A semiconductor power module includes a semiconductor chip thermally interfaced to a ceramic substrate and a leadframe defined by a flexible circuit disposed intermediate the chip and the ceramic substrate. An embodiment is a method including mounting a die to a top surface of a substrate to form a device, encapsulating the die and top surface of the substrate in a mold compound, the mold compound having a first thickness over the die, and removing a portion, but not all, of the thickness of the mold compound over the die. The invention has particular advantages in imaging within the cardiovascular system and highly vascularized or oxygen-dependent tissues. Each sector of the blocker track is aligned with and defines an opposite magnetic pole to an adjacent sector of the first track to alter the magnetic field of the first track extending toward the second track.