Blood and cerebrospinal fluid flow oscillations measured with real-time phase-contrast MRI: breathing mode matters

Abstract

Background Cervical blood and cerebrospinal fluid (CSF) flow rates can be quantified with Phase-contrast (PC) MRI, which is routinely used for clinical studies. Previous MRI studies showed that venous and CSF flow alterations are linked to various pathological conditions. Since it is well known that, besides the heart beating, the thoracic pump influences the blood and CSF dynamics, we studied the effect of different respiration modes on blood and CSF flow rates using a real-time (RT)-PC prototype. Methods Thirty healthy volunteers were examined with a 3 T scanner. A RT-PC sequence was acquired at the first cervical level to quantify the flow rates of internal carotid arteries, internal jugular veins (IJVs) and CSF. Each RT-PC acquisition was repeated three times, while the subjects were asked to breathe in three different ways for 60 s each: freely (F), with a constant rate (PN) and with deep and constant respiration rate (PD). The average flow rates were computed, they were removed from the respective signals and integrated in the inspiratory and expiratory phases (differential volumes). Finally, the power spectral density was computed for each detrended flow rate. High- and very-high frequency peaks were identified on the spectra while their frequencies were compared to the respiratory and cardiac frequencies estimated using a thoracic belt and a pulse oximeter. The area under the spectra was computed in four 0.5 Hz-wide ranges, centered on the high-frequency peak, on very-high frequency peak and its 2nd and 3rd harmonics, and then they were normalized by the flow rate variance. The effect of breathing patterns on average flow rates, on systolic and diastolic peaks, and on the normalized power was tested. Finally, the differential volumes of inspiration were compared to those of expiration. Results The frequencies of the high- and very-high spectral peaks corresponded to the respiratory and cardiac frequencies. The average flow rate progressively decreased from F to PN to PD breathing, and the cardiac modulations were less predominant especially for the IJVs. The respiratory modulation increased with PD breathing. The average volumes displaced in the inspiratory phases were not significantly different from those of the expiratory one. Conclusions The spectral analyses demonstrated higher respiratory modulations in PD compared to free breathing, even prevailing the cardiac modulation in the IJVs, showing an increment of the thoracic pump affecting the flow rate shape.

Dissecting Multiparametric Cerebral Hemodynamics using Integrated Ultrafast Ultrasound and Multispectral Photoacoustic Imaging

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Regulation of interstitial fluid flow in adventitia along vasculature by heartbeat and respiration

“…How such regulative mechanisms of heartbeat and respiration on adventitial ISF flow via vasculature takes a role in modulating the ISF flow around cells or capillaries of tissues or organs, or blood and CSF in brain needs more studies. 18 , 19 , 20 , 21 …”

“…Future research on the relationship between pressure and fluctuated flow rate may further modify this equation. 19 , 20 …”

“…In brain, the cerebrospinal fluid (CSF) and blood flow were found to be influenced by respiration and cardiac activity in human studies using MRI. 18 , 19 , 20 , 21 Recently, converging studies have shown that the ISF adjacent to arteries and veins can also flow in the adventitia along the vasculature into the heart and lungs under an unknown regulatory mechanism.…”

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