title: Estimating myocardial attenuation from M-mode ultrasonic backscatter.
abstract: The objective of this investigation was to determine whether measurements of myocardial attenuation can be obtained from analyses of M-mode images. We exploited the inherent anisotropy of myocardial properties as a means of systematically varying the attenuation to evaluate this M-mode image-based method for myocardial tissue characterization. A commercially available ultrasonic imaging system was used to acquire M-mode images of 24 excised cylindrical specimens from six formalin-fixed sheep hearts that were analyzed using video signal analysis. Data were compensated for the presence of bright intramural myocardial echoes, a potentially significant contributor to uncertainty in measurements of attenuation from backscattered ultrasound. The estimated attenuation coefficient in dB/cm at an effective center frequency of 2.75 MHz as a function of angle of insonification for measurements obtained from analyses of M-mode images is presented. Given a linear frequency-dependence of attenuation in myocardial tissue over frequencies ranging from 1.5 MHz to 8 MHz, as has been previously reported, M-mode image-based analyses were used to estimate the slope of attenuation. Results showed slopes of attenuation (over a -10 dB transmit bandwidth of 1.875 MHz to 3.75 MHz) ranging from 1.00 +/- 0.07 to 1.81 +/- 0.08 dB/(cm.MHz) for perpendicular and parallel insonification, respectively. These values were in good agreement with contemporaneously measured values (0.99 +/- 0.02 to 1.77 +/- 0.04 dB/(cm.MHz)) obtained over a frequency bandwidth of 4 MHz to 7 MHz using a through-transmission radio-frequency-based approach. These data suggest that robust measurements of myocardial attenuation can be obtained from analyses of M-mode images and that this method may be diagnostically feasible in the clinical setting.
authors.affiliation: Department of Physics, Washington University, St. Louis, MO 63130, USA.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Baldwin
authors.forename: Karen R
authors.initials: KR
authors.lastname: Marutyan
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Kirk D
authors.initials: KD
authors.lastname: Wallace
authors.forename: Mark R
authors.initials: MR
authors.lastname: Holland
authors.forename: James G
authors.initials: JG
authors.lastname: Miller
mesh_terms: D000818:Animals; D016880:Anisotropy; D002138:Calibration; D004452:Echocardiography / Q000295:instrumentation / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D023421:Models, Animal; D009206:Myocardium; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D012756:Sheep; D014741:Video Recording