Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
NMR Biomed. 2022 Dec;35(12):e4799. doi: 10.1002/nbm.4799. Epub 2022 Jul 28.
The goal of the current study is to include transcytolemmal water exchange in MR cell size imaging using the IMPULSED model for more accurate characterization of tissue cellular properties (e.g., apparent volume fraction of intracellular space ) and quantification of indicators of transcytolemmal water exchange. We propose a heuristic model that incorporates transcytolemmal water exchange into a multicompartment diffusion-based method (IMPULSED) that was developed previously to extract microstructural parameters (e.g., mean cell size and apparent volume fraction of intracellular space ) assuming no water exchange. For ≤ 5 ms, the water exchange can be ignored, and the signal model is the same as the IMPULSED model. For ≥ 30 ms, we incorporated the modified Kärger model that includes both restricted diffusion and exchange between compartments. Using simulations and previously published in vitro cell data, we evaluated the accuracy and precision of model-derived parameters and determined how they are dependent on SNR and imaging parameters. The joint model provides more accurate values for cell sizes ranging from 10 to 12 microns when water exchange is fast (e.g., intracellular water pre-exchange lifetime ≤ 100 ms) than IMPULSED, and reduces the bias of IMPULSED-derived estimates of , especially when water exchange is relatively slow (e.g., > 200 ms). Indicators of transcytolemmal water exchange derived from the proposed joint model are linearly correlated with ground truth values and can detect changes in cell membrane permeability induced by saponin treatment in murine erythroleukemia cancer cells. Our results suggest this joint model not only improves the accuracy of IMPULSED-derived microstructural parameters, but also provides indicators of water exchange that are usually ignored in diffusion models of tissues.
本研究的目的是在 IMPULSED 模型中纳入跨细胞层水交换，以更准确地描述组织细胞特性（例如，细胞内空间的表观体积分数），并量化跨细胞层水交换的指标。我们提出了一个启发式模型，该模型将跨细胞层水交换纳入先前开发的多隔室扩散方法（IMPULSED）中，以提取微结构参数（例如，平均细胞大小和细胞内空间的表观体积分数），假设没有水交换。对于 ≤ 5 ms，水交换可以忽略不计，信号模型与 IMPULSED 模型相同。对于 ≥ 30 ms，我们纳入了改良的 Kärger 模型，该模型包括限制扩散和隔室之间的交换。通过模拟和以前发表的体外细胞数据，我们评估了模型衍生参数的准确性和精密度，并确定了它们如何依赖于 SNR 和成像参数。当水交换较快（例如，细胞内水预交换寿命 ≤ 100 ms）时，联合模型为大小在 10 至 12 微米范围内的细胞提供了比 IMPULSED 更准确的 值，并且减少了 IMPULSED 衍生估计值的偏差，特别是当水交换相对较慢时（例如， > 200 ms）。从所提出的联合模型得出的跨细胞层水交换指标与真实值呈线性相关，并可以检测到皂素处理诱导的细胞膜通透性变化在鼠红白血病癌细胞中。我们的结果表明，该联合模型不仅提高了 IMPULSED 衍生微结构参数的准确性，而且还提供了通常在组织扩散模型中忽略的水交换指标。
