Background and Purpose

Magnetic resonance elastography (MRE) is a new technique for assessing tissue stiffness. MRE has been established as a noninvasive diagnostic tool for the assessment of hepatic fibrosis, and applied for other organs. However, there are only a few reports of MRE for uterine fibroids (1). The purpose of this study is to evaluate the feasibility of MRE for uterine fibroids and the effect of imaging sequences (i.e., spin-echo echo-planar imaging [SE-EPI] and gradient-echo [GRE]) on stiffness measurements.

Methods

This retrospective study was approved by the institutional review board; the requirement for informed patient consent was waived. Twenty-two patients (mean age, 45.4 years (38-52 years)) with 23 fibroids were enrolled. The mean size of the fibroids was 90.1 ± 23.1 mm. Location of the fibroids was intramural (n = 19), submucosal (n = 3), or subserosal (n = 1). All patients underwent MRE examinations with a 1.5-T MR system via two methods (SE-EPI and GRE) using a pneumatic vibrator which was placed on the lower abdominal wall and fixed with an elastic band. All MRE were performed in two cross-sectional planes (i.e., axial and sagittal). A two-dimensional postprocessing method was used for GRE-MRE, while a three-dimensional postprocessing method was used for SE-EPI-MRE. Table 1 summarizes the MR sequence parameters. Two radiologists measured the stiffness of fibroids. We manually placed as large a region of interest as possible to exclude crosshatching of areas inadequate for measurement on the stiffness map. Central slices were selected for SE-EPI-MRE. Interobserver agreement was assessed by intraclass correlation coefficients (ICC).

Results

The mean stiffness values of the fibroids were as follows: GREaxial, 4.43 ± 1.48 kPa; GREsagittal, 4.32 ± 1.78 kPa; SE-EPIaxial, 5.44 ± 2.10 kPa; and SE-EPIsagittal, 5.58 ± 2.33 kPa (Figure 1). The mean stiffness values of the fibroids measured by SE-EPIaxial were significantly higher than those measured by GREaxial (P = 0.0018) and GREsagittal (P = 0.0012). The mean stiffness values of the fibroids measured by SE-EPIsagittal were significantly higher than those measured by GREaxial (P = 0.0138) and GREsagittal (P < 0.0001). There were no significant differences between GREaxial and GREsagittal (P = 1.0000) or SE-EPIaxial and SE-EPIsagittal (P = 1.0000). The ICC between the 2 observers was excellent for all methods (ρ = 0.903-0.981, Figure 2). Figure 3 presents representative clinical case.

Discussion

We demonstrated that stiffness values measured by SE-EPI-MRE were significantly higher than those measured by GRE-MRE. In liver MRE, signal-to-noise ratio of SE-EPI-MRE is higher than that of GRE-MRE (2). This might have led to the difference between the stiffness of uterine fibroids.

Conclusion

SE-EPI-MRE showed lower fibroid stiffness values than GRE-MRE. Each MRE method is a valid and reliable technique for measuring the stiffness of uterine fibroids.

Acknowledgements

No acknowledgement found.