Long Ziyang, Yang Hsin-Jung, Binesh Nader, Malagi Archana Vadiraj, Shang Yun, Huang Li-Ting, Zepeda Jeremy, Serry Fardad Michael, Li Debiao, Han Hui
Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
Department of Radiology, Weill Cornell Medicine, New York, New York, USA.
Magn Reson Med. 2025 Jul;94(1):401-413. doi: 10.1002/mrm.30474. Epub 2025 Mar 19.
High-quality fat suppression is essential for various MRI applications. In musculoskeletal imaging, poor fat suppression caused by severe B inhomogeneity can obscure important lesions, potentially leading to inaccurate diagnoses. This problem is particularly exacerbated in off-isocenter imaging, where conventional shimming using second-order spherical harmonic shim coils often proves inadequate due to elevated B inhomogeneity. To address this challenge, we configured a simple local shim insert to provide additional localized B shimming for off-isocenter regions, offering a practical hardware solution.
We designed and constructed a seven-channel shim coil and evaluated its performance in comparison to conventional second-order spherical harmonic shimming within a targeted volume near the scanner bore. The coil was tested with both phantom and in vivo studies using a clinical 3 T MRI scanner.
The improved B homogeneity achieved with the local shim coil significantly enhanced fat saturation (fat-sat) uniformity across the imaged volumes. This improvement was particularly beneficial for areas far from the scanner isocenter, where B inhomogeneity is most severe. Our results indicated a 40% reduction in RMS error of the B field for elbow imaging and 35% for hand imaging, highlighting substantial improvements in B field homogeneity. Additionally, the image quality score increased by 1 point for both hand and elbow images, reflecting enhanced fat-sat quality.
The simple local shim insert we configured improves fat-sat capability in both hand and elbow imaging. It offers the potential for improving off-isocenter musculoskeletal MRI.
高质量的脂肪抑制对于各种MRI应用至关重要。在肌肉骨骼成像中，严重的磁场不均匀性导致的脂肪抑制不佳会掩盖重要病变，可能导致诊断不准确。在等中心外成像中，这个问题尤其严重，因为使用二阶球谐匀场线圈的传统匀场方法往往因磁场不均匀性增加而显得不足。为应对这一挑战，我们配置了一个简单的局部匀场插入件，为等中心外区域提供额外的局部磁场匀场，提供了一种实用的硬件解决方案。
我们设计并构建了一个七通道匀场线圈，并在靠近扫描 bore 的目标体积内，与传统的二阶球谐匀场方法相比，评估了其性能。使用临床3T MRI扫描仪对该线圈进行了体模和体内研究测试。
局部匀场线圈实现的磁场均匀性改善显著提高了成像体积内的脂肪饱和（fat-sat）均匀性。这种改善对于远离扫描等中心的区域尤其有益，那里的磁场不均匀性最为严重。我们的结果表明，肘部成像的磁场均方根误差降低了40%，手部成像降低了35%，突出了磁场均匀性的显著改善。此外，手部和肘部图像的图像质量评分均提高了1分，反映了脂肪饱和质量的提高。
我们配置的简单局部匀场插入件提高了手部和肘部成像中的脂肪饱和能力。它为改善等中心外肌肉骨骼MRI提供了潜力。
