External Calibration of the Spectral Coverage for Three-Dimensional Multispectral MRI
External Calibration of the Spectral Coverage for Three-Dimensional Multispectral MRI
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DOI：
10.1002/mrm.26065
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发表时间：
2016-11-01
影响因子：
3.3
通讯作者：
Koch, Kevin M.
中科院分区：
文献类型：
--
作者：
Kaushik, S. Sivaram;Marszalkowski, Cathy;Koch, Kevin M.
目的：通过组合在与拉莫尔频率不同的频率偏移处创建的图像，三维（3D）多光谱成像（3D-MSI）序列有助于克服由金属植入物引起的大空间频率分散。然而，这种频率分散随着植入物的尺寸、取向和成分而变化。使用MAVRIC 3D-MSI采集，我们试图前瞻性地校准3D-MSI扫描所需的光谱覆盖范围。这种校准应提供一个显着的改善图像质量，并减少扫描时间。方法：从校准扫描的24个频谱箱被用来生成一个地图的频率偏移周围的植入物。幅度图像用于去除相关频率偏移图中的任何异常值，并且该处理后的图用于确定截止频率偏移，从而确定频谱箱的数量。这种方法在13名受试者中进行了测试，通过回顾性重建MAVRIC-SL图像与更少的光谱箱。随后，在6名受试者中前瞻性校准MAVRIC-SL图像的光谱覆盖范围，并基于截止频率偏移，使用较少的光谱箱采集这些图像。结果：使用较少的光谱箱，回顾性和前瞻性校准的MAVRIC-SL图像都充分描绘了植入物边界。将此校准程序扩展到未来的3D-MSI检查中将有助于提高图像信噪比，缩短扫描时间，并在骨科植入物附近成像时显著改善临床工作流程。(C)2015年国际医学磁共振学会
Purpose: By combining images created at distinct frequency offsets from the Larmor frequency, three-dimensional (3D) multispectral imaging (3D-MSI) sequences help overcome the large spatial frequency dispersion caused by metal implants. This frequency dispersion, however, varies with the implant size, orientation, and composition. Using a MAVRIC 3D-MSI acquisition, we sought to prospectively calibrate the spectral coverage needed for 3D-MSI scans. This calibration should offer a significant improvement to image quality, and reduce the scan time.Methods: The 24 spectral bins from the calibration scan were used to generate a map of frequency offsets around the implant. The magnitude image was used to remove any outliers in the associated frequency offset map, and this processed map was used to determine the cutoff frequency offset and, hence, number of spectral bins. This approach was tested in 13 subjects, by retrospectively reconstructing MAVRIC-SL images with fewer spectral bins. Subsequently, the spectral coverage for MAVRIC-SL images was prospectively calibrated in six subjects, and based on the cutoff frequency offset, these images were acquired with fewer spectral bins.Results: With fewer spectral bins, both retrospectively and prospectively calibrated MAVRIC-SL images adequately delineated the implant boundary.Conclusion: Incorporating this calibration procedure into future 3D-MSI exams will help improve image signal-to-noise ratio, reduce scan time, and significantly improve clinical workflow when imaging near orthopedic implants. (C) 2015 International Society for Magnetic Resonance in Medicine