Stimulation apparatus

A medical apparatus for a patient, comprising:

• an implantable system including a first implantable device comprising:
• a first lead comprising a first set of multiple stimulation elements comprising at least a first stimulation element and a second stimulation element, wherein the first set of multiple stimulation elements are configured to deliver stimulation energy to the patient;
• and
• an implantable controller comprising a current source,
• wherein the controller is configured to:
• configure the first stimulation element elements as a cathode, and configure the second stimulation element and each of any additional stimulation elements as an anode;
• wherein the current source is configured to deliver a first current pulse to the first stimulation element, wherein the first current pulse passes through tissue and is received by the second stimulation element and each of the any additional stimulation elements;
• wherein the controller is further configured to measure a first voltage pulse that results at the first stimulation element due to the delivery of the first current pulse;
• and
• wherein the controller is further configured to determine the approximate impedance of the first stimulation element based on the resulting first voltage pulse.