Airport screening of people doesn't yield those results. It's able to notice a big inorganic mass, or a chunk of metal, but it wouldn't spot a tumour, it gives nowhere near the level of detail that an MRI or CAT scan will give. The airport scanners are also much cheaper, coming in at ~250k USD rather than ~2m USD.
Even the xray machines used for bags, while expensive and capable, are designed to differentiate metals, liquids, and organics, not organics from other organics.
Both airport security and healthcare funding have their issues, but I don't think this is one of them.