Table 5.
| ‘Optimized’ distribution | ‘Regular’ distribution | |||
|---|---|---|---|---|
| Mean ± std. dev. | Median | Mean ± std. dev. | Median | |
| f (%) | ||||
| Central region | 13.31 ± 2.75 | 11.26 | 12.54 ± 1.79 | 10.41 |
| Cerebellum | 13.85 ± 1.82 | 10.72 | 14.72 ± 2.20 | 10.47 |
| Frontal lobe | 11.69 ± 2.52 | 9.53 | 11.52 ± 2.47 | 8.92 |
| Limbic lobe | 11.95 ± 2.93 | 10.02 | 22.39 ± 7.37 | 16.42 |
| Occipital lobe | 17.60 ± 3.65 | 12.38 | 19.70 ± 6.20 | 13.01 |
| Parietal lobe | 16.36 ± 6.58 | 11.25 | 18.79 ± 6.96 | 11.72 |
| Subcortical nuclei | 9.77 ± 1.97 | 7.59 | 11.20 ± 2.85 | 7.94 |
| Temporal lobe | 11.80 ± 3.94 | 9.95 | 11.40 ± 2.85 | 9.00 |
| White matter | 12.38 ± 2.07 | 9.61 | 13.65 ± 2.44 | 9.27 |
| Average ± std. dev. (range) | 13.19 ± 2.45 (9.77–17.60) | 10.26 ± 1.37 (7.59–12.38) | 15.10 ± 4.16 (11.20–22.39) | 10.80 ± 2.62 (7.94–16.42) |
| Average CV | 0.23 ± 0.08 | 0.25 ± 0.08 | ||
| D* (× 10−3 mm2/s ) | ||||
| Central region | 15.64 ± 2.17 | 13.45 | 24.69 ± 7.39** | 16.98 |
| Cerebellum | 14.25 ± 2.99 | 10.67 | 19.73 ± 5.88 ** | 11.92 |
| Frontal lobe | 12.64 ± 2.76 | 10.84 | 18.53 ± 6.63 | 12.54 |
| Limbic lobe | 15.29 ± 2.32 | 12.38 | 30.31 ± 11.15** | 16.18 |
| Occipital lobe | 19.60 ± 14.61 | 14.24 | 19.89 ± 11.12 | 10.45 |
| Parietal lobe | 17.55 ± 9.14 | 14.24 | 28.59 ± 21.12 | 20.01 |
| Subcortical nuclei | 15.26 ± 5.02 | 10.86 | 19.55 ± 8.16 | 11.37 |
| Temporal lobe | 15.27 ± 3.65 | 11.75 | 24.76 ± 8.32** | 14.05 |
| White matter | 14.54 ± 4.24 | 11.59 | 20.44 ± 8.65 | 12.99 |
| Average ± std. dev. (range) | 15.56 ± 1.99 (12.64–19.60) | 12.24 ± 1.46 (10.67–14.37) | 22.94 ± 4.32 (18.53–30.31) | 14.05 ± 3.10 (10.45–20.01) |
| Average CV | 0.32 ± 0.20 | 0.42 ± 0.14 | ||
| D (× 10−3 mm2/s ) | ||||
| Central region | 0.92 ± 0.11 | 0.88 | 0.91 ± 0.10 | 0.88 |
| Cerebellum | 0.93 ± 0.13 | 0.89 | 0.92 ± 0.13 | 0.88 |
| Frontal lobe | 0.90 ± 0.09 | 0.86 | 0.90 ± 0.08 | 0.85 |
| Limbic lobe | 0.87 ± 0.10 | 0.84 | 0.87 ± 0.09 | 0.84 |
| Occipital lobe | 0.89 ± 0.13 | 0.86 | 0.91 ± 0.12 | 0.86 |
| Parietal lobe | 0.80 ± 0.12 | 0.78 | 0.81 ± 0.10 | 0.79 |
| Subcortical nuclei | 0.86 ± 0.09 | 0.83 | 0.86 ± 0.09 | 0.83 |
| Temporal lobe | 0.87 ± 0.11 | 0.84 | 0.88 ± 0.10 | 0.84 |
| White matter | 0.91 ± 0.12 | 0.87 | 0.91 ± 0.12 | 0.86 |
| Average ± std. dev. (range) | 0.89 ± 0.04 (0.80–0.93) | 0.85 ± 0.03 (0.78–0.89) | 0.88 ± 0.04 (0.81–0.92) | 0.85 ± 0.03 (0.79–0.88) |
| Average CV | 0.13 ± 0.02 | 0.12 ± 0.02 | ||
f, D* and D values obtained using the ‘regular’ and the ‘optimized’ b-value distribution using the two-steps fit method. Data are presented as mean and standard deviation for the ROIs identified within certain grey matter (GM) areas defined according to the AAL atlas30 or in white matter. Specifically: the “Central Region” is composed of GM in the precentral gyrus, postcentral gyrus, and Rolandic operculum. The “Frontal Lobe” region is composed of GM, in its lateral surface: superior frontal gyrus - dorsolateral, middle frontal gyrus, inferior frontal gyrus with opercular and triangular parts; in its medial surface: superior frontal gyrus-medial, supplementary motor area, paracentral lobule; in its orbital surface: superior frontal gyrus, orbital and medial orbital parts, middle and inferior frontal gyrus — orbital parts, gyrus rectus, olfactory cortex. The “Limbic Lobe” region is composed of GM in the temporal pole: superior temporal gyrus and middle temporal gyrus, anterior cingulate and paracingulate gyri, middle cingulate and paracingulate gyri, posterior cingulate gyrus; hippocampus, parahippocampal gyrus, insula. The “Occipital Lobe” region is composed of GM in its lateral surface: superior, middle and inferior occipital gyri; in its medial and inferior surfaces: cuneus, calcarine fissure, and surrounding cortex, lingual gyrus and fusiform gyrus. The “Parietal Lobe” region is composed of GM in its lateral surface: superior parietal gyrus, inferior parietal gyrus; in its medial surface: precuneus. The “subcortical nuclei” region is composed of amygdala, caudate nucleus, putamen, pallidum, thalamus. The “Temporal Lobe” region is composed of GM in its lateral surface: superior temporal gyrus, Heschl’s gyrus, middle and inferior temporal gyri.
Indicates significance difference between optimized and regular distribution (α: 1%). f, fraction; D*, pseudo-diffusion coefficient; D, diffusion coefficient; std. dev., standard deviation; CV, coefficients of variation.