Department of Biomedical Engineering, Columbia University, New York, NY, USA.
Department of Biomedical Engineering, Columbia University, New York, NY, USA; Department of Radiology, Columbia University Irving Medical Center, New York, NY, USA; Department of Neurological Surgery, Columbia University Irving Medical Center, New York, NY, USA.
Ultrasound Med Biol. 2025 Jan;51(1):169-179. doi: 10.1016/j.ultrasmedbio.2024.09.021. Epub 2024 Oct 19.
Elastography images tissue mechanical responses and infers the underlying properties to aid diagnosis and treatment response monitoring. The estimation of absolute or relative tumor properties may vary with dimensions even when the mechanical properties remain constant. Harmonic motion imaging (HMI) uses amplitude-modulated (AM) focused ultrasound to interrogate the targeted tissue's viscoelastic properties. In this study, effects of AM frequencies on HMI were investigated in terms of inclusion relative stiffness and size estimation.
AM frequencies from 200 to 600 Hz in steps of 100 Hz were considered using a 5.3-kPa phantom with cylindrical inclusions (Young's modulus: 22, 31, 44, 56 kPa, and diameter: 4.8, 8.1, 13.6, 19.8 mm) to optimize the performance of HMI in characterizing tumors with the same mechanical properties and of different dimensions.
Consistent displacement ratios (DRs) (17.5% variation) of the inclusion to background were obtained with 200-Hz AM for breast-tumor-mimicking inclusions albeit a suboptimal inclusion size estimation obtained. 400-Hz was otherwise used for small and low-contrast inclusions (4.8 mm, 22 or 31 kPa). A linear relationship (R = 0.9043) was found between the inverse DR at these frequencies and the Young's modulus ratio. 400 Hz obtained the most accurate inclusion size estimation with an overall estimation error on the lateral dimension of 0.5 mm. In vivo imaging of breast cancer patients (n = 5) was performed at 200 or 400 Hz.
The results presented herein indicate that the HMI AM frequency could be optimized adaptively in cases of different applications, i.e., at 200 or 400 Hz, depending on whether aimed for consistent DR measurement for tumor response assessment or tumor margin delineation for surgical planning. HMI may thus be capable of predicting the pathologic endpoint of tumors in response to neoadjuvant chemotherapy (NACT) as early as 3 weeks into treatment.
弹性成像是对组织力学响应进行成像，并推断其潜在特性，以辅助诊断和治疗反应监测。即使力学特性保持不变，绝对或相对肿瘤特性的估计也可能随尺寸而变化。谐波运动成像（HMI）使用调幅（AM）聚焦超声来检测目标组织的粘弹性特性。在这项研究中，从 200 到 600 Hz，以 100 Hz 的步长，考虑了 AM 频率对 HMI 的影响，包括包含物的相对刚度和尺寸估计。
使用 Young's 模量为 22、31、44 和 56 kPa，直径为 4.8、8.1、13.6 和 19.8 mm 的圆柱形包含物的 5.3-kPa 幻影，考虑了 200 至 600 Hz 的 AM 频率，以优化 HMI 对具有相同力学特性和不同尺寸的肿瘤进行特征描述的性能。
尽管对小的和低对比度的包含物（4.8 mm，22 或 31 kPa）获得了次优的包含物尺寸估计，但用 200-Hz AM 获得了乳腺肿瘤模拟包含物的一致的位移比（DR）（17.5%的变化）。否则，使用 400-Hz 用于小和低对比度的包含物（4.8 mm，22 或 31 kPa）。在这些频率下，反向 DR 与杨氏模量比之间存在线性关系（R = 0.9043）。400 Hz 获得了最准确的包含物尺寸估计，其横向尺寸的总体估计误差为 0.5 mm。对 5 名乳腺癌患者进行了体内成像（200 或 400 Hz）。
本文的结果表明，HMI 的 AM 频率可以根据不同的应用情况进行自适应优化，即在 200 或 400 Hz 下，这取决于是为肿瘤反应评估的一致 DR 测量还是手术计划的肿瘤边界描绘而进行的。因此，HMI 可能能够在新辅助化疗（NACT）治疗后 3 周内尽早预测肿瘤对治疗的病理终点。
