Three-Dimensional Quantitative Assessment of Uterine Fibroid Response after Uterine Artery Embolization Using Contrast-Enhanced MR Imaging

Abstract

Purpose: To evaluate the clinical feasibility and diagnostic accuracy of three-dimensional (3D) quantitative magnetic resonance (MR) imaging for the assessment of total lesion volume (TLV) and enhancing lesion volume (ELV) before and after uterine artery embolization (UAE).

Materials and methods: This retrospective study included 25 patients with uterine fibroids who underwent UAE and received contrast-enhanced MR imaging before and after the procedure. TLV was calculated using a semiautomated 3D segmentation of the dominant lesion on contrast-enhanced MR imaging, and ELV was defined as voxels within TLV where the enhancement exceeded the value of a region of interest placed in hypoenhancing soft tissue (left psoas muscle). ELV was expressed in relative (% of TLV) and absolute (in cm(3)) metrics. Results were compared with manual measurements and correlated with symptomatic outcome using a linear regression model.

Results: Although 3D quantitative measurements of TLV demonstrated a strong correlation with the manual technique (R(2) = 0.93), measurements of ELV after UAE showed significant disagreement between techniques (R(2) = 0.72; residual standard error, 15.8). Six patients (24%) remained symptomatic and were classified as nonresponders. When stratified according to response, no difference in % ELV between responders and nonresponders was observed. When assessed using cm(3) ELV, responders showed a significantly lower mean ELV compared with nonresponders (4.1 cm(3) [range, 0.3-19.8 cm(3)] vs 77 cm(3) [range, 11.91-296 cm(3)]; P < .01).

Conclusions: The use of segmentation-based 3D quantification of lesion enhancement is feasible and diagnostically accurate and could be considered as an MR imaging response marker for clinical outcome after UAE.

Figure 1

Software-assisted 3D quantification technique. (a) Representative contrast-enhanced MR imaging scan performed before the procedure. Arrow points to dominant fibroid lesion. (b) Semiautomated tumor segmentation, which includes the entire lesion on the scan performed before the procedure. Arrow indicates the rim of the segmented lesion. (c) Volume rendering for the segmented lesion in a maximum intensity projection on the scan performed before the procedure. Arrow indicates the lesion (in red). (d) Color map of the same lesion before UAE; the color coding varies from red representing maximum enhancement to blue representing no enhancement. Arrow indicates the ROI within the left psoas muscle, which was used as a reference. (e, f) Contrast-enhanced follow-up MR imaging scans from the same patient after UAE, with and without the color map overlay. Arrow in (e) indicates the centrally necrotic uterine fibroid. Arrow in (f) indicates the ROI, consistently placed within the left psoas muscle.

Figure 2

Quantification of fibroid volume. (a, b) Correlation between the semiautomatic assessment and manual measurements for baseline and follow-up MR imaging scans. (c) Overall effects of uterine fibroid embolization (UFE) on lesion volume, assessed using the software-assisted technique. (d) Stratification of volumetry values between responders and nonresponders on follow-up imaging. (Available in color online at www.jvir.org.)

Figure 3

Visual versus semiautomated quantification of fibroid enhancement. (a) The graph illustrates the correlation between visual and software-assisted measurements of fibroid enhancement on follow-up MR imaging. (b) The graph demonstrates the residuals resulting from the correlation under (a). UFE = uterine fibroid embolization. (Available in color online at www.jvir.org.)

Figure 4

Software-assisted quantification of fibroid enhancement. (a, b) Comparison of fibroid enhancement measured on contrast-enhanced baseline and follow-up MR imaging. (c, d) Stratification of the same values on follow-up imaging according to clinical patient response. The quantification using absolute units (cm³) shows significant differences between the groups. When assessed according to percentage of TLV, no significant difference between the groups is apparent.