Influence of tissue preparation on the high-frequency acoustic properties of normal kidney tissue

The influence of various tissue preparations on the acoustic properties of normal kidney tissue at high frequencies was investigated. Eight surgically excised normal kidney tissue specimens were classified into three groups: (i) fresh, frozen section, (ii) formalin-fixed, frozen section and (iii) formalin-fixed, paraffin section. Scanning acoustic microscopy operating in the frequency range of 100–200 MHz was used to display the two-dimensional distribution of attenuation constant and sound speed. Our results indicate that (i) there is no significant variation in both acoustic parameters between the three tissue groups, (ii) fixation by 10% formalin produces no significant change in the acoustic parameters, (iii) in fat-free tissue regions, the acoustic parameters are independent of preparation method and (iv) frozen sections must be used to assess the acoustic parameters in fat-rich tissues.     

Acoustic properties of normal and cancerous human liver—II Dependence on tissue structure

Ultrasonic speed, attenuation and backscattering were measured as a function of frequency and compared with measurements of water content, fat content and collagen content in specimens of excised human liver. It is observed that the ultrasonic velocity decreases with both increasing water and fat contents, although the water content appears to have the overriding influence. An increase in the water content correlates well with decreasing attenuation and backscattering coefficients (and the slope of their frequency dependence), but positive dependences are found between these acoustic characteristics and the fat content. It is believed that the dependences on fat content are of secondary importance to those on water content and possibly arise as a result of an inverse relationship between the fat content and the water content. For the collagen content of liver specimens, positive correlations, barely significant, were found for attenuation and backscattering only after the data had first been corrected for variations in water content, while no significant velocity dependence was seen.     

Acoustic properties of normal and cancerous human liver—I. Dependence on pathological condition

Ultrasonic speed, attenuation and backscattering were measured as functions of frequency and orientation in specimens of exercised human liver, with a view to establishing the usefulness of such measurements to characterize the pathology and structure of the tissue. It is observed that acoustic speed is superior to any attenuation or backscattering characteristics for distinguishing in vitro between specimens of tumours and normal human liver selected at random. However, when the data are corrected for variations between one subject and another, sound speed, attenuation and the mean back-scattering coefficient at a given frequency show a comparable degree of usefulness in this respect. Analysis of the periodicities present in the backscattering diffraction patterns did not contribute any improvement in the ability to distinguish between tissue states. On average, by comparison with normal liver, ultrasound travels about 1.5% (± 1%) slower, is attenuated by about 20% (± 30%) less at 3 MHz and is backscattered by about 80% (±115%) less at 3 MHz in the tumor specimens that were measured. Livers infiltrated by diffuse malignant disease appear to possess quite different ultrasonic propagation properties to normal liver although insufficient data are yet available for firm conclusions to be drawn.     

应用声辐射力脉冲成像技术评估非酒精性单纯性脂肪肝的初步经验

目的探讨声触诊组织定量分析（VTQ）技术对非酒精性单纯性脂肪肝定量评估的价值。方法应用基于声辐射力脉冲成像技术（ARFI）研制的超声弹性成像新技术——VTQ,对50例正常人和50例非酒精性单纯性脂肪肝患者行超声弹性量化检测,通过ROC曲线分析确定界值。结果正常人与非酒精性单纯性脂肪肝患者肝脏VTQ测值存在显著性差异（P〈0．01）。ROC曲线下最大面积为0．90±0．03,面积的标准误为0．03,VTQ用于评估非酒精性单纯性脂肪肝有统计学意义,95％可信区间为（0．839,0．959）。VTQ界值为1．06m／s时,对应的敏感度为94％,特异度为74％。结论VTQ技术对于非酒精性单纯性脂肪肝的诊断有一定价值。     

The acoustic properties, centered on 20 MHZ, of an IEC agar-based tissue-mimicking material and its temperature, frequency and age dependence

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.     

家兔脂肪肝肝压缩率、灰阶强度与声衰减对比研究

目的探讨观察诊断脂肪肝的肝压缩率、灰阶强度和衰减系数定量指标.方法超声检查40只正常家兔肝压缩率、灰阶强度及衰减系数;应用高糖、高脂、及酒精喂养后形成脂肪肝后,再次超声观察并对比.结果随脂肪肝程度加重和脂肪性肝炎的发生,肝脏进行性肿大,肝压迫率进行性下降,声衰减增大.中重度脂肪肝、尤其脂肪性肝炎肝脏灰阶强度高于轻度脂肪肝组.结论肝压缩率、灰阶强度和衰减系数可反映肝脂肪变和炎性病变程度及有无纤维化.