Ferromagnetic Metal Side-Rails on Air-Hover HDR Patient Transport Table Can Cause Severe Skin Burns to Patients During MR Simulation for Brachytherapy

Abstract

The air-hover system (Zephyr®, Diacor Inc) used for high-dose-rate brachytherapy (HDR BT) is designed for patient transfer between the HDR procedure suite and CT or MR simulation room. A recent case illustrated that the MR-conditional, ferromagnetic metal side-rails of the Zephyr system caused severe skin burns during our 3 Tesla MR simulation scan. Proposed solutions are presented to avoid potential patient skin burns when using a device with ferromagnetic metal side-rails or other components even if MR conditional. Institutional MR-guided, HDR BT program for cervical cancer consists of titanium Fletcher-Suit-Delclos tandem-and-ovoids (Varian Medical System, Inc.) implants under ultrasound guidance. Orthogonal X-rays before 3D simulation images and an AP X-ray after simulation scan were performed to validate applicator displacements during patient transfer between HDR and 3D image scan rooms. Our institutional MR scanning protocol for HDR BT includes 3D isotropically reconstructed T2- and T1-weighted MR, along with 2D sagittal T2-weighted MR (IJROBP 80;3:947-955;2011). The Zephyr system was implemented in August, 2014 after two cases of staff injury following patient transfer involving obese patients. A Zephyr arm support system was implemented in October, 2016 to facilitate intravenous access by anesthesiology staff. The Zephyr arm support system consists of two arm supports and two ferromagnetic metal side-rails. The ferromagnetic metal of these side-rails is a stainless steel alloy. In-house velcro straps are used to secure the arms and legs during transfer when using the Zephyr system. After 65 uneventful patient simulation scans a severe skin burn occurred on one patient’s arm which was in contact with the metal side rail during the 3T MR simulation scan (25 - 30 minutes duration) performed under anesthesia. The skin burn was initially identified as a third-degree burn by our institutional burn unit wound assessment team. This skin burn case was reported to institutional patient-safety-network (PSN). The vendor was immediately notified. A multi-disciplinary team of radiation therapists, MR-certified therapists, nurses, physicians, anesthesia team and medical physicists was created to evaluate and improve the clinical workflow and Zephyr system. New glass-fiber embedded polycarbonate side-rails were developed and built that should mitigate any risk of inductive heating. The glass-fiber embedded polycarbonate has tensile strength of 16,000 psi, along with impact strength of 2.06 f.-lbs per inch which meet the specifications of American Society for Testing Materials (ASTM: D3935 and D6098). Glass-fiber embedded polycarbonate side-rails that are MR-safe were developed and installed on an air-hover based HDR patient transfer system. This should eliminate the root cause of potential skin burns associated with ferromagnetic MR-compatible side rails in patients receiving MR scans for MRI-guided HDR brachytherapy.