The choroid plexus water density

To quantify normative ranges and circadian variability of the choroid plexus (ChP) water density in healthy adults.

Actigraphy assessments of circadian activity were performed for 5 days in healthy participants (n = 15; age = 28.5 ± 6.5 years) and subsequently participants underwent repeated, high spatial resolution proton density-weighted imaging (spatial resolution = 0.25 × 0.25 × 1.50 mm) with a driven equilibrium (DRIVE) module at 3 T across four time epochs during wakefulness: 7:00 to 9:00, 11:00 to 13:00, 16:00 to 18:00, and 19:00 to 21:00. ChP water density (unitless ratio of mL water/mL ChP) was calculated as the product of white matter water density and the ratio of the ChP and white matter signal intensity at the level of the atria of the lateral ventricles. Descriptive statistics (mean ± SD; range; median) of water density values at each time were recorded. Spearman and Kendall rank coefficients were used to assess relationships between time, circadian variability, and ChP water density (significance criterion: p < 0.05).

Across all participants and scans (n = 60), mean ChP water density was 0.895 ± 0.047 (range = 0.806-0.983; median = 0.892). Across time periods, water density was 0.891 ± 0.038 (time = 7:44), 0.891 ± 0.050 (time = 12:17), 0.896 ± 0.045 (time = 16:03), and 0.901 ± 0.058 (time = 19:31), and no relationships between ChP water density and time of day or circadian activity were observed.

The ChP water density at the level of the atria of the lateral ventricles is approximately 0.895 ± 0.047 in healthy adults and does not change significantly with time of day during wakefulness. This value should provide a useful reference for the growing number of neuroimaging protocols that aim to derive quantitative contrast and functional metrics from ChP MRI.