PMC:7305584 / 3867-10925 JSONTXT

{"project":"2_test","denotations":[{"id":"32563264-9530305-12762898","span":{"begin":4931,"end":4932},"obj":"9530305"},{"id":"32563264-843571-12762899","span":{"begin":6642,"end":6644},"obj":"843571"}],"text":"Methods\n\nPatients\nThis retrospective study was approved by the Institutional Review Board of our hospital. The requirement to obtain informed consent was waived due to its retrospective nature.\nWe retrospectively reviewed the PACS of our institution for subjects who received simultaneous head and neck MRA and carotid duplex sonography from January 2017 to June 2018 as part of a routine health examination. A total of 223 healthy subjects without any history or symptoms of cerebrovascular disease were identified.\nBased on the imaging studies, 3 subjects were excluded due to segmental narrowing (\u003e 50%) of the common/internal carotid arteries, 4 due to proximal anterior cerebral artery (ACA)/ middle cerebral artery stenosis, 1 due to a persistent trigeminal artery, 2 due to vascular anomalies such as cerebral aneurysm, 2 due to arteriovenous malformation/fistula, and 1 due to a moyamoya syndrome. These 13 excluded subjects were used for the interobserver reliability test. Thus, 210 subjects (133 males, 77 females; mean age 54 ± 9 years; range, 31 to 76 years) were included in the analysis.\n\nImaging studies\nThree-dimensional time-of-flight magnetic resonance angiography (TOF-MRA) of the head was obtained with the parameters: TR/TE, 21/2 ms; flip angle, 20°; FOV, 200 mm; matrix, 320 × 192; NEX, 1. The major extracranial arteries in the neck were visualized by contrast-enhanced MRA on a 3 T MR scanner (Discovery MR 750, GE Medical Systems, Milwaukee, WI, USA) using a single dose (0.1 mmol/ kg; 5–7 ml) of gadobutrol (Gd-BT-DO3A, Gadovist™, Bayer Healthcare, Leverkusen, Germany) with an injection rate of 1.5 ml/s and MR parameters of TR/TE, 4/1 ms; flip angle, 25°; FOV, 300 mm; matrix, 320 × 224; and NEX, 1. Carotid Doppler sonography was performed by the same technician with more than 10 years of experience using a Philips HD15 ultrasound system to evaluate bilateral ICA flow volume. For ICA flow volume measurement, a straight ICA segment at least 2 cm above the carotid bulb was selected with the doppler angle of incidence adjusted at or below 60 degrees. At the same site, the sample volume box was put to cover the entire vessel diameter (d). The angle-corrected time-average flow velocity (TAV) was determined over 3 to 5 complete cardiac cycles. The ICA flow volume was calculated as the product of TAV and the cross-sectional area (A) of the vessel according to the formula FV = TAV x A = TAV x [(d/2)2xπ].\n\nMR imaging interpretations\nAt first, vessel diameter and COW calcification of the 13 excluded subjects were recorded by two experienced neuroradiologists (TCW and TYC with 12 and 17 years of experience, respectively) for the interobserver reliability tests. Due to substantial to almost perfect reproducibility (ICC values of 0.82–0.97), the vessel diameter measurements of all 210 included subjects were completed by only one reader (TCW). For COW classification, the diameter ratios between the bilateral A1 segments and between the ipsilateral PcomA and P2 segments were recorded (Fig. 1a, b). The diameters of the bilateral distal cervical ICAs were measured at 1 cm below the petrous segment of the ICA (Fig. 1c). In each case, the diameter of the dominant A1 segment was set as 100%, and the diameter of the non-dominant A1 segment was set as the percentage compared to the dominant A1 segment. Bilateral PcomA diameters were transformed into the percentage of the ipsilateral P2 segment diameters. F-PCA was defined as a PcomA diameter equal to the ipsilateral P2 segment diameter with an absence of the ipsilateral P1 segment.\nFig. 1 Examples of vascular diameter measurement. a) Typical location of bilateral A1 diameter measurement at in the middle of the A1 segment. b) Typical location of PcomA and P2 diameter measurement at in the middle of the PcomA and proximal P2 segment, respectively. Note there was no PcomA on the contralateral side. c) Typical location of bilateral distal cervical ICA diameter measurement at 1 cm below the petrous ICA segment\nThe classification of COW variants is summarized in Fig. 2. Three ACA asymmetry (AA) groups were defined based on the diameter ratio difference of bilateral A1 segments: AA1 group, 1 side A1 aplasia; AA2, bilateral A1 diameter ratio difference ≥ 50%; AA3, bilateral A1 ratio difference between 10 and 50%. Similarly, 3 PcomA asymmetry (PA) groups were defined: PA1 group, 1 F-PCA, and absent PcomA on the contralateral side; PA2, bilateral PcomA diameter ratio difference ≥ 50%; PA3, bilateral PcomA diameter ratio difference between 10 and 50%. According to the vessel diameter, bilateral A1 segments and PcomAs in each patient were denoted as a dominant or non-dominant side. Symmetry was defined as both bilateral A1 segment and PcomA diameter ratio differences \u003c 10%, with the exclusion of cases with bilateral F-PCAs.\nFig. 2 Classification of Circle of Willis variants (modified from Krabbe-Hartkamp, Radiology 1998) [9]\nSeveral parameters were used to determine the ability of ICA diameter and flow volume for prediction of COW variants: (1) Bilateral ICA diameter difference; (2) Bilateral ICA flow volume difference; (3) Bilateral ICA flow volume difference percentage (2× bilateral ICA flow difference/ bilateral ICA sum); (4) Product of bilateral ICA diameter and flow volume difference (ICA-PDF), expressed as ICA diameter difference (right ICA diameter – left ICA diameter) × ICA flow volume difference percentage [2 × (right ICA flow - left ICA flow)/(right ICA flow + left ICA flow)].\n\nStatistical analysis\nVessel diameter and flow volume measurements were expressed as mean and standard deviation. Vessel diameter and flow volume were compared in the following ways with different statistical tests: 1) One-way ANOVA and Bonferroni method for multi-intergroup analysis; 2) Student t-test for comparisons between each AA/PA subgroup and symmetric group; 3) Paired t-test for intragroup analysis of each subgroup to compare dominant vs. non-dominant side and right vs. left side. Linear regression analysis was used to examine the relations between ICA diameter and flow volume in each COW type. To examine the ability of ICA diameter and flow parameters for prediction of each COW variant, receiver operating characteristic (ROC) curve analysis was performed. Inter-observer reliability for COW calcification of 13 excluded cases was determined by using the Cohen κ coefficient. For continuous data, the intraclass correlation coefficient (ICC) was calculated with the two-way random model and absolute agreement on average measures. The Cohen κ and ICC were interpreted according to methods described by Landis et al. [20]. Cohen K coefficient values of 0.85 ~ 0.96 were obtained for categorical COW classification and ICC values of 0.82–0.97 were obtained for the continuous data, both indicating almost perfect reproducibility. All data analyses were performed using the statistical software package SPSS for Windows version 24.0 (IBM, Chicago, IL, USA). Values of P-value \u003c 0.05 were considered to indicate statistical significance."}