OBJECTIVE In transcranial MR-guided focused ultrasound (TcMRgFUS), fiber tractography using diffusion tensor imaging (DTI) has been proposed as a direct method to identify the ventral intermediate nucleus (Vim), the ventral caudal nucleus (Vc), and the pyramidal tract (PT). However, the limitations of the DTI algorithm affect the accuracy of visualizing anatomical structures due to its low-quality fiber tractography, whereas the application of the generalized q-sampling imaging (GQI) algorithm enables the visualization of high-quality fiber tracts, offering detailed insights into the spatial distribution of motor cortex fibers. This retrospective study aimed to investigate the usefulness of high-precision fiber tractography using the GQI algorithm as a planning image in TcMRgFUS to achieve favorable clinical outcomes. METHODS This study included 20 patients who underwent TcMRgFUS. The Clinical Rating Scale for Tremor (CRST) scores and MR images were evaluated pretreatment and at 24 hours and 3-6 months after treatment. Cases were classified based on the presence and adversity of adverse events (AEs): no AEs, mild AEs without additional treatment, and severe AEs requiring prolonged hospitalization. Fiber tractography of the Vim, Vc, and PT was visualized using the DTI and GQI algorithm. The overlapping volume between Vim fibers and the lesion was measured, and correlation analysis was performed. The relationship between AEs and the overlapping volume of the Vc and PT fibers within the lesions was examined. The cutoff value to achieve a favorable clinical outcome and avoid AEs was determined using receiver operating characteristic curve analysis. RESULTS All patients showed improvement in tremors 24 hours after treatment, with 3 patients experiencing mild AEs and 1 patient experiencing severe AEs. At the 3- to 6-month follow-up, 5 patients experienced recurrence, and 2 patients had persistent mild AEs. Although fiber visualization in the motor cortex using the DTI algorithm was insufficient, the GQI algorithm enabled the visualization of significantly higher-quality fibers. A strong correlation was observed between the overlapping volume that intersects the lesion and Vim fibers and the degree of tremor improvement (r = 0.72). Higher overlapping volumes of Vc and PT within the lesion were associated with an increased likelihood of AEs (p < 0.05); the cutoff volume of Vim fibers within the lesion for a favorable clinical outcome was 401 mm3, while the volume of Vc and PT within the lesion to avoid AEs was 99 mm3. CONCLUSIONS This pilot study suggests that incorporating the high-precision GQI algorithm for fiber tractography as a planning imaging technique for TcMRgFUS has the potential to enhance targeting precision and achieve favorable clinical outcomes.

中文翻译：

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一种新型高精度纤维束成像技术，用于经颅磁共振引导聚焦超声手术中的核定位：一项试点研究。

目的 在经颅 MR 引导聚焦超声 (TcMRgFUS) 中，使用扩散张量成像 (DTI) 的纤维束成像已被提议作为识别腹侧中间核 (Vim)、腹侧尾核 (Vc) 和锥体束的直接方法（PT）。然而，DTI算法的局限性因其低质量的纤维束成像而影响了解剖结构可视化的准确性，而广义q采样成像（GQI）算法的应用可以实现高质量纤维束的可视化，提供详细的信息。深入了解运动皮层纤维的空间分布。这项回顾性研究旨在探讨使用 GQI 算法作为 TcMRgFUS 中规划图像的高精度纤维束成像的有用性，以实现良好的临床结果。方法 本研究纳入了 20 名接受 TcMRgFUS 的患者。治疗前、治疗后24小时和3-6个月评估震颤临床评定量表（CRST）评分和MR图像。根据不良事件 (AE) 的存在和严重程度对病例进行分类：无 AE、无需额外治疗的轻度 AE 和需要长期住院的严重 AE。使用 DTI 和 GQI 算法对 Vim、Vc 和 PT 的纤维束成像进行可视化。测量Vim纤维与病灶之间的重叠体积，并进行相关分析。检查了 AE 与病灶内 Vc 和 PT 纤维重叠体积之间的关系。使用受试者工作特征曲线分析确定实现良好临床结果并避免 AE 的截止值。结果 所有患者在治疗 24 小时后震颤均有所改善，其中 3 名患者出现轻度 AE，1 名患者出现严重 AE。在 3 至 6 个月的随访中，5 名患者出现复发，2 名患者出现持续的轻度 AE。尽管使用 DTI 算法对运动皮层中的纤维进行可视化还不够，但 GQI 算法可以实现质量明显更高的纤维的可视化。病变和 Vim 纤维相交的重叠体积与震颤改善程度之间观察到很强的相关性 (r = 0.72)。病灶内较高的 Vc 和 PT 重叠量与 AE 的可能性增加相关 (p < 0.05)；为了获得良好的临床结果，病灶内 Vim 纤维的截止体积为 401 mm3，而为了避免 AE，病灶内的 Vc 和 PT 的体积为 99 mm3。结论 这项试点研究表明，将纤维束成像的高精度 GQI 算法纳入 TcMRgFUS 的规划成像技术有可能提高靶向精度并实现良好的临床结果。