Protocol for testing suitability of compact US imaging systems for use inside MRI suites, and application to one commercial US system

This note presents a testing protocol developed to assess the suitability of a compact ultrasound (US) system for potential use inside a 1.5 T interventional magnetic resonance imaging (MRI) suite. Test results for specific commercial US and MRI systems in a particular clinical use case are also presented. The protocol consisted of safety testing and evaluations ofimage quality of both MRI and US systems at the proposed clinical use configuration. Safety tests included magnetic field measurements inside MRI suite, handheld magnet assessments of magnetic properties of the US system, and magnetic displacement force measurements. The safety tests were followedby direct assessments of USsystem components inside MRI suite. Each USsystem component was demonstratedto haveno risk of displacement at the proposed locations with a large safety margin. No clinically relevant difference in US image quality was observed comparedtoimages acquired outside MRI suite. While MR image quality met the American College of Radiology standards for clinical scanning, increases in noise levels and radi of requency (RF) interference associated with the presence of US scanner in MRI suite were observed. The 'sleep mode' operating condition of the USsystem resulting in consistent absence of RF interference and minimal noise increase was identified and proposed for use during MRI scanning. Our results demonstrate the utility of our testing methods, and the suitability of this particular compact USsystem for safe useinour site-specific configuration inside the 1.5 TMRI suite. These results would be dependent onthe specific test systems.