Preliminary experience with interactive guided brain biopsies using a vertically opened 0.5-T MR system

The purpose of our study was to evaluate the feasibility and accuracy of br ain biopsies performed within a vertically opened MR system. We worked with the interventional 0.5-T MR "SIGNA SP" (General Electric Medical Systems, Milwaukee, Wis.) with an integrated tracking device "Flashpoint Position En coder" (Image Guided Technologies, USA). As a holding device for this instr ument we constructed a special frame. The whole system allows an exact adju stment of an optimum biopsy direction and guidance of the biopsy in a non-s tereotactic, interactive mode in near real-time. As biopsy tools we used MR -compatible aspiration and specially made side-cut needles (Daum, Germany; E-Z-EM, USA). We performed a prospective diagnostic brain biopsy study in 1 8 patients. Guidance of the needle was carried out using gradient-echo sing le-slice technique. The sample was taken after controlling the exact positi on of the needle tip on spin-echo images. In 12 cases an exact neuropatholo gical diagnosis was possible. In 6 cases of negative biopsy (4 aspiration b iopsies) the samples were not representative. Our results demonstrate the f easibility of interactive MR-guided minimally invasive brain biopsies in an open MR system. The best results were achieved using cut needles for biops ies of contrast-enhancing lesions visible on T1-weighted gradient-echo guid ance sequence.