分段读出平面回波序列在高强度聚焦超声焦点快速定位中的应用

Application of Segmented Echo Plane Imaging to Magnetic Resonance Acoustic Radiation Force Imaging for Rapid Localization During High Intensity Focused Ultrasound Therapy

磁共振声辐射力成像作为一种新兴的高强度聚焦超声监控技术,能够通过检测组织内的微米级位移实现高强度聚焦超声焦点定位。文章提出将分段读出自旋平面回波序列应用于磁共振声辐射力成像检测。通过与目前常用的单次激发平面回波序列及二维自旋回波序列对比发现,该序列在有效缩短检测时间的同时不易引起图像畸变。位移定量结果显示,分段读出自旋平面回波序列检测到的位移大小与另两种方法有较高的一致性,并具有良好的重复性。此外,单次激发平面回波序列可以同时提供具有良好图像质量的垂直于声传播方向的冠状面位移图及平行于声传播方向的矢状面位移图,有助于把握高强度聚焦超声焦域的三维结构。

Magnetic resonance acoustic radiation force imaging（MR-ARFI）,a new guided technique for high intensity focused ultrasound（HIFU） therapy,can detect micro-scale displacement in soft tissue and implement HIFU focal localization.In this work,readout segmented echo plane imaging（rs-EPI） is used as a new MRARFI sequence to accelerate MR-ARFI imaging techniques.Compared with single shot echo plane imaging（ss-EPI） and 2DSE ARFI,the proposed method is time-efficient and more robust to image distortion.The quantification results show that the tissue displacements obtained by our method have high reproducibility and consistency compared with the other two methods.The displacement maps acquired in plane parallel and perpendicular to the ultrasound propagation direction are also consistent around the focal point.The capability of providing good image quality in both directions of rs-EPI facilitates better volumetric displacement mapping around the HIFU focal point.In general,segmented EPI is a potentially useful HIFU focal localization method in clinical application.