Abstract

Background

Chronic back pain due to facet related degenerative changes affects 4-6 million patients a year in the United States. Patients refractory to conservative therapy may warrant targeted injections of steroids into the joint or percutaneous medial branch nerve denervation with radiofrequency ablation. We numerically tested a novel noninvasive high intensity focused ultrasound transducer to optimize nerve ablation near a bone-soft tissue interface.

Methods

A transducer with 4 elements operating in an incoherent mode was modeled numerically and tested pre-clinically under fluoroscopic guidance. After 6 lumbar medial branch nerve ablations were performed in 2 pigs, they were followed clinically for 1 week and then sacrificed for pathological evaluation.

Results

Simulations show that the acoustic spot size in water at 6 dB was 14mm axial x 1.6mm lateral and 52mm axial x 1.6mm lateral for coherent and incoherent modes, respectively. We measured the size of N = 6 lesions induced in vivo in a pig model and compared them to the size of the simulated thermal dose. The best match between the simulated and measured lesion size was found with a maximum absorption coefficient in the cortical bone adjusted to 30 dB/cm/MHz. This absorption was used to simulate clinical scenarios in humans to generate lesions with no potential side effects at 1000 and 1500 J.

Conclusion

The elongated spot obtained with the incoherent mode facilitates the targeting during fluoroscopic-guided medial branch nerve ablation.

中文翻译：

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非相干HIFU换能器治疗内侧支神经：数值研究和体内验证

摘要

背景

在美国，因小面相关的退行性变化而引起的慢性背痛每年影响4-6百万患者。保守治疗无效的患者可能需要通过射频消融将类固醇靶向注射到关节或经皮内侧支神经去神经支配中。我们对新型无创高强度聚焦超声换能器进行了数值测试，以优化骨软组织界面附近的神经消融。

方法

对以非相干模式运行的具有4个元素的换能器进行了数值建模，并在荧光镜引导下进行了临床前测试。在对2头猪进行6次腰椎内侧分支神经消融后，对其进行临床随访1周，然后处死以进行病理评估。

结果

仿真表明，对于相干模式和非相干模式，水中在6 dB处的声点大小分别为轴向14mm x横向1.6mm和轴向52mm x横向1.6mm。我们测量了在猪模型中体内诱导的N = 6个病变的大小，并将它们与模拟热剂量的大小进行了比较。在皮损的最大吸收系数调整为30 dB / cm / MHz的情况下，发现了模拟和测量的病变大小之间的最佳匹配。这种吸收被用于模拟人类的临床情况，以产生在1000和1500 J下无潜在副作用的病变。

结论

用非相干模式获得的细长斑点有助于在荧光镜引导下的内侧分支神经消融过程中进行靶向。