SWI as an Alternative to Contrast-Enhanced Imaging to Detect Acute MS Lesions

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FIG 1.
Signal categories on SWI (right) with the corresponding T2-weighted images (left). The lesions are marked with arrowheads. A, Hypointense ring (complete). B, Hypointense ring (partial). C, Marked hypointensity (dot-shaped). D, Marked hypointensity (irregularly shaped). E, Mild hypointensity. F, Iso-/hyperintensity. In A, B, and E, the central vein sign is also visible.
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FIG 2.
Examples of MS lesions (arrowheads) with different signal patterns on SWI (left) and corresponding contrast-enhanced T1-weighted images (right). A, Hypointense ring. B, Marked hypointensity (dot-shaped). C, Mild hypointensity. D, Iso-/hyperintensity. Lesions in A and B do not show enhancement on postcontrast images, while lesions on C and D show enhancement on postcontrast images.
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FIG 3.
Exceptions to the associations found in our study. Three different MS lesions (arrowheads) are shown (left, SWI; right, contrast-enhanced T1-weighted image). A, Hypointense ring pattern on SWI with enhancement in postcontrast image. B, Marked hypointensity pattern on SWI (irregular dots) with enhancement in postcontrast image. C, Mild hypointensity pattern on SWI without enhancement on postcontrast T1-weighted image.

Table 1:

Distribution of SWI signal characteristics in new MS lesions

SWI Signal	No. (%)	Gd+	Gd−
Hypointense rings	52 (30.8%)	4 (7.7%)	48 (92.3%)
Marked hypointensity	88 (52.1%)	3 (3.4%)	85 (96.6%)
Mild hypointensity	11 (6.5%)	10 (90.9%)	1 (9.1%)
Iso/hyperintensity	18 (10.7%)	18 (100.0%)	0 (0.0%)
Indeterminate	14 (8.3%)	6 (42.9%)	8 (57.1%)

Note:—Gd+ indicates gadolinium-enhancing lesions; Gd–, gadolinium-nonenhancing lesions.

Table 2:

Association of each SWI signal category with the presence or absence of gadolinium enhancement^{^a}

SWI Signal	Sensitivity	Specificity	PPV	NPV	P
Association with Gd–
Hypointense rings	37.5% (29.6%–46.1%)	90.2% (77.5%–96.1%)	92.3% (81.8%–97.0%)	31.6% (23.9%–40.5%)	<.001
Marked hypointensity	66.4% (57.9%–74.0%)	92.7% (80.6%–97.5%)	96.6% (90.5%–98.8%)	46.9% (36.4%–57.7%)	<.001
Hypointense rings or marked hypointensity	93.0% (87.2%–96.3%)	82.9% (68.7%–91.5%)	94.4% (89.0%–97.3%)	79.1% (64.%8–88.6%)	<.001
Association with Gd+
Mild hypointensity	24.4% (13.8%–39.3%)	99.2% (95.7%–99.9%)	90.9% (62.3%–98.4%)	80.4% (73.5–85.8%)	<.001
Iso-/hyperintensity	43.9% (29.9%–59.0%)	100.0% (97.1%–100.0%)	100.0% (82.4%–100.0%)	84.8% (78.2%–89.6%)	<.001
Mild hypointensity or iso-/hyperintensity	68.3% (53.0%–80.4%)	99.2% (95.7%–99.9%)	96.6% (82.8%–99.4%)	90.7% (84.8%–94.5%)	<.001

Note:—PPV indicates positive predictive values; NPV, negative predictive values.
↵a Numbers in parentheses represent 95% confidence intervals. P values are Fisher exact test P values.