Faculty of Medicine and Health Sciences, McGill University, 845 Sherbrooke St W, Montreal, Quebec H3A 0G4, Canada; McGill University Health Centre, 1001 Decarie Blvd., Montreal, Quebec H4A 3J1, Canada.
McGill University Health Centre, 1001 Decarie Blvd., Montreal, Quebec H4A 3J1, Canada.
J Cardiovasc Magn Reson. 2024 Summer;26(1):100004. doi: 10.1016/j.jocmr.2023.100004. Epub 2024 Jan 9.
Cardiovascular Magnetic Resonance (CMR) native T1 and T2 mapping serve as robust, contrast-agent-free diagnostic tools, but hardware- and software-specific sources of variability limit the generalizability of data across CMR platforms, consequently limiting the interpretability of patient-specific parametric data. Z-scores are used to describe the relationship of observed values to the mean results as obtained in a sufficiently large normal sample. They have been successfully used to describe the severity of quantifiable abnormalities in medicine, specifically in children and adolescents. The objective of this study was to observe whether z-scores can improve the comparability of T1 and T2 mapping values across CMR scanners, field strengths, and sequences from different vendors in the same participant rather than different participants (as seen in previous studies).
Fifty-one healthy volunteers (26 men/25 women, mean age = 43 ± 13.51) underwent three CMR exams on three different scanners, using a Modified Look-Locker Inversion Recovery (MOLLI) 5-(3)- 3 sequence to quantify myocardial T1. For T2 mapping, a True Fast Imaging with steady-state free precession (TRUFI) sequence was used on a 3 T Skyra™ (Siemens), and a T2 Fast Spin Echo (FSE) sequence was used on 1.5 T Artist™ (GE) and 3.0 T Premier™ (GE) scanners. The averages of basal and mid-ventricular short axis slices were used to derive means and standard deviations of global mapping values. We used intra-class comparisons (ICC), repeated measures ANOVA, and paired Student's t-tests for statistical analyses.
There was a significant improvement in intra-subject comparability of T1 (ICC of 0.11 (95% CI= -0.018, -0.332) vs 0.78 (95% CI= 0.650, 0.866)) and T2 (ICC of 0.35 (95% CI= -0.053, 0.652) vs 0.83 (95% CI= 0.726, 0.898)) when using z-scores across all three scanners. While the absolute global T1 and T2 values showed a statistically significant difference between scanners (p < 0.001), no such differences were identified using z-scores (T1: p = 0.771; T2: p = 0.985). Furthermore, when images were not corrected for motion, T1 z-scores showed significant inter-scanner variability (p < 0.001), resolved by motion correction.
Employing z-scores for reporting myocardial T1 and T2 removes the variation of quantitative mapping results across different MRI systems and field strengths, improving the clinical utility of myocardial tissue characterization in patients with suspected myocardial disease.
心血管磁共振（CMR）的 native T1 和 T2 映射可作为强大的、无对比剂的诊断工具，但硬件和软件的特定来源的变异性限制了数据在 CMR 平台之间的通用性，从而限制了特定于患者的参数数据的可解释性。Z 分数用于描述观察值与在足够大的正常样本中获得的平均值之间的关系。它们已成功用于描述医学中可量化异常的严重程度，特别是在儿童和青少年中。本研究的目的是观察 Z 分数是否可以提高同一参与者而非不同参与者（如先前研究所示）之间 CMR 扫描仪、场强和来自不同供应商的序列的 T1 和 T2 映射值的可比性。
51 名健康志愿者（26 名男性/25 名女性，平均年龄=43±13.51 岁）在三台不同的扫描仪上进行了三次 CMR 检查，使用改良 Look-Locker 反转恢复（MOLLI）5-（3）-3 序列来定量心肌 T1。对于 T2 映射，使用 True Fast Imaging with steady-state free precession（TRUFI）序列在 3.0T Skyra（Siemens）上进行，使用 T2 快速自旋回波（FSE）序列在 1.5T Artist（GE）和 3.0T Premier（GE）扫描仪上进行。基底和中间心室短轴切片的平均值用于得出全局映射值的平均值和标准差。我们使用组内比较（ICC）、重复测量方差分析和配对学生 t 检验进行统计分析。
在使用 Z 分数时，T1（ICC 为 0.11（95%CI=-0.018，-0.332）与 0.78（95%CI=0.650，0.866））和 T2（ICC 为 0.35（95%CI=-0.053，0.652）与 0.83（95%CI=0.726，0.898））的个体内可比性有显著提高。尽管绝对全局 T1 和 T2 值在扫描仪之间存在统计学显著差异（p<0.001），但使用 Z 分数时则没有差异（T1：p=0.771；T2：p=0.985）。此外，当不对图像进行运动校正时，T1 Z 分数显示出扫描仪之间存在显著的变异性（p<0.001），通过运动校正解决了这种变异性。
在报告心肌 T1 和 T2 时使用 Z 分数可消除不同 MRI 系统和场强之间定量映射结果的变化，提高疑似心肌疾病患者心肌组织特征的临床实用性。
