Truly hybrid x-ray/MR imaging: Toward a streamlined clinical system

Rationale and Objective. We have installed an improved x-ray/MR (XMR) truly hybrid system with higher imaging signal-to-noise ratio (SNR) and versatility than our first prototype. In our XMR design, a fixed anode x-ray fluoroscopy system is positioned between the two donut-shaped magnetic poles of a 0.5T GE Signa-SP magnet (SP-XMR). This paper describes the methods for increased compatibility between the upgraded x-ray and MR systems that have helped improve patient management. Materials and Methods. A GE OEC 9800 system (GE OEC Salt Lake, City" UT) was specially reconfigured for permitting x-ray fluoroscopy inside the interventional magnet. A higher power x-ray tube, a new permanent tube mounting system, automatic exposure control (AEC), remote controlled collimators, choice of multiple frame rates, DICOM image compatibility, magnetically shimmed x-ray detector, x-ray compatible MR coil, and better RF shielding are the highlights of the new system. A total of 23 clinical procedures have been conducted with SP-XMR guidance of which five were performed using the new system. Results. The 70% increased power for fluoroscopy, and a new 6 times higher power single frame imaging mode, has improved imaging capability. The choice of multiple imaging frame rates, AEC, and collimator control allow reduction in x-ray exposure to the patient. The DICOM formatting has permitted easy transfer of clinical images over the hospital PACS network. The increased MR compatibility of the detector and the x-ray transparent MR coil has enabled faster switching between x-ray and MR imaging modes. Conclusion. The improvements introduced in our SP-XMR system have further streamlined x-ray/MR hybrid imaging. Additional clinical procedures could benefit from the new SP-XMR imaging.