Zhong Xiaodong, Armstrong Tess, Gao Chang, Nickel Marcel D, Han Fei, Dale Brian M, Li Xinzhou, Kafali Sevgi G, Hu Peng, Wu Holden H, Deshpande Vibhas
MR R&D Collaborations, Siemens Medical Solutions USA, Inc, Los Angeles, California, USA.
Department of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
Magn Reson Med. 2022 Jan;87(1):281-291. doi: 10.1002/mrm.28981. Epub 2021 Aug 19.
To develop an accelerated k-space shift calibration method for free-breathing 3D stack-of-radial MRI quantification of liver proton-density fat fraction (PDFF) and .
Accelerated k-space shift calibration was developed to partially skip acquisition of k-space shift data in the through-plane direction then interpolate in processing, as well as to reduce the in-plane averages. A multi-echo stack-of-radial sequence with the baseline calibration was evaluated on a phantom versus vendor-provided reference-standard PDFF and values at 1.5T, and in 13 healthy subjects and 5 clinical subjects at 3T with respect to reference-standard breath-hold Cartesian acquisitions. PDFF and maps were calculated with different calibration acceleration factors offline and compared to reference-standard values using Bland-Altman analysis. Bias and uncertainty were evaluated using normal distribution and Bayesian probability of difference (P < .05 considered significant).
Bland-Altman plots of phantom and in vivo data showed that substantial acceleration was highly feasible in both through-plane and in-plane directions. Compared to the baseline calibration without acceleration, Bayesian analysis revealed no significant differences on biases and uncertainties of PDFF and measurements with all acceleration methods in this study, except the method with through-plane acceleration equaling slices and averages equaling 20 for PDFF and (both P < .001) for the phantom. A six-fold reduction in equivalent calibration acquisition time (time saving ≥25 s and ≥80.7%) was achieved using recommended acceleration factors for the in vivo protocols in this study.
This proposed method may allow accelerated calibration for free-breathing stack-of-radial MRI PDFF and mapping.
开发一种加速k空间偏移校准方法，用于自由呼吸状态下肝脏质子密度脂肪分数（PDFF）的三维径向MRI定量分析。
开发加速k空间偏移校准方法，以部分跳过层面方向上k空间偏移数据的采集，然后在处理过程中进行插值，并减少平面内平均次数。在1.5T场强下，对带有基线校准的多回波径向序列在体模上进行评估，并与供应商提供的参考标准PDFF和值进行比较；在3T场强下，对13名健康受试者和5名临床受试者进行评估，并与参考标准屏气笛卡尔采集进行比较。离线计算不同校准加速因子下的PDFF和图，并使用Bland-Altman分析与参考标准值进行比较。使用正态分布和差异贝叶斯概率评估偏差和不确定性（P <.05认为具有显著性）。
体模和体内数据的Bland-Altman图表明，在层面方向和平面内方向上进行大幅加速都是高度可行的。与无加速的基线校准相比，贝叶斯分析显示，本研究中所有加速方法在PDFF和测量的偏差和不确定性方面均无显著差异，但对于体模，层面加速等于层数且平面内平均次数等于20的方法除外（两者P <.001）。使用本研究中体内协议的推荐加速因子，等效校准采集时间减少了六倍（节省时间≥25 s且≥80.7%）。
所提出的方法可能允许对自由呼吸的径向MRI PDFF和成像进行加速校准。
