Interventional MR imaging: percutaneous abdominal and skeletal biopsies and drainages of the abdomen.

Since the introduction of open magnets and short-bore closed magnets, and the availability of fast imaging sequences, MR imaging has become a tool for guidance and control of percutaneous nonvascular and vascular procedures. In general, percutaneous biopsies or drainages require no specific hardware or software modifications. For lesion localization and control of the needle track, simple fast imaging sequences such as fast T1-weighted gradient-echo techniques or fast single-shot T2-weighted spin-echo sequences are sufficient and can be applied depending on the best tissue-to-lesion contrast. Typical scan times range from 1 to 3 s. Different types of biopsy needles are commercially available, allowing sampling of sufficient amounts of tissue. For drainage procedures non-ferromagnetic materials, such as nitinol wires, should be preferred to minimize image distortion by metallic artifacts. Indications for percutaneous biopsies include subdiaphragmatic liver lesions, lesions poorly visible on ultrasound or contrast-enhanced computed tomography, and lesions of the bone marrow characterized by an unspecific bone marrow edema. For percutaneous drainages, subdiaphragmatic lesions appear to be a good indication. With some experience the procedure time is not longer than that under CT or US guidance.