Lyu Haiying, He Naying, Wu Bo, Trujillo Paula, Yan Fuhua, Lu Yong, Mark Haacke E
Department of Radiology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, No.197 Ruijin Er Road, Shanghai 200025, China.
Zhuyan Limited, Shanghai, China.
Neuroimage. 2025 Sep;318:121372. doi: 10.1016/j.neuroimage.2025.121372. Epub 2025 Jul 15.
The locus coeruleus (LC) is a key noradrenergic nucleus of the brain. Its dysfunction is implicated in neurodegenerative diseases like Alzheimer's disease and Parkinson's disease, as well as in psychiatric disorders. However, imaging the LC with sufficient contrast-to-noise ratio (CNR) is challenging due to its small size and deep location in the brainstem. This study optimizes a 3D gradient echo (GRE) sequence with magnetization transfer contrast (MTC) to enable rapid, high-resolution LC imaging in under five minutes.
A high-resolution 3D-GRE-MTC sequence was optimized on a 3T scanner in 11 healthy volunteers (6 young and 5 older adults). Tissue properties were measured using in vivo MRI data, and simulations were performed to identify the optimal flip angle. LC visualization was evaluated by two independent raters using relative contrast ratio (rCR) and CNR. The diameter and the length of the LC were also evaluated. Each volunteer underwent MRI sessions over three days to assess test-retest reliability. The intra-class correlation coefficient (ICC) for inter-rater reliability and the mean ± standard deviation of LC rCR across sessions for test-retest reproducibility were calculated.
A total of 98 scans were collected. The optimized protocol achieved 0.67 × 0.73 × 2 mm³ resolution with an 18° flip angle, 6.18 ms first echo, 52 ms repetition time, flow compensation, arterial suppression, and strict head immobilization. The LC exhibited a CNR of 8.27 ± 1.03, and rCR of 16.70% ± 1.77% (left) and 13.97% ± 2.19% (right), with good inter-rater reliability (ICC = 88.51%). Contrast stability between scans had a variability of 4%-11%. The bilateral LC was visible across 3-6 slices (6-12 mm). Using the full width at quarter maximum measure, the LC diameter was 1.94 ± 0.40 mm for the left side and 1.67 ± 0.34 mm for the right side.
The optimized protocol enabled reliable, high-resolution LC imaging in under five minutes, providing a valuable tool for clinical and research applications.
蓝斑（LC）是大脑中一个关键的去甲肾上腺素能核团。其功能障碍与阿尔茨海默病和帕金森病等神经退行性疾病以及精神疾病有关。然而，由于蓝斑体积小且位于脑干深处，以足够的对比度噪声比（CNR）对其进行成像具有挑战性。本研究优化了一种具有磁化传递对比（MTC）的三维梯度回波（GRE）序列，以实现五分钟内快速、高分辨率的蓝斑成像。
在11名健康志愿者（6名年轻人和5名老年人）中，在3T扫描仪上对高分辨率三维GRE-MTC序列进行了优化。使用体内MRI数据测量组织特性，并进行模拟以确定最佳翻转角。由两名独立评估者使用相对对比度比（rCR）和CNR评估蓝斑的可视化情况。还评估了蓝斑的直径和长度。每位志愿者在三天内接受MRI检查，以评估重测信度。计算评估者间信度的组内相关系数（ICC）以及各次检查间蓝斑rCR的均值±标准差，以评估重测重复性。
共收集了98次扫描数据。优化后的方案在翻转角为18°、首次回波时间为6.18 ms、重复时间为52 ms、采用流动补偿、动脉抑制和严格头部固定的条件下，实现了0.67×0.73×2 mm³的分辨率。蓝斑的CNR为8.27±1.03，rCR左侧为16.70%±1.77%，右侧为13.97%±2.19%，评估者间信度良好（ICC = 88.51%）。各次扫描间的对比度稳定性变化为4%-11%。双侧蓝斑在3-6个层面（6-12 mm）可见。使用半高宽测量方法，左侧蓝斑直径为1.94±0.40 mm，右侧为1.67±0.34 mm。
优化后的方案能够在五分钟内实现可靠的高分辨率蓝斑成像，为临床和研究应用提供了一个有价值的工具。
