Abstract

Background

Patient suitability for magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) therapy of pelvic tumors is currently assessed by visual estimation of the proportion of tumor that can be reached by the device’s focus (coverage). Since it is important to assess whether enough energy reaches the tumor to achieve ablation, a methodology for estimating the proportion of the tumor that can be ablated (treatability) was developed. Predicted treatability was compared against clinically achieved thermal ablation.

Methods

MR Dixon sequence images of five patients with recurrent gynecological tumors were acquired during their treatment. Acousto-thermal simulations were performed using k-Wave for three exposure points (the deepest and shallowest reachable focal points within the tumor, identified from tumor coverage analysis, and a point halfway in-between) per patient. Interpolation between the resulting simulated ablated tissue volumes was used to estimate the maximum treatable depth and hence, tumor treatability. Predicted treatability was compared both to predicted tumor coverage and to the clinically treated tumor volume. The intended and simulated volumes and positions of ablated tissues were compared.

Results

Predicted treatability was less than coverage by 52% (range: 31–78%) of the tumor volume. Predicted and clinical treatability differed by 9% (range: 1–25%) of tumor volume. Ablated tissue volume and position varied with beam path length through tissue.

Conclusion

Tumor coverage overestimated patient suitability for MRgHIFU therapy. Employing patient-specific simulations improved treatability assessment. Patient treatability assessment using simulations is feasible.

中文翻译：

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磁共振引导下高强度聚焦超声定量预测盆腔肿瘤消融程度

摘要

背景

目前，通过目视估计设备的焦点（覆盖范围）可以达到的肿瘤比例来评估患者对磁共振引导的高强度聚焦超声 (MRgHIFU) 治疗盆腔肿瘤的适用性。由于评估是否有足够的能量到达肿瘤以实现消融很重要，因此开发了一种估计可消融的肿瘤比例（可治疗性）的方法。将预测的可治疗性与临床实现的热消融进行比较。

方法

在治疗期间获得了五名复发性妇科肿瘤患者的 MR Dixon 序列图像。使用 k-Wave 对每个患者的三个暴露点（肿瘤内最深和最浅的可到达焦点，通过肿瘤覆盖分析确定，以及中间的一个点）进行声热模拟。所得模拟消融组织体积之间的插值用于估计最大可治疗深度，从而估计肿瘤可治疗性。将预测的可治疗性与预测的肿瘤覆盖率和临床治疗的肿瘤体积进行比较。比较了消融组织的预期和模拟体积和位置。

结果

预测的可治疗性低于肿瘤体积的 52%（范围：31-78%）的覆盖率。预测和临床可治疗性相差 9%（范围：1-25%）的肿瘤体积。消融的组织体积和位置随着通过组织的光束路径长度而变化。

结论

肿瘤覆盖率高估了患者对 MRgHIFU 治疗的适用性。采用特定于患者的模拟改进了可治疗性评估。使用模拟进行患者可治疗性评估是可行的。