Department of Innovative Biomedical Visualization (iBMV), Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
Department of Radiology, Nagoya University, Nagoya, Aichi, Japan.
Magn Reson Med Sci. 2024 Jul 1;23(3):268-290. doi: 10.2463/mrms.rev.2023-0175. Epub 2024 Apr 2.
More than 5 years have passed since the Diffusion Tensor Image Analysis ALong the Perivascular Space (DTI-ALPS) method was proposed with the intention of evaluating the glymphatic system. This method is handy due to its noninvasiveness, provision of a simple index in a straightforward formula, and the possibility of retrospective analysis. Therefore, the ALPS method was adopted to evaluate the glymphatic system for many disorders in many studies. The purpose of this review is to look back and discuss the ALPS method at this moment.The ALPS-index was found to be an indicator of a number of conditions related to the glymphatic system. Thus, although this was expected in the original report, the results of the ALPS method are often interpreted as uniquely corresponding to the function of the glymphatic system. However, a number of subsequent studies have pointed out the problems on the data interpretation. As they rightly point out, a higher ALPS-index indicates predominant Brownian motion of water molecules in the radial direction at the lateral ventricular body level, no more and no less. Fortunately, the term "ALPS-index" has become common and is now known as a common term by many researchers. Therefore, the ALPS-index should simply be expressed as high or low, and whether it reflects a glymphatic system is better to be discussed carefully. In other words, when a decreased ALPS-index is observed, it should be expressed as "decreased ALPS-index" and not directly as "glymphatic dysfunction". Recently, various methods have been proposed to evaluate the glymphatic system. It has become clear that these methods also do not seem to reflect the entirety of the extremely complex glymphatic system. This means that it would be desirable to use various methods in combination to evaluate the glymphatic system in a comprehensive manner.
自提出弥散张量图像分析沿血管周围空间（DTI-ALPS）方法评估神经胶质淋巴系统以来，已经过去了 5 年多。该方法具有非侵入性、提供简单公式中的简单指标以及进行回顾性分析的可能性，因此，该 ALPS 方法已被许多研究用于评估多种疾病的神经胶质淋巴系统。本文旨在回顾和讨论目前的 ALPS 方法。ALPS 指数被发现是许多与神经胶质淋巴系统相关的疾病的指标。因此，尽管这在最初的报告中已经预期到，但 ALPS 方法的结果通常被解释为唯一对应于神经胶质淋巴系统的功能。然而，随后的许多研究指出了数据解释方面的问题。正如他们正确指出的那样，较高的 ALPS 指数表示侧脑室体水平水分子在径向方向上的布朗运动占主导地位，不多也不少。幸运的是，术语“ALPS 指数”已经变得很常见，现在许多研究人员都知道这是一个常用术语。因此，ALPS 指数应该简单地表示为高或低，并且是否反映神经胶质淋巴系统更好地进行仔细讨论。换句话说，当观察到较低的 ALPS 指数时，应该表示为“降低的 ALPS 指数”，而不是直接表示为“神经胶质淋巴功能障碍”。最近，已经提出了各种方法来评估神经胶质淋巴系统。很明显，这些方法似乎也不能反映极其复杂的神经胶质淋巴系统的全貌。这意味着，最好使用各种方法相结合，全面评估神经胶质淋巴系统。
