Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755.
Med Phys. 2013 Oct;40(10):103101. doi: 10.1118/1.4820361.
Breast magnetic resonance imaging is highly sensitive but not very specific for the detection of breast cancer. Opportunities exist to supplement the image acquisition with a more specific modality provided the technical challenges of meeting space limitations inside the bore, restricted breast access, and electromagnetic compatibility requirements can be overcome. Magnetic resonance (MR) and microwave tomography (MT) are complementary and synergistic because the high resolution of MR is used to encode spatial priors on breast geometry and internal parenchymal features that have distinct electrical properties (i.e., fat vs fibroglandular tissue) for microwave tomography.
The authors have overcome integration challenges associated with combining MT with MR to produce a new coregistered, multimodality breast imaging platform--magnetic resonance microwave tomography, including: substantial illumination tank size reduction specific to the confined MR bore diameter, minimization of metal content and composition, reduction of metal artifacts in the MR images, and suppression of unwanted MT multipath signals.
MR SNR exceeding 40 dB can be obtained. Proper filtering of MR signals reduces MT data degradation allowing MT SNR of 20 dB to be obtained, which is sufficient for image reconstruction. When MR spatial priors are incorporated into the recovery of MT property estimates, the errors between the recovered versus actual dielectric properties approach 5%.
The phantom and human subject exams presented here are the first demonstration of combining MT with MR to improve the accuracy of the reconstructed MT images.
乳腺磁共振成像具有很高的敏感性，但特异性不高，可用于检测乳腺癌。有机会通过补充更具特异性的模态来补充图像采集，只要能够克服在孔径内满足空间限制、限制乳房进入和电磁兼容性要求的技术挑战。磁共振（MR）和微波层析成像（MT）是互补和协同的，因为 MR 的高分辨率用于对具有不同电特性（即脂肪与纤维腺体组织）的乳腺几何形状和内部实质特征进行空间先验编码，以便微波层析成像使用。
作者已经克服了将 MT 与 MR 结合以产生新的配准、多模态乳腺成像平台——磁共振微波层析成像的集成挑战，包括：针对受限的 MR 孔径直径，大幅减小照明罐的尺寸，最小化金属含量和组成，减少 MR 图像中的金属伪影，并抑制不需要的 MT 多径信号。
可以获得超过 40dB 的 MR SNR。适当的 MR 信号滤波可以减少 MT 数据的降级，从而可以获得 20dB 的 MT SNR，足以进行图像重建。当将 MR 空间先验纳入 MT 特性估计的恢复中时，恢复的与实际介电特性之间的误差接近 5%。
这里呈现的体模和人体受试者检查是首次将 MT 与 MR 结合以提高重建 MT 图像准确性的演示。
