Article Figures & Data
Figures
- FIG 1.
The circle of Willis. 3D volume-rendering of the CoW from a TOF-MRA in a young child. This shows the key segments comprising the vascular ring, including AcomA (blue), the first segment of the anterior cerebral artery (A1, orange), the PcomA (red), and the first segment of the posterior cerebral artery (P1, green). Other arteries feeding the CoW (the ICA and the basilar artery [BA]) and supplied by the CoW (second segment of the anterior cerebral artery [A2], MCA, and second segment of the posterior cerebral artery [P2]) are also labeled.
- FIG 2.
Double-oblique multiplanar reconstruction for vessel-diameter measurement. Two orthogonal planes of reconstruction were aligned along the long axis of each arterial segment to be measured. These were then used to construct a cross-sectional plane through the midportion of the vessel segment on which 2 perpendicular diameters were measured and averaged. Note that partial volume effects at the margins of the artery could result in a slight degree of measurement bias and error. WL indicates window level; WW, window width.
- FIG 3.
Measurement of the CoW-di. A group average of the ratio of each CoW segment to the mean CoW diameter was calculated. For each individual CoW, similar ratios were calculated for each of the 7 segments. The CoW-di was then calculated as the Euclidean distance between the individual CoW ratios and the group-average ratios, thus representing the degree to which an individual CoW deviated in size from the group average. Examples are shown for two 23 -year-old individuals, one with a very low CoW-di (0.29) and another with a high CoW-di (1.48), largely due to a nonvisualized left P1 segment.
- FIG 4.
Differences in CoW size and symmetry in children versus adults. The total CoW cross-sectional area was measured in healthy children (n = 19) and adults (n = 42) on TOF-MRA images as described in the text. The mean total CoW cross-sectional area was larger in children than in adults (children’s mean CoW-area = 27.7 mm2 versus adults’ mean CoW-area = 17.8 mm2, P < .0001). Note that T2-SPACE measurements replicated these results, though with a smaller effect size as discussed in the text. CoW topology in children also more closely resembled the average topology found in the whole group, despite there being more adults in the whole group (children’s mean CoW-di = 0.48 versus adults’ mean CoW-di = 0.84, P < .001). As described in the text, the difference in CoW topology is, in part, due to a higher prevalence of nonvisualized CoW segments in adults.
- FIG 5.
CoW size tracks with CBF changes during development. Total CoW cross-sectional area based on TOF-MRA and whole-brain CBF was measured in participants ranging from 4 to 74 years of age. There is a gradual decrease in whole-brain CBF from childhood to adulthood that parallels the decrease in total CoW cross-sectional area. Across participants, CoW size also correlated with whole-brain CBF (Pearson r = 0.68, P < 10−7). Smoothing lines are for visualization purposes and are based on LOcally WEighted Scatter-plot Smoother fits with span = 1.
Tables
Summary CoW measurements in healthy children versus adults
Children (0–18 years of age) Adults (19–74 years of age) No. of participants 23 43 Age (range) (yr) 9.5 (4–18) 40.7 (19–74) Sex (female, male) 11, 12 21, 22 Excluded data 4 of 23 1 of 43 TOF-MRA CoW-area (mean) (mm2) 27.7 (SD, 7.9) 17.8 (SD, 4.2) TOF-MRA CoW-di (mean) 0.48 (SD, 0.30) 0.84 (SD, 0.49) T2-SPACE CoW-area (mean) (mm2) 16.6 (SD, 4.1) 14.2 (SD, 4.0) T2-SPACE CoW-di (mean) 0.68 (SD, 0.29) 0.93 (SD, 0.49) Nonvisualized segments 5/133 (3.8%) 31/294 (10.5%) Whole-brain CBF (mean) (L/min) 1.10 (SD, 0.24) 0.69 (SD, 0.21)
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