Venous Oxygenation Measurements in the Upper Arm: Reproducibility and Sensitivity to a Physical Challenge.

PURPOSE: The feasibility and reproducibility of adapting the T2-Relaxation-Under-Spin-Tagging (TRUST) MRI sequence for noninvasive measurement of venous oxygenation in the upper arm were investigated, aiming to enable future in vivo validation of T2b-oxygenation calibration curves in sickle cell disease (SCD). METHODS: The TRUST sequence, originally developed for the brain, was optimized for the upper arm by comparing control, label and difference signal. Accuracy was assessed using a phantom experiment. Twelve healthy volunteers underwent repeated TRUST scans using two different protocols: Three-averages and One-average. Reproducibility and temporal resolution were investigated, and a handgrip exercise was used to assess sensitivity to physiological changes. Statistical analyses included coefficient of variation (CV), within-subject CV (wsCV), and Bland-Altman analysis. RESULTS: Phantom experiments demonstrated accurate T2 estimation at low expected velocities with deviations from reference less than 16 ms (11.2%). In vivo, the adapted sequence provided faster and reproducible T2b (86.0 ± 30.0 ms) and Yv measurements (66.1% ± 11.7%). Reducing the number of averages improved temporal resolution without compromising measurement reproducibility (bias: 16.3 to 7.6 ms, wsCV: 39.8% to 35.3%). During exercise, significant decreases in T2b and Yv were observed in both the superficial and deep vein: mean T2b decreased from 87.2 to 58.9 ms (p < 0.001) in the cephalic vein, and from 93.3 to 71.3 ms (p < 0.001) in the brachial vein. CONCLUSION: The adapted TRUST protocol enables reproducible assessment of venous oxygenation in the upper arm, providing a technique for future validation and recalibration of T2b-oxygenation curves in SCD.