Improved reconstruction stability for chemical shift encoded hyperpolarized 13 C magnetic resonance spectroscopic imaging using k-t spiral acquisitions.
Improved reconstruction stability for chemical shift encoded hyperpolarized 13 C magnetic resonance spectroscopic imaging using k-t spiral acquisitions.
复制标题
使用 k-t 螺旋采集提高化学位移编码超极化 13 C 磁共振波谱成像的重建稳定性。
DOI：
10.1002/mrm.28122
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发表时间：
2020
影响因子：
3.3
通讯作者：
Fain,SeanB
中科院分区：
文献类型：
--
作者：
Macdonald,ErinB;Barton,GregoryP;Cox,BenjaminL;Johnson,KevinM;Strigel,RobertaM;Fain,SeanB
多回波、视场(FOV)-过采样k-t螺旋采集和具有回波不对称和最小二乘估计重建的水和脂肪的直接迭代分解可以改善超极化13C磁共振波谱成像的稳定性，其中存在由于低信噪比(SNR)、代谢物峰值的局部不确定性和回声信号不一致而引起的信号模糊。理论上k-t螺旋采集通过采集η过采样的FOV和矩阵来重新分布读出点，使其在k-空间中的径向分布更加密集。这些更密集的螺旋回波构成了有效的吸气内回波，可以补充传统的螺旋间回波，以改善光谱分离和减少光谱串扰，从而更好地分辨13C标记的物种以进行光谱成像。方法使用多回波，k-t螺旋采集对一系列螺旋间回波间隔和η进行数字模拟和成像模型实验。图像光谱串扰伪影被定性和定量地评估为测量的代谢物比率的百分比误差。小鼠体内实验评估了多回声，k-t螺旋[1-13C]丙酮酸盐磁共振成像在3种不同重建稳定性的情况下减少光谱串扰的可行性。结果数字模拟和成像模型实验都显示，随着η的增加和回声间隔的更好选择，图像光谱串扰和测量代谢物比率的误差百分比都减小或相当。体内图像显示η=7与η=1采集的乳酸盐图像的光谱串扰显著降低。结论在存在低信噪比物种、代谢物共振的局部不确定性以及回声信号不一致的情况下，超极化13C代谢成像和定量的精度可以通过使用视场过采样k-t螺旋采集来提高。
PurposeA multiecho, field of view (FOV)‐oversampled k‐t spiral acquisition and direct iterative decomposition of water and fat with echo asymmetry and least‐squares estimation reconstruction is demonstrated to improve the stability of hyperpolarized13C magnetic resonance spectroscopic imaging (MRSI) in the presence of signal ambiguities attributed to low‐SNR (signal‐to‐noise‐ratio) species, local uncertainties in metabolite peaks, and echo‐to‐echo signal inconsistencies.Theoryk‐t spiral acquisitions redistribute readout points to be more densely spaced radially in k‐space by acquiring an FOV and matrix that are oversampled byη. These more densely spaced spiral turns constitute effective intraspiral echoes and can supplement conventional interspiral echoes to improve spectral separation and reduce spectral cross‐talk to better resolve13C‐labeled species for spectroscopic imaging.MethodsDigital simulations and imaging phantom experiments were performed for a range of interspiral echo spacings andηusing multiecho, k‐t spiral acquisitions. Image spectral cross‐talk artifacts were evaluated both qualitatively and quantitatively as the percent error in measured metabolite ratios. In vivo murine experiments evaluated the feasibility of multiecho, k‐t spiral [1‐13C]pyruvate MRSI to reduce spectral cross‐talk for 3 scenarios of different expected reconstruction stability.ResultsDigital simulations and imaging phantom experiments both demonstrated reduced or comparable image spectral cross‐talk and percent errors in measured metabolite ratios with increasingηand better choices of echo spacings. In vivo images displayed markedly reduced spectral cross‐talk in lactate images acquired withη= 7 versusη= 1.ConclusionThe precision of hyperpolarized13C metabolic imaging and quantification in the presence of low‐SNR species, local uncertainties in metabolite resonances, and echo‐to‐echo signal inconsistencies can be improved with the use of FOV‐oversampled k‐t spiral acquisitions.