Simegn Gizeaddis Lamesgin, Gagoski Borjan, Song Yulu, Dean Douglas C, Hupfeld Kathleen E, Murali-Manohar Saipavitra, Davies-Jenkins Christopher W, Simicic Dunja, Fujita Shohei, Wisnowski Jessica, Yedavalli Vivek, Gudmundson Aaron T, Zöllner Helge J, Oeltzschner Georg, Edden Richard A E
Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
Quant Imaging Med Surg. 2025 May 1;15(5):3807-3823. doi: 10.21037/qims-24-1870. Epub 2025 Apr 24.
Relaxometry, specifically T and T mapping, has become an essential technique for assessing the properties of biological tissues related to various physiological and pathological conditions. Many techniques are being used to estimate T and T relaxation times, ranging from the traditional inversion or saturation recovery and spin-echo sequences to more advanced methods. Choosing the appropriate method for a specific application is critical since the precision and accuracy of T and T measurements are influenced by a variety of factors including the pulse sequence and its parameters, the inherent properties of the tissue being examined, the magnetic resonance imaging (MRI) hardware, and the image reconstruction. The aim of this cohort study is to evaluate and compare the test-retest repeatability of two advanced MRI relaxometry techniques: Driven Equilibrium Single Pulse Observation of T and T (DESPOT), and three-dimensional Quantification using an interleaved Look-Locker acquisition Sequence with a T preparation pulse (3D-QALAS), for T and T mapping in a healthy volunteer cohort.
Ten healthy volunteers underwent brain MRI at 1.3 mm isotropic resolution, acquiring DESPOT and 3D-QALAS data (~11.8 and ~5 min duration, including field maps, respectively), test-retest with subject repositioning, on a 3.0 Tesla Philips Ingenia Elition scanner. To reconstruct the T and T maps, we used an equation-based algorithm for DESPOT and a dictionary-based algorithm that incorporates inversion efficiency and B1-field inhomogeneity for 3D-QALAS. The test-retest repeatability of this cohort study was assessed using the coefficient of variation (CoV), intraclass correlation coefficient (ICC) and Bland-Altman plots.
Our results indicate that both the DESPOT and 3D-QALAS techniques demonstrate good levels of test-retest repeatability for T and T mapping across the brain. Higher whole-brain voxel-to-voxel ICCs are observed in 3D-QALAS for T (0.84±0.039) and in DESPOT for T (0.897±0.029). The Bland-Altman plots show smaller bias and variability of T estimates for 3D-QALAS (mean of -0.02 s, and upper and lower limits of -0.14 and 0.11 s, 95% confidence interval) than for DESPOT (mean of -0.02 s, and limits of -0.31 and 0.27 s). 3D-QALAS also showed less variability (mean 1.08 ms, limits -1.88 to 4.04 ms) for T compared to DESPOT (mean of 2.56 ms, and limits -17.29 to 22.41 ms). The within-subject CoVs for 3D-QALAS range from 0.6% [T in cerebrospinal fluid (CSF)] to 5.8% [T in gray matter (GM)], while for DESPOT they range from 2.1% (T in CSF) to 6.7% (T in GM). The between-subject CoVs for 3D-QALAS range from 2.5% (T in GM) to 12% (T in CSF), and for DESPOT they range from 3.7% [T in white matter (WM)] to 9.3% (T in CSF).
Overall, 3D-QALAS demonstrated better repeatability for T and T measurements than DESPOT, in addition to reduced acquisition time.
弛豫测量法，特别是T1和T2映射，已成为评估与各种生理和病理状况相关的生物组织特性的重要技术。许多技术被用于估计T1和T2弛豫时间，从传统的反转或饱和恢复以及自旋回波序列到更先进的方法。为特定应用选择合适的方法至关重要，因为T1和T2测量的精度和准确性受到多种因素的影响，包括脉冲序列及其参数、被检查组织的固有特性、磁共振成像（MRI）硬件以及图像重建。这项队列研究的目的是评估和比较两种先进的MRI弛豫测量技术的重测重复性：驱动平衡单脉冲T1和T2观测法（DESPOT），以及使用带有T1准备脉冲的交错式Look-Locker采集序列的三维定量法（3D-QALAS），用于健康志愿者队列中的T1和T2*映射。
10名健康志愿者在3.0特斯拉飞利浦Ingenia Elition扫描仪上接受各向同性分辨率为1.3毫米的脑部MRI检查，采集DESPOT和3D-QALAS数据（持续时间分别约为11.8分钟和5分钟，包括场图），在重新定位受试者的情况下进行重测。为了重建T1和T2*映射，我们对DESPOT使用了基于方程的算法，对3D-QALAS使用了基于字典的算法，该算法纳入了反转效率和B1场不均匀性。使用变异系数（CoV）、组内相关系数（ICC）和布兰德-奥特曼图评估该队列研究的重测重复性。
我们的结果表明，DESPOT和3D-QALAS技术在全脑T1和T2映射方面均表现出良好的重测重复性水平。在3D-QALAS中观察到T1的全脑体素间ICC更高（0.84±0.039），在DESPOT中观察到T2的全脑体素间ICC更高（0.897±0.029）。布兰德-奥特曼图显示，与DESPOT相比，3D-QALAS的T1估计偏差和变异性更小（平均值为-0.02秒，95%置信区间的上下限分别为-0.14秒和0.11秒）（DESPOT的平均值为-0.02秒，上下限分别为-0.31秒和0.27秒）。与DESPOT相比，3D-QALAS的T2变异性也更小（平均值为1.08毫秒，上下限为-1.88至4.04毫秒）（DESPOT的平均值为2.56毫秒，上下限为-17.29至22.41毫秒）。3D-QALAS的受试者内CoV范围从0.6%[脑脊液（CSF）中的T1]到5.8%[灰质（GM）中的T1]，而DESPOT的受试者内CoV范围从2.1%（CSF中的T2）到6.7%（GM中的T2*）。3D-QALAS的受试者间CoV范围从2.5%（GM中的T1）到12%（CSF中的T1），而DESPOT的受试者间CoV范围从3.7%[白质（WM）中的T2*]到9.3%（CSF中的T2*）。
总体而言，3D-QALAS在T1和T2*测量方面表现出比DESPOT更好的重复性，同时采集时间也更短。
