Classical and Learned MR to Pseudo-CT Mappings for Accurate Transcranial Ultrasound Simulation.
Classical and Learned MR to Pseudo-CT Mappings for Accurate Transcranial Ultrasound Simulation.
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经典和学习的 MR 到伪 CT 映射，用于精确的经颅超声模拟。
DOI：
10.1109/tuffc.2022.3198522
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发表时间：
2022
期刊：
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通讯作者：
Miscouridou M
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作者：
Miscouridou M
经颅超声治疗的基于模型的治疗计划通常涉及根据头部的 X 射线计算机断层扫描 (CT) 图像绘制颅骨的声学特性。此处，比较了三种从磁共振 (MR) 图像生成伪 CT (pCT) 图像的方法作为 CT 的替代方法。在成对的 MR-CT 图像上训练卷积神经网络 (U-Net)，以从 T1 加权或零回波时间 (ZTE) MR 图像（分别表示为 tCT 和 zCT）生成 pCT T 图像。还实现了从 ZTE 到 pCT 的直接映射（表示为 cCT）。当比较测试集的 pCT 和真实 CT 图像时，整个头部的平均绝对误差分别为 133、83 和 145 Hounsfield 单位 (HU)，tCT、zCT 和 cCT 图像的颅骨内平均绝对误差分别为 398、222 和 336 HU。还使用生成的 pCT 图像进行超声模拟，并与基于 CT 的模拟进行比较。使用环形阵列传感器瞄准视觉或运动皮层。基于 tCT 图像的模拟，模拟焦压、焦位置和焦体积的平均差异分别为 9.9%、1.5 mm 和 15.1%； zCT 为 5.7%、0.6 mm 和 5.7%； cCT 为 6.7%、0.9 mm 和 12.1%。中兴通讯映射图像的改进结果凸显了使用成像序列的优势，提高了颅骨的对比度。总体而言，这些结果表明，基于 MR 图像的声学模拟可以提供与基于 CT 的声学模拟相当的精度。
Model-based treatment planning for transcranial ultrasound therapy typically involves mapping the acoustic properties of the skull from an X-ray computed tomography (CT) image of the head. Here, three methods for generating pseudo-CT (pCT) images from magnetic resonance (MR) images were compared as an alternative to CT. A convolutional neural network (U-Net) was trained on paired MR-CT images to generate pCT T images from either T1-weighted or zero-echo time (ZTE) MR images (denoted tCT and zCT, respectively). A direct mapping from ZTE to pCT was also implemented (denoted cCT). When comparing the pCT and ground-truth CT images for the test set, the mean absolute error was 133, 83, and 145 Hounsfield units (HU) across the whole head, and 398, 222, and 336 HU within the skull for the tCT, zCT, and cCT images, respectively. Ultrasound simulations were also performed using the generated pCT images and compared to simulations based on CT. An annular array transducer was used targeting the visual or motor cortex. The mean differences in the simulated focal pressure, focal position, and focal volume were 9.9%, 1.5 mm, and 15.1% for simulations based on the tCT images; 5.7%, 0.6 mm, and 5.7% for the zCT; and 6.7%, 0.9 mm, and 12.1% for the cCT. The improved results for images mapped from ZTE highlight the advantage of using imaging sequences, which improves the contrast of the skull bone. Overall, these results demonstrate that acoustic simulations based on MR images can give comparable accuracy to those based on CT.