Vessel‐specific quantification of blood oxygenation with T 2 ‐relaxation‐under‐phase‐contrast MRI

Purpose Measurement of venous oxygenation ( Y v ) 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 noninvasive, rapid, and reproducible method to measure Y v in a vessel‐specific manner. Theory The method, T 2 ‐Relaxation‐Under‐Phase‐Contrast MRI, utilizes complex subtraction of phase‐contrast to isolate pure blood signal, applies nonslice‐selective T 2 ‐preparation to measure T 2 , and converts T 2 to oxygenation using a calibration plot. Methods Following feasibility demonstration, several technical aspects were examined, including validation with an established global Y v technique, test–retest reproducibility, sensitivity to detect oxygenation changes due to hypoxia and caffeine challenges, applicability of echo‐planar‐imaging (EPI) acquisition to shorten scan duration, and ability to study veins with a caliber of 1–2 mm. Results T 2 ‐Relaxation‐Under‐Phase‐Contrast was able to simultaneously measure Y v in all major veins in the brain, including sagittal sinus, straight sinus, great vein, and internal cerebral vein. T 2 ‐Relaxation‐Under‐Phase‐Contrast 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 T 2 ‐Relaxation‐Under‐Phase‐Contrast MRI is a promising technique for vessel‐specific oxygenation measurement. Magn Reson Med 71:978–989, 2014. © 2013 Wiley Periodicals, Inc.