In vitro assessment of MRI issues at 3-Tesla for a breast tissue expander with a remote port

Exploring the role of CT scouts in expediting MRI in acute stroke

PURPOSE

For acute stroke patients requiring MR examination and unable to provide a reliable history, screening for potentially MRI-incompatible objects (PMIOs) typically necessitates the use of plain-film radiographs (PFRs). However, using a whole body CT scout at the time of non-contrast head CT scans can preclude critical delays. Here, we aim to compare the effectiveness of PFRs and CT scouts in detecting PMIOs.

METHODS

A case-control study was conducted at a tertiary care institution, involving 408 imaging studies from 200 patients, half of which contained PMIOs. The diagnostic performances of CT scouts and PFRs were evaluated by six blinded readers, including two board-certified neuroradiologists, one neuroradiology fellow, and three radiology residents.

RESULTS

2448 interpretations from the 6 readers were analyzed. The diagnostic performance of combined CT scout images (full-body and regional) was not significantly different from that of PFRs for all six readers (p = 0.06). However, PFRs outperformed full-body CT scouts in PMIO detection (p = 0.01), with no significant differences observed between PFRs and regional CT scouts (p = 0.4). Notably, the diagnostic accuracy of the radiology residents was found to be equivalent to radiologists across all imaging techniques.

CONCLUSION

Integrating CT scouts in acute stroke protocols may help expedite MRI screening. The scouts should include the head, neck, chest, upper arms, abdomen, pelvis, and thighs. Including radiology residents in the screening process for PMIOs may be an avenue for resource optimization in acute care settings.

Benefits of Using Magnetic Resonance Imaging During Breast Tissue Expansion: Literature Review and Case Series

Breast cancer results in up to 1.6 million new candidates for yearly breast reconstruction (BR) surgery. Two-stage breast reconstruction surgery with the use of a tissue expander (TE) is a common approach to reconstructing the breast after mastectomy. However, a common disadvantage encountered with the traditional breast TE is the magnetic injection port, which has been reported to cause injuries in patients undergoing magnetic resonance (MR) imaging. Therefore this type of breast TE is labeled "MR unsafe." Recent technological advances have incorporated radio-frequency identification (RFID) technology in the TE to allow for the location of the injection port without magnetic components, resulting in an MR-conditional TE. This paper aims to review the information regarding the safety profile of TEs with magnetic ports and to gather distinct clinical scenarios in which an MR-conditional TE benefits the patient during the BR process. A literature review ranging from 2018 to 2022 was performed with the search terms: "tissue expander" OR "breast tissue expander" AND "magnetic resonance imaging" OR "MRI." Additionally, a case series was collected from each of the authors' practices. The literature search yielded 13 recent peer-reviewed papers, and 6 distinct clinical scenarios were compiled and discussed. Most clinicians find MRI examinations to be the state-of-art diagnostic imaging modality. However, due to the preexisting risks associated with TEs with magnetic ports, the MRI labeling classification should be considered when deciding which TE is the most appropriate for the patient requiring MRI examinations.

LEVEL OF EVIDENCE: 4

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

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.

Reconsidering the "MR Unsafe" breast tissue expander with magnetic infusion port: A case report and literature review

Breast tissue expanders (TEs) with magnetic infusion ports are labeled “MR Unsafe.” Therefore, patients with these implants are typically prevented from undergoing magnetic resonance imaging (MRI). We report a patient with a total submuscular breast TE who inadvertently underwent an MRI exam. She subsequently developed expander exposure, requiring explantation and autologous reconstruction. The safety profile of TEs with magnetic ports and the use of MRI in patients with these implants is surprisingly controversial. Therefore, we present our case report, a systematic literature review, and propose procedural guidelines to help ensure the safety of patients with TEs with magnetic ports that need to undergo MRI exams.

MRA of the skin: mapping for advanced breast reconstructive surgery

Autologous breast reconstruction using muscle-sparing free flaps are becoming increasingly popular, although microvascular free flap reconstruction has been utilised for autologous breast reconstructions for >20 years. This innovative microsurgical technique involves meticulous dissection of artery-vein bundle (perforators) responsible for perfusion of the subcutaneous fat and skin of the flap; however, due to unpredictable anatomical variations, preoperative imaging of the donor site to select appropriate perforators has become routine. Preoperative imaging also reduces operating time and enhances the surgeon's confidence in choosing the appropriate donor site for harvesting flaps. Although computed tomography angiography has been widely used for preoperative imaging, concerns over excessive exposure to ionising radiation and poor iodinated contrast agent enhancement of the intramuscular perforator course has made magnetic resonance angiography, the first choice imaging modality in our centre. Magnetic resonance angiography with specific post-processing of the images has established itself as a reliable method for mapping tiny perforator vessels. Multiple donor sites can be imaged in a single setting without concern for ionising radiation exposure. This provides anatomical information of more reconstruction donor site options, so that a surgeon can design a flap of tissue centralised around the best perforator, as well as a back-up perforator, and even a back-up flap option located on a different region of the body. This information is especially helpful in patients with a history of scar tissue from previous surgeries, where the primary choice perforator is found to be damaged or unsuitable intraoperatively. In addition, chest magnetic resonance angiography evaluates recipient site blood vessel suitability including vessel diameters, course, and branching patterns. In this article we provide a broad overview of various skin flaps, clinical indications, advantages and disadvantages of each of these flaps, basic imaging technique, along with advanced sequences for visualising tiny arteries in the groin and in the chest. Post-processing techniques, structure of the report and how automation of the reporting system improves workflow is described. We also describe applications of magnetic resonance angiography in postoperative imaging.

Effect of MRI on breast tissue expanders and recommendations for safe use

INTRODUCTION

Ferromagnetic port-containing breast tissue expanders are currently labeled MRI-unsafe because of the presumption that magnets should not enter the machine. However, designating these devices as MRI-unsafe can lead to unnecessary procedures or suboptimal imaging choices. This study provides an ex vivo analysis of how breast tissue expanders behave when subjected to strong magnetic fields to determine which variables might affect clinical risk.

METHODS

Three different brands of tissue expanders were evaluated in three MRI environments. Translational force was determined using the deflection angle method. Torque on empty, saline-filled, and air-filled expanders was evaluated on a 0-4 scale. Magnetic field was measured using a gaussmeter. The weight required to prevent displacement of the expanders was determined for both air- and saline-filled expanders. Temperature over time was measured using an alcohol thermometer.

RESULTS

Magnetic field strength, deflection angle, and torque were the greatest in 3T MRI environments and varied by device manufacturer (Sientra > Mentor > Allergan). Saline-filled expanders required 240 mL and air-filled required 360 mL volume to make the torque undetectable, and the effect of torque could be mitigated with prone positioning. A weight of 120 g was required to prevent displacement of a saline-filled tissue expander and 870 g for an empty expander. There were no appreciable changes in temperature.

CONCLUSIONS

Previously described risks may be reduced by using a 1.5T MRI, device selection, filling expanders with saline, and prone positioning. MRI can be considered in patients with breast tissue expanders when appropriate peri-procedural choices have been made so that the benefits of undergoing MRI outweigh the risks.

Breast Tissue Expanders with Magnetic Ports: Clinical Experience at 1.5 T

BACKGROUND

The purpose of this study was to evaluate breast tissue expanders with magnetic ports for safety in patients undergoing abdominal/pelvic magnetic resonance angiography before autologous breast reconstruction.

METHODS

Magnetic resonance angiography of the abdomen and pelvis at 1.5 T was performed in 71 patients in prone position with tissue expanders with magnetic ports labeled "MR Unsafe" from July of 2012 to May of 2014. Patients were monitored during magnetic resonance angiography for tissue expander-related symptoms, and the chest wall tissue adjacent to the tissue expander was examined for injury at the time of tissue expander removal for breast reconstruction. Retrospective review of these patients' clinical records was performed. T2-weighted fast spin echo, steady-state free precession and gadolinium-enhanced spoiled gradient echo sequences were assessed for image artifacts.

RESULTS

No patient had tissue expander or magnetic port migration during the magnetic resonance examination and none reported pain during scanning. On tissue expander removal (71 patients, 112 implants), the surgeons reported no evidence of tissue damage, and there were no operative complications at those sites of breast reconstruction.

CONCLUSION

Magnetic resonance angiography of the abdomen and pelvis in patients with certain breast tissue expanders containing magnetic ports can be performed safely at 1.5 T for pre-autologous flap breast reconstruction perforator vessel mapping.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.