Jensen Jens H
Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, USA.
Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA.
Magn Reson Med. 2025 Jun 10. doi: 10.1002/mrm.30608.
To demonstrate a method of reducing pulse duration effects for the diffusional kurtosis of the multi-compartment Kärger model (KM) as estimated with a Stejskal-Tanner DWI sequence.
An effective diffusion time is introduced that corrects errors in the apparent diffusional kurtosis arising from a nonzero pulse duration δ for the multi-compartment KM. The correction is exact to first order in the diffusion time Δ, and numerical calculations are used to assess how well it reduces pulse duration effects. Specifically, for the two-compartment KM, the deviations of the apparent kurtosis obtained with the Stejskal-Tanner sequence from the exact kurtosis are calculated for the full range of δ and Δ, and similar calculations are performed for the deviation in the derivative of the kurtosis with respect to Δ. For the general multi-compartment KM, upper bounds on the maximum magnitude of the deviations are determined. Application of the correction to estimation of intercompartmental exchange rates is illustrated with several examples.
For the two-compartment KM, the correction reduces the deviation of the apparent kurtosis and its time derivative for most values of δ and Δ. For the general multi-compartment KM, the maximum deviation magnitude, relative to the initial kurtosis, is 2.26% for the uncorrected kurtosis and 0.57% after correction. The correction reduces the maximum deviation magnitude of the derivative from 46% to less than 1%.
Pulse duration effects for the kurtosis of the multi-compartment KM can be strongly suppressed by applying the effective diffusion time correction.
展示一种减少脉冲持续时间对多室Kärger模型（KM）扩散峰度影响的方法，该模型通过Stejskal-Tanner扩散加权成像（DWI）序列进行估计。
引入有效扩散时间，以校正多室KM中因非零脉冲持续时间δ导致的表观扩散峰度误差。该校正对于扩散时间Δ精确到一阶，并且使用数值计算来评估其减少脉冲持续时间影响的效果。具体而言，对于双室KM，计算在整个δ和Δ范围内，通过Stejskal-Tanner序列获得的表观峰度与精确峰度之间的偏差，并对峰度关于Δ的导数偏差进行类似计算。对于一般的多室KM，确定偏差最大幅度的上限。通过几个例子说明了该校正方法在估计室间交换率中的应用。
对于双室KM，在大多数δ和Δ值下，该校正减少了表观峰度及其时间导数的偏差。对于一般的多室KM，相对于初始峰度，未校正峰度的最大偏差幅度为2.26%，校正后为0.57%。该校正将导数的最大偏差幅度从46%降低到小于1%。
通过应用有效扩散时间校正，可以强烈抑制多室KM峰度的脉冲持续时间影响。
