Factors influencing MR changes associated with sacral injury after high-intensity focused ultrasound ablation of uterine fibroids

Figures & data

Table 1. Univariate analysis to evaluate the relationship between the sacral injury and the features of fibroids.

Clinical characteristics	Mean ± SD or no of patients (%)		p
	Without injury (211)	With injury (135)
Age	37.86 ± 6.17	39.08 ± 6.04	.072^a
Volume of fibroids (cm^3)	77.37 ± 70.41	93.12 ± 65.81	.038^a
Fibroid ventral side to skin (cm)	5.28 ± 2.06	5.18 ± 2.25	.663^a
Maximum diameter of fibroids (cm)	5.40 ± 1.60	5.83 ± 1.46	.012^a
Fibroid dorsal side to sacrum (cm)	0.77 (0.69, 0.86)	0.74 (0.63, 0.83)	.000^b
Position of uterus			.105^c
Anteverted	102 (29.5%)	56 (16.2%)
Mid position	70 (20.2%)	41 (11.3%)
Retroverted	39 (11.3%)	38 (11.0%)
Location of fibroids			.263^c
Anterior	71 (20.5%)	39 (11.3%)
Fundus	21 (6.1%)	23 (6.6%)
Lateral wall	61 (17.6%)	36 (10.4%)
Posterior wall	58 (16.8%)	38 (10.7%)
Type of fibroids			.002^c
Intramura	111 (32.1%)	61 (17.6%)
Subserosal	45 (13.0%)	16 (4.6%)
Submucosal	30 (8.7%)	23 (6.6%)
Tansmural	25 (7.2%)	35 (10.1%)
T2WI			.479^c
Hypo	78 (22.5%)	41 (11.8%)
Iso	63 (18.2%)	42 (12.1%)
Hetero	35 (10.1%)	22 (6.4%)
Marked	35 (10.1%)	30 (8.7%)
Degree of enhancement			.003^c
Slight	41 (11.9%)	27 (7.8%)
Intermediate	94 (27.2%)	72 (20.8%)
Progressive	76 (22.0%)	36 (10.4%)

SD: standard deviation; T2WI: T2-weighted imaging; MRI T2-weighted imaging: hypo, hypointense; iso, isointense; hetero, heterogeneous; marked, markedly homogeneous hyperintense.

^aFrom the independent sample t test.

^bThe rank sum test.

^cFrom the χ² test.

Table 2. Multivariable binary logistic regression analysis to evaluate the correlation of sacral injury with the significant factors of univariate analysis.

Variables	B	S.E.	Wald	p	ORs [Exp (B)]	95% CI
						Lower	Upper
Constant	0.696	0.522	1.782	.182	2.006
Type of fibroids			12.331	.006
Intramura	–1.001	0.324	9.526	.002	0.368	0.195	0.694
Subserosal	–1.267	0.414	9.383	.002	0.282	0.125	0.634
Submucosal	–0.667	0.404	2.725	.099	0.513	0.233	1.133
Distance from fibroid to sacrum (cm)	–0.466	0.096	23.560	.000	0.628	0.520	0.758
Degree of enhancement	0.409	0.171	5.725	.017	1.505	1.077	2.103

CI: confidence interval; SE: standard error; OR: odd ratio; Wald: statistic value of regression coefficient test.

Table 3. Evaluation of the relationship between sacral injury and treatment parameters according to univariate analysis.

Variables	Without injury (N = 211)	With injury (N = 135)	Statistics	p
TD* (J)	419271.73 ± 3.34534E5	587140.24 ± 3.45960E5	T = –4.493	.000^a
EEF* (J/mm^3)	6.69 ± 5.31	8.55 ± 6.03	T = –3.014	.003^a
NPV (cm^3)	58.71 ± 55.53	64.68 ± 48.85	T = –1.021	.308^a
Treatment efficiency (mm^3/s)	26.22 ± 22.64	30.90 ± 20.86	T = –1.934	.054^a
NPV ratio* (%)	2.70 (1.90, 4.10)	1.90 (1.30, 2.80)	Z = –2.151	.031^b

TD: therapeutic dose; EEF: energy efficiency factor; NPV: non-perfused volume; NPV ratio: the ratio (%) of NPV-to-fibroid volume.

^a From the independent sample t test.

^b From the rank sum test.

*Significantly difference was observed between the two groups, p < .05.

Table 4. corralation of the sacral injury with the significant treatment parameters according to multivariate analysis.

Predictor variables	B	S.E.	Wald	p	ORs [Exp (B)]	95% CI
						Lower	Upper
Constant	–1.393	0.240	33.649	.000	0.248
EEF (J/cm^3)	0.043	0.021	4.009	.045	1.044	1.001	1.088
TD (J)	0.000	0.000	13.844	.000	1.000	1.000	1.000

TD: therapeutic dose; EEF: energy efficiency factor; CI: confidence interval; SE: standard error; OR: odd ratio; Wads: statistic value of regression coefficient test.

Table 5. Summary of postprocedural adverse effects.

SIR classification	Adverse event	Without injury (N = 211)	With injury (N = 135)	p
Class A	Lower abdominal pain	92 (43.6%)	63 (46.7%)	.576
	Sacrum/buttock pain	21 (9.5%)	19 (14.1%)	.242
	Vaginal discharge	5 (2.4%)	1 (0.7%)	.258
	Leg numbness /pain	6 (2.8%)	7 (5.2%)	.264
	Erythema on skin	8 (3.8%)	7 (5.2%)	.535
Class B	Lower abdominal pain	33 (15.6%)	22 (16.3%)	.871
	Sacrum/buttock pain	2 (0.9%)	5 (3.7%)	.076
	Leg numbness /pain	1 (0.5%)	3 (2.2%)	.138
	Erythema on skin	3 (1.4%)	2 (1.5%)	.964
Class C	Skin burns	1 (0.5%)	0	.423
	Leg pain	0	2 (1.5%)	.076
Class D	Sciatic nerve injury	0	2 (1.5%)	.076
Class E&F	–	0	0	–

Figure 1. CE-MRI before and after USgHIFU ablation: (A) sacrum shows normal before treatment; (B) sacrum shows non-perfused upon CE-MRI immediately after treatment.

Figure 2. CE-MRI before and after USgHIFU ablation: (A) the fifth lumbar spine shows normal before treatment; (B) the front edge of the fifth lumbar spine shows non-perfused upon CE-MRI immediately after treatment.