Monitoring blood-brain barrier (BBB) opening is of great interest in terms of brain drug delivery in the treatment of brain lymphoma and maybe in the future in other diseases like dementia. A method involving BBB disruption (BBBD) by mannitol infusion has been developed in University of Portland, USA, and then exploited in Oulu University Hospital in treatment of primary CSN lymphoma. Proper opening of the BBB is crucial for the treatment, yet there are no methods available for its real-time clinical monitoring. Recently, we presented a combined method using direct-current electroencephalography (DC-EEG) and near-infrared spectroscopy (NIRS) for monitoring BBBD in human. Carotid artery mannitol infusion generated a strongly lateralized DC-EEG response and in NIRS a prolonged increase in the oxy/deoxyhemoglobin ratio.
This study explores further BBBD, by focusing on monitoring its cardiovascular effects, when measured in human and mouse. For this, we used photoplethysmography (PPG) and opto-electro-mechanical sensors to gather the signals in human and mouse. Mannitol infusion in human causes strong fluctuations in blood pressure, heart rate and PPG signals, and here we discuss how the acquired signals in mouse model compares to human data.
In addition, we present our scale-free monitoring concept that enables monitoring physiological signals similarly when performing experiments in mouse and human neuroimaging setups. By combining microscopic and macroscopic imaging in mouse setup enables us to study correlations between mechanistic cellular data and clinical functional data. Further, this allows us to validate and optimize macroscopic sensing and imaging techniques aimed to be used in human imaging.
The lymph system is responsible for cleaning the tissues of metabolic waste products, soluble proteins and other harmful fluids etc. Lymph flow in the body is driven by body movements and muscle contractions. Moreover, it is indirectly dependent on the cardiovascular system, where the heart beat and blood pressure maintain force of pressure in lymphatic channels. Over the last few years, studies revealed that the brain contains the so-called glymphatic system, which is the counterpart of the systemic lymphatic system in the brain. Similarly, the flow in the glymphatic system is assumed to be mostly driven by physiological pulsations such as cardiovascular pulses. Thus, continuous measurement of blood pressure and heart function simultaneously with functional brain imaging is of great interest, particularly in studies of the glymphatic system.
We present our MRI compatible optics based sensing system for continuous blood pressure measurement and show our current results on the effects of blood pressure variations on cerebral brain dynamics, with a focus on the glymphatic system. Blood pressure was measured simultaneously with near-infrared spectroscopy (NIRS) combined with an ultrafast functional brain imaging (fMRI) sequence magnetic resonance encephalography (MREG, 3D brain 10 Hz sampling rate).
In brain studies, the function of the cerebrospinal fluid (CSF) awakes growing interest, particularly related to studies of the glymphatic system in the brain, which is connected with the complex system of lymphatic vessels responsible for cleaning the tissues. The CSF is a clear, colourless liquid including water (H2O) approximately with a concentration of 99 %. In addition, it contains electrolytes, amino acids, glucose, and other small molecules found in plasma. The CSF acts as a cushion behind the skull, providing basic mechanical as well as immunological protection to the brain. Disturbances of the CSF circulation have been linked to several brain related medical disorders, such as dementia.
Our goal is to develop an in vivo method for the non-invasive measurement of cerebral blood flow and CSF circulation by exploiting optical and capacitive sensing techniques simultaneously. We introduce a prototype of a wearable probe that is aimed to be used for long-term brain monitoring purposes, especially focusing on studies of the glymphatic system. In this method, changes in cerebral blood flow, particularly oxy- and deoxyhaemoglobin, are measured simultaneously and analysed with the response gathered by the capacitive sensor in order to distinct the dynamics of the CSF circulation behind the skull. Presented prototype probe is tested by measuring liquid flows inside phantoms mimicking the CSF circulation.
It is very common for noise to have an influence on analog circuits. In order to preserve the quality of measurements taken by specific sensors and any noise dependent amplifiers which are correlated to them, all of these devices must be powered by low-noise power supplies. Therefore a necessity exists to develop new ultra-low noise power supplies which can cooperate with specified amplifiers and preamplifiers. Many well-known power supplies are particularly expensive and yet still have their disadvantages. This paper proposes a simple and inexpensive solution, which fulfills a specific criteria and can be treated as a base for improvement.