Feasibility of MR guided direct arthrography

S. Wakeley, M. J. Graves, P. Bearcroft, R. T. Black, E. van Rooyen, D. J. Lomas Radiology, University of Cambridge & Addenbrooke's Hospital, Cambridge, United Kingdom, Medical Physics, University of Cambridge & Addenbrooke's Hospital, Cambridge, United Kingdom Introduction Direct MR arthrography is increasingly the preferred imaging investigation for diagnosing subtle intra-articular joint pathology, such as labral tears in the shoulder and hip. Current techniques require X-ray fluoroscopic guidance for initial joint puncture and introduction of contrast medium, followed by transfer to an MR system and subsequent joint imaging. The disadvantages of this approach include use. A technique that allows the procedure to be entirely carried out using an MR system would overcome the disadvantage of needing two adjacent radiology facilities and using ionising radiation. This has been previously described using low field strength open systems [1,2] and on a 1T closed system with in room display [3] but not using 1.5T whole body closed bore MRI systems that make up the majority of the installed base used for musculoskeletal imaging worldwide. These “closed” systems in general provide higher performance for both fast and high spatial resolution musculoskeletal imaging. This work develops a method using animal joint simulations and demonstrates the feasibility of performing the initial needle placement and contrast medium injection on a standard commercial 1.5T MR system using in room scanner control and display, with adaptations that are simple to implement, that allows a direct arthrogram to take place in a single MR examination. Methods A strategy was developed based on in-room direct control of the MR system and the current approaches used for CT & X-ray fluoroscopic interventions i.e. to confirm the position of the target and needle using interval imaging but to modify the needle position and perform the injection with the patient just outside the bore on the couch. Interactive MR fluoroscopy (IMRF) with a range of susceptibility contrast would allow needle location demonstration: T2w or T2/T1w contrast for observing the injection of lignocaine and T1w imaging for demonstrating the dilute gadolinium used in the joint injection phase. The ability to use thick section “projection” imaging to monitor contrast medium dispersal during the injection phase was also considered desirable.