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 t he 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 need le track, simple fast imaging sequences such as fast T1-weighted gradient-e cho techniques or fast single-shot T2-weighted spin-echo sequences are suff icient 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 a re commercially available, allowing sampling of sufficient amounts of tissu e. For drainage procedures non-ferromagnetic materials, such as nitinol wir es, should be preferred to minimize image distortion by metallic artifacts. Indications for percutaneous biopsies include subdiaphragmatic liver lesio ns, lesions poorly visible on ultrasound or contrast-enhanced computed tomo graphy, and lesions of the bone marrow characterized by an unspecific bone marrow edema. For percutaneous drainages, subdiaphragmatic lesions appear t o be a good indication. With some experience the procedure time is not long er than that under CT or US guidance.