Adjustable breast tissue expanders and mammary implants are utilized for breast reconstruction following mastectomy, for the correction of breast and chest-wall deformities and underdevelopment, for tissue defect procedures, and for cosmetic augmentation. These devices are typically equipped with either an integral injection site or a remote injection dome that is utilized to accept a needle for placement of saline for expansion of the prosthesis intra-operatively and/or postoperatively.
There are many different types of breast tissue expanders. For example, the Becker and the Siltex prostheses provide a choice of a standard injection dome or a micro-injection dome. The Radovan expander is indicated for temporary implantation only. The injection port for this device contains 316L stainless steel to guard against piercing the injection port by the needle used to fill the implant. In this case, 316L stainless steel does not pose a serious hazard for a patient undergoing MRI.
Notably, there are various breast tissue expanders that have magnetic ports to allow for a more accurate detection of the injection site. These devices are substantially attracted to the static magnetic fields of MR systems and, therefore, may be uncomfortable, injurious, or contraindicated for patients undergoing MR procedures. One such device is the Contour Profile Tissue Expander (Mentor, Santa Barbara, CA), which contains a magnetic injection dome and is considered to be unsafe (i.e., MR Unsafe) for an MR examination.
Breast tissue expanders with magnetic ports produce relatively large artifacts on MR images and, therefore, assessment of the breast using MRI is problematic. Various manufacturers make these particular implants.
Importantly, there may be a situation during which a patient is referred for MR imaging for the determination of breast cancer or a breast implant rupture, such that the presence of the metallic artifact could obscure the precise location of the abnormality. In view of this possibility, it is recommended that a patient with a breast tissue expander that has a metallic component be identified prior to MRI so that the radiologist is aware of the potential problems related to the generation of artifacts as well as a possible injury
McGhan Medical Breast Tissue Expanders and MRI Issues. McGhan Medical Breast Tissue Expanders are intended for temporary subcutaneous implantation to develop surgical flaps and additional tissue coverage (Product Information documents, McGhan Medical/INAMED Aesthetics; Allergan, Inc.). These breast tissue expanders are constructed from silicone elastomer and consist of an expansion envelope with a textured surface, and a MAGNA-SITE integrated injection site. The expanders are available in a wide range of styles and sizes to meet diverse surgical needs. Specific styles include: Style 133 FV with MAGNA-SITE injection site, Style 133 LV with MAGNA-SITE injection site, Style 133 MV with MAGNA-SITE injection site, and Style 133 V with MAGNA-SITE injection site.
The MAGNA-SITE injection site and MAGNA-FINDER external locating device contain rare-earth, permanent magnets for an accurate injection system. When the MAGNA-FINDER is passed over the surface of the tissue being expanded, its rare-earth, permanent magnet indicates the location of the MAGNA-SITE injection site.
The Product Information documents for these breast tissue expanders states: “DO NOT use MAGNA-SITE expanders in patients who already have implanted devices that would be affected by a magnetic field (e.g., pacemakers, drug infusion devices, artificial sensing devices). DO NOT perform diagnostic testing with Magnetic Resonance Imaging (MRI) in patients with MAGNA-SITE expanders in place.”
Furthermore, in the Warnings section of the Product Information document, the following is indicated: “Diagnostic testing with Magnetic Resonance Imaging (MRI) is contraindicated in patients with MAGNA-SITE expanders in place. The MRI equipment could cause movement of the MAGNA-SITE breast tissue expander, and result in not only patient discomfort, but also expander displacement, requiring revision surgery. In addition, the MAGNA-SITE magnet could interfere with MRI detection capabilities.”
Therefore, MR procedures are deemed unsafe for patients with these specific breast tissue expanders.
Zegzula and Lee (2001) presented a case of bilateral tissue expander infusion port dislodgment associated with an MRI examination. The report involved a 56-year-old woman that underwent bilateral mastectomy and immediate reconstruction with McGhan BIOSPAN tissue expanders. As noted, these implants contain the “MAGNA-SITE” components. Several weeks postoperatively the patient underwent MR imaging of her spine. Subsequently, the infusion ports could not be located with the finder magnet (used to re-fill the tissue expander). A chest radiograph was obtained that demonstrated bilateral dislodgment of the infusion ports. Surgical removal and replacement of the tissue expanders were required. This incident emphasizes that all patients undergoing tissue expansion with implants that contain magnetic ports should be thoroughly warned about the potential hazards of MRI and managed appropriately.
In another incident involving a tissue expander, Duffy and May (1995) reported a case of a woman who developed a burning sensation at the site of the tissue expander during an MR procedure. The sensation resolved rapidly once the scan was discontinued. The implications of the symptoms in this case are unclear. Nevertheless, a patient with a tissue expander that requires an MR procedure should be alerted to the possibility of localized symptoms in the region of the implant during scanning.
Breast Tissue Expander with Remote Port. A recent investigation performed by Linnemeyer H, et al. (2014) evaluated MRI issues (i.e., magnetic field interactions, heating, and artifacts) at 3-Tesla for a breast tissue expander with a remote port. The breast tissue expander, Integra Breast Tissue Expander, (Model 3612-06 with Standard Remote Port, PMT Corporation, Chanhassen, MN) underwent evaluations for magnetic field interactions (translational attraction and torque), MRI-related heating, and artifacts using standardized techniques. The findings indicated that a patient with this breast tissue expander with a remote port may safely undergo MRI at 3-Tesla or less under the conditions used for this investigation.
Importantly, the findings reported by Linnemeyer H, et al. (2014) are highly specific to the particular tissue expander with remote port that underwent testing and the MR conditions that were used for the evaluation. Other similar products exist from various manufacturers but it is unknown how these devices respond relative to the use of MRI.
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Product Information, Style 133 Family of Breast Tissue Expanders with Magna-Site Injection Sites, McGhan Medical/INAMED Aesthetics, Santa Barbara, CA.
Product Information, Directions for Use, Style 133V Series Tissue Expander Matrix, With Magna-Site Injection Sites, Allergan, Inc.
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