Heating and safety of a new MR-compatible guidewire prototype versus a standard nitinol guidewire

Abstract

Our purpose in this study was to examine heating of nitinol and polyetheretherketone (PEEK) guidewires during near-real-time MR imaging in an artificial vascular model an "aorta phantom". The first 100cm of the nitinol- and PEEK-based guidewires both 145×0.08cm were immersed in a saline-filled aorta phantom. The probes of a fiber-optic thermometer were positioned at the tips of both wires. Balanced steady-state free precession (bSSFP) [TE 1.6ms; TR 3.5ms; flip angle (FA) 60°; field of view (FOV) 40cm; matrix 256×256; specific absorption rate (SAR); 1.15 Watt (W)/kg] and spoiled gradient-echo (SPGR) (TE 1.8ms; TR 60ms; FA 60°; FOV 40cm; matrix 256×256; SAR 1.15W/kg) pulse sequences were acquired in a 1.5-T MR scanner with use of an 8-channel array coil. Temperatures were recorded while the phantom was placed centrally in the bore of a MR scanner and in an off-center position (x=24cm, y=-5cm, z=-10/10cm). The temperature of the nitinol guidewire increased by 0.3°C (center) and 1.1°C (off-center position) with use of the bSSFP and by 9.6 and 13°C (off-center position) with use of the SPGR sequence. Only minor temperature changes up to a maximum of 0.4°C were observed with the MR-compatible PEEK guidewire when any position or sequence was applied. The PEEK guidewire showed substantially lower heating as compared to the nitinol guidewire in near-real-time imaging sequences in a phantom.