MR-guidance is the least likely modality to be initially chosen for non-vascular interventional procedures. The procedures are more complex and cost is higher than Ultrasonography and Computed tomography. Additionally temporal resolution is lower than with the other two modalities when we use low magnetic field open type MR imagers. On the other hand, the MR image has some excellent characteristics such as high tissue contrast, the ability to acquire images in any arbitrary slice direction, ionizing radiation free imaging and real time thermometry. In this chapter, only nonvascular interventions (punctures, biopsy and percutaneous thermal ablations) are considered.
Low magnetic field open type MR imager is more favorable for MR-guided nonvascular interventional procedures because of high accessibility to patients, wide range of puncture direction and higher safety margin to metallic instruments. Recently, some reports of interventional procedures using higher magnetic field (1.5T and 3T) have been published.
Susceptibility artifact is a very important phenomenon. Thickness of the metallic needles and applicators are increased on MR images. This phenomenon depends on the volume of metallic needle or applicator, angle between magnetic field and needle and also parameters of scanning. We should understand the behavior of this artifact.
At the end of this chapter, a few clinical cases of MR-guided cryoablation will be presented.
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