Abstract：
OBJECTIVE: Development of a technique for measuring the mechanical properties of zygomaticus major (ZM) may aid advances in clinical treatments for correcting abnormal oral posture. The objective of this work was to demonstrate the feasibility of measuring the stiffness of ZM using an MR elastography technique that incorporates a custom local driver and a phase-gradient (PG) inversion.
METHODS: 2D MRE investigations were performed for 3 healthy subjects using a vibration frequency of 90 Hz to test the prediction that the stiffness of ZM would be greater in the mouth-open compared to the mouth-closed position. MRE wave images were acquired along the long axis of ZM and processed using a 2D spatial-temporal directional filter applied in the direction of wave propagation along the long axis of the muscle. Stiffness measurements were obtained by applying the PG technique to a 1D-profile drawn in the phase image of the first harmonic of the wave images and a one-tailed paired t-test was used to compare the ZM stiffness between the two mouth postures (p < 0.05).
RESULTS: The mean stiffness and standard deviation (SD) of ZM across the three participants in the mouth-closed and mouth-open postures was 6.75 kPa (SD 3.36 kPa) and 15.5 kPa (SD 5.15 kPa), respectively. Changes of ZM stiffness were significantly greater in the mouth-open than the mouth-closed posture (p = 0.038).
CONCLUSIONS: The feasibility of using the PG MRE technique to measure stiffness changes in a small muscle such as ZM for different mouth postures has been demonstrated. Further investigations are required in a larger cohort of participants to investigate the sensitivity and reproducibility of the technique for potential clinical application as well as in health and beauty related studies.
METHODS: 2D MRE investigations were performed for 3 healthy subjects using a vibration frequency of 90 Hz to test the prediction that the stiffness of ZM would be greater in the mouth-open compared to the mouth-closed position. MRE wave images were acquired along the long axis of ZM and processed using a 2D spatial-temporal directional filter applied in the direction of wave propagation along the long axis of the muscle. Stiffness measurements were obtained by applying the PG technique to a 1D-profile drawn in the phase image of the first harmonic of the wave images and a one-tailed paired t-test was used to compare the ZM stiffness between the two mouth postures (p < 0.05).
RESULTS: The mean stiffness and standard deviation (SD) of ZM across the three participants in the mouth-closed and mouth-open postures was 6.75 kPa (SD 3.36 kPa) and 15.5 kPa (SD 5.15 kPa), respectively. Changes of ZM stiffness were significantly greater in the mouth-open than the mouth-closed posture (p = 0.038).
CONCLUSIONS: The feasibility of using the PG MRE technique to measure stiffness changes in a small muscle such as ZM for different mouth postures has been demonstrated. Further investigations are required in a larger cohort of participants to investigate the sensitivity and reproducibility of the technique for potential clinical application as well as in health and beauty related studies.
摘要：
目的：一种测量主要zygomatus（ZM）的机械特性的技术的开发可能有助于在纠正异常口腔姿势的临床治疗中取得进展。这项工作的目的是证明使用MR弹性成像技术测量ZM刚度的可行性，该技术结合了自定义局部驱动器和相位梯度（PG）反演。
方法：使用90Hz的振动频率对3名健康受试者进行了2DMRE调查，以测试ZM的刚度在张口位置相比于闭口位置更大的预测。沿ZM的长轴获取MRE波图像，并使用沿肌肉长轴的波传播方向应用的2D时空方向滤波器进行处理。通过将PG技术应用于在波图像的第一谐波的相位图像中绘制的一维轮廓来获得刚度测量值，并使用单尾配对t检验来比较两个口腔姿势之间的ZM刚度每个参与者（p<0.05）。
结果：三个参与者在闭口和张口姿势中的ZM的平均刚度和标准偏差（SD）分别为6.75kPa（SD3.36kPa）和15.5kPa（SD5.15kPa），分别。张口姿势的ZM刚度变化明显大于闭口姿势（p=0.038）。
结论：已经证明了使用PGMRE技术测量ZM等小肌肉在不同口腔姿势下的刚度变化的可行性。需要在更大的参与者队列中进行进一步的调查，以调查该技术在潜在临床应用以及健康和美容相关研究中的敏感性和可重复性。
方法：使用90Hz的振动频率对3名健康受试者进行了2DMRE调查，以测试ZM的刚度在张口位置相比于闭口位置更大的预测。沿ZM的长轴获取MRE波图像，并使用沿肌肉长轴的波传播方向应用的2D时空方向滤波器进行处理。通过将PG技术应用于在波图像的第一谐波的相位图像中绘制的一维轮廓来获得刚度测量值，并使用单尾配对t检验来比较两个口腔姿势之间的ZM刚度每个参与者（p<0.05）。
结果：三个参与者在闭口和张口姿势中的ZM的平均刚度和标准偏差（SD）分别为6.75kPa（SD3.36kPa）和15.5kPa（SD5.15kPa），分别。张口姿势的ZM刚度变化明显大于闭口姿势（p=0.038）。
结论：已经证明了使用PGMRE技术测量ZM等小肌肉在不同口腔姿势下的刚度变化的可行性。需要在更大的参与者队列中进行进一步的调查，以调查该技术在潜在临床应用以及健康和美容相关研究中的敏感性和可重复性。
