Table 2:

Accuracy and precision of MR imaging measurements

	No.^{^a}	Mean^{^b}	B-A^{^c}	B-A (%)^{^d}	t Test^{^e}	P	SEM^{^f}	CV_SEM^{^g}	r^{^h}	P
PCF	165	28.61	0.022	0.08	0.17		1.148	4.01	0.059
Cerebral FOD	168	56.77	−3.258	−5.74	−18.53	<.01	1.611	2.84	0.158	<.05
Cerebral BPD	169	42.12	−1.263	−3.00	−11.68	<.01	0.995	2.36	−0.141
Vermian APD	167	7.08	0.014	0.20	0.21		0.611	8.64	0.192	<.05
Cerebellar LLD	166	21.81	−1.020	−4.68	−10.41	<.01	0.893	4.09	0.111
Vermian CCD	168	10.13	−0.934	−9.22	−13.29	<.01	0.644	6.36	−0.004
CSA	168	72.25	1.020	1.41	1.77		5.278	7.30	0.192	<.05
LCC	152	17.97	0.176	0.98	1.75		0.878	4.89	0.071
LCC/cerebral FOD (%)	151	31.69	2.252	7.11	11.87	<.01	1.648	5.20	0.238	<.01
Thecal FOD	167	63.47	0.360	0.57	2.97	<.01	1.106	1.74	0.002
Thecal BPD	169	49.74	0.682	1.37	4.45	<.01	1.410	2.83	0.106
Mesencephalic APD	118	4.46	0.197	4.41	3.08	<.01	0.490	10.99	0.143
Pontine APD	159	6.69	−0.074	−1.10	−1.34		0.491	7.34	0.241	<.01
Pontine CCD	158	7.53	−0.384	−5.10	−6.24	<.01	0.547	7.27	0.184	<.05
Lateral ventricles	161	6.76	0.568	8.40	8.15	<.01	0.625	9.25	−0.214	<.01

Note:—SEM indicates standard error of the measurements; APD, antero-posterior diameter; BPD, biparietal diameter; CCD, cranio-caudal diameter; CV, coefficient of variation; CSA, clivosupraoccipital angle; LCC, length of the corpus callosum; LLD, latero-lateral diameter; FOD, fronto-occipital diameter; PCF, latero-lateral diameter of the posterior cranial fossa.
↵a The number of observations.
↵b Mean of all measurements.
↵c Mean difference between assessor B and assessor A (difference in accuracy of assessors A and B).
↵d Percentage interassessor difference [100 × (B−A) / mean].
↵e t test for difference in B−A.
↵f Measuring error—that is, the SD of the measures of the same fetus (lack of precision).
↵g Measuring error expressed as coefficient of variation (%) of (100 × SEM / mean).
↵h Correlation coefficient between interassessor B−A difference and the mean of the measurements made on a single fetus.