There are some areas of healthcare where it is very cut and dry what defines good healthcare management. These are where we've developed good reporting outcomes that tie closely to clinical and resource utilization outcomes from the published literature. Think of your high volume routines cases such as diabetes (monitoring of A1C)[0] and knee replacements [1] that make of a large portion of health care cases. These are certainly not covering all healthcare episodes, but represent areas where significant fat can be trimmed.
With regard to your above clinical case, there are specific approaches for (what I assume is an incidental finding from a coronary CTA) reporting lung nodules and requesting follow up studies [2]. However, this represents an area where there is significant good faith professional disagreement of reporting.
I will agree that high-evidence clinical guidelines are not always followed, and payment reform has not been influenced all medical professions equally. The way healthcare is delivered is changing, and is being highly influenced by national policy level decisions.
[0]: https://www.healthaffairs.org/do/10.1377/hpb20121011.90233/f... [1]: http://files.kff.org/attachment/Evidence-Link-FAQs-Bundled-P... [2]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5903561/