Andikoetxea Begoña Garate, Martín-Bastida Antonio, Vidorreta Marta, Rodríguez-Oroz María Cruz, Soustelle Lucas, Troalen Thomas, Fernández-Seara Maria A
Department of Neurology, Clínica Universidad de Navarra, Pamplona, Spain.
Universidad de Deusto, Bilbao, Spain.
NMR Biomed. 2025 Sep;38(9):e70123. doi: 10.1002/nbm.70123.
Neuromelanin (NM) magnetic resonance imaging has been used to evaluate the loss of melanized neurons in the substantia nigra, the main characteristic of Parkinson disease, typically by measuring the contrast ratio (CR) between the NM-rich areas and the cerebral peduncles in the midbrain. Neuromelanin contrast can be generated by employing a 3D gradient-echo (GRE) sequence with magnetization transfer (MT). In this work, we first evaluated the effect of the MT pulse frequency on the CR and contrast-to-noise ratio (CNR), analyzing a large frequency range from 500 to 100K Hz. Secondly, the impact of the 3D GRE sequence flip angle (FA) was evaluated using angles from 5° to 40°. Additionally, images were acquired both with and without MT for each FA, providing an opportunity to examine the effect of MT on tissue proton density, T1, and T2* values. Results showed that the highest CR and CNR were obtained for the lower MT frequencies (500-2000 Hz) and lower FAs (5°-10°). The lower FAs improved the visualization of the neuromelanin-rich area in the substantia nigra and facilitated delineating its volume. In addition, this work showed that the MT pulse decreased the T1 and PD of the tissue. Furthermore, simulations supported the obtained in vivo results.
神经黑色素（NM）磁共振成像已被用于评估黑质中黑色素化神经元的损失，这是帕金森病的主要特征，通常通过测量富含NM的区域与中脑大脑脚之间的对比度（CR）来实现。可以通过采用具有磁化传递（MT）的3D梯度回波（GRE）序列来生成神经黑色素对比度。在这项工作中，我们首先评估了MT脉冲频率对CR和对比度噪声比（CNR）的影响，分析了从500到100K Hz的大频率范围。其次，使用5°至40°的角度评估了3D GRE序列翻转角（FA）的影响。此外，针对每个FA，在有和没有MT的情况下都采集了图像，从而有机会研究MT对组织质子密度、T1和T2*值的影响。结果表明，在较低的MT频率（500 - 2000Hz）和较低的FA（5° - 10°）下可获得最高的CR和CNR。较低的FA改善了黑质中富含神经黑色素区域的可视化，并有助于勾勒其体积。此外，这项工作表明MT脉冲降低了组织的T1和质子密度（PD）。此外，模拟结果支持了所获得的体内实验结果。
