Changes in Magnetic Resonance Signal Fluctuation in Superior Sagittal Sinus: Deterioration of Arteriolar Vasomotor Function of Young Smokers

Abstract

(1) Cerebral arteriolar vasomotor function is vital for brain health and has been examined through CO₂ inhalation or breath-holding, which are both challenging for patients. We have developed a non-invasive method to evaluate this function with magnetic resonance imaging (MRI) by utilizing respiration-induced natural changes in partial pressure of arterial CO₂ (PaCO₂). In this study, we applied this method for 20s to evaluate the chronic effect of a few years smoking on the cerebral arteriolar vasomotor function. (2) A single slice (five slice thicknesses: 15 mm to 7 mm) perpendicular to the superior sagittal sinus of was imaged successively for 45 s using spin-echo echo-planar imaging by 3T MRI for ten smokers (24.5 ± 1.6 years) and ten non-smokers (24.3 ± 1.4 years), respectively. The venous oxygenation fluctuation (ΔY_r) caused by the respiration-induced changes of PaCO₂, which reflects the arteriolar vasomotor function, was calculated from the time series MR signal changes of superior sagittal sinus. (3) The ΔY_r values of the smokers (0.7 ± 0.6) were significantly lower than those of the non-smokers (1.3 ± 0.8) (p = 0.04). (4) Degeneration of the cerebral arteriolar vasomotor function due to chronic smoking (even after 20s) was demonstrated by our non-invasive MRI-based method.

Keywords: MRI; arteriolar vasomotor function; smoking; venous blood.

Figure 1

Enlarged view of the superior sagittal sinus of a SE-EPI image. The black dotted line represents the ROI (11 pixels) for the signal measurement in the superior sagittal sinus.

Figure 2

Power spectral intensity (PSI) of the time series MR signal of the superior sagittal sinus of a non-smoker volunteer (a) before and (b) after application of the Hamming window. The PSI values in (b) were multiplied by the square of the correction factor (1.59) of the Hamming window. Both MR signals were obtained through imaging with 15 mm slice thickness. Black thick bars represent the respiratory frequency range. The open circles represent the data in the respiratory frequency range (0.2–0.3 Hz).

Figure 3

Power spectral intensity (PSI) of the time series MR signal of the superior sagittal sinus from imaging with slice thicknesses of (a) 7 mm, (b) 9 mm, (c) 11 mm, (d) 13 mm, and (e) 15 mm of a non-smoker volunteer; (f) spectral fluctuation intensity at the respiratory frequency (SFIr) versus average signal intensity of the same volunteer. Black thick bars in (a–e) represent the respiratory frequency range. Dashed line in (f) represents the regression line. The data of this volunteer showed the highest coefficient of determination of the regression line (R² = 0.90).

Figure 4

Respiratory changes in venous blood oxygenation (ΔY_r) of non-smokers and smokers. The error bars indicate the standard deviation. *: p < 0.05. See Supplementary Material for further details.