Hi,
I'm not familiar with this situation but, you stated that "Our cardiologist supervises the SPECT studies in a hospital settiing" To me, that doesn't sound like they are doing what the 26 modifier describes. The 26 modifier indicates the professional component, reading the test. It sounds like your cardiologist is just overseeing the test to make sure it is performed correctly, right? If so, that would be included in the TC portion of the billing.
Let me know if I missed it.
Thanks
Michele