Optimization of b-value schemes for estimation of the diffusion coefficient and the perfusion fraction with segmented intravoxel incoherent motion model fitting
Optimization of b-value schemes for estimation of the diffusion coefficient and the perfusion fraction with segmented intravoxel incoherent motion model fitting
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DOI：
10.1002/mrm.27826
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发表时间：
2019-10-01
影响因子：
3.3
通讯作者：
Ljungberg, Maria
中科院分区：
文献类型：
--
作者：
Jalnefjord, Oscar;Montelius, Mikael;Ljungberg, Maria
目的：体素内非相干运动(IVIM)模型用于估计弥散系数(D)和血流灌注分数(F)日益流行，但对标准方案尚无共识。为减少分段模型拟合的D和f的估计不确定度，提供了一个优化b值方案的框架。理论：推导出分段模型拟合的D和f的不确定度的解析表达式为Cramer-Rao下界(CRLBS)。方法：通过CRLBS的约束最小化，得到3~12次采集和无限次采集的最优b值方案，b值约束为0或200~800 S/mm(2)。结果：无论采集总次数(0,200,800 S/mm(2))，所有优化的b值方案都只包含3个唯一的b值，重复采集近似为1：2：2。与线性分布的b值相比，在模拟和体内重复测量中，D和f估计的变异性降低了约30%。结论：使用优化的b值方案可以减少IVIM D和f估计的不确定性。
Purpose: Intravoxel incoherent motion (IVIM) modeling for estimation of the diffusion coefficient (D) and perfusion fraction (f) is increasingly popular, but no consensus on standard protocols exists. This study provides a framework for optimization of b-value schemes for reduced estimation uncertainty of D and f from segmented model fitting.Theory: Analytical expressions for uncertainties of D and f from segmented model fitting were derived as Cramer-Rao lower bounds (CRLBs).Methods: Optimized b-value schemes were obtained for 3 to 12 acquisitions and in the limit of infinitely many acquisitions through constrained minimization of the CRLBs, with b-values constrained to be 0 or 200 to 800 s/mm(2). The optimized b-value scheme with eight acquisitions was compared with b-values linearly distributed in the allowed range using simulations and in vivo liver data from seven healthy volunteers.Results: All optimized b-value schemes contained exactly three unique b-values regardless of the total number of acquisitions (0, 200, and 800 s/mm(2)) with repeated acquisitions distributed approximately as 1:2:2. Compared with linearly distributed b-values, the variability of estimates of D and f was reduced by approximately 30% as seen both in simulations and in repeated in vivo measurements.Conclusion: The uncertainty of IVIM D and f estimates can be reduced by the use of optimized b-value schemes.