Background: Venous blood oxygenation (Yv), which can be derived from venous blood T 2 (T 2 b), combined with oxygen-extraction fraction (OEF) and cerebral metabolic rate of oxygen, is considered indicative for tissue viability and brain functioning and frequently assessed in patients with sickle cell disease. Recently, T 2 -Prepared-Blood-Relaxation-Imaging-with-Inversion-Recovery (T 2 -TRIR) was introduced allowing for simultaneous measurements of blood T 2 and T 1 (T 1 b), potentially improving Yv estimation by overcoming the need to estimate hematocrit. Purpose: To optimize and compare T 2 -TRIR with T 2 -relaxation-under-spin-tagging (TRUST) sequence. Study Type: Prospective. Population: A total of 12 healthy volunteers (six female, 27 AE 3 years old) and 7 patients with sickle cell disease (five female, 32 AE 12 years old). Field Strength/Sequence: 3 T; turbo field echo planar imaging (TFEPI), echo planar imaging (EPI), and fast field echo (FFE). Assessment: T 2 b, Yv, and OEF from TRUST and T 2 -TRIR were compared and T 2 -TRIR-derived T 1 b was assessed. Withinand between-session repeatability was quantified in the controls, whereas sensitivity to hemodynamic changes after acetazolamide (ACZ) administration was assessed in the patients. Statistical Tests: Shapiro-Wilk, one-sample and paired-sample t-test, repeated measures ANOVA, mixed linear model, Bland-Altman analysis and correlation analysis. Sidak multiple-comparison correction was performed. Significance level was 0.05. Results: In controls, T 2 b from T 2 -TRIR (70 AE 11 msec) was higher compared to TRUST (60 AE 8 msec). In patients, T 2 b values were lower pre-compared to post-ACZ administration (TRUST: 80 AE 15 msec and 106 AE 23 msec and T 2 -TRIR: 95 AE 21 msec and 125 AE 36 msec). Consequently, Yv and OEF were lower and higher pre-compared to post-ACZ administration (TRUST Yv: 68% AE 7% and 77% AE 8%, T 2 -TRIR Yv: 74% AE 8% and 80% AE 6%, TRUST OEF: 30% AE 7% and 21% AE 8%, and T 2 -TRIR OEF: 25% AE 8% and 18% AE 6%). Data Conclusion: TRUST and T 2 -TRIR are reproducible, but T 2 -TRIR-derived T 2 b values are significantly higher compared to TRUST, resulting in higher Yv and lower OEF estimates. This bias might be considered when evaluating cerebral oxygen homeostasis.