and acutely ischemic myocardium for periods of up to 2 h of ischemia. In contrast, frequency dependence in regions of remote infarct (1.8 +/- 0.1, mean +/- standard error) was significantly lower than that in acutely ischemic or nonischemic regions (2.3 +/- 0.1) (p less than 0.01). These results suggest that remote myocardial infarction can be differentiated from acutely injured but still potentially salvageable myocardium in vivo on the basis of the frequency dependence of backscatter.

Ultrasonic tissue characterization with integrated backscatter. Acute myocardial ischemia, reperfusion, and stunned myocardium in patients.

“…The clinical characteristics of patients studied are shown in Table 1. Some (16) were treated within 4 hours of the onset of chest pain with intravenous recombinant tissue-type plasminogen activator (rt-PA) as part of the multicenter Thrombolysis in Myocardial Infarction (TIMI) trial at the Washington University Medical Center, and one patient was treated within 4 hours with intravenous streptokinase. One (patient 7) was not given a thrombolytic agent but underwent acute percutaneous transluminal coronary angioplasty (PTCA).…”

Anisotropy of the backscatter coefficient of formalin-fixed ovine myocardium

“…The quantity reflecting the intrinsic scattering properties of myocardial tissue is the backscatter coefficient. There have been a number of studies carried out to measure the backscatter coefficient in myocardium ͑Hall et Wear et al, 1989͒. The study by O'Donnell et al ͑1981͒ utilized a modified compensation method for backscatter coefficient estimates in myocardium and limited their measurements to one angle of insonification relative to the myofiber direction. Wear et al ͑1989͒ implemented an enhanced formalism to study the backscatter properties of myocardium with assumed attenuation properties at a specific insonification angle.…”

A backscatter difference technique for ultrasonic bone assessment

“…The approach that follows was developed by Sigelmann and Reid (1973) and later adapted for tissue characterization studies by O'Donnell and Miller (1981). Different approaches have been suggested by other investigators (Madsen et al, 1984;Wear et al, 1989;Chen et al, 1997).…”