Interventional magnetic resonance imaging - Non-invasive imaging for interventions

As a prerequisite for MR-guidance of interventional procedures, instruments have to be well depicted in the MR image without obscuring or distorting t he underlying anatomy. For non-vascular interventions the imaging speed has to be in the range of seconds while control of vascular interventions requ ires real time imaging speed. The imaging contrast has to be maintained as well as a high spatial resolution. Furthermore, sufficient patient access h as to be provided by the MR scanner. Neither an ideal magnet nor the optima l single sequence are available to fulfill the above-mentioned criteria. Th e type of sequence - gradient echo versus spin echo together with changing of the echo time and phase encoding direction will-ensure an appropriate si ze of the artifact and thereby of the appearance of the instrument in the M R image. The feasibility of non-vascular MR-guided interventions has been p roved at field strengths ranging from 0.064T to 1.5T Bone:biopsies, soft ti ssue biopsies, drainages, and control of interstitial thermo- and cryothera py have been reported. For vascular interventions, different real time MR s trategies are currently under investigation. The development of dedicated c atheters and guide wires has enabled MR-guided dilatations, stenting, place ment of vena cava filters, and TlPS procedures. Considering the fast progre ss being made in this field, there can be no question that interventional M RI will become a well-accepted clinical tool offering potential advantages such as excellent soft tissue contrast, multiplanar imaging, flow measureme nts, high resolution imaging of vessel walls, and lack of ionizing radiatio n.