Figure 3

MRI catheter designs. (A) Conventional X-ray catheters are maneuverable in part because they contain steel braiding that distorts MR images. (B) With steel braiding removed, the same "passive" catheter is inconspicuous. (C) An "active" version of the same catheter in (B) has a loopless-design MRI receiver coil along its length, and another loopless-design guidewire receiver coil inside. Both are conspicuous along their shaft or profile. (D) A clinical grade balloon-tipped catheter can be filled with CO2 gas and appears as a black spot (dashed white arrow). This catheter has been manipulated from the femoral vein to the right ventricle in a patient (courtesy Reza Razavi, King's College London). (E) "Active tracking" in a porcine right ventricle (courtesy Steffen Weiss, Phillips Research Europe). A computer-synthesized cross-hair indicates the catheter position on an interleaved image. (F) Multiple channel "active imaging" catheter prototype where the shaft is seen in blue, proximal and distal tip microcoil markers are seen in green, and the catheter bend is seen as an orange signal.