Chronic active lesions (CAL) are an important manifestation of chronic inflammation in multiple sclerosis (MS) and have implications for non-relapsing biological progression. In recent years, the discovery of innovative magnetic resonance imaging (MRI) and PET derived biomarkers has made it possible to detect CAL, and to some extent quantify them, in the brain of persons with MS, in vivo. Paramagnetic rim lesions on susceptibility-sensitive MRI sequences, MRI-defined slowly expanding lesions on T1-weighted (T1-w) and T2-w scans, and 18-kDa translocator protein-positive lesions on PET are promising candidate biomarkers of CAL. While partially overlapping, these biomarkers do not have equivalent sensitivity and specificity to histopathological CAL. Standardization in the use of available imaging measures for CAL identification, quantification, and monitoring is lacking. To fast-forward clinical translation of CAL, the North American Imaging in Multiple Sclerosis Cooperative developed a Consensus Statement, which provides guidance for the radiological definition and measurement of CAL. The proposed manuscript presents this Consensus Statement, summarizes the multistep process leading to it, and identifies the remaining major gaps in knowledge.

中文翻译：

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多发性硬化症慢性活动性病变的成像：共识声明

慢性活动性病变（CAL）是多发性硬化症（MS）慢性炎症的重要表现，对非复发性生物进展具有影响。近年来，创新型磁共振成像 (MRI) 和 PET 衍生生物标志物的发现使得在多发性硬化症患者的体内检测 CAL 并在一定程度上对其进行量化成为可能。磁敏感敏感 MRI 序列上的顺磁性边缘病变、T1 加权 (T1-w) 和 T2-w 扫描上 MRI 定义的缓慢扩张病变以及 PET 上的 18-kDa 易位蛋白阳性病变是 CAL 有希望的候选生物标志物。虽然部分重叠，但这些生物标志物对组织病理学 CAL 不具有同等的敏感性和特异性。用于 CAL 识别、量化和监测的可用成像测量的使用缺乏标准化。为了快速推进 CAL 的临床转化，北美多发性硬化症影像合作组织制定了一份共识声明，为 CAL 的放射学定义和测量提供了指导。拟议的手稿提出了这份共识声明，总结了导致该声明的多步骤过程，并确定了知识中剩余的主要差距。