I have not been able to find a CMS or MAC article (I've checked IOMs, LCDs, NCDs, even just google) stating which primary codes can be used. Medicare denies this code A LOT, even when following CPT guidelines regarding qualifying codes.
I spoke with Medicare just this morning so they could point me in the right direction and they didn't even have an answer- they instructed me to file a FOIA request in order to get my answer. If I get a resolution in a reasonable timeframe, I will respond again and post the answer. It may be good to file your own request for the same issue as well. This applies to 61781-61783.