Evaluation of a non-metallic dual-port expander for intensity modulated proton therapy.

PURPOSE: To provide a methodology for characterization of the technical properties of a newly developed non-metallic tissue expander for intensity modulated proton therapy. METHODS: Three tissue expanders (AlloX2-Pro: plastic-dual port, AlloX2: metal-dual port, and Dermaspan: metal-single port) were deconstructed, CT-scanned, and modeled in RayStation12A. A 165 MeV single spot was used to create RayStation dose planes, and the integrated depth dose profiles were calculated and the DR90 extracted to predict water equivalent thickness (WET). These predictions were compared to measurements taken with an IBA Giraffe MLIC. Native, water, and fully modelled overrides were compared for the AlloX2 Pro to quantify differences in override choices. Geometric considerations between expanders were compared using a ray-tracing technique to contour the "no-fly" zone around metallic components using a clinical, three beam arrangement. Lastly, a planning and evaluation framework was provided using a single plan as an illustration. RESULTS: The measured AlloX2-Pro WET values were within 0.22 cm of RayStation predictions while metallic values ranged from 0.08 to 0.46 cm. Using natively scanned density values for the AlloX2 Pro improved the discrepancy in WET between predicted and measured from -0.22 to -0.09 cm (drain) and from -0.17 to -0.12 cm (injection). The "no-fly" zone volume of all three beams reduced 95% between the AlloX2-Pro and Dermaspan, which geometrically allowed more uniform coverage behind the port and reduced need for beam modulation. CONCLUSION: The beam perturbation of the AlloX2-Pro is well modeled, but improved agreement with measured WET values was observed when utilizing native densities in calculations. The AlloX2 Pro can support beam arrangements that traverse the ports, which can enable simpler beam geometry and a reduction in dose modulation around the port to promote improved robustness and treatment delivery quality.

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 τb. 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 τb 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.

Technical Note: Clinical modeling and validation of breast tissue expander metallic ports in a commercial treatment planning system for proton therapy.

PURPOSE: To validate breast tissue expander metallic port (MP) models in a commercial treatment planning system (TPS) in proton pencil beam scanning (PBS) treatments for breast cancer patients with breast tissue expanders. METHODS AND MATERIALS: Three types of MPs taken out of a Mentor CPX4, a Natrelle 133, and a PMT Integra breast tissue expanders and a 650 cc saline filled Mentor CPX4 expander were placed on top of acrylic slabs, and scanned using a Siemens Somatom Definition AS Open RT CT scanner. Structure templates for each of the MPs were designed within Eclipse TPS. The CT numbers for the metallic parts were overridden to reflect measured or calculated relative proton stopping powers (RPSPs). Mock targets were contoured in acrylic to represent postmastectomy chest-wall radiation therapy (PMRT) targets. Plans with different beam incident angles were optimized using the Eclipse TPS to deliver uniform prescription dose to the target using Hitachi Probeat-V PBS beams. Eclipse calculated doses and an in-house Monte Carlo (MC) code calculated doses were compared to the measured Gafchromic EBT3 film doses in acrylic. RESULTS: TPS/MC and film dose comparison results showed that (1) 3%/2 mm/10% threshold Gamma pass rates were better than 90.8% in the acrylic target region for all plans; (2) comparing TPS and film doses for the individual beam plans in the MP dose shadow areas, the area with dose difference above 5% ([ΔA] 5%) ranged from 1.1 to 5.0 cm2 , and the maximum dose difference ([ΔD] 0.01 cm2 ) ranged from 12.5% to 25.0%; (3) comparing MC and film doses for the individual beam plans in the MP dose shadow areas, the (ΔA) 5% varied from 1.1 to 2.9 cm2 and (ΔD) 0.01 cm2 varied from 8.5% to 24.2%; (4) for a plan composed of three individual beams treating through the Mentor CPX4 expander, the TPS (ΔA) 5% was less than 0.13 cm2 , and the (ΔD) 0.01 cm2 was less than 6% in the MP dose shadow areas. CONCLUSIONS: It is feasible to treat patients with tissue expanders using multiple PBS beams using a structure template with CT number overridden to represent the measured/calculated RPSP for MPs for PBS treatment planning. MC dose was more accurate than analytical dose in the areas with high dose gradient caused by the density heterogeneity of the breast tissue expander MPs.

Inadvertent Disabling of Implantable Cardiac Defibrillator Antitachycardia Therapies Following Breast Reconstructive Surgery.

A 47-year-old woman with an implantable cardiac defibrillator and breast cancer underwent left breast mastectomy with simultaneous reconstruction using a breast tissue expander. She was found to have intermittent disabling of tachyarrhythmia detection and therapy functions of her implantable cardiac defibrillator that were triggered by the breast tissue expander magnetic port.

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.

Diagnostic value and safety of dynamic MRI of contralateral breast and axilla in subjects with tissue expander.

INTRODUCTION: To verify the diagnostic value of contrast-enhanced breast and axillary MRI in patients with tissue expander labeled as "MR-unsafe" and to confirm its safety. PATIENTS AND METHODS: Breast MRI examinations performed in patients with tissue expander in the period from August 2010 to December 2017 were reviewed after IRB approval. In the case of breast lesion or lymph node, breast MRI exams after definitive prosthetic replacement were used for comparison. Breast MRI was performed using 1.5 T equipment with a dedicated coil. The protocol included axial STIR sequence and axial dynamic sequence with fat suppression (1 pre-contrast and 4 post-contrast phases). Two radiologists experienced in breast imaging reviewed images using six parameters for image quality evaluation. t-Test for dependent samples, Wilcoxon and Sign test were used. RESULTS: Twenty-three patients (49 ±â€¯9 years, range 34-68 years) with tissue expander who underwent contrast-enhanced MRI were reviewed. Thirteen breast lesions (12.92 ±â€¯4.84 mm) and eleven lymph nodes (11.00 ±â€¯4.29 mm) were found. In breast MRI examinations used for comparison no significant difference was observed in breast lesions (12.69 ±â€¯4.71 mm, P = 0.707) or lymph node dimensions (10.58 ±â€¯3.00 mm, P = 0.538). No significant difference was observed in lesion classification. A significantly lower visibility was observed for vascular maps (P < 0.001). None of the patients reported sensations of heating or skin burns. None of the patients revealed any clinical effects or signs of pathology after MRI examination. CONCLUSION: When necessary, after adequate information and preparation, contrast-enhanced breast MRI can be performed in patients with tissue expanders maintaining its diagnostic value and safety.

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.