MRI-based measurements of whole-brain global cerebral blood flow: Comparison and validation at 1.5T and 3T.

Background: Whole-brain global cerebral blood flow (CBF) determined by MRI techniques, calculated using total CBF (TCBF) from phase-contrast MRI (PC-MRI), and brain parenchyma volume (BPV) from T -weighted image, have become increasingly popular in many applications.

Purpose/hypothesis: To determine if MRI-based measurements of whole-brain global CBF data obtained across different field strengths could be merged, TCBF and BPV data acquired at 1.5T and 3T were compared.

Study Type: Prospective study.

Population: Seventeen healthy subjects (eight females, aged 21-29 years old).

Field Strength/sequence: Fast spoiled gradient echo (FSPGR) and PC-MRI at both 1.5T and 3T.

Assessment: TCBF and BPV data acquired at 1.5T and 3T were compared.

Statistical Tests: The relationships of TCBF and whole-brain global CBF between two field strengths were examined by using the Pearson correlation coefficient analysis and intraclass correlation coefficient (ICC).

Results: Regression analysis revealed a strong correlation between TCBF at two field strengths (R  = 0.78, P < 0.001), and the ICC was 0.85, suggesting measurements of TCBF at 1.5T were comparable and correlated with those at 3T. There was a significant difference in BPV between field strengths, where the white matter estimate was significantly larger at 1.5T when compared with that at 3T (P < 0.001). When TCBF was further normalized to the brain parenchyma mass to obtain whole-brain global CBF, it only showed a moderate correlation between measurements at the two field strengths (R  = 0.46, P = 0.003) and lower ICC of 0.66, reflecting the slightly higher interstrength variability in the whole-brain global CBF measurements.

Data Conclusion: TCBF measurements could be performed equally well with comparable results at both field strengths, but specific attention should be given when TCBF is further normalized to BPV to obtain whole-brain global CBF.

Level Of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1273-1280.