Smith Alex K, By Samantha, Lyttle Bailey D, Dortch Richard D, Box Bailey A, Mckeithan Lydia J, Thukral Saakshi, Bagnato Francesca, Pawate Siddharama, Smith Seth A
Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
Vanderbilt University Institute of Imaging Sciences, Vanderbilt University, Nashville, TN, USA.
Neuroimage Clin. 2017 Jul 14;16:58-65. doi: 10.1016/j.nicl.2017.07.010. eCollection 2017.
Spinal cord (SC) damage is linked to clinical deficits in patients with multiple sclerosis (MS), however, conventional MRI methods are not specific to the underlying macromolecular tissue changes that may precede overt lesion detection. Single-point quantitative magnetization transfer (qMT) is a method that can provide high-resolution indices sensitive to underlying macromolecular composition in a clinically feasible scan time by reducing the number of MT-weighted acquisitions and utilizing a two-pool model constrained by empirically determined constants. As the single-point qMT method relies on a priori constraints, it has not been employed extensively in patients, where these constraints may vary, and thus, the biases inherent in this model have not been evaluated in a patient cohort. We, therefore, addressed the potential biases in the single point qMT model by acquiring qMT measurements in the cervical SC in patient and control cohorts and evaluated the differences between the control and patient-derived qMT constraints (k, TR, and T) for the single point model. We determined that the macromolecular to free pool size ratio (PSR) differences between the control and patient-derived constraints are not significant (p > 0.149 in all cases). Additionally, the derived PSR for each cohort was compared, and we reported that the white matter PSR in healthy volunteers is significantly different from lesions (p < 0.005) and normal appearing white matter (p < 0.02) in all cases. The single point qMT method is thus a valuable method to quantitatively estimate white matter pathology in MS in a clinically feasible scan time.
脊髓（SC）损伤与多发性硬化症（MS）患者的临床缺陷相关，然而，传统的MRI方法对于在明显病变检测之前可能发生的潜在大分子组织变化并不具有特异性。单点定量磁化传递（qMT）是一种方法，通过减少MT加权采集的数量并利用由经验确定的常数约束的双池模型，能够在临床可行的扫描时间内提供对潜在大分子组成敏感的高分辨率指标。由于单点qMT方法依赖于先验约束，它尚未在患者中广泛应用，因为这些约束可能会有所不同，因此，该模型固有的偏差尚未在患者队列中进行评估。因此，我们通过在患者和对照队列的颈髓中获取qMT测量值来解决单点qMT模型中的潜在偏差，并评估了单点模型中对照和患者来源的qMT约束（k、TR和T）之间的差异。我们确定对照和患者来源的约束之间的大分子与自由池大小比（PSR）差异不显著（所有情况下p>0.149）。此外，比较了每个队列得出的PSR，我们报告在所有情况下，健康志愿者的白质PSR与病变（p<0.005）和正常外观白质（p<0.02）有显著差异。因此，单点qMT方法是一种在临床可行的扫描时间内定量估计MS中白质病理的有价值方法。
