Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.
The Wilfred and Joyce Posluns Centre for Image Guided Innovation and Therapeutic Intervention, The Hospital for Sick Children, Toronto, ON, Canada.
Mol Imaging Biol. 2022 Oct;24(5):732-739. doi: 10.1007/s11307-022-01722-4. Epub 2022 Apr 29.
Magnetic resonance (MR) imaging detection of methemoglobin, a molecular marker of intraplaque hemorrhage (IPH), in atherosclerotic plaque is a promising method of assessing stroke risk. However, the multicenter imaging studies required to further validate this technique necessitate the development of IPH phantoms to standardize images acquired across different scanners. This study developed a set of phantoms that modeled methemoglobin-laden IPH for use in MR image standardization.
A time-stable material mimicking the MR properties of methemoglobin in IPH was created by doping agarose hydrogel with gadolinium and sodium alginate. This material was used to create a phantom that consisted of 9 cylindrical IPH sites (with sizes from 1 to 8 mm). Anatomical replicas of IPH-positive atherosclerosis were also created using 3D printed molds. These plaque replicas also modeled other common plaque components including a lipid core and atheroma cap. T1 mapping and a magnetization-prepared rapid acquisition gradient echo (MPRAGE) carotid imaging protocol were used to assess phantom realism and long-term stability.
Cylindrical phantom IPH sites possessed a T1 time of 335 ± 51 ms and exhibited little change in size or MPRAGE signal intensity over 31 days; the mean (SD) magnitude of changes in size and signal were 6.4 % (2.7 %) and 7.3 % (6.7 %), respectively. IPH sites incorporated into complex anatomical plaque phantoms exhibited contrast comparable to clinical images.
The cylindrical IPH phantom accurately modeled the short T1 time characteristic of methemoglobin-laden IPH, with the IPH sites exhibiting little variation in imaging properties over 31 days. Furthermore, MPRAGE images of the anatomical atherosclerosis replicas closely matched those of clinical plaques. In combination, these phantoms will allow for IPH imaging protocol standardization and thus facilitate future multicenter IPH imaging.
磁共振（MR）成像检测动脉粥样硬化斑块中的正铁血红蛋白（methemoglobin，一种斑块内出血（intraplaque hemorrhage，IPH）的分子标志物）是评估中风风险的一种很有前途的方法。然而，为了进一步验证该技术，需要进行多中心成像研究，这就需要开发 IPH 体模来标准化不同扫描仪采集的图像。本研究开发了一套模拟含正铁血红蛋白的 IPH 的体模，用于 MR 图像标准化。
通过向琼脂糖水凝胶中掺杂钆和海藻酸钠，制备了一种模拟 IPH 中正铁血红蛋白的 MR 特性的稳定材料。该材料用于创建一个由 9 个圆柱形 IPH 部位（大小从 1 到 8 毫米）组成的体模。还使用 3D 打印模具创建了 IPH 阳性动脉粥样硬化的解剖学复制品。这些斑块复制品还模拟了其他常见的斑块成分，包括脂质核心和动脉粥样硬化帽。使用 T1 映射和磁化准备快速获取梯度回波（magnetization-prepared rapid acquisition gradient echo，MPRAGE）颈动脉成像方案评估体模的现实性和长期稳定性。
圆柱形体模 IPH 部位的 T1 时间为 335 ± 51 ms，在 31 天内其大小或 MPRAGE 信号强度几乎没有变化；大小和信号强度的平均（标准差）变化幅度分别为 6.4%（2.7%）和 7.3%（6.7%）。包含在复杂解剖斑块体模中的 IPH 部位表现出与临床图像相当的对比。
圆柱形 IPH 体模准确地模拟了富含正铁血红蛋白的 IPH 的短 T1 时间特征，在 31 天内，IPH 部位的成像特性几乎没有变化。此外，解剖动脉粥样硬化复制品的 MPRAGE 图像与临床斑块的图像非常匹配。综上所述，这些体模将允许 IPH 成像方案标准化，从而促进未来的多中心 IPH 成像。
