Nogueira Ricardo C, Beishon Lucy C, Castro Pedro, Claassen Jurgen A H R, Minhas Jatinder S
Neurology Department, Hospital das Clinicas, School of Medicine, University of São Paulo, São Paulo, Brazil.
Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
Cerebrovasc Dis. 2025 Aug 1:1-9. doi: 10.1159/000547676.
Transcranial Doppler (TCD) and transcranial color-coded duplex sonography (TCCS) have been referred to as the "brain stethoscope" as they provide real-time monitoring of both hemodynamic parameters and the structural image of the vessel and neighboring tissues. Its use has made important contributions to the field, with the ability to monitor important variables such as cerebral blood velocity to study cerebrovascular function. Although the use of B-mode with color-coded imaging allows identification of the vessel of interest in a more user-friendly approach compared to non-imaging TCD, TCD has unique functions that are complementary to TCCS studies. The aim of this review was to introduce these unique functions of TCD and discuss scenarios where the use of TCD would be justified without the combined use of TCCS.
Due to its portability and noninvasive nature, TCD is a reliable option for monitoring cerebrovascular conditions; with the ability to perform long periods of monitoring via a dedicated head frame or band. This provides an opportunity to monitor cerebrovascular function which could be named TCD functional monitoring (TCD fm). Importantly, TCD can be used to evaluate the main mechanisms involved in cerebral blood flow regulation such as cerebral autoregulation (CA) and neurovascular coupling (NVC). CA refers to the ability of the brain to maintain CBF despite changes in systemic arterial blood pressure. NVC evaluates the CBF response to local cerebral metabolism and neural activation. Both mechanisms are important in physiological and pathological conditions. Understanding and monitoring cerebrovascular regulation could develop new insights to design personalized treatments which may lead to better prognosis and outcome for patients. Moreover, TCD fm may be implemented for microembolism detection during long periods of recording, enhancing the ability to detect embolic activity. All these unique applications of TCD strengthen the importance of the method. Furthermore, several functions of TCCS could be accomplished using TCD, which is less expensive when compared to modern TCCS devices, and therefore is a reasonable option for low-income countries.
TCD has utilities that are not covered by TCCS and considering the economic impact of broadening its use in specific areas, such as those with resource limitations, it is a reasonable option for the standard method for evaluation of cerebrovascular function. Further research is needed to combine these two modalities to provide a solution to the current limitations of using TCD and TCCS in isolation.
经颅多普勒（TCD）和经颅彩色编码双功能超声（TCCS）被称为“脑听诊器”，因为它们能够实时监测血流动力学参数以及血管和邻近组织的结构图像。其应用为该领域做出了重要贡献，具备监测诸如脑血流速度等重要变量以研究脑血管功能的能力。尽管与非成像TCD相比，使用带有彩色编码成像的B模式能够以更用户友好的方式识别感兴趣的血管，但TCD具有一些独特功能，可补充TCCS研究。本综述的目的是介绍TCD的这些独特功能，并讨论在不联合使用TCCS的情况下使用TCD合理的场景。
由于其便携性和非侵入性，TCD是监测脑血管状况的可靠选择；能够通过专用头架或头带进行长时间监测。这为监测脑血管功能提供了机会，可称之为TCD功能监测（TCD fm）。重要的是，TCD可用于评估参与脑血流调节的主要机制，如脑自动调节（CA）和神经血管耦合（NVC）。CA是指大脑在体循环动脉血压变化时维持脑血流量的能力。NVC评估脑血流对局部脑代谢和神经激活的反应。这两种机制在生理和病理状况下都很重要。理解和监测脑血管调节可为设计个性化治疗提供新的见解，这可能为患者带来更好的预后和结局。此外，TCD fm可在长时间记录过程中用于微栓子检测，增强检测栓子活动的能力。TCD的所有这些独特应用都强化了该方法的重要性。此外，TCCS的一些功能可以用TCD来实现，与现代TCCS设备相比，TCD成本更低，因此对于低收入国家来说是一个合理的选择。
TCD具有TCCS未涵盖的实用功能，考虑到在特定领域（如资源有限的地区）扩大其使用的经济影响，它是评估脑血管功能标准方法的合理选择。需要进一步研究将这两种模式结合起来，以解决目前单独使用TCD和TCCS的局限性。
