The value of susceptibility weighted imaging for immediate assessing the hyperacute outcome of MRgFUS ablation for uterine fibroids: a preliminary study

Figures & data

Table 1. Magnetic resonance imaging parameters.

Parameters	SWI	CE T1-weighted
Imaging plane	Axial	Axial
Contrast enhanced	No	Yes
Sequence	SWAN	FSPGR
TR/TE (ms)	78.1/45.0	250.0/1.9
Flip angle (°)	15	90
FOV (cm)	36.0 × 28.8	36.0 × 36.0
Frequency direction	R/L	R/L
Matrix	320 × 320	256 × 128
Section thickness (mm)	5	5
Intersection gap (mm)	0	1
Pixel size (mm^2)	1.1 × 1.1	1.4 × 2.8
Shim	On	On
Fat suppression	None	Fat sat
Acquisition time	2 min 50 s	1 min 6 s

Note: SWI: susceptibility weighted imaging; CE: contrast-enhanced; SWAN: T2-star weighted angiography; FSPGR: fast spoiled gradient recalled; TR: time of repetition; TE: time of echo; FOV: field of view.

Figure 1. The lower relative signal intensity of leiomyomas on SWI after MRgFUS treatment. The left, Middle, and right figures show the CE, SWI imaging, and SWI sketch of the same leiomyoma. (Left) The axial CE imaging shows the ablated necrotic lesion is observed as non-enhancing hypointense zones (star), and surrounding residual leiomyoma appeared as enhancing hyperintense zones (arrow). (Middle) the corresponding axial SWI shows the signal intensity of the ablated necrotic lesion (star) is lower than the surrounding residual leiomyoma (arrow). (Right) the sketch map illustrates the extent of the ablated lesion (black area) and residual leiomyoma (white area).

Figure 2. The similar relative signal intensity of leiomyomas on SWI after MRgFUS treatment. The left, Middle, and right figures show the CE, SWI imaging, and SWI sketch of the same leiomyoma. (Left) The axial CE imaging shows that the ablated necrotic lesion is observed as non-enhancing hypointense zones (star), and surrounding residual leiomyoma appeared to be an enhancing hyperintense zone (arrow). (Middle) The corresponding axial SWI shows that the ablated necrotic lesion (star) signal intensity is similar to residual leiomyoma (arrow). (Right) The sketch map illustrates the extent of the ablated lesion (black area) and residual leiomyoma (white area).

Figure 3. The complete hypointense peripheral rim on SWI. The left, Middle, and right figures are the CE, SWI imaging, and SWI sketch of the same leiomyoma. (Left) The axial CE imaging shows the range of ablated necrotic lesions, which appear as a non-enhancing hypointense zone (star). (Middle) The corresponding axial SWI shows a complete hypointense peripheral rim (arrow). (Right) The sketch map illustrates the range of the hypointense peripheral rim (black line); it involves ≥90% of the circumference of the ablated zone.

Figure 4. The partial hypointense peripheral rim on SWI. The left, Middle, and right figures are the CE, SWI imaging, and SWI sketch of the same leiomyoma. (Left) The axial CE imaging shows the range of ablated necrotic lesions, which appear as a non-enhancing hypointense zone (star). (Middle) the corresponding axial SWI shows a partial hypointense peripheral rim (arrow). (Right) The sketch map illustrates the range of the hypointense peripheral rim (black line); it involves 50%–90% of the circumference of the ablated zone.

Figure 5. The partial hypointense peripheral rim on SWI. The left, middle, and right figures are the CE, SWI imaging, and SWI sketch of the same leiomyoma. (Left) The axial CE imaging shows the range of ablated necrotic lesions, which appear as a non-enhancing hypointense zone (star). (Middle) the corresponding axial SWI shows an absent hypointense peripheral rim (arrow). (Right) the sketch map illustrates the range of the hypointense peripheral rim (black line); it is non-continuous and involves less than 50% of the circumference of the ablated zone.

Table 2. SWI characteristics of lesions after MRgFUS ablation.

Characteristic	Reader 1 (n = 27)	Reader 2 (n = 27)	ICC value	P value
Relative signal intensity			0.613	<.001
Lower	17 (63.0)	16 (59.3)
Similar	10 (37.0)	11 (40.7)
Hypointense peripheral rim			0.843	<.001
Complete	15 (55.6)	14 (51.9)
Partial	6 (22.2)	6 (22.2)
Absent	6 (22.2)	7 (25.9)

Note: Data are n(%). SWI: susceptibility weighted imaging; MRgFUS: magnetic resonance-guided focused ultrasound; ICC: intraclass correlation coefficient.

Table 3. Relationship between characteristic of SWI and NPV ratio groups.

Characteristic of SWI	NPV ratio ≥ 90% (n = 14)	NPV ratio < 90% (n = 13)	P value*
Relative signal intensity
Reader 1
Lower	8 (57.1)	9 (69.2)	.695
Similar	6 (42.9)	4 (30.8)
Reader 2
Lower	8 (57.1)	8 (61.5)	1.00
Similar	6 (42.9)	5 (38.5)
Hypointense peripheral rim
Reader 1
Complete	12 (85.7)	3 (23.1)	.002
Partial	1 (7.1)	5 (38.5)
Absent	1 (7.1)	5 (38.5)
Reader 2
Complete	11 (78.6)	3 (23.1)	.016
Partial	2 (14.3)	4 (30.8)
Absent	1 (7.1)	6 (46.2)

Note: Data are n(%). SWI: susceptibility weighted imaging; NPV: non-perfused volume.

*Fisher’s exact test.

Table 4. Diagnostic value of a hypointense peripheral rim to NPV ratio ≥ 90% (n = 27).

	Cutoff value 1*		Cutoff value 2**
	Reader 1	Reader 2	Reader 1	Reader 2
Sensitivity (%)	85.7	78.6	92.9	92.9
Specificity (%)	76.9	76.9	38.5	46.2
Accuracy (%)	81.5	77.8	66.7	70.4
Positive predictive value (%)	80.0	78.6	61.9	65.0
Negative predictive value (%)	83.3	76.9	83.3	85.7
Positive likelihood ratio	3.7	3.4	1.5	1.7
Negative likelihood ratio	0.19	0.28	0.19	0.15

Note: NPV: non-perfused volume. *Complete hypointense peripheral rim. **Complete or partial hypointense peripheral rim.

Data availability statement

Patient data cannot be publicly shared because of the national legislature on patient data. But the data used to support the findings of this study are available from the corresponding author upon request.