Urs Raksha, Potter Elizabeth, Barker Warren, Appel Jason, Loewenstein David A, Zhao Weizhao, Duara Ranjan
Department of Biomedical Engineering, University of Miami, Coral Gables, FL, USA.
J Comput Assist Tomogr. 2009 Jan-Feb;33(1):73-8. doi: 10.1097/RCT.0b013e31816373d8.
Subjects with mild cognitive impairment (MCI) and mild Alzheimer disease (AD) can be distinguished from elderly subjects with no cognitive impairment (NCI) by the degree of atrophy in the entorhinal cortex (ERC) and the hippocampus (HPC), quantified by volumetric magnetic resonance image (MRI) studies. Because volumetric MRI requires rigorous standards for image acquisition and analysis and is not suitable for routine clinical use, we have used calibrated visual rating to measure atrophy in the ERC, HPC, and perirhinal cortex (PRC) and evaluated its utility in the diagnosis of very early AD.
Thus far, visual rating methods, which have been found to be reliable and sensitive only for measurement of atrophy of the HPC or for the entire medial temporal region, have been found to be relatively insensitive for discriminating mild AD from elderly NCI subjects. We have developed a computer-based visual rating system (VRS) using reference images for calibration of atrophy ratings in several discrete brain regions, including the ERC, HPC, and PRC. The VRS reference images facilitate training of raters and promote standardization of all atrophy ratings. Interrater and intrarater reliability measurements were assessed; subsequently, the ability of VRS to discriminate the diagnoses among 73 elderly subjects was studied (NCI = 27, MCI = 23, and AD = 23).
Kappa values for interrater reliability of the ERC, HPC, and PRC were between 0.75 and 0.94, and for intrarater reliability, they were between 0.84 and 0.93, indicating that VRS enables highly reliable ratings to be obtained. Atrophy ratings in the ERC, HPC, and PRC distinguished AD from NCI subjects but did not distinguish AD from MCI subjects who tended to have intermediate levels of atrophy. Right and left ERC ratings and the right HPC rating distinguished MCI from NCI subjects.
The visual rating system is the first semiquantitative method that enables reliable measurements of ERC atrophy, and ERC measurement was found to be the best discriminator between MCI and NCI subjects. Visual rating system is a user-friendly tool that can allow a radiologist or a clinician to use structural MRI scans to be used as a biomarker in the diagnosis of prodromal AD.
轻度认知障碍（MCI）和轻度阿尔茨海默病（AD）患者可通过内嗅皮质（ERC）和海马体（HPC）的萎缩程度与无认知障碍（NCI）的老年人相区分，这种萎缩程度可通过容积磁共振成像（MRI）研究进行量化。由于容积MRI对图像采集和分析需要严格标准，且不适用于常规临床应用，我们采用校准视觉评分法来测量ERC、HPC和嗅周皮质（PRC）的萎缩情况，并评估其在极早期AD诊断中的效用。
迄今为止，视觉评分方法仅在测量HPC萎缩或整个内侧颞叶区域萎缩时被发现可靠且敏感，而在区分轻度AD与老年NCI受试者时相对不敏感。我们开发了一种基于计算机的视觉评分系统（VRS），使用参考图像对包括ERC、HPC和PRC在内的多个离散脑区的萎缩评分进行校准。VRS参考图像便于评估者培训，并促进所有萎缩评分的标准化。评估了评估者间和评估者内的可靠性测量；随后，研究了VRS在73名老年受试者（NCI = 27，MCI = 23，AD = 23）中区分诊断的能力。
ERC、HPC和PRC的评估者间可靠性的Kappa值在0.75至0.94之间，评估者内可靠性的Kappa值在0.84至0.93之间，表明VRS能够获得高度可靠的评分。ERC、HPC和PRC的萎缩评分可区分AD与NCI受试者，但无法区分AD与往往具有中等萎缩水平的MCI受试者。右侧和左侧ERC评分以及右侧HPC评分可区分MCI与NCI受试者。
视觉评分系统是第一种能够可靠测量ERC萎缩的半定量方法，并且发现ERC测量是区分MCI和NCI受试者的最佳指标。视觉评分系统是一种用户友好的工具，可使放射科医生或临床医生利用结构MRI扫描作为前驱AD诊断中的生物标志物。
