(a) CT scan showing calcification at the edge of the popliteal artery just behind the knee. (b) Magniture gradient echo image showing the signal loss from the calcification of the same area. (c) Phase image showing the diamagnetic effect from the calcification. Note the simliar shape and extent of the calcification in both the CT and MR results. Inserts are zoomed images of the cross-section of the vessels in reformatted transverse images.