Comparison of tri-exponential decay versus bi-exponential decay and full fitting versus segmented fitting for modeling liver intravoxel incoherent motion diffusion MRI
Comparison of tri-exponential decay versus bi-exponential decay and full fitting versus segmented fitting for modeling liver intravoxel incoherent motion diffusion MRI
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DOI：
10.1002/nbm.4155
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发表时间：
2019-07-30
影响因子：
2.9
通讯作者：
Wang, Yi Xiang J.
中科院分区：
文献类型：
--
作者：
Chevallier, Olivier;Zhou, Nan;Wang, Yi Xiang J.
目的确定双指数或三指数模型以及完整或分段拟合是否更好地拟合健康肝脏的体素内非相干运动（IVIM）成像信号。方法使用3 T扫描仪，采用经颅触发平面回波序列，16个b值（0-800 s/mm（2）），获得弥散加权图像。18名健康志愿者在同一个阶段扫描了他们的肝脏两次，然后在另一个阶段扫描了一次。采用双指数和三指数模型处理基于感兴趣区域的肝实质测量值，包括完全拟合和分段拟合（阈值b值= 200 s/mm（2））。结果取所有扫描信号的平均值，双指数模型全拟合D-slow = 1.14 × 10 - 3 mm 2/s，D-fast = 193.6 × 10 - 3 mm 2/s，灌注分数（PF）= 16.9%，分段拟合D-slow = 0.98 × 10 - 3 mm 2/s，D-fast = 42.2 x 10（-3）mm（2）/s，PF = 23.3%。从三指数模型中得出的IVIM参数对于完全拟合和分段拟合是相似的，慢（D '（慢）= 0.98 × 10（-3）mm（2）/s; F'（慢）= 76.4或76.6%），快（D '（快）= 15.1或15.4 × 10（-3）mm（2）/s; F '（快）= 11.8或11.7%）和非常快（D'（Vfast）= 445.0或448.8 × 10（-3）mm（2）/s; F '（Vfast）= 11.8或11.7%）扩散室。三指数模型提供了比双指数模型更好的整体拟合。对于双指数模型，与分段拟合相比，完全拟合在非常低和低的b值下提供了更好的拟合，后者倾向于低估D-fast;然而，分段方法在高b值的信号预测中表现出更低的误差。与完全拟合相比，三指数分段拟合具有更好的扫描重复性。结论对于健康肝脏，三指数模型优于双指数模型。对于双指数模型，分段拟合低估了D-fast，但提供了更准确的D-slow估计。
Objectives To determine whether bi- or tri-exponential models, and full or segmented fittings, better fit the intravoxel incoherent motion (IVIM) imaging signal of healthy livers. Methods Diffusion-weighted images were acquired with a 3 T scanner using a respiratory-triggered echo-planar sequence and 16 b-values (0-800 s/mm(2)). Eighteen healthy volunteers had their livers scanned twice in the same session, and then once in another session. Liver parenchyma region-of-interest-based measurements were processed with bi-exponential and tri-exponential models, with both full fitting and segmented fitting (threshold b-value = 200 s/mm(2)). Results With the signal of all scans averaged, bi-exponential model full fitting showed D-slow = 1.14 x 10(-3) mm(2)/s, D-fast = 193.6 x 10(-3) mm(2)/s, and perfusion fraction (PF) = 16.9%, and segmented fitting showed D-slow = 0.98 x 10(-3) mm(2)/s, D-fast = 42.2 x 10(-3) mm(2)/s, and PF = 23.3%. IVIM parameters derived from the tri-exponential model were similar for full fitting and segmented fitting, with slow (D'(slow) = 0.98 x 10(-3) mm(2)/s; F'(slow) = 76.4 or 76.6%), fast (D'(fast) = 15.1 or 15.4 x 10(-3) mm(2)/s; F'(fast) = 11.8 or 11.7%) and very fast (D'(Vfast) = 445.0 or 448.8 x 10(-3) mm(2)/s; F'(Vfast) = 11.8 or 11.7%) diffusion compartments. The tri-exponential model provided an overall better fit than the bi-exponential model. For the bi-exponential model, full fitting provided a better fit at very low and low b-values compared with segmented fitting, with the latter tending to underestimate D-fast; however, the segmented method demonstrated lower error in signal prediction for high b-values. Compared with full fitting, tri-exponential segmented fitting offered better scan-rescan reproducibility. Conclusion For healthy liver, tri-exponential modeling is preferred to bi-exponential modeling. For the bi-exponential model, segmented fitting underestimates D-fast, but offers a more accurate estimation of D-slow.