Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT, USA.
Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT, USA.
Magn Reson Imaging. 2023 Nov;103:1-7. doi: 10.1016/j.mri.2023.06.018. Epub 2023 Jun 29.
Alternative contrast agents for MRI are needed for individuals who may respond adversely to gadolinium, and need an intravascular agent for specific indications. One potential contrast agent is intracellular methemoglobin, a paramagnetic molecule that is normally present in small amounts in red blood cells. An animal model was used to determine whether methemoglobin modulation with intravenous sodium nitrite transiently changes the T1 relaxation of blood.
Four adult New Zealand white rabbits were treated with 30 mg intravenous sodium nitrite. 3D TOF and 3D MPRAGE images were acquired before (baseline) and after methemoglobin modulation. T1 of blood was measured with 2D ss EPl acquisitions with inversion recovery preparation performed at two-minute intervals up to 30 min. T1 maps were calculated by fitting the signal recovery curve within major blood vessels.
Baseline T1 was 1758 ± 53 ms in carotid arteries and 1716 ± 41 ms in jugular veins. Sodium nitrite significantly changed intravascular T1 relaxation. The mean minimum value of T1 was 1126 ± 28 ms in carotid arteries 8 to 10 min after the injection of sodium nitrite. The mean minimum value of T1 was 1171 ± 52 ms in jugular veins 10 to 14 min after the injection of sodium nitrite. Arterial and venous T1 recovered to baseline after a period of 30 min.
Methemoglobin modulation produces intravascular contrast on T1-weighted MRI in vivo. Additional studies are needed to safely optimize methemoglobin modulation and sequence parameters for maximal tissue contrast.
对于可能对钆类药物产生不良反应的患者，以及有特定适应证需要血管内造影剂的患者，需要寻找替代磁共振成像（MRI）的造影剂。一种潜在的造影剂是细胞内高铁血红蛋白，这是一种顺磁性分子，正常情况下在红细胞中含量很少。本动物模型旨在确定静脉内亚硝酸钠是否可以通过调节高铁血红蛋白，使血液的 T1 弛豫时间短暂改变。
4 只成年新西兰白兔接受 30mg 静脉内亚硝酸钠治疗。在高铁血红蛋白调节前后（基线），使用 3D TOF 和 3D MPRAGE 序列进行图像采集。采用 2D ss EPI 序列，使用反转恢复准备，在 2 分钟的间隔内进行两次测量，每次测量 30 分钟，以获得 T1 值。通过拟合主要血管内的信号恢复曲线，计算 T1 图。
颈动脉的基线 T1 值为 1758±53ms，颈静脉为 1716±41ms。亚硝酸钠显著改变了血管内 T1 弛豫。颈动脉在注射亚硝酸钠 8 至 10 分钟后 T1 的最小值为 1126±28ms，颈静脉在注射亚硝酸钠 10 至 14 分钟后 T1 的最小值为 1171±52ms。动脉和静脉 T1 在 30 分钟后恢复到基线。
高铁血红蛋白调节可在体内 T1 加权 MRI 上产生血管内对比。需要进一步研究以安全优化高铁血红蛋白调节和序列参数，以获得最大的组织对比。
