Department of Radiology, Juntendo University Hospital, Tokyo, Japan.
Department of Radiology, Juntendo University Hospital, Tokyo, Japan.
Magn Reson Imaging. 2021 May;78:90-97. doi: 10.1016/j.mri.2021.01.001. Epub 2021 Jan 11.
Recently, three-dimensional (3D) quantitative synthetic magnetic resonance imaging (MRI), which quantifies tissue properties and creates multiple contrast-weighted images, has been enabled by 3D-quantification using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (3D-QALAS). However, the relatively long scan time has hindered its introduction into clinical practice. A hybrid of compressed sensing and parallel imaging (Compressed sensing-sensitivity encoding: CS-SENSE) can accelerate 3D-QALAS; however, whether CS-SENSE affects the quantitative values acquired by 3D-QALAS remains unexplored. Therefore, this study aimed to examine the effects of reduction factors of CS-SENSE (R) on the quantitative values derived from 3D-QALAS, by assessing the signal-to-noise ratio (SNR) of the quantitative maps, as well as accuracy (linearity and bias) and repeatability of measured quantitative values.
In this study, the ISMRM/NIST standardized phantom was scanned on a 1.5-T MRI scanner with 3D-QALAS using R in the range between 1 and 3, with intervals of 0.2, and between 3 and 10 with intervals of 0.5. The T1, T2, and proton density (PD) values were calculated from the imaging data. For each quantitative value, the SNR, the coefficient of determination (R) of a linear regression model, the error rate, and the within-subject coefficient of variation (wCV) were calculated for each R and compared.
Within the clinically-relevant dynamic range of the brain of T1 and T2 (T1: 200-1400 ms; T2; 50-400 ms) and PD value of 15-100% calculated from 3D-QALAS, the effects of R on quantitative values was small between 1 and 2.8, with SNR ≧ 10, R ≧ 0.9, error rate ≦ 10%, and wCV ≦ 10%, except for T2 values of 186.1 and 258.4 ms.
CS-SENSE enabled the reduction of the scan time of 3D-QALAS by 63.5% (R = 2.8) while maintaining the SNR of quantitative maps and accuracy and repeatability of the quantitative values.
最近，通过使用带有 T2 准备脉冲的交错 Look-Locker 采集序列（3D-QALAS）进行 3D 定量，实现了三维（3D）定量磁共振成像（MRI），该方法可以定量组织特性并创建多个对比加权图像。然而，较长的扫描时间阻碍了其在临床实践中的应用。压缩感知和并行成像的混合（压缩感知灵敏度编码：CS-SENSE）可以加速 3D-QALAS；然而，CS-SENSE 是否会影响 3D-QALAS 获得的定量值尚不清楚。因此，本研究旨在通过评估定量图的信噪比（SNR）以及测量的定量值的准确性（线性和偏差）和重复性，来研究 CS-SENSE 的降采因子（R）对 3D-QALAS 衍生的定量值的影响。
在这项研究中，在 1.5T MRI 扫描仪上使用 R 在 1 到 3 之间的范围内对 ISMRM/NIST 标准化体模进行 3D-QALAS 扫描，步长为 0.2，在 3 到 10 之间的范围内以 0.5 的间隔进行扫描。从成像数据中计算 T1、T2 和质子密度（PD）值。对于每个定量值，计算每个 R 的 SNR、线性回归模型的决定系数（R）、误差率和个体内变异系数（wCV），并进行比较。
在所研究的大脑的 T1 和 T2 的临床相关动态范围内（T1：200-1400 ms；T2：50-400 ms）和从 3D-QALAS 计算出的 PD 值 15-100%，R 在 1 到 2.8 之间时，定量值的 R 影响很小，SNR≧10，R≧0.9，误差率≦10%，wCV≦10%，除了 T2 值为 186.1 和 258.4 ms。
CS-SENSE 使 3D-QALAS 的扫描时间减少了 63.5%（R=2.8），同时保持了定量图的 SNR 和定量值的准确性和重复性。
