用于金属附近成像的多光谱3D相位编码涡轮自旋回波：通过模拟和体模实验展示的局限性与可能性
Multispectral 3D phase-encoded turbo spin-echo for imaging near metal: Limitations and possibilities demonstrated by simulations and phantom experiments.
作者信息
van Gorp Jetse S, Nizak Razmara, Bouwman Job G, Saris Daniël B F, Seevinck Peter R
机构信息
Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, The Netherlands.
Department of Orthopedics, University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, The Netherlands.
出版信息
Magn Reson Imaging. 2017 Jun;39:31-43. doi: 10.1016/j.mri.2017.01.016. Epub 2017 Jan 25.
To see improvements in the imaging performance near biomaterial implants we assessed a multispectral fully phase-encoded turbo spin-echo (ms3D-PE-TSE) sequence for artifact reduction capabilities and scan time efficiency in simulation and phantom experiments. For this purpose, ms3D-PE-TSE and ms3D-TSE sequences were implemented to obtain multispectral images (±20kHz) of a cobalt-chromium (CoCr) knee implant embedded in agarose. In addition, a knee implant computer model and the acquired ms3D-PE-TSE images were used to investigate the possibilities for scan time acceleration using field-of-view (FOV) reduction for off-resonance frequency bins and compressed sensing reconstructions of undersampled data. Both acceleration methods were combined to acquire a +10kHz frequency bin in a second experiment. The obtained ms3D-PE-TSE images showed no susceptibility related artifacts, while ms3D-TSE images suffered from hyper-intensity artifacts. The limitations of ms3D-TSE were apparent in the far off-resonance regions (±[10-20]kHz) located close to the implant. The scan time calculations showed that ms3D-PE-TSE can be applied in a clinically relevant timeframe (~12min), when omitting the three central frequency bins. The feasibility of CS acceleration for ms3D-PE-TSE was demonstrated using retrospective reconstructions before combining CS and rFOV imaging to decrease the scan time for the +10kHz frequency bin from ~10.9min to ~3.5min, while also increasing the spatial resolution fourfold. The temporally resolved signal of ms3D-PE-TSE proved to be useful to decrease the intensity ripples after sum-of-squares reconstructions and increase the signal-to-noise ratio. The presented results suggest that the scan time limitations of ms3D-PE-TSE can be sufficiently addressed when focusing on signal acquisitions in the direct vicinity of metal implants. Because these regions cannot be measured with existing multispectral methods, the presented ms3D-PE-TSE method may enable the detection of inflammation or (pseudo-)tumors in locations close to the implant.
为了观察生物材料植入物附近成像性能的改善情况，我们在模拟和体模实验中评估了一种多光谱全相位编码涡轮自旋回波（ms3D-PE-TSE）序列在减少伪影能力和扫描时间效率方面的表现。为此，实施了ms3D-PE-TSE和ms3D-TSE序列，以获取嵌入琼脂糖中的钴铬（CoCr）膝关节植入物的多光谱图像（±20kHz）。此外，使用膝关节植入物计算机模型和获取的ms3D-PE-TSE图像，研究了通过减小非共振频率区间的视野（FOV）和对欠采样数据进行压缩感知重建来加速扫描时间的可能性。在第二个实验中，将这两种加速方法结合起来，以获取+10kHz频率区间的图像。所获得的ms3D-PE-TSE图像未显示出与磁化率相关的伪影，而ms3D-TSE图像则存在高强度伪影。ms3D-TSE的局限性在靠近植入物的远非共振区域（±[10-20]kHz）中很明显。扫描时间计算表明，当省略三个中心频率区间时，ms3D-PE-TSE可以在临床相关的时间范围内（约12分钟）应用。在将压缩感知（CS）和缩小视野（rFOV）成像相结合以将+10kHz频率区间的扫描时间从约10.9分钟减少到约3.5分钟的同时，还将空间分辨率提高了四倍，从而证明了CS加速对ms3D-PE-TSE的可行性。ms3D-PE-TSE的时间分辨信号被证明有助于减少平方和重建后的强度波动，并提高信噪比。呈现的结果表明，当专注于金属植入物直接附近的信号采集时，ms3D-PE-TSE的扫描时间限制可以得到充分解决。由于这些区域无法用现有的多光谱方法测量，所提出的ms3D-PE-TSE方法可能能够检测植入物附近位置的炎症或（假）肿瘤。
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