Diameters of A1 and P1 and volume flow rates of 6 subjects with A1 hypolasia (nos. 1–6) and 6 with P1 hypoplasia (nos. 7–12)
| Subject No. | Diameter (mm) | Volume Flow Rates (mL/min) (Relative Percentage Contribution (%)) | |||||
|---|---|---|---|---|---|---|---|
| Ipsilateral to Hypolastic A1 or P1 | Contralateral to Hypoplastic A1 or P1 | ICA Ipsilateral to Hypoplastic A1 or P1 | ICA Contralateral to Hypoplastic A1 or P1 | Basilar Artery | |||
| A1 | P1 | A1 | P1 | ||||
| 1 | 0.0* | 2.3 | 1.4 + 1.3† | 2.4 | 267 (29) | 468 (51) | 188 (20) |
| 2 | 0.7 | 1.0 | 2.0 | 1.7 | 305 (38) | 405 (51) | 88 (11) |
| 3 | 0.9 | 2.0 | 2.7 | 2.4 | 257 (32) | 380 (47) | 166 (21) |
| 4 | 0.8 | 1.4 | 1.5 | 2.1 | 212 (35) | 274 (45) | 119 (20) |
| 5 | 0.0* | 1.8 | 2.3 | 2.0 | 179 (26) | 348 (50) | 169 (24) |
| 6 | 0.0* | 1.9 | 2.7 | 2.0 | 199 (31) | 325 (51) | 116 (18) |
| 7 | 1.5 | 0.8 | 2.2 | 2.1 | 438 (48) | 349 (38) | 120 (13) |
| 8 | 1.8 | 0.9 | 2.2 | 1.4 | 298 (44) | 303 (45) | 76 (11) |
| 9 | 1.3 | 0.9 | 1.7 | 2.0 | 379 (52) | 254 (35) | 91 (13) |
| 10 | 2.1 | 0.8 | 2.0 | 1.1 | 296 (48) | 266 (43) | 52 (8) |
| 11 | 1.4 | 0.0* | 2.0 | 1.8 | 300 (42) | 312 (43) | 108 (15) |
| 12 | 1.5 | 0.9 | 2.5 | 1.9 | 422 (45) | 418 (45) | 95 (10) |
Note:— A1 indicates precommunicating segment of the anterior cerebral artery; P1, precommunicating segment of the posterior cerebral artery; ICA, internal carotid artery. An artery with a diameter ≤0.9 mm was considered to be hypoplastic.
* The relevant artery was not depicted.
† Duplicate A1s were observed.