Repeatability of Arterial Spin Labeling MRI in Measuring Blood Perfusion in the Human Eye

Background Quantifying blood perfusion in ocular tissues is challenging, partly because the majority of the blood is carried by the choroid, which is difficult to visualize because it is located between the retina and sclera. Purpose/Hypothesis To evaluate the intra- and interday repeatability of MRI measures of chorio-retinal blood perfusion. Study Type Prospective, cross-sectional, observational study. Population Twenty young healthy adults (six male, age: 25 +/- 5 years) scanned twice within a single session repeated at the same time of day on 2 days. Field Strength/Sequence Arterial spin labeling (ASL) MRI at 3.0T using pseudocontinuous ASL (PCASL) labeling scheme and a 3D turbo-gradient-spin-echo (TGSE) acquisition, including axial T-2-weighted structural images using a 2D turbo-spin-echo (TSE) sequence. Assessments Region-of-interest analysis for assessment of chorio-retinal blood perfusion. Statistical Tests Intra- and interday repeatability of measures analyzed using intraclass correlation coefficients (ICC), Pearson's correlation analysis, paired t-tests, and Bland-Altman plots. Results The mean chorio-retinal perfusion was 77.86 (standard deviation [SD] = 29.80) ml/100ml/min. Perfusion measurements correlated strongly within a single session (r = 0.95, 95% confidence interval [CI] [0.880-0.980], P < 0.001) and between the two sessions based on a single run (r = 0.80 [0.582-0.913], P < 0.001), and two runs (r = 0.80 [0.479-0.918], P < 0.001). There were mean differences of 2.69 [16.85 to -22.23] ml/100ml/min for intraday measures, -7.44 [27.45 to -42.32] ml/100ml/min for single-run interday measures, and 5.73 [28.71 to -40.17] ml/100ml/min for two-run interday measures, but none were significant (all P > 0.05). Data Conclusion Quantitative ASL-MRI measurements of chorio-retinal blood perfusion showed high intra- and interday repeatability. The ASL-MRI technique provides reliable measures of chorio-retinal perfusion in vivo.