Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada.
Department of Medical Biophysics, Temerty Faculty of Medicine, University of Toronto, 101 College Street Suite 15-701, Toronto, ON M5G 1L7, Canada.
Phys Med Biol. 2024 Nov 19;69(23). doi: 10.1088/1361-6560/ad8fed.
To evaluate the feasibility of transspine focused ultrasound using simulation-based phase corrections from a CT-derived ray acoustics model.Bilateral transspine focusing was performed inhuman vertebrae with a spine-specific ultrasound array. Ray acoustics-derived phase correction was compared to geometric focusing and a hydrophone-corrected gold standard. Planar hydrophone scans were recorded in the spinal canal and three metrics were calculated: target pressure, coronal and sagittal focal shift, and coronal and sagittal Sørensen-Dice similarity to the free-field.analysis was performedto assess the impact of windows between vertebrae on focal shift.Hydrophone correction reduced mean sagittal plane shift from 1.74 ± 0.82 mm to 1.40 ± 0.82 mm and mean coronal plane shift from 1.07 ± 0.63 mm to 0.54 ± 0.49 mm. Ray acoustics correction reduced mean sagittal plane and coronal plane shift to 1.63 ± 0.83 mm and 0.83 ± 0.60 mm, respectively. Hydrophone correction increased mean sagittal similarity from 0.48 ± 0.22 to 0.68 ± 0.19 and mean coronal similarity from 0.48 ± 0.23 to 0.70 ± 0.19. Ray acoustics correction increased mean sagittal and coronal similarity to 0.53 ± 0.25 and 0.55 ± 0.26, respectively. Target pressure was relatively unchanged across beamforming methods.analysis found that, for some targets, unoccluded paths may have increased focal shift.. Gold standard phase correction significantly reduced coronal shift and significantly increased sagittal and coronal Sørensen-Dice similarity (< 0.05). Ray acoustics-derived phase correction reduced sagittal and coronal shift and increased sagittal and coronal similarity but did not achieve statistical significance. Across beamforming methods, mean focal shift was comparable to MRI resolution, suggesting that transspine focusing is possible with minimal correction in favourable targets. Future work will explore the mitigation of acoustic windows with anti-focus control points.
评估基于 CT 射线声学模型的基于仿真的相位校正的经脊柱聚焦超声的可行性。使用特定于脊柱的超声阵列在人体椎骨上进行双侧经脊柱聚焦。将射线声学衍生的相位校正与几何聚焦和水听器校正的金标准进行了比较。在椎管内记录了平面水听器扫描，并计算了三个指标：目标压力、冠状面和矢状面焦点移位以及与自由场的冠状面和矢状面 Sørensen-Dice 相似度。进行了分析以评估椎骨之间窗口对焦点移位的影响。水听器校正将平均矢状面移位从 1.74 ± 0.82 mm 降低至 1.40 ± 0.82 mm，将平均冠状面移位从 1.07 ± 0.63 mm 降低至 0.54 ± 0.49 mm。射线声学校正将平均矢状面和冠状面移位分别降低至 1.63 ± 0.83 mm 和 0.83 ± 0.60 mm。水听器校正将平均矢状面相似度从 0.48 ± 0.22 增加到 0.68 ± 0.19，将平均冠状面相似度从 0.48 ± 0.23 增加到 0.70 ± 0.19。射线声学校正将平均矢状面和冠状面相似度分别增加至 0.53 ± 0.25 和 0.55 ± 0.26。在波束成形方法中，目标压力相对不变。分析发现，对于某些目标，未被遮挡的路径可能会增加焦点移位。金标准相位校正显著降低了冠状面移位，并显著增加了矢状面和冠状面 Sørensen-Dice 相似度（<0.05）。射线声学衍生的相位校正降低了矢状面和冠状面的移位，并增加了矢状面和冠状面的相似度，但未达到统计学意义。在各种波束成形方法中，平均焦点移位与 MRI 分辨率相当，这表明在有利的目标中，经脊柱聚焦是可能的，只需进行最小的校正。未来的工作将探索使用反焦点控制点来减轻声窗的影响。
