Detection of Optic Neuritis on Routine Brain MRI without and with the Assistance of an Image Postprocessing Algorithm

A. Schroeder; G. Van Stavern; H.L.P. Orlowski; L. Stunkel; M.S. Parsons; L. Rhea; A. Sharma

doi:10.3174/ajnr.A7068

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FIG 1.
Axial FLAIR (A and B), coronal CE-T1WI (C and D), and axial CE-T1WI (E and F) images from routine brain MR imaging of a patient with clinically proven left optic neuritis before (A, C, and E) and after (B, D, and F) processing with a proprietary postprocessing algorithm showing accentuation of the signal intensity of the diseased optic nerve and the unaffected contralateral optic nerve. Axial FLAIR (G and H), coronal 3D-FLAIR (I and J), and axial CE-T1WI of different patients with clinically proven unilateral optic neuritis again demonstrating accentuation of intensity in diseased optic nerves (arrows) after processing (H, J, and L). Note that the detection of alteration in the optic nerve signal is especially challenging in images obtained without fat saturation (E, I, and K).

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Table 1:

Scan parameters for axial 2D FLAIR,^{^a} coronal CE-T1WI, and axial CE-T1WI used in the study

	FLAIR^{^a,^b}	Coronal CE-T1WI^{^b}	Axial CE-T1WI^{^b}
Section thickness (mm)	5	5	5
TR (ms)	8000–11,000	300–742	276–780
TE (ms)	82–142	9–17	8.4–20
TI (ms)	2000–2500	–	–
FOV (mm)	172–230 × 210–230	172–230 × 172–230	172–230 × 210–230
Matrix	224–512 × 256–512	224–512 × 256–512	224–384 × 256–512
Subset of scans obtained with fat saturation	19 (63.3%)	17 (73.9%)	6 (20%)

Note:— – indicates N/A.
↵a In 3 patients, FLAIR images had been acquired using a 3D sequence with a 1-mm section thickness of images reconstructed in the coronal plane (TR = 5000 ms, TE = 395 ms, TI = 1800 ms, FOV = 256 × 256 mm, matrix = 256 × 256).
↵b For patients with optic neuritis, 19/30 (63.3%), 17/23 (73.9%), and 6/30 (20%) FLAIR, coronal CE-T1WI, and axial CE-T1WIs were performed using fat saturation.

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Table 2:

Results of diagnostic performance of 2 neuroradiologists in the detection of changes of optic neuritis on T2-weighted FLAIR, coronal CE-T1WI, and axial CE-T1WI of brain without and with the availability of postprocessed images that aimed to selectively accentuate the signal intensity of diseased optic nerves

Parameter	Reader 1		P^{^a} Value	Reader 2		P^{^a} Value	Average
Parameter	Before Processing	After Processing	P^{^a} Value	Before Processing	After Processing	P^{^a} Value	Before Processing	After Processing
Sensitivity (FL)	56.7%	56.7%	.34	53.3%	53.3%	.31	55.0%	55.0%
Specificity (FL)	62.1%	89.7%	.01	89.7%	93.1%	.5	75.9%	91.4%
Accuracy (FL)	59.3%	72.9%	.03	71.2%	72.9%	.5	65.3%	72.9%
PPV (FL)	60.7%	85%	NA	84.2%	88.9%	NA	72.5%	86.9%
NPV (FL)	58.1%	66.7%	NA	65%	65.9%	NA	61.5%	66.3%
Sensitivity (CCE)	47.8%	56.5%	.31	56.5%	56.5%	.24	52.2%	56.5%
Specificity (CCE)	81.8%	100%	.07	95.5%	100%	.5	88.7%	100%
Accuracy (CCE)	64.4%	77.8%	.04	75.5%	77.8%	.5	69.9%	77.8%
PPV (CCE)	73.3%	100%	NA	92.9%	100%	NA	83.1%	100%
NPV (CCE)	60%	68.8%	NA	67.7%	68.8%	NA	63.9%	68.8%
Sensitivity (ACE)	20.0%	30.0%	.22	13.3%	30.0%	.07	16.7%	30.0%
Specificity (ACE)	86.2%	100%	.07	100%	100%	0	93.1%	100.0%
Accuracy (ACE)	52.5%	64.4%	.04	55.9%	64.4%	.07	54.2%	64.4%
PPV (ACE)	60%	100%	NA	100%	100%	NA	80.0%	100%
NPV (ACE)	51%	58%	NA	52.7%	58%	NA	51.9%	58%

Note:—FL indicates FLAIR; CCE, coronal CE-T1WI; ACE, axial CE-T1WI; NPV, negative predictive value; NA, not applicable.
↵a One-tailed McNemar test.

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Table 3:

Effect of fat saturation on the sensitivity of readers in detecting changes of optic neuritis on FLAIR and CE images before and after postprocessing

Sequence Type	Reader 1		Reader 2
Sequence Type	Fat Saturation+	Fat Saturation–	Fat Saturation+	Fat Saturation–
FL before processing	13/19 (68.4%)	4/11 (36.6%)	12/19 (63.1%)	4/11 (36.4%)
FL after processing	12/19 (63.2%)	5/11 (45.5%)	11/19 (57.9%)	5/11 (45.5%)
CCE before processing	10/17 (58.8%)	1/6 (16.7%)	11/17 (64.7%)	2/6 (33.3%)
CCE after processing	12/17 (70.6%)	1/6 (16.7%)	12/17 (70.6%)	1/6 (16.7%)
ACE before processing	1/6 (16.7%)	5/24 (20.8%)	2/6 (33.3%)	2/24 (8.3%)
ACE after processing	2/6 (33.3%)	7/24 (29.2%)	2/6 (33.3%)	7/24 (29.2%)

Note:—FL indicates FLAIR; CCE, coronal CE-T1WI; ACE, axial CE-T1WI.

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Table 4:

Effect of processing on the CNR of optic nerves relative to ipsilateral normal-appearing white matter in cases with optic neuritis and controls with normal optic nerve function

Sequence Type	Median CNR (25th–75th Percentiles) for Optic Nerves with Optic Neuritis	P Value	Median CNR (25th–75th Percentiles) for Normal Optic Nerves	P Value
FL before processing	−1.05 (−46.7−81.3)	<.001	−12.7 (−86.9−106.9)	.25
FL after processing	54.4 (−46.7−795.6)	<.001	−12.7 (−86.9−137.9)	.25
CCE before processing	9.8 (−181.8−129.2)	<.001	2.6 (−83.2–179.1)	.50
CCE after processing	6.2 (−181.8−238.1)	<.001	−0.37 (−83.2−66.8)	.50
ACE before processing	11.8 (−29.6−267.8)	.03	−14.3 (−63.1−2.5)	.27
ACE after processing	93.9 (−29.6−543.3)	.03	−14.3 (−63.1−2.5)	.27