Thats a good point. Alternatively the PC could be used on battery to avoid some problems with providing mains isolation but this isn't ideal, temporary and risky since operators can connect mains, etc. Not recommended.
You'd still need to ensure acceptable leakage currents i.e. "equivalent enclosure and patient leakage" from between conductive accessible parts of the internally powered PC to patient applied parts of the medical system and earth, etc.
