一种基于IEC琼脂的组织模拟材料以20兆赫兹为中心的声学特性及其温度、频率和老化依赖性。
The acoustic properties, centered on 20 MHZ, of an IEC agar-based tissue-mimicking material and its temperature, frequency and age dependence.
作者信息
Brewin M P, Pike L C, Rowland D E, Birch M J
机构信息
Department of Clinical Physics, Royal London Hospital, London, UK.
出版信息
Ultrasound Med Biol. 2008 Aug;34(8):1292-306. doi: 10.1016/j.ultrasmedbio.2007.12.017. Epub 2008 Mar 14.
The purpose of this study was to characterize the ultrasonic properties of agar-based tissue-mimicking materials (TMMs) at ultrasound frequencies centered around 20 MHz. The TMM acoustic properties measured are the amplitude attenuation coefficient alpha (dB cm(-1)MHz(-1)), the speed of sound (ms(-1)) and the backscattered power spectral density (distribution of power per unit frequency normalized to the total received power) characteristics of spectral slope (dB MHz(-1)), y-axis intercept (dB) and reflected power (dB). The acoustic properties are measured over a temperature range of 22 to 37 degrees C. An intercomparison of results between two independent ultrasound measurement laboratories is also presented. A longitudinal study of the acoustic properties over a period of two years is also detailed, and the effect of water immersion on the acoustic properties of TMM is measured. In addition, the physical parameters of mass density rho (kg m(-3)) and specific heat capacity C (J kg(-1) K(-1)) are included. The measurement techniques used were based on the substitution technique using both broadband and narrowband pulses centered on 20 MHz. Both the attenuation coefficient and speed of sound (both group and phase) showed good agreement with the expected values of 0.5 dB cm(-1) MHz(-1) and 1540 ms(-1), respectively, with average values over the three-year period of 0.49 dBcm(-1)MHz1 (SD +/- 0.05) and 1540.9 ms(-1) (SD +/- 8.7). These results also showed agreement between the two independent measurement laboratories. Speed of sound and attenuation coefficient were shown to change with temperature with rates of + 2.1 m s(-1) degrees C(-1) and -0.005 dB cm(-1) MHz(-1) degrees C(-1), respectively. Attenuation changed linearly with frequency at the high frequency range of 17 to 23 MHz, and speed of sound was found to be independent of frequency in this range. The spectral slope of relative backscattered power for the material increased with frequency at typically 1.5 dB MHz(-1). This compared favorably with theoretical spectral slope values, calculated for a variety of scatterer sizes, albeit at a lower frequency range. It is also noticed that, on extrapolation back to lower frequencies, the backscatter is comparable with that measured at 7 MHz. Overall, this non-commercial agar-based TMM is shown to perform as expected at the higher frequency range of 17 to 23 MHz and is seen to retain its acoustic properties of attenuation and speed of sound over a three-year period.
本研究的目的是表征基于琼脂的组织模拟材料（TMM）在以20 MHz为中心的超声频率下的超声特性。所测量的TMM声学特性包括幅度衰减系数α（dB cm⁻¹MHz⁻¹）、声速（m s⁻¹）以及后向散射功率谱密度（每单位频率的功率分布，归一化为总接收功率）的谱斜率（dB MHz⁻¹）、y轴截距（dB）和反射功率（dB）等特性。声学特性在22至37摄氏度的温度范围内进行测量。还给出了两个独立超声测量实验室之间结果的相互比较。详细介绍了为期两年的声学特性纵向研究，并测量了水浸对TMM声学特性的影响。此外，还包括质量密度ρ（kg m⁻³）和比热容C（J kg⁻¹ K⁻¹）的物理参数。所使用的测量技术基于替代技术，使用以20 MHz为中心的宽带和窄带脉冲。衰减系数和声速（群速度和相速度）分别与预期值0.5 dB cm⁻¹ MHz⁻¹和1540 m s⁻¹显示出良好的一致性，三年期间的平均值分别为0.49 dBcm⁻¹MHz⁻¹（标准差±0.05）和1540.9 m s⁻¹（标准差±8.7）。这些结果也显示了两个独立测量实验室之间的一致性。声速和衰减系数随温度变化，变化率分别为+2.1 m s⁻¹℃⁻¹和 -0.005 dB cm⁻¹ MHz⁻¹℃⁻¹。在17至23 MHz的高频范围内，衰减随频率呈线性变化，并且在此频率范围内声速与频率无关。该材料相对后向散射功率的谱斜率通常以1.5 dB MHz⁻¹的速率随频率增加。这与针对各种散射体尺寸计算的理论谱斜率值相比具有优势，尽管是在较低频率范围内。还注意到，外推到较低频率时，后向散射与在7 MHz处测量的结果相当。总体而言，这种非商业性的基于琼脂的TMM在17至23 MHz的较高频率范围内表现符合预期，并且在三年期间保持其衰减和声速的声学特性。
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