Mri conditionally safe lead with low-profile conductor for longitudinal expansion

An implantable electrical lead, comprising:

• a lead body having a longitudinal body lumen;
• an electrode coupled to the flexible body in the distal region;
• and
• a conductor extending within the longitudinal body lumen and coupled to the electrode, wherein at least one parameter of the coil conductor is configured such that the lead exhibits a predetermined axial stiffness or bending stiffness, wherein the at least one parameter of the coil conductor is at least one of a coil filar thickness, a number of filars, a filar material, a coil winding direction, or a coil diameter, and wherein the coil conductor is configured such that the coil conductor has an axial stiffness substantially equal to an axial stiffness of the lead body adjacent to the coil conductor.