Mapping of mechanical properties, dependent on the frequency of motion, is relevant in diagnosis, monitoring treatment response, or intra-operative surgical resection planning. While shear wave speeds at different frequencies have been described elsewhere, the effect of frequency on the “on-axis” acoustic radiation force (ARF)-induced displacement has not been previously investigated. Instead of generating single transducer-harmonic motion imaging (ST-HMI)-derived peak-to-peak displacement (P2PD) image at a particular frequency, a novel multi-frequency excitation pulse is proposed to generate P2PD images at 100–1000 Hz simultaneously. The performance of the proposed excitation pulse is compared with the ARFI by imaging 16 different inclusions (Young’s moduli of 6, 9, 36, 70 kPa and diameters of 1.6, 2.5, 6.5, and 10.4 mm) embedded in an 18 kPa background. Depending on inclusion size and stiffness, the maximum CNR and contrast were achieved at different frequencies and were always higher than ARFI. The frequency, at which maximum CNR and contrast were achieved, increased with stiffness for fixed inclusion’s size and decreased with size for fixed stiffness. In vivo feasibility is tested by imaging a 4T1 breast cancer mouse tumor on Day 6, 12, and 19 post-injection of tumor cells. Similar to phantoms, the CNR of ST-HMI images was higher than ARFI and increased with frequency for the tumor on Day 6. Besides, P2PD at 100–1000 Hz indicated that the tumor became stiffer with respect to the neighboring non-cancerous tissue over time. These results indicate the importance of using a multi-frequency excitation pulse to simultaneously generate displacement at multiple frequencies to better delineate inclusions or tumors.

中文翻译：

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同时在多个振荡频率下对单个换能器谐波运动成像衍生位移进行成像

取决于运动频率的机械特性映射与诊断、监测治疗反应或术中手术切除计划相关。虽然在其他地方已经描述了不同频率的剪切波速度，但以前没有研究过频率对“轴上”声辐射力 (ARF) 引起的位移的影响。不是在特定频率下生成单个换能器谐波运动成像 (ST-HMI) 衍生的峰峰值位移 (P2PD) 图像，而是提出了一种新颖的多频激励脉冲来同时生成 100-1000 Hz 的 P2PD 图像. 通过对 16 种不同的包裹体（杨氏模量为 6、9、36、70 kPa 和直径为 1.6、2.5、6.5 和 10. 4 毫米）嵌入在 18 kPa 背景中。根据夹杂物大小和刚度，最大 CNR 和对比度在不同频率下实现，并且始终高于 ARFI。达到最大 CNR 和对比度的频率随着固定夹杂物尺寸的刚度而增加，并随着固定刚度的尺寸而降低。通过在注射肿瘤细胞后第 6、12 和 19 天对 4T1 乳腺癌小鼠肿瘤进行成像来测试体内可行性。与幻影相似，ST-HMI 图像的 CNR 高于 ARFI，并且在第 6 天随着肿瘤频率的增加而增加。此外，100-1000 Hz 的 P2PD 表明肿瘤相对于邻近的非癌组织变得更硬时间。