Department of Medical Physics, 1111 Highland Ave., University of Wisconsin, Madison, WI 53703, USA.
Ultrason Imaging. 2010 Jul;32(3):131-42. doi: 10.1177/016173461003200302.
The objective of this preliminary study was to determine whether quantitative ultrasound (QUS) can provide insight into, and characterization of, uterine cervical microstructure. Throughout pregnancy, cervical collagen reorganizes (from aligned and anisotropic to disorganized and isotropic) as the cervix changes in preparation for delivery. Premature changes in collagen are associated with premature birth in mammals. Because QUS is able to detect structural anisotropy/isotropy, we hypothesized that it may provide a means of noninvasively assessing cervical microstructure. Thorough study of cervical microstructure has been limited by lack of technology to detect small changes in collagen organization, which has in turn limited our ability to detect abnormal and/or premature changes in collagen that may lead to preterm birth. In order to determine whether QUS may be useful for detection of cervical microstructure, radiofrequency (rf) echo data were acquired from the cervices of human hysterectomy specimens (n = 10). The angle between the acoustic beam and tissue was used to assess anisotropic acoustic propagation by control of transmit/receive angles from -20 degrees to +20 degrees. The power spectrum of the echo signals from within a region of interest was computed in order to investigate the microstructure of the tissue. An identical analysis was performed on a homogeneous phantom with spherical scatterers for system calibration. Power spectra of backscattered rf from the cervix were 6 dB higher for normal (0 degree) than steered (+/- 20 degrees) beams. The spectral power for steered beams decreased monotonically (0.4 dB at +5 degrees to 3.6 dB at +20 degrees). The excess difference (compared to similar analysis for the phantom) in normally-incident (0 degree) versus steered beams is consistent with scattering from an aligned component of the cervical microstructure. Therefore, QUS appears to reliably identify an aligned component of cervical microstructure; because collagen is ubiquitously and abundantly present in the cervix, this is the most likely candidate. Detection of changes in cervical collagen and microstructure may provide information about normal versus abnormal cervical change and thus guide development of earlier, more specific interventions for preterm birth.
本初步研究的目的是确定定量超声（QUS）是否可以提供有关子宫颈微观结构的深入了解和特征描述。在整个怀孕期间，随着宫颈为分娩做准备而发生变化，宫颈胶原会重新组织（从排列有序和各向异性变为组织无序和各向同性）。哺乳动物中胶原的过早变化与早产有关。由于 QUS 能够检测结构各向异性/各向同性，我们假设它可能提供一种非侵入性评估宫颈微观结构的方法。由于缺乏检测胶原组织微小变化的技术，对宫颈微观结构的深入研究受到限制，这反过来又限制了我们检测胶原可能导致早产的异常和/或过早变化的能力。为了确定 QUS 是否可用于检测宫颈微观结构，从人类子宫切除术标本（n = 10）的宫颈获取射频（rf）回波数据。通过控制发射/接收角度从-20 度到+20 度，可以利用声束与组织之间的角度来评估各向异性声传播。为了研究组织的微观结构，计算了感兴趣区域内回波信号的功率谱。对具有球形散射体的均质仿体进行了相同的分析，以进行系统校准。正常（0 度）定向波束的回波 rf 的功率谱比转向（+/- 20 度）波束高 6 dB。转向波束的光谱功率单调下降（+5 度时为 0.4 dB，+20 度时为 3.6 dB）。与类似的仿体分析相比，正常入射（0 度）与转向波束之间的多余差异与宫颈微观结构的对齐成分的散射一致。因此，QUS 似乎可以可靠地识别宫颈微观结构的对齐成分；由于胶原在宫颈中普遍且丰富存在，这是最有可能的候选者。检测宫颈胶原和微观结构的变化可能提供有关正常与异常宫颈变化的信息，从而指导早产的早期、更具体的干预措施的发展。
