Study design: A prospective, single-center study comprising 29 female patients who underwent breast reconstruction using Motiva SmoothSilk® (Establishment Labs Alajuela, Costa Rica) implants with RFID-M between 2018 and 2019. Breast MRI was performed two and six months postoperatively at a Breast Imaging Center in São Paulo, Brazil.
Patient population: Twenty-nine patients were submitted to breast reconstruction with SSI (total of 56 implants), as defined by having a breast cancer diagnosis and underwent partial and total mastectomy as surgical treatment. The mean age was 41.5 years (range, 27–53 years). Most patients had clinical stage I breast cancer (51%), followed by stage II (33%) and stage III (16%). In 17/29 patients (58.6%) the mastectomies were unilateral and in 12/29 (41.4%), were bilateral.
Before the MRI, the patients signed an informed procedural consent form explaining the objective of the radiological procedure. The local institutional review board approved the retrospective review of these patients’ clinical records.
Breast Implants and RFID-M Technology: All SmoothSilk implants use the Q inside Safety Technology™, an RFID-M system with a glass-encased device, measuring 2.1 mm x 9 mm (JAMM Technologies, Minneapolis, USA) (Fig. 1). The RFID-M device contains an application-specific integrated circuit (ASIC) with a ferrite core/copper antenna, located on the posterior inner surface of the implant, contained within a sealed biocompatible glass tube.
Data acquisition and imaging protocol: Non-contrast MRI was performed with the patient in a prone position, using a 1.5T MRI unit (Optima MR450w GE Medical Systems, Milwaukee) with a dedicated eight-channel breast coil. The MRI protocol included a sagittal and axial T2-weighted water-suppressed fast spin-echo sequence (matrix size, 288 × 256; slice thickness, 3.0 mm; spacing 0.3 mm), axial T2-weighted water-suppressed inversion recovery sequence (matrix size, 288 × 256; slice thickness, 3.0 mm; spacing 0.3 mm) and sagittal and axial high-resolution 3D T1-weighted fat-suppressed gradient echo sequence (matrix size, 352 x 352; section thickness, 1-2 mm; no gap). Many parameters were variable depending on patient factors and were set to maximize spatial resolution. The field of view was adjusted to adequately cover the breast(s).
Data analysis: The exams were independently reviewed in a dedicated workstation (Advantage workstation GE aw 4.1-4.2) by three breast-imaging radiologists (with at least 10 years of experience), blinded to the patient's clinical data and by consensus. The criteria analyzed included safety; implant integrity; presence, and extension of artifacts; and implant malposition. The presence and extension of artifacts produced by the RFID-M were quantified by their estimated volume, its ratio with the volume implant (Fig. 2) and adjacent structures involvement (breast tissue and skin; thoracic wall - pectoral muscle and ribs, lung and heart).
In order to analyze displacement/rotation of the implant, RFID-M, angles in relation to the implant central portion were measured (0°, <45°, 45-90°, 90-180°) (Fig. 3).
The following points of reference were standardized: MSL (medium sternal line), L and R MBL (left and right medium breast line), L and R EL (left and right elastomer line). In order to identify any changes in the position and symmetry of the implant within the pocket, the following measures were used: D-MBL-MSL (distance between MSL and MBL, right and left), D-ALE and D-AME (distance between the artifact to lateral elastomer and the artifact to medial elastomer) (Fig. 4).
Statistical analysis: Analyses were performed using the JASP computer software (JASP Version 0.10.2, 2019). The collected data were analyzed by descriptive parameters using summary measures as mean, range and standard deviation with their respective 95% CIs. The Student’s T-test was used for sample matching and to calculate statistical significance. P-values below 0.01 were deemed to be statistically significant.