MRI-Conditional Breast Tissue Expander: First In-Human Multi-Case Assessment of MRI-Related Complications and Image Quality

Abstract

This study aims to assess potential complications and effects on the magnetic resonance imaging (MRI) image quality of a new MRI-conditional breast tissue expander (Motiva Flora^®) in its first in-human multi-case application. Twenty-four patients with 36 expanders underwent non-contrast breast MRI with T1-weighted, T2-weighted, and diffusion-weighted imaging (DWI) sequences on a 3 T unit before breast tissue expander exchange surgery, being monitored during and after MRI for potential complications. Three board-certified breast radiologists blindly and independently reviewed image quality using a four-level scale ("poor", "sufficient", "good", and "excellent"), with inter-reader reliability being assessed with Kendall's τ_b. The maximum diameters of RFID-related artifacts on T1-weighted and DWI sequences were compared with the Wilcoxon signed-rank test. All 24 examinations were completed without patient-related or device-related complications. The T1-weighted and T2-weighted sequences of all the examinations had "excellent" image quality and a median 11 mm (IQR 9-12 mm) RFID artifact maximum diameter, significantly lower (p < 0.001) than on the DWI images (median 32.5 mm, IQR 28.5-34.5 mm). DWI quality was rated at least "good" in 63% of the examinations, with strong inter-reader reliability (Kendall's τ_b 0.837, 95% CI 0.687-0.952). This first in-human study confirms the MRI-conditional profile of this new expander, which does not affect the image quality of T1-weighted and T2-weighted sequences and moderately affects DWI quality.

Keywords: MRI safety; MRI-conditional; artifacts; breast reconstruction; breast tissue expander; diffusion-weighted imaging; image quality; magnetic resonance imaging; mastectomy.

Figure 1

T1-weighted (panels (a,b)) and T2-weighted (panels (c,d)) MRI images of a patient that underwent a skin sparing mastectomy of the right breast with pre-pectoral implantation of the MRI-conditional breast tissue expander. (Panels (a,c)) show preoperative MRI images, while (panels (b,d)) show MRI images acquired prior to planned exchange surgery to definitive implant, with no negative effects on image quality caused by the presence of the tissue expander and its non-metallic port.

Figure 2

DWI images (b value 1000 s/mm²) of four patients showing different levels of overall image quality degradation caused by the presence of unilateral breast tissue expander, as rated by both readers. (a) “Poor” image quality”; (b) “Sufficient” image quality; (c) “Good” image quality; (d) “Excellent” image quality. Of note, in panels (a,b), the high field inhomogeneity makes the expander signal appear particularly hyperintense.

Figure 3

Fluctuation plots of Reader 1 and Reader 2 ratings of DWI image quality (Kendall’s τ_b 0.837, 95% CI 0.687–0.952) and fat suppression in DWI images (Kendall’s τ_b 0.577, 95% CI 0.295–0.852).

Figure 4

Fluctuation plot of Reader 1 and Reader 2 assessments of ghosting artifacts (Kendall’s τ_b 0.513, 95% CI 0.177–0.748).

Figure 5

(a) T1-weighted Dixon in-phase image of a patient that underwent bilateral nipple sparing mastectomy and pre-pectoral implantation of MRI-conditional breast tissue expanders, showing two intact expanders in place. (b) MRI examination showing partial deflation of the right tissue expander after iatrogenic rupture. Even after substantial deflation of the tissue expander, the RFID-related artifact of the expander port does not impair the visualization of surrounding breast tissue, skin, and chest wall structures.