Ask Dr. Z

I was reading an article published in an endovascular magazine. They had several examples, one of which was a peripheral intervention. We understand that if a true diagnostic study was done prior to an intervention in the leg, we can code it, however, not to show the catheter placements. In the example we are questioning is the following quote: "Code 36246 is reported in addition to the stent placement because the higher degree of selective catheter placement was performed for the diagnostic study, not the intervention." Is this true? If so, then would then the reverse be true on greater selectivity for interventions that don't include catheter placements (say diagnostic cerebral imaging and then greater selectivity to do the intervention)?