Work starts with a clinician who wants part of their job faster, cheaper, or less subjective. We scope it first: would a working model change any decision?
Collection and annotation at the hospital take months. We build on public data meanwhile, so a model is ready for the first site cases.
Site data first tests what public data taught the model, then joins the training set. It keeps growing with every batch.
Once accuracy is reasonable, the clinicians who raised the question look at what the model actually produces. What they flag sets the next round of work.
Our clinical data comes from one hospital. Before claiming a model generalises, we run it on other centres and other scanners.