Laboratory of FMRI Technology, Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Lawson Health Research Institute, London, Ontario, Canada.
Magn Reson Med. 2023 May;89(5):1990-2004. doi: 10.1002/mrm.29581. Epub 2023 Jan 9.
To present a pulse sequence and mathematical models for quantification of blood-brain barrier water exchange and permeability.
Motion-compensated diffusion-weighted (MCDW) gradient-and-spin echo (GRASE) pseudo-continuous arterial spin labeling (pCASL) sequence was proposed to acquire intravascular/extravascular perfusion signals from five postlabeling delays (PLDs, 1590-2790 ms). Experiments were performed on 11 healthy subjects at 3 T. A comprehensive set of perfusion and permeability parameters including cerebral blood flow (CBF), capillary transit time (τ ), and water exchange rate (k ) were quantified, and permeability surface area product (PS ), total extraction fraction (E ), and capillary volume (V ) were derived simultaneously by a three-compartment single-pass approximation (SPA) model on group-averaged data. With information (i.e., V and τ ) obtained from three-compartment SPA modeling, a simplified linear regression of logarithm (LRL) approach was proposed for individual k quantification, and E and PS can be estimated from long PLD (2490/2790 ms) signals. MCDW-pCASL was compared with a previously developed diffusion-prepared (DP) pCASL sequence, which calculates k by a two-compartment SPA model from PLD = 1800 ms signals, to evaluate the improvements.
Using three-compartment SPA modeling, group-averaged CBF = 51.5/36.8 ml/100 g/min, k = 126.3/106.7 min , PS = 151.6/93.8 ml/100 g/min, E = 94.7/92.2%, τ = 1409.2/1431.8 ms, and V = 1.2/0.9 ml/100 g in gray/white matter, respectively. Temporal SNR of MCDW-pCASL perfusion signals increased 3-fold, and individual k maps calculated by the LRL method achieved higher spatial resolution (3.5 mm isotropic) as compared with DP pCASL (3.5 × 3.5 × 8 mm ).
MCDW-pCASL allows visualization of intravascular/extravascular ASL signals across multiple PLDs. The three-compartment SPA model provides a comprehensive measurement of blood-brain barrier water dynamics from group-averaged data, and a simplified LRL method was proposed for individual k quantification.
介绍一种用于量化血脑屏障水交换和通透性的脉冲序列和数学模型。
提出了一种运动补偿扩散加权（MCDW）梯度和自旋回波（GRASE）伪连续动脉自旋标记（pCASL）序列，以从五个标记后延迟（PLD，1590-2790ms）获取血管内/血管外灌注信号。在 3T 上对 11 名健康受试者进行了实验。通过三房室单通过近似（SPA）模型在组平均数据上同时量化了包括脑血流量（CBF）、毛细血管转运动力学（τ）和水交换率（k）在内的一系列灌注和通透性参数，并推导了通透性表面积乘积（PS）、总提取分数（E）和毛细血管体积（V）。利用三房室 SPA 模型获得的信息（即 V 和 τ），提出了一种简化的对数线性回归（LRL）方法用于个体 k 的定量，并可从长 PLD（2490/2790ms）信号估计 E 和 PS。将 MCDW-pCASL 与先前开发的扩散准备（DP）pCASL 序列进行了比较，后者通过 2 房室 SPA 模型从 PLD=1800ms 信号计算 k，以评估改进效果。
使用三房室 SPA 模型，组平均 CBF=51.5/36.8ml/100g/min，k=126.3/106.7min，PS=151.6/93.8ml/100g/min，E=94.7/92.2%，τ=1409.2/1431.8ms，V=1.2/0.9ml/100g，分别为灰质/白质。与 DP pCASL 相比，MCDW-pCASL 灌注信号的时间 SNR 增加了 3 倍，通过 LRL 方法计算的个体 k 图达到了更高的空间分辨率（3.5mm 各向同性）。
MCDW-pCASL 允许跨多个 PLD 可视化血管内/血管外 ASL 信号。三房室 SPA 模型可从组平均数据中全面测量血脑屏障水动力学，并且提出了一种简化的 LRL 方法用于个体 k 的定量。
