A noninvasive, continuous brain monitoring method: rheoencephalography (REG)

Abstract

This paper deals with the sustainability under anoxic conditions of human beings, both when healthy, and diseased. As our attention is focused these days on the environment, sustainability, and green energy, a similar effort is being made in neuromonitoring to switch from invasive to noninvasive monitoring methods. Keys to these changes are computerization and shrinking size of electronic hardware. Computerization is going on in all areas of biomedical engineering, both in research and in clinical fields of medicine. In neurology, brain imaging is the most characteristic change in recent decades. These modalities of imaging (MRI, CT, PET scan, etc.) are predominantly utilized for localizing brain pathology. Brain imaging offers great spatial resolution, but poor time resolution. Therefore, for continuous monitoring, neurocritical care departments require an additional tool with good time resolution. There are invasive and noninvasive neuromonitoring methods. The standard method to monitor intracranial pressure (ICP) is an invasive method. Computerization allows for calculating the cerebral blood flow autoregulation (CBF AR) index (pressure reactivity index - PRx) from ICP and systemic arterial pressure (SAP) in real time, continuously, but invasively. The new development, discussed in this paper, is to calculate this index noninvasively by using rheoencephalography (REG), called REGx. We present the road to this invention and summarize multifold REG related results, such as using REG for primary stroke prevention screening, comparison incidence of arteriosclerotic risk factors, various studies by using CBF manipulations, and correlations with other neuromonitoring methods, and validation with in vitro and in vivo methods. REG by using different algorithms allow for real time calculation of autoregulated blood flow. This paper presents results of validation of CBF algorithms as an effective, noninvasive method. The author’s intent is to supply sufficient physiological background information. This review covers the author’s research efforts over several decades; it pertains multiple studies and has an updated addition to human sustainability by considering that Covid-19 is increasing stroke and cardiovascular disease (CVD) morbidity and mortality.

Characteristics of Rheoencephalography and some associated factors on menopausal women

“…Because of the small sample size, the difference between groups with and without central obesity may be difficult to discern. The mean thickness of the common carotid intimamedia layer in MetS patients was found to have no correlation with BMI but a positive correlation with waist circumference and the waist-hip ratio (WHR) [12]. This finding is like ours.…”

“…REG can detect cerebrovascular atherosclerosis at a more presymptomatic stage than Doppler ultrasound [4], [10]. This is also a non-invasive technique, which is easy to perform and can be used for continuous measurement in the diagnosis of cerebral atherosclerosis [11][12]. Although REG has less clinical value in the diagnosis of cerebrovascular disease, it may provide information on changes in cerebral circulation which occurs with aging or diffuse cerebrovascular disease [13].…”

Automatic calculation for pulse wave morphology change: a rheoencephalographic study

“…Details of the REG pulse wave in uencing factors can be found here [28]. Several REG correlation/validation studies are summarized here [29,30].…”

Review of wearable technologies and machine learning methodologies for systematic detection of mild traumatic brain injuries

“…Rheoencephalography provides measurement of head bioimpedance and hence evaluation of CBF. Moreover, it is possible by modifying parameters of impedance measurement to determine CBF velocity, CBF/CSF ratio, and other indices [122][123][124] (here CSF stands for cerebrospinal fluid).…”