Table 2:

Mantel-Haenzel row mean score test statistic (P value) based on a χ² distribution with 1 degree of freedom (3 degrees of freedom for the overall analysis), stratified on matched pairs, for every vessel and image quality parameter by reader

Vessel	Reader 1	Reader 2	Reader 3	Overall
Arterial score 1: CCA	9.3077 (0.0023)	4.0000 (0.0455)	2.0000 (0.1573)	15.3077 (0.0016)
Arterial score 2: Bifurcation	9.0000 (0.0027)	8.3333 (0.0039)	5.0000 (0.0253)	22.3333 (<0.0001)
Arterial score 3: ICA	8.8947 (0.0029)	8.0000 (0.0047)	4.0000 (0.0455)	20.8947 (0.0001)
Arterial score 4: ECA	8.8947 (0.0029)	9.0000 (0.0027)	4.0000 (0.0455)	21.8947 (<0.0001)
Arterial score 5: Intraosseous portion of ICA	9.2807 (0.0023)	8.8947 (0.0029)	5.0000 (0.0253)	23.1754 (<0.0001)
Arterial score 6: Vertebral arteries	6.4000 (0.0114)	8.3333 (0.0039)	7.0000 (0.0082)	21.7333 (<0.0001)
Arterial score 7: Basilar artery	8.9091 (0.0028)	10.000 (0.0016)	6.2308 (0.0126)	25.1399 (<0.0001)
Arterial score 8: Communicating arteries	8.8947 (0.0029)	8.8947 (0.0029)	6.2308 (0.0126)	24.0202 (<0.0001)
Arterial score 9: First segments: A1, M1, P1	8.3333 (0.0039)	6.0000 (0.0143)	9.0000 (0.0027)	23.3333 (<0.0001)
Arterial score 10: Second segments: A2, M2, P2	9.0000 (0.0027)	8.3333 (0.0039)	9.3077 (0.0023)	26.3333 (<0.0001)
Arterial score 11: Third segments: A3, M3, P3	9.3226 (0.0023)	9.1429 (0.0025)	10.000 (0.0016)	28.4655 (<0.0001)
Venous score 1: Internal and bridging cerebral veins	5.4000 (0.0201)	7.0000 (0.0082)	4.4545 (0.0348)	16.8545 (0.0008)
Venous score 2: Cavernous sinus	9.0000 (0.0027)	4.0000 (0.0455)	6.0000 (0.0143)	19.0000 (0.0003)
Venous score 3: Superior saggital sinus	2.0000 (0.1573)	1.0000 (0.3173)	0 (1)^‡	3.0000 (0.3916)
Venous score 4: Transverse and sigmoid sinus	1.0000 (0.3173)	1.0000 (0.3173)	1.0000 (0.3173)	3.0000 (0.3916)
Venous score 5: Jugular veins	1.0000 (0.3173)	1.0000 (0.3173)	0 (1)^†††	2.0000 (0.5724)
Quality score 1: Quality overall: 1 (poor) to 5 (excellent)	7.3636 (0.0067)	9.0000 (0.0027)	1.0000 (0.3173)	17.3636 (0.0006)
Quality score 2: Artifacts: 1 (cannot be interpreted) to 5 (no artifacts)	4.0000 (0.0455)	1.0000 (0.3173)	0 (1)^†††	5.0000 (0.1718)
Quality score 3: Dental artifacts: 1 (cannot be interpreted) to 5 (no artifacts)	1.0000 (0.3173)	1.0000 (0.3173)	0 (1)^†††	2.0000 (0.5724)
Quality score 4: Delineation of vascular calcification: 1 (poor) to 5 (excellent)	9.000 (0.0027)^†	7.118 (0.0076)^†	4.000 (0.0455)^†	20.1176 (0.0002)^†
Quality score 5: Subjective contrast: 1 (insufficient) to 5 (excellent)	0 (1)^‡	6.0000 (0.0143)	0 (1)^‡	6.0000 (0.1116)

Note:—In every instance where the test was significant, the shift in row mean scores was due to a higher distribution of scores for MIP. Significant results are marked in bold. CCA indicates common carotid artery; ICA, internal carotid artery; ECA, external carotid artery.
† In one of the 10 subjects, all readers chose n/a, as no calcifications were discerned with either technique.
‡ Only 2 of the possible 5 scores were used for every subject, for both MIP and MPR. The resulting 2 × 2 table has identical MIP and MPR scores within every subject. Thus, the Mantel-Haenzel row mean score test, stratified on matched pairs, cannot be computed due to a singular covariance matrix. However, in this situation, McNemar’s test for 2 × 2 tables can be used. Here, McNemar’s test statistic is 0 with a P value of 1.
††† MIP and MPR scores are identical within every subject, and thus the Mantel-Haenzel row mean score test, stratified on matched pairs, cannot be computed due to a singular covariance matrix.