Ribot Emeline J, Duriez Tom J, Trotier Aurélien J, Thiaudiere Eric, Franconi Jean-Michel, Miraux Sylvain
Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536, CNRS-Université Bordeaux, France.
J Magn Reson Imaging. 2015 May;41(5):1413-21. doi: 10.1002/jmri.24688. Epub 2014 Jul 2.
To develop and evaluate three-dimensional (3D) self-gated balanced steady state free precession (bSSFP) imaging at high magnetic fields to track iron-labeled cells and metastases in murine abdomens.
Mice were injected intravenously with iron-labeled melanoma cells and imaged at 7 Tesla (T). Respiration peaks were identified using Free Induction Decay acquired immediately after the radiofrequency pulse. Respiration-corrupted k-space lines were deleted. Four images were acquired to reconstruct final images using the Sum-Of-Square technique. Image sharpness, metastasis contrast and iron-labeled cell detection with SG-bSSFP sequence (acquired with echo time [TE] = 3 ms or TE = 6 ms) were compared with standard methods (gradient echo (GRE) and RARE).
After reconstruction, the 3D SG-bSSFP images were 75-80% sharper, free from banding (75% liver signal-to-noise ratio recovery) and respiratory motion (26-42% improvement in signal homogeneity) artifacts. Metastasis contrast was twice higher on SG-bSSFP with TE = 3 ms than on RARE images. Iron-labeled cells and metastases were simultaneously detected on SG-bSSFP images with TE = 6 ms, with similar void intensity and tumor contrast to GRE and RARE, respectively. Halving acquisition time preserved iron sensitivity and metastasis contrast, allowing for 3D abdomen imaging in 13 min (TE = 3 ms) or 26 min (TE = 6 ms).
Combining a self-gating technique with bSSFP sequences at 7T provides high-resolution 3D artifact-free abdominal images of small animals.
开发并评估高磁场下的三维（3D）自门控平衡稳态自由进动（bSSFP）成像技术，以追踪小鼠腹部铁标记的细胞和转移灶。
给小鼠静脉注射铁标记的黑色素瘤细胞，并在7特斯拉（T）磁场下进行成像。利用射频脉冲后立即采集的自由感应衰减信号识别呼吸峰值。删除受呼吸影响的k空间线。采集四张图像，使用平方和技术重建最终图像。将使用SG-bSSFP序列（回波时间[TE]=3 ms或TE=6 ms）获得的图像清晰度、转移灶对比度和铁标记细胞检测结果与标准方法（梯度回波（GRE）和快速自旋回波（RARE））进行比较。
重建后，3D SG-bSSFP图像的清晰度提高了75%-80%，无带状伪影（肝脏信噪比恢复75%）和呼吸运动伪影（信号均匀性提高26%-42%）。TE=3 ms时，SG-bSSFP上的转移灶对比度比RARE图像高两倍。在TE=6 ms的SG-bSSFP图像上同时检测到铁标记的细胞和转移灶，其空洞强度和肿瘤对比度分别与GRE和RARE相似。采集时间减半可保持铁敏感性和转移灶对比度，从而能够在13分钟（TE=3 ms）或26分钟（TE=6 ms）内完成三维腹部成像。
在7T磁场下将自门控技术与bSSFP序列相结合，可为小动物提供高分辨率的三维无伪影腹部图像。
