Vessel‐specific quantification of blood oxygenation with T₂‐relaxation‐under‐phase‐contrast MRI

Abstract

Purpose Measurement of venous oxygenation (Yv) is a critical step toward quantitative assessment of brain oxygen metabolism, a key index in many brain disorders. The present study aims to develop a non-invasive, rapid, and reproducible method to measure Yv in a vessel-specific manner. Theory The method, T2-Relaxation-Under-Phase-Contrast (TRU-PC) MRI, utilizes complex subtraction of phase-contrast to isolate pure blood signal, applies non-slice-selective T2-preparation to measure T2, and converts T2 to oxygenation using a calibration plot. Methods Following feasibility demonstration, several technical aspects were examined, including validation with an established global Yv technique, test-retest reproducibility, sensitivity to detect oxygenation changes due to hypoxia and caffeine challenges, applicability of EPI acquisition to shorten scan duration, and ability to study veins with a caliber of 1–2 mm. Results TRU-PC was able to simultaneously measure Yv in all major veins in the brain, including sagittal sinus, straight sinus, great vein, and internal cerebral vein. TRU-PC results showed an excellent agreement with the reference technique, high sensitivity to oxygenation changes, and test-retest variability of 3.5±1.0%. The use of segmented-EPI was able to reduce the scan duration to 1.5 minutes. It was also feasible to study pial veins and deep veins. Conclusion TRU-PC MRI is a promising technique for vessel-specific oxygenation measurement.

Rapid T2- and susceptometry-based CMRO2 quantification with interleaved TRUST (iTRUST)

“…T 2 -relaxation-under-phase-contrast (TRU-PC), which uses phase-contrast rather than tag-control isolation of venous blood (Krishnamurthy et al, 2013), and which can probe vessels as small as 1 mm, contains an equivalent signal waiting period as in TRUST. Addition of flow quantification within TRU-PC would provide a means of quantifying oxygen flux rather than simply oxygen saturation in small regional vessels not suitable to SBO.…”

“…Recently, a number of MR-based approaches for direct quantification of cerebral venous oxygen saturation ( Y v ) have been proposed (Jain et al, 2010, 2014; Haacke et al, 1997; Fernandez-Seara et al, 2006; Fan et al, 2012, 2014; Wright et al, 1991; Golay et al, 2001; Lu and Ge, 2008; Chen and Pike, 2009; Bolar et al, 2011; Qin et al, 2011; Guo and Wong, 2012; Krishnamurthy et al, 2013; An and Lin, 2000; He and Yablonskiy, 2007; Bulte et al, 2012; Gauthier et al, 2012). In combination with phase-contrast MRI (PC-MRI) or arterial spin labeling (ASL) CBF quantification, these techniques allow for determination of CMRO 2 via the Fick Principle (Kety and Schmidt, 1948):…”

“…Techniques for Y v quantification can be categorized based on the contrast mechanism – venous blood magnetic susceptibility (Jain et al, 2010; Haacke et al, 1997; Fernandez-Seara et al, 2006; Fan et al, 2012, 2014), T 2 (Wright et al, 1991; Golay et al, 2001; Lu and Ge, 2008; Chen and Pike, 2009; Bolar et al, 2011; Qin et al, 2011; Guo and Wong, 2012; Jain et al, 2014; Krishnamurthy et al, 2013), T 2 ′ (An and Lin, 2000; He and Yablonskiy, 2007), or T 2 * (BOLD) (Bulte et al, 2012; Gauthier et al, 2012) – as well as spatial specificity – large-vessel/whole-brain (Jain et al, 2010, 2014; Haacke et al, 1997; Fernandez-Seara et al, 2006; Fan et al, 2012; Wright et al, 1991; Golay et al, 2001; Lu and Ge, 2008; Chen and Pike, 2009; Qin et al, 2011), small-vessel/regional (Fan et al, 2014; Krishnamurthy et al, 2013), or parenchymal/voxel-wise (Bolar et al, 2011; Guo and Wong, 2012; An and Lin, 2000; He and Yablonskiy, 2007; Bulte et al, 2012; Gauthier et al, 2012). Regional and voxel-wise approaches are clearly desirable due to the heterogeneous nature of brain functional activation and pathology.…”

Cerebral Oxygen Metabolism in Neonatal Hypoxic Ischemic Encephalopathy during and after Therapeutic Hypothermia

“…Although a regional variant of this method is being developed it has not been applied to neonates. 35 In addition, it is currently not practical to screen for abnormal CMRO 2 with MRI before the necessary rapid initiation of TH, nor is MRI a practical tool to monitor response to TH or other future therapies because On each box, the central mark is the median, the black square is the mean, the edges of the box are the 25th and 75th percentiles, and the whiskers show the 95% confidence interval. Empty circles denote outliers and significant statistical comparisons are indicated with its corresponding P value as well as the number of measurements for each group/condition.…”

Regional quantification of cerebral venous oxygenation from MRI susceptibility during hypercapnia

“…However, the need for high-cost specialized equipment, radiation exposure, and invasive arterial sampling limit the clinical utility of 15 O PET. Several magnetic resonance imaging (MRI) methods have been recently proposed to quantify cerebral oxygenation from magnetic susceptibility (Fan et al, 2012; Rodgers et al, 2013), T 2 relaxation measurements in venous blood (Krishnamurthy et al, 2013; Lu and Ge, 2008), and calibrated blood-oxygen-level-dependent (BOLD) signal changes (Bulte et al, 2012; Gauthier et al, 2012). T 2 -relaxation-under-spin tagging (TRUST) MRI provides measures of cerebral OEF through estimates of T 2 relaxation of venous blood in large veins, e.g.…”