title: Scatterer number density considerations in reference phantom-based attenuation estimation.
abstract: Attenuation estimation and imaging have the potential to be a valuable tool for tissue characterization, particularly for indicating the extent of thermal ablation therapy in the liver. Often the performance of attenuation estimation algorithms is characterized with numerical simulations or tissue-mimicking phantoms containing a high scatterer number density (SND). This ensures an ultrasound signal with a Rayleigh distributed envelope and a signal-to-noise ratio (SNR) approaching 1.91. However, biological tissue often fails to exhibit Rayleigh scattering statistics. For example, across 1647 regions of interest in five ex vivo bovine livers, we obtained an envelope SNR of 1.10 ± 0.12 when the tissue was imaged with the VFX 9L4 linear array transducer at a center frequency of 6.0 MHz on a Siemens S2000 scanner. In this article, we examine attenuation estimation in numerical phantoms, tissue-mimicking phantoms with variable SNDs and ex vivo bovine liver before and after thermal coagulation. We find that reference phantom-based attenuation estimation is robust to small deviations from Rayleigh statistics. However, in tissue with low SNDs, large deviations in envelope SNR from 1.91 lead to subsequently large increases in attenuation estimation variance. At the same time, low SND is not found to be a significant source of bias in the attenuation estimate. For example, we find that the standard deviation of attenuation slope estimates increases from 0.07 to 0.25 dB/cm-MHz as the envelope SNR decreases from 1.78 to 1.01 when estimating attenuation slope in tissue-mimicking phantoms with a large estimation kernel size (16 mm axially × 15 mm laterally). Meanwhile, the bias in the attenuation slope estimates is found to be negligible (<0.01 dB/cm-MHz). We also compare results obtained with reference phantom-based attenuation estimates in ex vivo bovine liver and thermally coagulated bovine liver.
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA. Electronic address: Rubert@wisc.edu.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Rubert
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Tomy
authors.initials: T
authors.lastname: Varghese
mesh_terms: D003198:Computer Simulation; D004735:Energy Transfer; D019220:High-Energy Shock Waves; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*
keywords: Attenuation; Envelope signal-to-noise ratio; Liver; Multi-taper; Reference phantom; Scatterer number density; Thermal ablation
references.citation: Ultrason Imaging. 1988 Oct;10(4):248-64
references.pmid: 3074549
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2008 May;55(5):1153-9
references.pmid: 18519224
references.citation: Phys Med Biol. 2008 Nov 7;53(21):6027-44
references.pmid: 18836223
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Jun;60(6):1061-73
references.pmid: 25004470
references.citation: Ultrason Imaging. 1983 Oct;5(4):331-45
references.pmid: 6686899
references.citation: Med Biol Eng Comput. 2006 Jul;44(7):583-91
references.pmid: 16937194
references.citation: Ultrason Imaging. 1993 Jul;15(3):238-54
references.pmid: 8879094
references.citation: Ultrason Imaging. 1997 Jul;19(3):221-33
references.pmid: 9447670
references.citation: Ultrasound Med Biol. 2011 Dec;37(12):2096-104
references.pmid: 21963038
references.citation: Ultrasound Med Biol. 2001 Sep;27(9):1231-8
references.pmid: 11597364
references.citation: J Biomech. 2008;41(2):347-55
references.pmid: 18028934
references.citation: Ultrason Imaging. 1986 Jan;8(1):1-10
references.pmid: 3521042
references.citation: J Acoust Soc Am. 1997 Jul;102(1):628-34
references.pmid: 9228822
references.citation: Ultrasonics. 2013 Sep;53(7):1325-31
references.pmid: 23648210
references.citation: Ultrason Imaging. 2011 Oct;33(4):251-63
references.pmid: 22518955
references.citation: Med Phys. 2013 Aug;40(8):082904
references.pmid: 23927359
references.citation: J Acoust Soc Am. 2011 Apr;129(4):2316-24
references.pmid: 21476687
references.citation: Ultrasound Med Biol. 1997;23(9):1395-403
references.pmid: 9428138
references.citation: Ultrasonics. 2011 Aug;51(6):758-67
references.pmid: 21477832
references.citation: J Acoust Soc Am. 2004 Jun;115(6):2859-65
references.pmid: 15237809
references.citation: J Acoust Soc Am. 2012 Jul;132(1):533-43
references.pmid: 22779499
references.citation: Ultrason Imaging. 2013 Apr;35(2):146-61
references.pmid: 23493613
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Jun;59(6):1193-200
references.pmid: 22711414
references.citation: Hepatology. 1996 Aug;24(2):289-93
references.pmid: 8690394
references.citation: Ultrason Imaging. 2014 Apr;36(2):79-97
references.pmid: 24554290
references.citation: Ultrason Imaging. 2013 Jul;35(3):214-34
references.pmid: 23858055
references.citation: Ultrasound Med Biol. 2012 Dec;38(12):2130-7
references.pmid: 23062365
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2007 Mar;54(3):510-9
references.pmid: 17375820
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 1999;46(3):690-9
references.pmid: 18238469
references.citation: Ultrasound Med Biol. 2006 May;32(5):649-57
references.pmid: 16677924
references.citation: Ultrasonics. 2012 Feb;52(2):215-22
references.pmid: 21907377
references.citation: Ultrasound Med Biol. 2001 Mar;27(3):379-87
references.pmid: 11369124
references.citation: Ultrasound Med Biol. 1983 Jul-Aug;9(4):363-9
references.pmid: 6649154
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2003 Apr;50(4):402-7
references.pmid: 12744396
references.citation: Ultrasound Med Biol. 2001 May;27(5):673-82
references.pmid: 11397532
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2012 May;59(5):893-904
references.pmid: 22622974
references.citation: J Acoust Soc Am. 1984 Sep;76(3):913-23
references.pmid: 6491053
references.citation: J Acoust Soc Am. 1994 Jan;95(1):77-85
references.pmid: 8120267
references.citation: Ultrasound Med Biol. 2008 Nov;34(11):1808-19
references.pmid: 18621468
references.citation: Ultrasound Med Biol. 1993;19(9):789-801
references.pmid: 8134979
references.citation: Ultrason Imaging. 1990 Jan;12(1):58-70
references.pmid: 2184569
references.citation: Ultrasound Med Biol. 2001 Jun;27(6):809-17
references.pmid: 11516541
references.citation: IEEE Trans Med Imaging. 2011 Mar;30(3):666-78
references.pmid: 21075719