title: Influence of attenuation on measurements of ultrasonic myocardial integrated backscatter during cardiac cycle (an in vitro study).
abstract: The purpose of this study was to investigate the dependence of ultrasonic integrated backscatter (IB) and attenuation in myocardium on wall thickness in a state of acute ischemia. Therefore, an in vitro experiment was set up in which attenuation, IB and wall thickness of a piece of freshly excised myocardium could be measured almost simultaneously. The myocardium was taken from 11 Yorkshire pigs (25-30 kg) that were killed less than 45 min before the experiment. The myocardium was placed in the far field of an ultrasound transducer (3.2-7.2 MHz) and then compressed by a stainless steel sphere. Data were processed off-line. Backscatter and attenuation were also measured as a function of frequency at 100% and 75% wall thickness, respectively. Both attenuation and IB varied during compression. Attenuation had an initial value of 2.19 +/- 0.76 dB/cm and a slope of 0.015 +/- 0.017 dB/cm% wall thickness. IB had an initial value of -76.9 +/- 2.7 dB and a slope of -0.12 +/- 0.07 dB/% wall thickness. After subtracting the influence of the attenuation from the IB the initial value of IB was -74.0 +/- 2.7 dB and the slope -0.08 +/- 0.07 dB/% wall thickness. Attenuation appeared to have a linear dependency on frequency. Backscatter appeared not to increase with increasing frequency without correction of the spectrum for the frequency dependent insonified volume.
authors.affiliation: Thorax Centre, Erasmus University Rotterdam, The Netherlands.
authors.forename: A F
authors.initials: AF
authors.lastname: van der Steen
authors.forename: H
authors.initials: H
authors.lastname: Rijsterborgh
authors.forename: F
authors.initials: F
authors.lastname: Mastik
authors.forename: C T
authors.initials: CT
authors.lastname: Lancée
authors.forename: W M
authors.initials: WM
authors.lastname: van Hoorn
authors.forename: N
authors.initials: N
authors.lastname: Bom
mesh_terms: D000818:Animals; D004452:Echocardiography / Q000379:methods*; D006321:Heart / Q000033:anatomy & histology; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D013552:Swine; D014465:Ultrasonics