Evaluating the Effects of White Matter Multiple Sclerosis Lesions on the Volume Estimation of 6 Brain Tissue Segmentation Methods

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Fig 1.
T1-weighted images from the 3 hospitals and scanners involved in the study: 1.5T Magnetom Symphony Quantum (Siemens) from H1 (first row), 1.5T Intera (R12) (Philips) from H2 (middle row), and 1.5T Signa HDxt (GE Healthcare) from H3 (last row).
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Fig 2.
Our pipeline approach. From the 30 T1-weighted scans of patients with MS, nonbrain parts are stripped and brain voxels are corrected for intensity inhomogeneities. From the same corrected set (original), a new set is generated by removing WML masks from scans before segmentation (masked). The scans of both sets are segmented into 1 of the 3 tissue classes (GM, WM, and CSF). Lesion voxels are added as WM after segmentation on masked images.
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Fig 3.
Percentage of voxels in WML regions having been classified as GM (top) and WM (bottom) for each segmentation method and hospital, H1 (♢), H2 (□) or H3 (○). Reported values are means and SDs.
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Fig 4.
Classification output returned by each segmentation method on the same image. A, T1-weighted scan. B, Zoomed part of the scan with lesions outlined in red. Brain tissue segmentation outputs also with lesions outlined for ANN (C), FCM (D), FANTASM (E), FAST (F), SPM5 (G), and SPM8 (H). C–H, Segmented GM tissue is represented in gray; WM, in white; and CSF, in black.

Table 1:

Average percentage of change in total tissue volume estimation between original and masked images^{^a}

Method	H1			H2			H3
Method	GM	WM	CSF	GM	WM	CSF	GM	WM	CSF
ANN	0.33 ± 0.42	−0.23 ± 0.28	0.11 ± 0.11	1.59 ± 1.37	−0.56 ± 0.46	0.78 ± 0.76	0.25 ± 0.31	−0.16 ± 0.28	−0.09 ± 0.09
FCM	0.28 ± 0.37	−0.22 ± 0.29	0.09 ± 0.11	2.28 ± 2.26	−0.90 ± 0.83	0.94 ± 0.90	0.28 ± 0.23	−0.25 ± 0.20	0.08 ± 0.09
FANTASM	0.23 ± 0.26	−0.18 ± 0.21	0.08 ± 0.08	1.34 ± 1.13	−0.49 ± 0.37	0.80 ± 0.73	0.26 ± 0.22	−0.24 ± 0.19	0.07 ± 0.08
FAST	0.29 ± 0.36	−0.29 ± 0.36	0.12 ± 0.13	1.92 ± 1.59	−1.28 ± 1.03	0.47 ± 0.39	0.34 ± 0.28	−0.37 ± 0.31	0.12 ± 0.17
SPM5	0.20 ± 0.30	−0.21 ± 0.20	−0.14 ± 0.54	0.10 ± 2.68	−1.04 ± 3.01	0.53 ± 0.51	0.04 ± 0.17	−0.18 ± 0.36	0.15 ± 0.23
SPM8	0.08 ± 0.09	−0.08 ± 0.08	−0.04 ± 0.18	0.55 ± 0.34	−0.93 ± 0.55	0.54 ± 0.42	0.09 ± 0.15	−0.23 ± 0.25	0.17 ± 0.23

↵a The results are divided by tissue and hospital. Reported values are the means ± SD. Positive values indicate a tissue overestimation on original images compared with masked.

Table 2:

Pearson correlation coefficients between method differences in total volume estimation and WML size^{^a}

Method	GM	WM	CSF
H1
ANN	0.94	−0.90	0.89
FCM	0.93	−0.89	0.83
FANTASM	0.87	−0.80	0.78
FAST	0.97	−0.97	0.96
SPM5	0.58^{^b}	−0.89	−0.21^{^b}
SPM8	0.92	−0.63	−0.69
H2
ANN	0.91	−0.88	0.93
FCM	0.92	−0.94	0.92
FANTASM	0.89	−0.87	0.84
FAST	0.95	−0.96	0.82
SPM5	−0.35^{^b}	−0.06^{^b}	0.72
SPM8	0.76	−0.79	0.57^{^b}
H3
ANN	0.56^{^b}	−0.55^{^b}	0.88
FCM	0.77	−0.84	0.88
FANTASM	0.74	−0.82	0.85
FAST	0.88	−0.94	0.92
SPM5	−0.06^{^b}	−0.03^{^b}	0.21^{^b}
SPM8	0.56^{^b}	−0.48^{^b}	0.09^{^b}

↵a Correlation was computed for each method and hospital separately. All values were found to be significant (P value < .05) unless otherwise noted.
↵b Not significant.

Table 3:

Average percentage change in the volume estimation of tissue outside the lesion regions between original and masked scans^{^a}

Method	H1			H2			H3
Method	GM	WM	CSF	GM	WM	CSF	GM	WM	CSF
ANN	0.15 ± 0.26	−0.10 ± 0.18	0.07 ± 0.08	0.70 ± 0.61	−0.31 ± 0.24	0.67 ± 0.69	−0.01 ± 0.28	0.04 ± 0.24	−0.12 ± 0.08
FCM	0.09 ± 0.16	−0.07 ± 0.13	0.05 ± 0.08	1.27 ± 1.69	−0.56 ± 0.62	0.82 ± 0.81	0.01 ± 0.03	−0.03 ± 0.05	0.05 ± 0.07
FANTASM	0.06 ± 0.05	−0.05 ± 0.05	0.03 ± 0.05	0.48 ± 0.48	−0.25 ± 0.18	0.68 ± 0.63	0.00 ± 0.04	−0.02 ± 0.05	0.04 ± 0.07
FAST	0.08 ± 0.14	−0.09 ± 0.14	0.07 ± 0.08	0.56 ± 0.87	−0.45 ± 0.64	0.22 ± 0.33	0.02 ± 0.07	−0.06 ± 0.13	0.08 ± 0.16
SPM5	0.06 ± 0.25	0.02 ± 0.13	−0.19 ± 0.54	−0.29 ± 2.61	−0.47 ± 2.91	0.21 ± 0.32	−0.20 ± 0.24	0.23 ± 0.34	0.06 ± 0.15
SPM8	−0.03 ± 0.06	0.09 ± 0.15	−0.10 ± 0.23	0.13 ± 0.30	−0.29 ± 0.33	0.25 ± 0.26	−0.15 ± 0.12	0.14 ± 0.15	0.10 ± 0.20

↵a The results are divided by hospital and tissue. Reported values are the means ± SD. Positive values indicate a tissue overestimation on original images compared with masked.

Table 4:

Pearson correlation coefficients among method differences in volume estimation of tissue outside the lesion regions and WML size^{^a}

Method	GM	WM	CSF
H1
ANN	0.77	−0.74	0.83
FCM	0.82	−0.80	0.71
FANTASM	0.80	−0.73	0.66
FAST	0.86	−0.93	0.97
SPM5	0.11	0.51^{^b}	−0.30^{^b}
SPM8	−0.57^{^b}	0.95	−0.77
H2
ANN	0.85	−0.92	0.93
FCM	0.71	−0.84	0.94
FANTASM	0.66	−0.82	0.87
FAST	0.33^{^b}	−0.46^{^b}	0.62^{^b}
SPM5	−0.43^{^b}	0.18^{^b}	0.65^{^b}
SPM8	0.16^{^b}	−0.37^{^b}	0.30^{^b}
H3
ANN	0.07	−0.16^{^b}	0.79
FCM	0.50	−0.77	0.89
FANTASM	0.17	−0.57^{^b}	0.87
FAST	0.45	−0.73	0.89
SPM5	−0.78^{^b}	0.72	0.14^{^b}
SPM8	−0.64^{^b}	0.72	−0.01^{^b}

↵a Correlation was computed for each method and hospital separately. All values were found to be significant (P value <.05) unless otherwise noted.
↵b Not significant.